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7D - want more in focus but higher f.stop seems to lose sharpness

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Gavin Williams
7D - want more in focus but higher f.stop seems to lose sharpness
on Oct 14, 2012 at 1:11:02 pm

Hi

I've been shooting a few bands with a 7D and sometimes want the whole band in focus so put the f.stop around 7 thinking that will expand by depth of field. I light the set too but still I never get a sharp image compared to the 2.8 or 3.2 f.stops even though it all looks nicely lit in my viewfinder. ISO's I never go above 800

What is going on? Any ideas on this - please??

Gav


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Terence Kearns
Re: 7D - want more in focus but higher f.stop seems to lose sharpness
on Oct 18, 2012 at 3:18:14 am

Are you gonna tell us which lens you have?


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Gavin Williams
Re: 7D - want more in focus but higher f.stop seems to lose sharpness
on Oct 18, 2012 at 3:01:45 pm

ahh yes - sorry!

I am using the Canon EF-S 17-55mm f/2.8 IS USM Lens with the 7D

Gavin


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Malcolm Matusky
Re: 7D - want more in focus but higher f.stop seems to lose sharpness
on Oct 21, 2012 at 6:09:32 pm

I have the same camera/lens.

Every lens has a "sweet spot" You have to test your lens with a resolution chart, or equivalent to determine how much "sharpness" you are willing to accept. EX: f2.8 & f22 will generally be less sharp than f4,5.6,8. Most lenses are "sharper" toward the middle of their aperture, and with zooms, you also have to contend with focal length, but the "center of the lens" maxim still holds true, most of the time. You really have to test the lens at each focal length and with a variety of apertures to know your lens.

Lens flair, will reduce sharpness, as will under/over exposure as will filters. So test, test, test.

Cheers,

Malcolm

Malcolm
http://www.malcolmproductions.com


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