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Old Jul 2, 2005, 8:00 AM   #1
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Please explain to me how the aperature works, and why you would want to change the settings. When would you use certain settings? THANKS:|
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Old Jul 2, 2005, 8:59 AM   #2
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The aperture is the size on the hole that lets the light into the lens. Each F stop of aperture lets in half or twice as much light as the next one. The F numbers are a unusual series of numbers where the larger the number the less light is allowed through. The shutter speeds on the camera also change in steps which either half or double the exposure time so let in half or twice as much light for each step.

As to why you'd want to change it there are two reasons. There are a large number of aperture and shutter combinations that will correctly expose any shot. A larger aperture gives a faster shutter speed allowing you to stop action. On the other hand a small aperture slows the shutter speed and allows you to introduce deliberate motion or blur, for example when shooting moving water.

The aperture also has an effect on the depth of field. This is the depth front to back that appears in focus. A large aperture say f2 F2.8 F4 will give a shallow depth of field go for throwing the background out of focus in portraits. A small aperture F11 F16 F22 gives a large depth of field where everything is in focus, good for landscapes.
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Old Jul 2, 2005, 10:38 AM   #3
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thank you for the explanation...now another question. I am getting a new camera so that I can get better wildlife shots. A couple of years ago we went to Yellowstone, saw some awesome wildlife. However, when I got the pictures the grizzlies and moose were mere dots. SO we are getting a 12x zoom, either Sony H1 or Canon S2, can't decide. Anyway it has auto program for the aperature/shutter. I was told we could manually set the aperature and the setting would auto adjust. WOuld I want to change the aperature for shooting wildlife at a distance?
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Old Jul 2, 2005, 3:27 PM   #4
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The only way an unsharp picture looks good is if it looks like it was done on purpose. Something slightly out of focus looks like you goofed. Under ideal conditions, use F stops to control depth of field,but do not sacrifice sharpness for the ideal goal. It is best to use a tripod in order to not have to use wider F stops in order to gain shutter speed.
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Old Jul 2, 2005, 7:35 PM   #5
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I have several thoughts on what you ask. Some are beyond what you're looking for, but I think you'll find it useful.

First off, get something with a good lens. I've heard about too many people with small cameras with limited zoom lenses walk right up to wild animals at places like Yellowstone. They don't realize that it really is a wild animal and they are risking their lives. We want to you live long enough to come back here and post shots from that vacation! It sounds like you're trying to get a good zoom... so thanks! But I just had to say this, as this problem happens way to often.

The next thing is about the "12x" description of those two cameras. That is really almost completely meaningless information. Its really marketing jargon that has little meaning in reality. Here is why. By "12x" they are describing the ratio of the short end of the zoom to the long end of the zoom. What really matters is the "35mm equivalent" description of the lens. With that info, you can actually compare lenses. Let me give you an example. A 50mm lens produces the same image as the human eye. A 100mm lens makes everything twice as big. And so on. With this info, you can say "a 200mm lens will make things 4 times as big" and that actually means something to you. But 12x just says the ration of the short end of the zoom to the long end of the zoom. For example,
a 10mm to 120mm lens is a 12x zoom.
a 20mm to 240mm lens is a 12x zoom.

Now both of those will say "12x zoom" on the camera box, but they are completely different cameras. The first has a very wid angle lens (amazingly wide, actually) but offers only slightly more than twice the magnification than the human eye. The second camera starts at 20mm, which is fairly wide (wider than anything I have) but goes out to 240mm, which is almost 5 times the magnification of the human eye. Huge difference, huh?

So lets look at those cameras. Interesting... I think both use the same lens. They are both:

36mm - 432mm

That makes them around 8.5 times the magnification of the human eye. That should work very well for wild animals. Now, unfortunalyte 36mm isn't very wide angle, so you might have trouble capturing really big landscapes... but you can always take multiple pictures and combine them on your computer.

So purely on lens reasons, there is basically no difference between the two cameras. You'll have to pick on things like battery life, quality of picture, usability (don't forget that one. I suggest going to a store and actually handling the cameras to see how they feel in your hands.)

Now, on to your question. For animals at a really lon distance, you might want to change the aperture. This would let you get a larger depth of field, which might let you get the mother bear and her cubs all within the depth of field.

Most of the higher end cameras let you set a mode where you change either the aperture or shutter speed and the camera automatically adjusts the other one. I bet both those cameras do that (but you should read the reviews to be sure!)

Does that help?

Eric
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Old Jul 4, 2005, 12:15 AM   #6
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I was just going to post this :-)

So for shooting moving aircraft it is better to use a larger aperture? higher number?
and for shutter speeds what is faster 1/30 or 1/1000?

Also what is ISO? how does a 100 or 400 setting affect a photo?




Thanks
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Old Jul 4, 2005, 1:58 AM   #7
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I just got a Canon S2, and I THINK that it 12x zoom is from 35 mm equivalent. I thought 12x zoom would be HUGE, but its not so long a zoom as you might think. If you want a closeup of a lions face at 100m, think again. I dont even think the lion will fill the whole frame at 100m.

1/1000 is the faster shutterspeed. It is a 1000th of a second, as opposed to a 30th of a second.

I would think that if you shoot aircraft during the day, your shutterspeed would be fast enough no matter what aperature you use. And it might be difficult to focus on the aircraft, so using a small aperature (large number) would be best.
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Old Jul 4, 2005, 5:39 PM   #8
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Depends on which way the plane is going. I've taken plane pics with 1/1000, 1/500 and fromf2.8 to f6.3.

Some were landing, flying by, real high, low. I use auto most of the time.
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Old Jul 4, 2005, 7:53 PM   #9
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experimental_pilot

The real question is what you are trying to achieve. If you want to stop a plane in flight, that requires some a bit of shutter speed. 1/30th won't do it. On the other hand, if you really stop the plane in flight, it will look artificial (like its hanging in space and not flying.) The smaller apertures will give you more depth of field, which might make it easier to get the plane in focus (but reduce the shutter speed.)

I guess I would suggest trying it different ways and see which works well for you. The harder part will be to pan with the plane and keeping it in the field of view.

Carrots,
I don't believe you understood what I said. "12x" isn't a question of 35mm or any other system of measure. It will always be "12x". But 12x is almost completely meaningless. What matters (at least should matter to you) is how much wide angle the lens has and how much telephoto it has. The only way to figure that out (and compair two cameras) is to translate the actual focal length into a "35mm" equivalent. Then you can compare it to what your eye see and what the different cameras say.

The Canon S2 is 36-432mm in 35mm equivalent. That means it a bit less than 1/2 as wide as the human eye, and almost 9 times more powerful than the human eye.

But nothing, even the most expensive lenses (and I have one, the Canon 600mm f4) won't take large pictures of a lion at 100m. Nothing will, even small portable telescopes.

Eric
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Old Jul 5, 2005, 1:43 AM   #10
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I understood that, yes. I think my use of the word "equivalent" was wrong. What I meant was that the widest angle is 35mm. Thus 12x35 = 420mm. Which is wider than if it had a widest of say 20mm. Like you explained earlier in the post.

And yes, I greatly overestimated zoom. (before I had an optical zoom camera)
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