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Old Jan 16, 2007, 7:37 PM   #11
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I'm really not trying to put you down, but this is the time to say RTFM (Read The Fine Manual). And do enough other reading to figure out how shutter speed, aperature, and ISO interact. Get an EXIF viewer (likely one came with your camera) so you can see what you did for each shot.

It does take a while and can involve pounding your head on the corner of the desk trying to get things to sink in. When that happens, go shoot some pictures. Enjoy yourself doing it. Then go back and spend some time seriously looking at pictures of the kind you are trying to make and ask yourself, "How did they do that?"

I have no idea whatsoever what AV or TV modes are. I think in terms of ISO, shutter speed, and f/stop with little side detours into white balance, contrast, saturation, ...
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Old Jan 16, 2007, 7:58 PM   #12
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BillDrew wrote:
I have no idea whatsoever what AV or TV modes are.
You probably just know them by different terms.

Av = Aperture Value (a.k.a., Aperture Priority, a.k.a., Aperture Preferred). You pick the aperture and let the camera pick the shutter speed.

Tv = Time Value (a.k.a., Shutter Priority, a.k.a., Shutter Preferred). You pick the shutter speed and let the camera pick the aperture.

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Old Jan 16, 2007, 8:24 PM   #13
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Ceddy wrote:
For the dog's and sports car picture, what exactly setting should I be using on my 20D? AV or TV? This is what I don't get it clear on how it works.
I'd suggest getting a book from your local library on basic photography. It doesn't need to be specific to digital, as the concepts of are the same for both film and digital.

Then, experiment with settings so that you see what they do. For example, the car photo is not using the fastest shutter speed. Instead, the photographer panned with the car to give more emphasis to the movement. If a much fast shutter speed would have been used, it would have frozen the wheels and the background may have been more defined versus blurred. So, you'd lose some of the impact of the shot.

Could you have used a faster shutter speed? Sure, as long as light was good enough for your aperture setting and ISO speed. It's a matter of preference.

I sometimes make "long winded" posts that describe some of the basic concepts. So, I'll copy most of this info from a previous thread:

You don't want to use settings at random.

In most conditions, I like to use Aperture Priority more control. It's also a good way to get a faster shutter speed (open up the aperture by selecting a smaller f/stop number), without worrying about running out of aperture. For example, if you selected a 1/500 second shutter speed in low light, you may get an underexposed image if the camera can't open up the aperture far enough for proper exposure (because it will only open so far, based on a lens design).

So, using Aperture in low light can give you a better way to control it. It's a matter of preference. In bright light, you could have the opposite issue (select an aperture that's too wide for the fastest available shutter speed). So, be aware of when your camera can't properly expose an image because your settings won't allow it (and most will give you a blinking aperture or shutter speed indication when you exceed the capabilities of the camera or lens with your setttings).

Think of the aperture opening in a lens as a pupil in your eye. If you open up the aperture wider (smaller f/stop numbers), more light gets through, allowing you to expose the image faster for the same lighting and ISO speed (ISO speed represents how sensitive the sensor or film is to light).

If you use a smaller aperture (higher f/stop number), less light gets through (so it will take longer to "expose" the film or sensor, requiring slower shutter speeds for proper exposure for a given ISO speed and lighting).

Lenses are rated by their largest available apertures (smaller f/stop numbers), and for most (but not all) zoom lenses, you'll see two aperture ratings... the first one is for the widest aperture at the wide end of the lens (least apparent magnification), and the second is the widest aperture at the long end of the lens (most apparent magnification).

You can still use smaller apertures (higher f/stop numbers). Most lenses can go down to at least f/22 (and some can go all the way to f/45).

The largest available aperture (smallest f/stop number) will fall somewhere in between the two numbers you'll see for a lens' specs at focal lengths in between the two extremes.

Some zoom lenses can maintain a constant aperture throughout their focal range (with f/2.8 being the most common).

Aperture as expressed by f/stop is a ratio, and is determined by dividing the focal length of the lens by the size of the iris opening.

The aperture scale (in one stop increments) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22, etc. With each one stop move to a smaller aperture (represented byhigher f/stop numbers), you will need shutter speeds twice as long for proper exposure.

So, a lens with a larger available aperture (smaller f/stop number) is desired to get fast enough shutter speeds to reduce motion blur (either from camera shake or subject movement) in many conditions.

Note that a larger aperture will result in a shallower depth of field. This can be a pro or a con, depending on what you're shooting. For portraits, you may want a shallower depth of field to help your subject stand out from distracting backgrounds. But, for landscapes, you may want to use a smaller aperture so that more of a scene is in focus.

For more information on how aperture impacts Depth of Field, see this Depth of Field Calculator:


Again, lenses can also use smaller apertures than the largest available (and a lens isn't going to be as sharp at wide open apertures anyway, so "stopping down" (setting the aperture to a smaller than "wide open" value) can yield sharper photos,

But, you need to keep an eye on shutter speeds in less than optimum lighting, no matter what lens or aperture setting you use.

Here is a handy online exposure calculator that lets you see how aperture impacts shutter speed. Film speed in this calculator is the same thing as ISO speed.


You'll need to decide what settings are appropriate for what you want to accomplish with a given shot (and there is no one right answer, as a number of aperture/shutter speed combinations will give you identical exposure).


I tried the set to TV mode last night in my room and it reads the shutter speed with number like 8" ....etc. how does 8" compare to number like 1/500 or something like that.

You had it set to 8 seconds (when you see " after the number, you're reading the shutter speed in full seconds). Without the ", most cameras are showing you the shutter speed in fractions of a second (8 would be 1/8 second, 8" would be 8 seconds).

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