Shooting at largest aperture - is sharpness affected?


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red_ryder

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Jun 23, 2003
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Is it true for all lenses that shooting at the widest aperture will result in a "soft" picture? That we need to stop down to achieve maximum sharpness? If so, doesn't that mean that a 50mm f1.8 is effectively 50mm f2.8, in order to get the best sharpness?
 

Somewhat true. Some lenses are already pretty sharp wide open, but of course performance always improve when stopped down. How much to stop down by also depends on the lens itself.

However, when you stop down too much, for example F22, diffraction occurs and this affects sharpness as well. In photography, everything's pretty much a give and take compromise so you have to balance things for yourself.
 

well, you will have to find which you prefer, better sharpness (stop down) or better bokeh (wide open or stop down just a bit to achieve blurred background) in your photo.
 

Now, if we use the 1.5 or 1.6 ratio camera like the 30D, we would be using the centre "sweet" spot for our lenses (assuming we are using the Full Frame versions, and not EFS), would the above assumption still applies?
 

Aiyo, if u want the sharpness, then stop 1 or 2 down lor, then focus somewhere in front of the subject to achieve the bokeh lor. :)
 

That'll depend on what's the edge to edge shaprness of the lens. Some lenses have pretty high ratings, meaning that its the same sharpness at the corners and at the center. For such lenses, I guess it applies more or less the same on a 1.6crop. For lenses with sharper centers than corners, using a cropped camera would probably give slightly sharper results. I hate to be so techincal about photography since it's all theory and there are so many factors out there to consider. At the end of the day, as long as you are able to produce the results, who cares how you got it :bsmilie:
 

It all depends now... are you shooting a flat object or a 3d object?

Coz with a wide open aperture, you lose DOF. On a flat object, this does not matter even if you can find a f 0.7 lens coz once you get the subject in focus, it's in focus.

But when it's 3D, you can lose the focus when the subject moves or you move. Also due to DOF, mebbe only a very think part of the subject is in focus and the rest is not in focus at all...

I have shot at wide open on a few lense and on some, they lose the sharpness. But on some, there's not much affect on it.
 

Mostly every lens have its best its aperture at 2 or 3 stop down from maximum open. Depends on lens. Closing down aperture to minimum will create another diffraction distortion on photo.

Regards,
Arto.
 

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