Apertures and focal length

jryans10

jryans10

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Hi all,

I asked a photographer if he would use f4 over his f2.8's, and he told me that he would for wide angle, but not for telephoto.

But why is it okay to use a lower aperture for wide angle lenses compared to telephoto?

Thanks.
 
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Obviously it depends on the light transmission qualities of the lens, but generally speaking the exposure would be the same on both F4 lenses

I'm not sure what you are inferring from what he said - because based on what you posted alone, there is no mention of the tele's being darker.

There are other reasons for wanting F2.8
1. Faster shutter speeds - to hand hold a tele lens you need a faster shutter speed than a wide angle. F2.8 allows this
2. Autofocus - tele lenses benefit from better autocofus capabilities, and many camera bodies have improved AF with F2.8 or faster lenses.
 
I'm not sure you (or he, or me) understood your question.

"I asked a photographer if he would use f4 over his f2.8's, and he told me that he would for wide angle, but not for telephoto."

Due to the fact we can use slower shutter speeds at shorter focal lengths, and the fact that it's rare to get / need a shallow DoF on wide angle shots - the only variable aperture zoom in my kit is the UWA. So whilst I generally shoot close to wide open on all my tele's the std zoom often comes down to f5.6 or f8 and the UWA is always at 5.6 or smaller.

None of that means that the exposure would be different. f4 = f4 no matter what the focal length.

I hope that's clearer than the jumbled logic in your question / understanding of the response.
 
all he has said is he would use them..not why or what he thinks would happen... as for which would you use....that depends on what your trying to achieve..
 
Hi guys,

Thanks for the replies - I was just wondering why he wouldn't use f4's for telephotos, but I think it's because with wide angle you can use much slower shutter speeds without it blurring out (as stated by all of you, thanks).

I was just wondering if perhaps for some reason a telephoto lens took in less light than the wide angle equivalent. I cleared up my original question in case someone is wondering the same and can't understand my question lol :).

Thanks for clearing it up :).
 
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jryans10 said:
Hi guys,

Thanks for the replies - I was just wondering why he wouldn't use f4's for telephotos, but I think it's because with wide angle you can use much slower shutter speeds without it blurring out (as stated by all of you, thanks).

I was just wondering if perhaps for some reason a telephoto lens took in less light than the wide angle equivalent. I cleared up my original question in case someone is wondering the same and can't understand my question lol :).

Thanks for clearing it up :).
Click to expand...

There are many telephoto lens out there that only go as wide as f4 and give great images in most aspects of photography.
 
It could be down to how the lenses are used, rather than their light gathering capabilities.

I wouldn't use a wide angle lens to isolate something, and so usually aim for a deep DOF. Telephoto's use their tighter angle of view to - pardon the pun - focus on one thing in particular, and so a wider aperture and shallower DOF would be used to remove distracting backgrounds.
 
Of course, what you really need to do, is go back to that photographer and ask him, or her, why?
 
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