Exposure Basics

Exposure Basics: Correctly Expose Your Photographs

by Bryan F Peterson

Every picture taking opportunity allows you to record no less than six correct exposures!

Perhaps you have already figured it out after reading the above, but if not, you will soon know that most picture taking situations have at least six possible combinations of f/stops and shutters speeds that will all result in a correct exposure; not a creatively correct exposure but a correct exposure. But only one, sometimes two, of these combinations of f/stops and shutter speeds is the creatively correct motion-filled exposure.

Again, let’s review, that every ‘correct’ exposure is nothing more then the quantitative value of an aperture and shutter speed working together within the ‘confines’ of a predetermined ‘ISO’. For the sake of argument we are both out photographing a city skyline at dusk, using a film speed of 100 ISO and an aperture opening of f/5.6 and whether we are shooting in manual mode or aperture priority mode the light meter indicates a correct exposure at 1 second. What other combinations of aperture openings (f/stops) and shutter speeds can we use and still record a ‘correct’ exposure? If I suggest we use an aperture of f/8 what would the shutter speed now be? Since we have cut the lens opening in half (f/5.6 to f/8) I will now need to double my shutter speed time to two seconds to record a correct exposure, (1 sec + 1 sec= 2 seconds.) On the other hand, If I suggested that we use an aperture of f/4 what would the shutter speed now be? Since we have just doubled the size of the lens opening (f/5.6 to f/4) I will now need to cut my shutter speed in half (1/2 second) to record the same ‘quantitative value exposure’.

Easy yet hard, right?

For a refresher on these terms, take a look at Bryan’s intro article on Basic Photo Tips: Aperture, Shutter Speed, and ISO.

The Equations

The following are equivalent:

• f/4 at 1/2 second
• f/5.6 at 1 second
• f/8 at 2 seconds
• f/11 at 4 seconds
• f/16 at 8 seconds
• f/22 at 16 seconds

Add them up and what have you got? Six possible combinations of aperture and shutter speeds that will all result in exactly the same exposure. I want to stress the word ‘same’; it is meant to mean the ‘same’ in terms of quantitative value only!

Likewise, if we find ourselves taking an outdoor portrait at the park with our telephoto zoom, we find that with our aperture set to f/16 and with an ISO of 100, a correct exposure is indicated at a shutter speed of a 1/125 second (s). If I suggest we use an aperture of f/8, what would the shutter speed now indicate as a correct exposure? If you said 1/500s, you are correct, which also means that you know at f/22 the correct exposure would be a 1/60s and at f/11 1/250s and at f/5.6 your shutter speed would now be 1/1000s. Again, why all the ‘fuss’; what difference does it really make which combinations of apertures and shutter speeds we use as long as the meter indicates a correct exposure?

Knowing that every picture taking opportunity offers you no less than six possible aperture/shutter speed combinations in and of itself may seem immaterial, but when you consider the impact of the creative possibilities influenced by the shutter speed (freezing actions, implying motion or panning) and aperture (a great depth of field, or a background of muted tones and/or out of focus foregrounds) you will have a much greater appreciation for why you are choosing that particular shutter speed and aperture combination. The reason will not be simply because you want to record a correct exposure, but rather because you want each and every time to record the CREATIVELY CORRECT EXPOSURE! The difference between a “correct exposure” and a “creatively correct exposure” is often huge! Let’s take a look!

Let’s pretend we’ve invited ten other photographers to join us in capturing this scene and we break into three groups:

• One third of the group shot this scene at f/11 for four seconds
• Another third shot the scene at a f/8 for a two seconds
• The remaining third shot the scene at f/5.6 for 1 second.

You know what? All of us just shot the exact same correct exposure! Even though each group’s f/stops and shutter speeds were different, the end result was the same; the quantitative value of each group’s exposures are the same. It doesn’t matter if you are photographing with a film-based camera or a digital camera, you must learn and embrace a simple fact; every picture taking opportunity offers you no less then six possible aperture/shutter speed combinations. Why must you know this? Even though each group has the ‘same’ exposure, the motion-filled opportunity that each group captured may look radically different. Knowing that each motion-filled exposure opportunity offers up six possible combinations is a start but knowing which one of two exposures best conveys or capture the motion before is the key. Once you are armed with this knowledge you can begin to fully explore the truly endless road of creatively correct motion-filled exposures!

Now let’s imagine that we all awoke the following morning, once again splitting into three groups and we all head into a flower garden. All of us are armed with our telephoto zooms and we are going to record correct exposures of a single flower bloom.

• One third of the group shoots that lone flower at a correct exposure of f/4 at 1/1000s.
• Another third of the group at f/8 at 1/250s.
• The last third of the group shot that same flower at f/16 at 1/60s.

Fifteen minutes later we all get together and compare results and guess what? Every one of us has recorded the ‘same’ and correct exposure in terms of its quantitative value, but, each group also recorded a visually different yet correct exposure. The visual difference is the key to understanding the difference between a correct exposure and a creatively correct exposure. Although the quantitative value of each exposure was the same, the aperture choices were different and therein lies the visual difference. Depth of field increases each and every time we stop the lens down and in the case of the flower composition, the smaller apertures recorded a greater depth of field than did the aperture of f/4. Again, the exposures taken by all three groups were the same quantitative value but visually they were quite different solely due to the aperture choice.

Image 1

Image 2

So to recap: there are six possible aperture and shutter speed combinations that will result in the correct exposure, yet only one, maybe two, is in fact the “creatively correct” exposure. It is that one creatively correct exposure that gives you the precise depth of field you were hoping to achieve or that one creatively correct exposure that gives the the precise action stopping shutter speed or the precise shutter speed that guarantees a motion-filled image, e.g. the cotton candy effect often seen in waterfall compositions.

Let’s take a real world look at just how different a correct exposure is versus that of a “creatively” correct exposure.

Exercise 1: Flower Composition

Head outside with your camera set to 200 ISO and a telephoto lens, say a 200mm, and frame up a flower. Once you focus on the flower, shoot six correct exposures, each one using a different aperture and shutter speed. For example, with the aperture set to f/4, you get a correct exposure indication at 1/1000s. Shoot this one exposure and than move on to f/5.6 and then shoot another at 1/500s, f/8 at 1/250s and another at f/11 at 1/125 second, f/16 at 1/60s and finally another at f/22 at 1/30s. You will soon see that all six exposures are correct in their quantitative value, but radically different in their “visual weight”. Note in just these two examples where the first image was shot at f/5.6 at 1/500 second and the second image shot at f/22 at 1/30s. They are the “same” exposure in their quantitative value, but oh my, look at how much busier the background is in the correct exposure taken at f/22 versus the much cleaner and more isolated flower composition of the correct exposure taken at f/5.6 at 1/500s.

Image 3

Image 4

Image 5

All three of these images are exactly the same exposure (Images 3, 4, and 5). Their quantitative volume of aperture, (light) and shutter speed (duration of time) is exactly the same, yet you can clearly see that visually they are each different. All three photographs were taken with my tripod mounted Nikon D2X and 200mm Micro-Nikkor lens.

Image 3 was taken at f/5.6 at a 1/500 second, Image 4 was taken at f/11 at 1/125s and Image 5 was taken at f/22 at 1/30s. Again, their quantitative values are identical, which is to say that the volume of light that passed through the lens and the amount of time that light was allowed to render an image on the CCD or film was the same. When I composed all three of these images, they looked exactly the same inside my cameras viewfinder. Yet when I reviewed these same three exposures on the camera’s digital monitor, they were clearly different and that difference in this case was with their backgrounds.

In Image 3, the background is limited to subtle out-of-focus tones, color and very few shapes. In Image 4, the background begins to offer up a bit more information in both shapes and sharper tones and by Image 5, it’s ‘clear’ that the background, consists of other nearby flowers due to the much greater defined shapes and tones that are presented. All three are the same exposure, but as is often the case, only one, and sometimes two, are the “creatively” correct exposure.

Use of Motion

When capturing this simple composition of an S-curve on Interstate 5 approaching downtown Seattle, I was presented with six possible options of recording a correct exposure, three of which you see here (Images 6, 7, and 8). In terms of their ‘quantitative value’, all three of these images are exactly the same exposure, BUT one can clearly see that they are vastly different in their creative exposure, with the creative emphasis on the use of motion. It has and will always be my goal to present motion-filled opportunities in the most motion-filled way and more often than not when there is a motion filled scene, the longer the exposure time, the greater the motion is conveyed. In our first example, Image 6 was captured at f/4 for 1/2s, Image 7 was shot at f/8 for 2s and Image 8 was shot at f/16 for 8s. All three of these exposures were made with my Nikon D2X and Nikkor 200-400mm zoom at the focal length of 400mm, mounted on tripod with my ISO set to 100 and my WB set to Cloudy.

Image 6

Image 7

Image 8

An exercise such as this is truly eye-opening. The next time you head out the door to shoot city lights at dusk, there won’t be a lot of hesitation on your part about using the slower shutter speeds, since by this example, the slowest shutter speed exposure had the best effect. (I am assuming that you prefer the third image, the image taken at f/22 for 8s and just so there is no confusion, this is not ‘bracketing’ since they are all the same exposure in terms of their quantitative value. I will cover bracketing and other issues related to “where should I take my meter reading” in a future article).

Going to Extremes with Shutter Speed

As you begin to digest more and more this simple rule of exposure, it will soon become clear that the need to pay attention to what aperture choice or shutter speed choice will in fact lead you to conclude that there is but one truly creatively correct exposure most of the time and this is particularly true as you begin to notice that the world offers up an unlimited supply of motion-filled opportunities. When capturing these motion filled opportunities you will find yourself, more often than not, on either end of the shutter speed spectrum; using fast shutter speeds to freeze the action in crisp sharp detail or using slow shutter speeds and the resulting blur to suggest or imply the motion present. There is rarely a ‘middle ground’ when it comes to the motion-filled world and with that in mind, it won’t be long before you discover that most of your time is being spent on action-filled scenes between 1/500s and 1/1000s OR between 1/4s to 8s.

Image 9

Image 10

With my camera and 80-400mm Nikkor zoom mounted on tripod and the lens set to 300mm, I captured Image 9 at f/4 and 1/500s. Image 10 was shot at f/22 and 1/15s. Both exposures are exactly the same in terms of quantitative value, BUT quite different in the arena of ‘creative exposure’. Note how at the wide open aperture of f/4 (Image 9) the splash is frozen in crisp sharp detail but at f/22 (Image 10) that same splash is much more ethereal.

Recording a correct exposure will always be your responsibility, so why not make it a point to make the most deliberately and visually compelling ‘creative’ exposure possible!?

Exercise 2: Motion-Filled Exposures

One of the best lessons I know of is one that I have offered up to countless students over the years in my on-location workshops and at my on-line photography school www.ppsop.net. It is a very revealing lesson and not surprisingly will lead you further into the world of creatively correct motion-filled exposures. Choose a moving subject, such as a waterfall or a child on a swing or shoot something as simple as someone pounding a nail into a piece of wood.

With your camera set to Aperture Priority Mode, your ISO set to 100, (or 200 ISO if that is the lowest your camera offers) and your aperture set to wide open, (f/2.8, f/3.5 or f/4) take an image of the action before you. You have just recorded an exposure at the fastest possible shutter speed based on the ISO in use, the light that is falling on your subject and of course your use of the largest lens opening. Now stop the lens down one full stop, (if you started at an aperture of f/2.8 then go to f/4 and if your lens starts with f/4 then go to f/5.6) and once again take another exposure of the action filled subject. Repeat this each time with the aperture set next to f/8, then f/11, then f/16 and finally f/22. Each time you change the aperture by what is called a ‘full stop’, your camera does a quick recalculation and offers up the ‘new’ shutter speed to maintain a correct exposure and since you are stopping the lens down with each full stop change in aperture, (making the hole in the lens half as big as it was before) your shutter speed has now doubled in time to compensate, or in other words, your shutter speed is becoming progressively slower. The slower your shutter speed the more likely it is that your action filled subject before you is showing signs of ‘blurring’, since the shutter speed is too slow to ‘freeze it’.

Conclusion

To re-cap, the fastest possible shutter speed with any given ISO will always be found when you use the largest lens opening and the slowest possible shutter speed (barring the use of any filters) will always be found when you use the smallest lens opening.

There is one thing I hope you will never forget after reading this article: correct exposures can be found just about anywhere, but why settle for just a correct exposure when you can in fact record a truly creatively correct exposure each and every time? You really can take charge of your own creative vision when it comes to exposure!

What Is... Aperture?

When you look at the technical specifications of a digital camera, one of the very first specification mentioned is its maximum aperture and/or its aperture range.

What is 'aperture,' what is a good aperture range, and how is aperture relevant when it comes to choosing a digital camera?

What Is Aperture?

The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris.The larger the diameter of the aperture, the more light reaches the film / image sensor.

Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).

[Note: Many camera user manuals today will refer to the aperture in terms of "aperture value" instead of f/value. I'm not sure when this trend started but don't get confused between "aperture" and "aperture value." Aperture value" is simply another way of saying f/value.]

In practice, unless you are dealing with a fixed-aperture lens (many simple point-and-shoot cameras have only one fixed aperture), the aperture of a lens is usually expressed as a range of fstops.

When you read the specifications of a camera, the aperture may be expressed in a number of different ways, the following three being the most common:

• Maximum Aperture:

Max. Aperture

F2.8

This simply states that the maximum aperture for the lens is F2.8.

• Aperture Range:

Aperture Range

F2.8-F8.0

This states the max. and min. aperture, the assumption being that there are standard increments between them.

• Maximum Wide-Angle and Telephoto Apertures:

Aperture

F2.8-3.5 or F2.8(W)-F3.5(T)

This gives the max. aperture for the wide-angle (F2.8) and telephoto (F3.5) focal lengths of a zoom lens.

It is usually not too difficult to figure out that a stated range deals with maximum apertures and not max and min apertures: the mimimum aperture should be quite small at F8, F11, F16 or F22.

A "fast" lens is one that has a large maximum aperture (F2.4, F2.0 for current digital cameras; F1.4, F1.2 for 35mm film cameras).

Quick Quiz: which lens has a larger opening (aperture): one with an aperture of F1.8 or one with an aperture of F2.8?

Answer: F1.8 (remember, the smaller the F-stop, the larger the aperture)

A Good Aperture Range

My personal preference for a 'good' aperture range is:

F1.8 - F16

F1.8

F2.8

F4

F5.6

F8

F11

F16

This tells us that the camera has an aperture range of F1.8 to F16; the maximum aperture is F1.8, and the minimum aperture is F16.

There are 5 f-stops between the max and min aperture. If your camera's lens is currently set at an aperture of F5.6, closing it by 1 f-stop would mean selecting F8; opening it up by 1 f-stop would mean selecting F4.

F1.8

F2.8

F4

F5.6

F8

F11

F16

How Is A Large Maximum Aperture Relevant?

A large maximum aperture is preferable to a smaller one since it gives the photographer more latitude in the kind of pictures that can be taken.

For example, it is pretty obvious that the larger the aperture, the better your digital camera will perform in low-light situations, since a larger lens opening is able to admit more light than a smaller lens opening.

A larger max. aperture also allows you to use a faster shutter speed to freeze action.

So, let's say the light meter in your digital camera calculates that for proper exposure in that indoor arena, you need an aperture of F4 and a shutter speed of 1/60 sec.

F4

1/60

To use a faster shutter speed (say, 1/250 sec.) to freeze action, you have to open up the aperture to allow more light in for that shorter amount of time.

For every shutter speed increment we go up, we need to open up a f-stop of aperture. From 1/60 sec. to 1/250 sec. there are 2 increments, so we open up the aperture by 2 f-stops, going from F4 to F1.8. Note that the camera would give proper exposure at 1/60 sec. at F4, 1/125 sec. at F2.8, and 1/250 sec. at F1.8, since all three aperture/shutter speed combinations allow the same amount of light into the camera. [Some digital cameras provide a 'Program Shift' function to allow that very shifting of aperture/shutter speed combinations in tandem.]

F1.8	F2.8	F4	F5.6	F8	F11	F16
1/250	1/125	1/60	1/30	1/15	1/8	1/4

Of course, in a digital camera set on Auto mode, you can select Sports scene mode, and the camera will automotically select a fast shutter speed and the appropriate aperture. Likewise, in Shutter-Priority mode, you can choose which shutter speed you want (fast or slow), and the camera will select the appropriate aperture for proper exposure.

In our example above, let's say the lens on your digital camera only opens up to a max. aperture of F2.8. If you now select 1/250 sec. (in Shutter-Priority mode), the camera will not be able to select an aperture larger than F2.8 (in our example, it really needs F1.8). It would then give you an "underexposure" warning. If you go ahead and take the picture anyway, your picture would be 1 f-stop underexposed (i.e. you really needed to open up the aperture by 1 more f-stop for correct exposure).

Similarly, if you select a shutter speed of 1/4 sec. and the lens only closes down to a min. aperture of F8 (in our example, it really needs F16), the camera would give you an "overexposure" warning. If you go ahead and take a picture anyway, your picture would be 2 f-stops overexposed (i.e. you really needed to close down the aperture by 2 more f-stops for correct exposure).

[Editor's note: There is a third variable in the above example which we have purposefully not introduced. This is the sensitivity of the image sensor -- the ISO. We'll cover this in a later tutorial.]

How Is A Small Minimum Aperture Relevant?

A small minimum aperture is preferable to a larger one since it also gives the photographer more latitude in the kind of pictures that can be taken.

Suppose we want to take a picture of flowing water. As mentioned above, to depict flowing water, we usually want to use a slow shutter speed so that the water blurs. It is this blurring that makes the picture so effective in depicting water motion.

So, let's say the light meter in your digital camera calculates that for proper exposure on a bright sunny day, you need an aperture of F8 and a shutter speed of 1/125 sec.

F8

1/125

Well, if you decide to use a slower shutter speed (say, 1/30 sec.), this means that you have to compensate by closing down the aperture to allow less light in.

It makes sense really. Since you have increased the time the shutter remains open to allow light in, you must compensate by allowing less light in to expose the image sensor in that longer amount of time, if you still want a properly exposed picture.

But, what if the lens on your digital camera closes to a minimum of F8? You're stuck at the shutter speed of 1/125 sec. If you use 1/30 sec. at F8, your picture will be overexposed, i.e. burnt out. At 1/125 sec. and F8, your picture will be properly exposed but the fast shutter speed will freeze the water motion and you won't obtain the blurring effect you desire.

If the lens in your digital camera closed down to F16, presto, your problem is solved! 1/125 sec. at F8 is equivalent to 1/30 sec. at F16, which means that you would have a perfectly exposed purposefully-blurred-for-effect flowing water shot. [If your lens does not close down to F16, you could use a Neutral Density (ND) filter to reduce the amount of light coming into the lens, and thus allowing you to use a slower shutter speed.]

F1.8	F2.8	F4	F5.6	F8	F11	F16
1/2,000	1/1,000	1/500	1/250	1/125	1/60	1/30

[Editor's note: There is a third variable in the above example which we have purposefully not introduced. This is the sensitivity of the image sensor -- the ISO. We'll cover this in a later tutorial.]

Aperture and Depth of Field (DOF)

We mentioned this above but feel it is important enough to repeat in its own paragraph.

The Depth of Field is the distance wherein objects are in focus.

There are times when you desire a great depth of field, i.e. where objects both close to you and far from you are in focus. This is especially true when you are taking a landscape picture and want as much as possible to be in crisp focus.

Then there are times when you want to isolate your subject, as when you are taking a portrait and want your subject to be in sharp focus but the background to be out of focus. In this case, you desire a shallow depth of field.

One way to influence DOF is by selecting the appropriate aperture.

The rule of thumb is this:

• Select a large aperture (or small f/value or small aperture value), e.g. f/2.8, to obtain a shallow DOF
• Select a small aperture (or large f/value or large aperture value), e.g. f/8.0, to achieve great DOF

Here are some real images that demonstrate the use of aperture to influence DOF:

Aperture and Depth of Field (DOF) AF area is on yellow pistils of flower in front
Shallow DOF	Great DOF
Note how the use of a large aperture (small aperture value) throws the flowers in the background out of focus. Focus has to be precise.	Using a small aperture (large aperture value) extends the DOF from the foreground all the way to the background.
49.8 mm, Av, Spot, 1/30 sec., f/3.5, +0.7EV, Macro, Tripod used	49.6mm, Av, Spot, 1/5 sec., f/11, +0.7EV, Macro, Tripod used

Note: Since we are on the subject of DOF, DOF also changes with focal length. Use a small focal length to increase DOF, a longer focal length obtain a shallower DOF. I.E. if you zoom, the DOF decreases. [OK, to be technically correct, focal length does not really affect DOF, but gives the effect that it does. And, that's good enough for us since that's what we're after. We'll cover DOF in a later tutorial.]

Due to the small image sensors used, digital cameras use such small focal lengths that it is very difficult to obtain shallow depth of field even when using a large aperture. In the example above, we used a large aperture AND a long focal length (telephoto macro) to achieve a shallow DOF.

Recap

A large maximum aperture is a good thing. It allows more light to reach the image sensor, and so allows you to use a faster shutter speed. A faster shutter speed freezes action and negates the effect of camera shake, resulting in pictures that are not blurred.

Another advantage of a large maximum aperture is to provide a shallow depth of field. This allows the background to blur nicely thus isolating your subject (especially effective when taking portraits).

A small minimum aperture is also a good thing. It allows you to use a slow shutter speed on a bright sunny day. A slow shutter speed allows you to depict motion.

Another advantage of a small minimum aperture is to increase the depth-of-field. An increased depth-of-field allows you to take landscape pictures where as much of the picture in the foreground and reaching all the way to the background (usually, 'infinity') is in sharp focus.

What is lens aperture in digital cameras?

There is no difference between the aperture in a film camera or in a digital camera.

The aperture is the diameter of the adjustable iris that controls the amount of light passing through the lens and onto the film plane or digital sensor. An aperture is expressed as an f-stop, which is equal to Focal_Length / Aperture_Diameter, and is written: f/number.

For example, if a lens has a focal length of 50mm - the 'normal' 35mm film camera lens - and the aperture diameter is 5mm, then the f-stop is 50/5 or f/10.

If you know what f-stop a lens is set to, you can determine the physical diameter of the aperture. For example, with an aperture of f/11:
- On a 50mm lens, the aperture is 4.55mm in diameter (50/11).
- On a 100mm lens, the aperture is 9.09mm in diameter (100/11).
- On a 20mm lens, the aperture is 1.82mm in diameter (20/11).

F-stops are used because they are a standard way to express the amount of light passing through a lens. The amount of lens passing through a 50mm lens set to an aperture of f/11 is the same as the amount of light passing through a 300mm lens set to f/11. This is far simpler than measuring the diameter of the aperture to calculate relative levels of illumination..

Difference between setting aperture by lens and camera

The "choice of focus" is a choice for the focus spot. With a bigger aperture (lower F number), the focus point gets more and more isolated and everything else is more and more blurred. This effect generally works better, the bigger the sensor is. That is why you don't really see this effect on point and shoot cameras; small aperture and small chip.
But that is really putting it way too simple. You will see what I mean when you get the cam and a nice bright lens.

Some lenses, especially the older ones, have an aperture ring. With most of these, you have to set the aperture on the lens; if you change it on the camera's dial it won't on the lens. With automatic lenses, which do not have an aperture ring, the number set in-camera will be electronically transmitted to the lens and then set.

Your camera has 4 "Exposure Modes" : "P" for Program, "M" for Manual, "S" for Shutter Priority and "A" for Aperture Priority.

In "P" your camera will select an aperture and shutter speed to give a correct exposure.

In "M" you can set the aperture and shutter speed any way you want.

In "S" you select a shutter speed and the camera will select a correct aperture.

In "A" you select an aperture and the camera will select a correct shutter speed.

Using "P" turns your DSLR into a glorified "point & shoot" since you have no control over the settings the camera chooses.

If you're shooting night scenes without flash then you'd use "M" so you can select both shutter speed and aperture to achieve the results you want. This requires a tripod to mount your camera on since shutter speeds are usually long - 2 seconds or more.

If you're shooting action - kids running and playing, sports or other fast moving subjects - then you'd choose "S" so you can keep the shutter speed high enough to stop the action.

If you're shooting nature or scenics you'd choose "A" since you'll want to control your aperture to give more or less Depth of Field (DOF)*. You must remember to check the shutter speed the camera selects to make sure it isn't too slow to hand-hold the camera.

A company called "The Magic Lantern" offers an instructional DVD for your camera. You should be able to find it at Circuit City or Amazon. It would, IMO, be very helpful.

Actual classes in photography would be the very best way to learn if any are available.

You might want to visit http://www.fotosharp.com and buy their "Day & Night Exposure Guide" if you plan on doing low-light, non-flash photography.

* DOF is loosely defined as the area in acceptable focus in front of and behind your subject. If you google "depth of field" you'll find numerous examples and discussions. If you go to http://www.expoimaging.net you can read about their ExpoAperture2. This is a circular chart showing the DOF for different focal lengths, apertures and sensor sizes.

There is no difference between the aperture in a film camera or in a digital camera. The aperture is the diameter of the adjustable iris that controls the amount of light passing through the lens and onto the film plane or digital sensor. An aperture is expressed as an f-stop, which is equal to Focal_Length / Aperture_Diameter, and is written: f/number. For example, if a lens has a focal length of 50mm - the 'normal' 35mm film camera lens - and the aperture diameter is 5mm, then the f-stop is 50/5 or f/10. If you know what f-stop a lens is set to, you can determine the physical diameter of the aperture. For example, with an aperture of f/11: - On a 50mm lens, the aperture is 4.55mm in diameter (50/11). - On a 100mm lens, the aperture is 9.09mm in diameter (100/11). - On a 20mm lens, the aperture is 1.82mm in diameter (20/11). F-stops are used because they are a standard way to express the amount of light passing through a lens. The amount of lens passing through a 50mm lens set to an aperture of f/11 is the same as the amount of light passing through a 300mm lens set to f/11. This is far simpler than measuring the diameter of the aperture to calculate relative levels of illumination..

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How big an aperture do I need? Do I need IS?

Bigger apertures are better, but they cost you a lot of extra money. Why do you need a bigger aperture anyways? There are several reasons for wanting a big aperture.

Bigger apertures are most commonly used in situations where there’s poor lighting and if you cannot use flash. To take a picture, the camera will either need a bigger aperture or it will need to make the shutter speed slower to expose the shot properly. Using a larger ISO value (1600, 3200) will help too, but going too high may sometimes introduce unwanted noise into the picture. If you are handholding the shot in this situation, the need for a bigger aperture is that much more important because a slower shutter speed will lead to camera shake and blurriness.

You will also need a bigger aperture when you want to blur the background in a shot. When you use a larger aperture, the depth of field becomes shallow, placing only closer things (to the focus point) in focus, leaving the rest out of focus, or blurred. Conversely, when you use a smaller aperture, the depth of field becomes deeper, making a larger part of the image in focus.

What apertures do I need?

If you are doing available-light indoor photography, f/2.8 is the bare minimum. I recommend f/2.0 or larger.

If you are doing indoor sports or action photography, f/2.0 and larger is virtually required, so you can get fast shutter speeds to freeze the action in addition to bumping up the ISO to 800 or 1600.

If you are working in decent light (i.e. outdoors), f/4 will work just fine. If you work mostly outdoors in great lighting, f/5.6 and above will suffice. If you plan on bringing a monopod or a tripod to stabilize things, you can even get away with even smaller apertures.

V. What is an extender?



An extender is a special kind of lens which mounts itself between the main lens and your camera. As its name suggests, an extender increases the focal length of your lens by some set amount. At this moment, there are two kinds of extenders, 1.4x and 2.0x. As a quick example, if you have a 100mm lens, the 1.4x and 2.0x extenders will transform the focal length into 140mm and 200mm respectively.

For this reason alone, extenders can be quite useful in extending the reach of your lenses at a relatively low cost while taking less space.

As always though, there's a tradeoff when you gain convenience. You sacrifice image quality, and the lens becomes "slower." Here's an explanation for both points.

1) You might recall that f-stop is a simple ratio between the diameter of the aperture of the lens (how big the hole is) and the focal length of the lens. For example, a 50mm lens with a 25mm diameter has an f-stop value of 2, hence the f/2 branding. Naturally, this means then that doubling the focal length will double the f-stop value, causing you to lose TWO whole stops. Using a 1.4x extender makes you lose ONE stop. If the f-stop value gets too high, sometimes auto focus will no longer function. Check with your manufacturer for exact details.

2) Extenders also degrade image quality, especially if you use a 2x extender. Think of an extender as a magnifying glass for a moment. If an extender is a magnifying glass, all of the "faults" in a lens will effectively become that much more noticeable. For examples, images may be softer, be more distorted or may lack contrast. But this is the price you pay for convenience. I'm sure that most of us would be happy lugging around a 200mm lens with an extender rather than a 400mm lens and a tripod.

To sum it up, extenders are useful tools for getting more utility out of your lens collection. I personally recommend buying a 1.4x converter as the degradation in speed and image quality is less noticeable in practice. If you start with a very good lens, you may not notice a difference at all!

Lens Recommendations

These recommendations are geared towards a budget-minded DSLR buyer. I've also included some nicer lenses that are popular choices for those who've outgrown kit lenses and wish to upgrade.

The prevailing theme is: Less is more. Spend your money on fewer lenses rather than spreading your money out. It's better to acquire lenses slowly but steadily. Buy one lens at a time and evaluate your needs. Never buy a lens for the sake of buying a lens!

Disclaimer: Prices are estimates taken from Amazon.com as of the time of this post. I do NOT count rebates in the price, so please check with your preferred merchant before buying.


A) Starting Out?
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The following 4 setups are the among the most common starting kits I've come across.

Setup A ($250 and up) - Single Convenience Lens



Recommended for those who want one lens to handle it all. These are perfect lenses for traveling when portability is a concern. These lenses compromise some quality because of the large range, but the upside is that you can figure out what focal lengths you use the most and work from there.

Sigma 18-125mm f/3.5-5.6 ($250)
Cheap and good price-performance. A great traveling lens.

Sigma 18-200mm OS f/3.5-6.3 ($450)
A solid and versatile lens for non-Nikon users.

Nikon 18-200mm VR f/3.5-5.6 ($680)
The current king of convenience lenses. It's not flawless, so make sure you try this lens out before you buy.


Setup B ($300 and up) - Single "Walkaround" Lens



A walkaround lens is another name for standard zoom lens. These lenses are faster and better in optical quality than convenience lenses, but they lose range and portability. They also cost more.

Sigma 17-70mm f/2.8-4.5 ($350)
A solid replacement for a kit lens.Great optical quality (sharp!) and fairly fast.

Tamron 17-50mm f/2.8 ($450)
This Tamron lens is widely regarded as the cream of the crop for third party lenses. Highly recommended if you are after a constant aperture zoom lens.


Setup C (add $80) - "Walkaround Lens" + Prime



Pair any of the lenses above with the 50mm f/1.8 prime. The prime is ideal for portraits, available-light photography and more.


Setup D ($700 and up) - Prosumer Lenses



For those who want something more than the entry level. These lenses aren't cheap, but they are lasting investments that will serve you well.

Canon 17-40mm f/4 L ($700)
A popular choice for those who want to splurge on a quality wide-angle lens with top-notch build quality and autofocus. As good as this is, consider the EF-S 17-55 if you are not using a full-frame body.

Canon 70-200mm f/4 L ($600)
Arguably Canon's most popular lens. It's one of the best zoom lenses on the market (optically speaking) and comes at a moderate price. If f/4 is OK for you, look no further. The IS version costs $1100.

Canon 17-55mm f/2.8 IS ($1000)
The best of the best when it comes to a standard zoom lens. L-class optical quality, L-class autofocus and an L-class price to boot. Alas, build quality is a bit weak relative to the price point, but this is the best lens for an APS-C body at the moment.

Canon 24-105mm f/4 IS ($1100)
A convenient standard zoom lens at a premium price. The focal length is a little awkward to use on an APS-C body, but if it fits your needs better than the 17-55, it's a good choice.


B) Convenience Lenses
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The rest of this guide splits up lenses into various categories. This category contains compact, super-convenient lenses which are good for outdoor shots and for budget-minded photographers.

Sigma 18-125mm f/3.5-5.6 ($250) – It's not without its flaws, but it's a convenient starter lens and also good for vacations. For $100 more, you can get the 18-200, a similar lens with longer reach. For $100 more, you can add image stabilization to either lens.

Canon EF-S 17-85mm f/4-5.6 IS ($550) - A popular alternative to the kit lens. It has its flaws, but it's a convenient lens for traveling and general use.

Nikon 18-200mm f/3.5-5.6 VR DX ($680) - This is a very good lens relative to other "convenience lenses," but it still has its shortcomings. Try before you buy.


C) Walkaround Lenses
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If you want a wide or standard zoom lens, put these at the top of your list. These are less versatile than the do-it-all lenses, but they are faster and have better optics.

Sigma 17-70mm f/2.8-4.5 ($350) - An excellent alternative to a kit lens at a slightly higher price. This lens is sharp throughout its range and roughly replicates a classic 28-105 lens.

Tamron 17-50mm f/2.8 ($450) - A spectacular lens for APS-C cameras. If you're in the market for a quality standard zoom with a fixed aperture but can't splurge on the Canon 17-55 IS, this is the one to get.

Canon 17-40mm f/4 L ($700) – Arguably Canon's most popular lens, this great wide-angle walkaround lens can be used everywhere as long as the lighting is good. While third party alternatives are budget friendly, the Canon still trumps them in focus speed/accuracy and build quality.

Canon/Nikon 28-105mm f/3.5-4.5 ($230) - One of the best bargains out there and is easily one of the best consumer zooms available. It beats a kit lens by a long shot, but it's less convenient due to the crop factor. Do not confuse with the f/4-5.6 variations which are cheaper and far worse in quality.


D) Telephoto Zooms
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Need that extra reach to capture distant subjects? If you are on a tight budget, I highly recommend buying a decent walkaround lens first and then dealing with telephoto later. In addition, you'll learn how to use the camera and be able to better evaluate your situation when the time comes to buy your second lens.

There are lots of choices, but my top recommendations are the Sigma 70-300 APO for budget users, the 70-200 f/4 L for discerning users, and the Canon 70-300 IS for everybody else.


APS-C Telephoto Zooms

Sigma 50-150mm f/2.8 EX ($600) – A compact and economical alternative to a classic 70-200 lens for APS-C cameras. Optically sound, but early adopters are reporting front focusing issues. Try before you buy.

Tokina 50-135mm f/2.8 EX ($700) – A similar lens to the Sigma, without the front focusing issues but with a reduced range.


Up to 200mm

Canon 70-200mm f/4 L ($600) - An entry-level L lens which is a big leap up from consumer telephoto lenses. Stunning optical quality as long as you aren't taking low light shots. Lightweight and compact enough to bring everywhere. One common use of this lens is for zoo/short-range wildlife photography.

Nikon 55-200mm f/4.5-5.6 VR ($250) - A cheap telephoto kit lens that has image stabilization. Recommended for those starting out. Don't expect much, but having VR at this price is a boon. Canon has a similar lens (55-250 IS).


300mm+

Sigma 70-300mm f/4-5.6 APO DG ($200) - If you need a telephoto lens and only have $200 to spend, this is the lens to buy. Be sure to buy the APO version.

Canon 70-300mm f/4-5.6 IS ($550) - Canon has replaced its popular 75-300 IS with a brand new version that contains a UD element, an updated IS mechanism and an updated body. This is a much sharper and better lens than the old version. Some consider it to be close to the 70-200/4 L mentioned above.

Nikon 70-300mm f/4.5-5.6 VR ($530) - Similar to the Canon lens, with some of the same strengths and flaws.


Worth a Mention (Good but flawed choices)

Sigma 70-200mm f/2.8 EX DG ($750) – An alternative to the first party offerings for hundreds less, IF you get a good copy. Be sure that your merchant accepts exchanges, or be ready to send to Sigma for calibration. I'm only including this here because it's a nice lens when it works properly.

Tamron 70-200mm f/2.8 ($700) – A cheap and fairly lightweight alternative to first party offerings. Optically equivalent to first party offerings, but early reviews and user reports find that autofocus speed and accuracy are disappointing. Try before you buy.


E) Ultra Wide Zooms
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With the advent of digital bodies with a crop factor came the need for ultra-wide lenses to make up for lost coverage at the wide end. Consequently, almost all of these lenses are only suitable for such bodies and if used on a full-frame camera, will exhibit vignetting. In general, there are a lot of ultra-wide lenses on the market, and most of them are pretty good. The first party offerings are better, but like always, they may not be worth twice the price.

What may sway your decision most (besides price) may be how each lens fits into your current lens lineup. Because each one starts and stops at different focal lengths, what works for one person may not work for you.

Canon EF-S 10-22mm f/3.5-4.5 ($700) – This is a sharp, relatively distortion-free (for this focal length) lens that has L-class optics. Don't be misled by the f/3.5-4.5 designation. It's f/3.5 up to 20mm and f/4.5 for the last 2mm.

Tokina 12-24mm f/4 ATX-PRO ($470) – This lens is a great alternative to first party ultra wide lenses. Build quality is superb, and the image quality is similar. The newly released 11-16/2.8 is even better.

The other good third party lens to look at is the Sigma 10-20mm f/4-5.6 EX ($470). It's not perfect, but it's similar to the Tokina. I would avoid the Tamron 11-18 which is more expensive and has more faults than the Tokina and Sigma. Nikon has a similar lens that is similar to the Canon and Tokina, but it's priced close to $1000, putting it out of range for most.


F) Primes
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Primes are the best bangs for the buck if you need them. You lose flexibility, but you gain it all back in sharpness (especially wide-open), low distortion, less lens flare, and less ghosting.

Do you shoot indoor sports like hockey or indoor action? Do you shoot indoors in low-light in places where flash is prohibited? If you work in these kinds of tricky conditions, consider these lenses. Primes are also superb for portraits though high grade zooms also do the trick.

I am only listing shorter primes (less than 200mm) here.

50mm f/1.8 (< $100) – Should be part of everybody’s collection. If you use this prime a lot and you own a Canon body, step up to the f/1.4 version for the better build quality and better optics.

85mm f/1.8 ($360) – An ideal lens for candids and portraits. Also works as a short range telephoto lens in low light. Canon offers a similar 100mm f/2 lens for a little more if 85mm is too short for you.

Canon 135mm f/2 L ($900) – This is one of Canon’s best lenses. This gem will serve you extremely well if you shoot indoor sports or concerts. It's also a superb portrait lens. Nikon has a similar lens, but it costs more.

Canon 200mm f/2.8 L ($700) - This lens is very similar in quality and size to the 135 and is a great, compact alternative to a 70-200 f/2.8 zoom which is heavy and attention grabbing.

You may notice that I have not listed any wide primes here. Generally speaking, consumer-grade wide primes aren't a whole lot better than quality wide zooms. You are better off buying a quality zoom instead.


G) Macro Lenses
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In a gist, macro lenses let you get closer to your subject than a normal lens can, effectively letting you fill up the frame with a small subject. This is how small subjects like bees and flowers can appear "magnified." Macro lenses can also double as standard lenses. The downside? They tend to have higher f-stop numbers than an equivalent lens, and they also tend to hunt a bit in low light.

Sigma 50mm f/2.8 EX Macro ($230) – A good bang for the buck. This lens renders life size images (1:1) as opposed to the Canon model which only has 0.5x magnification (1:2).

Canon EF-S 60mm f/2.8 Macro ($370) - Although it's an EF-S lens, this is a spectacular macro lens made to replicate a classic 100mm macro lens. Sharpness is top notch. Great for product photography. I personally use it for taking pictures of food.

Tamron 90mm f/2.8 Macro ($400) – Popular telephoto macro. The Canon/Nikon 100mm versions are better (particularly in focusing) but cost more. The Sigma 105mm f/2.8 EX ($350) is also very similar to the Tamron.

Sigma 180mm f/2.8 EX APO Macro HSM ($650) - Sharpness is undeniably good though focusing speed is lacking compared to first party choices. Sigma also makes a popular 150mm macro lens if 180mm is a bit too long.

APO

Apochromatic - the lens focuses 3 frequencies of light
(probably Red, Green and Blue) to the focal plane.
This helps minimize color fringing.

A lesser quality lens might be Achromatic, focusing 2 frequencies to the
focal plane. You would get color fringing of the third primary color.

Note that just because a lens is Apochromatic, that doesn't say anything
about what 3 frequencies it focuses at the focal plane or anything about
the performance of any other frequencies at all. (it would be possible if
stupid to create an Apochromatic lens that focused 3 infrared frequencies
at the focal plane, but focused red, green and blue at incompatible
distances - such a lens would be totally useless for visible light
photography)

Penjelasan mengenai Spec.

Digital Optical ( for Audio )

RGB ( Red, Green and Blue ) can use for input YPbPr Video.

Jack to Jack ( for single input Audio )

Phono to Phono (for Video)

Jack to phono

Phono ( red and white) for L and R to single L/R (phono)

I am not going to recommend an all in one box, I recommend that you get separate components, and that way tailor a system for your needs/wants.
To better equip you for this task, here are the meanings to some of the more popular technologies out right now:

1) Dolby Digital-
Dolby digital was originally created for VHS; it’s a superior stereo sound. It is also
Referred to as Dolby digital 2.0 /2.1

2) Dolby Digital 5.1 –
This is the current surround sound standard. The 5 (in 5.1) stands for 5 full range
Speakers Left Front, right front, left rear, right rear, and center. The .1 stands for a
Subwoofer, or a speaker for low lever frequencies (1hz – 220hz)

3) DTS –
This is a rival format to Dolby digital 5.1; the main difference is that DTS has a higher
Bit rate, and therefore takes up more space on a disc (physically). Because of the
Higher bit rate, it sounds a little better. The good part is that most audio video
Receivers can do both DD 5.1 and DTS.

4) THX –
If you are going to drop some money, then get a THX certified receiver. All THX
means is that after your signal (sound) has been converted from digital to analog (so
we can hear it) there is some further processing. This certification provides a high
standard, and I have yet to hear a THX receiver that does not sound amazing. THX is
brought to you by our friends at Lucas film (the people who made star wars)

5) DTS 6.1 / Dolby Digital 6.1 matrix –
There is now a 6th channel (which is becoming the new standard ?) this is a rear
center channel. This gives a more accurate 3-D sound. A 6.1 matrix is when instead
of having a 6th channel hook up on the back of a receiver, its encoded into the two
back channels. I have never seen this hooked up

6) DTS Discrete 6.1-
Same as #5 but this time the 6th channel has its own speaker jack in the receiver, this
provides a much cleaner sound.

7) DTS, Dolby 7.1 -
Now you have seven speakers, center, two in the front, two in the rear, and two on the
side. It is only matrix right now, I have not seen a discrete.


Do some research into Axiom, Mirage, Paradigm, Klipsch, Polk, Koss, Cambridge Soundworks

What the different between digital coaxial and digital optical

Optical transmits audio information in the form of a beam of light, digital coax uses an electrical impulse. There are differences, and you'll hear arguements for and against both, but they are so close you won't tell the difference.

Make sure you have the same connection on your source and your receiver. If you have both, I prefer optical, but get a cable that's long enough to ensure there are no sharp turns in it. (Light doesn't make sharp turns)

SPDIF

SPDIF:
A common use for the S/PDIF interface is to carry compressed digital audio as defined by the standard IEC 61937. This mode is used to connect the output of a DVD player to a home theater receiver that supports Dolby Digital or DTS surround sound. Another common use is to carry uncompressed digital audio from a CD player to a receiver. This specification also allows for the coupling of personal computer digital sound (if equipped) via optical or coax to Dolby or DTS capable receivers.

1) RGB mean Red,Green and Blue.

2) HDMI mean High Defenition Media Interface

3) YPbPr mean Improvement fron RGB ( sent more colour signal to sharp picture)