Do you ever need to use f/22 on a UWA lens?

[Hknivers]

I was just wondering if you ever need to use f/22 at 17mm on a 5D? Isn't f/16 enough for most of the time?

[tupper]

In very bright conditions when you want a slow shutter speed.. that's when I would use it.

[Hknivers]

Yeah, but I mean for depth of field? Is there any time where one would need so small aperture?

[tupper]

Not particularly.. the only reason I could think of was the one I said.

[terry_glover]

It's great for showing how much dust is on your sensor.

[jacobsen1]

if you're after sharpness/DOF, F/22 is where diffraction is coming in anyway, so you'll get more DOF but what's in focus will be less sharp. it won't ruin an image, but it's there. But yeah, it's great for getting slow shutters in good light. Sometimes I wish they'd give us f/32 and f/64 just for fun.... :)

[PhotosGuy]

if you're after sharpness/DOF, F/22 is where diffraction is coming in anyway, so you'll get more DOF but what's in focus will be less sharp. it won't ruin an image, but it's there. Every lens has a sweet spot, that is the aperture at which the lens is the sharpest. I would find out what apertures give you the sharpest images for each of your lenses. The better the glass, the closer you are to the sweet spot of the lens (2-3X stopped down from max aperture), & the more in focus the area you're looking at is, the less artifacts you will see.
There's a reason that "L" glass costs a lot. :)

[argyle]

I was just wondering if you ever need to use f/22 at 17mm on a 5D? Isn't f/16 enough for most of the time?

Absolutely, depending on the situation (and especially when using hyperfocal distance with very close foreground objects). The below pic was shot with my 17-40L on a 5D2, set to 17mm. In this instance, the foreground rock was at the lens' MFD (less than 1 foot). Looking at my hyperfocal chart, the HFD at this foreground distance called for an aperture of f/22. If I had used f/16, a good portion of the foreground rock would not have been in focus. Also, as you can see, the image is sharp from front to back, and edge to edge (too damn bad about those two water splashes that got onto the lens). I don't pay any bother to, nor do I worry about, diffraction...I think its effects are greatly exaggerated.

http://northlake.smugmug.com/photos/562053243_237Q6-XL.jpg

[tonybear007]

That's one extremely sharp image!

[canon_shots]

That's one extremely sharp image!
+1
Hell yes!
I see individual leaves of foliage at what appears to be 100+ feet away-and yet foreground is sharp. Nice shot!

[fly my pretties]

http://i26.tinypic.com/2ekne35.jpg

f20 for this picture at 11mm, I believe. It was the only way I could balance the lights without overexposing.

[Hknivers]

http://farm3.static.flickr.com/2645/3794143841_e88017db7a_b.jpg

Took this one last night. I was pretty close to that little log, maybe 50 cm or so. Taken with Canon 5D and a 17-40 f/4L at 17mm and f/16. I don't think that f/22 would have made it any sharper.

[Hknivers]

http://i26.tinypic.com/2ekne35.jpg

f20 for this picture at 11mm, I believe. It was the only way I could balance the lights without overexposing.

That is probably also at the extremes of near focus as well. Very nice shot btw. :)