Aperature Question

[TexasBob]

Didn't want to hijack Codie's thread, but it got me thinking. I have a basic understanding of aperature with regard to letting in more light for certain situations and affecting dept of field. Does it also affect focus distance? for instance the Sigma 70-200 f/2.8- could the lens be shot at 200mm wide open and still focus on a deer say 75 yards away. Would the deer be sharp and all else blurred, as a subject would be close up with a large aperature?

[Hillary]

Ap should no affect the camera's focusing performance. You could shoot 200mm wide open or closed and still be able to focus on the animal. The DOF would be different, but it won't affect the focus distance, but it will affect the DOF of the subject you are shooting...

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I love this book.
I still read it all the time.

[Shane]

Hilly nailed it. Aperture size affects depth of field. A really wide open aperture like f/2.8 will have a narrower depth of field than a small aperture like f/22. If you want the deer at 75 yards and the cactus at 5 yards and the hill at 150 yards to all be in focus, then try a larger aperture (if you have a tripod, because the shutter speed is going to need to be slow). If you want the buck to be in focus and the hill behind it to be blurred out (bokeh), then shoot at f/4 or 2.8 or something large.

[Casey]

And to further confuse you!

http://www.dofmaster.com/dofjs.html

Play around with that tool. It will help you understand depth of field.

[Hillary]

Casey,
That made me feel like I need to sell my camera gear, Haha.
Woo. Information overload.

I liked it.

[TexasBob]

Thanks everyone

[Snakelover]

Hilly nailed it. Aperture size affects depth of field. A really wide open aperture like f/2.8 will have a narrower depth of field than a small aperture like f/22. If you want the deer at 75 yards and the cactus at 5 yards and the hill at 150 yards to all be in focus, then try a larger aperture (if you have a tripod, because the shutter speed is going to need to be slow). If you want the buck to be in focus and the hill behind it to be blurred out (bokeh), then shoot at f/4 or 2.8 or something large.

Just to be clear, I think that where I bold underlined it, Shane actually meant larger f-stop (smaller aperture). As f-stop numbers increase, the aperture gets smaller. It makes it all too easy to say one thing a mean another.

[yaqui]

Another way to see it, is that you will end up with what you see when using the camera and lens combo, as most camera are at their widest fstop when focusing.

[yaqui]

I guess I should have said seeing through the camera. Just to clarify.