XSI & Zion Underground

Started Apr 29, 2008 | Discussions thread
CityLights
Forum ProPosts: 12,536
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Re: Very nice as always! Question ....
In reply to Ed Richer, May 1, 2008

Actualy my problems with the XT are with faster lenses, obviously
from the narrower DOF. With my EF 50/1.4mm and Tamron 17-50/2.8 wide
open the XT has problems focusing. Not consistent front or back
focusing, just erratic. With the EF-S 17-85 XT nails the focus most
of the times.

Shallow depth of field focussing is difficult, expecially when the depth if paper thin. If the depth of field is 4 inches or more deep, you shouldn't be having problems with the XT. I shoot with my 50mm f/1.8, which is notorious for focus issues, and usually have no trouble at f/2.8 or smaller apertures where the depth hides small focus issues. The 17-85 is slow enough at (f/4 wide open) that it should also hide small focus issues.

Erratic focus at paper thin depth is expected in anything less than a 1 series camera. But not stopped down a little with depth 4 inches or more.

I was refering to checking the focus in play mode after you take the
picture. On the XT (and XTi, 40D,etc) the play mode uses a small jpeg
preview that is not good enough for checking the focus. Is it the
same with the XSi? Of course I am asking about the preview when
shooting in RAW mode.

Now, I see. But I don't know. Live view must certainly be from a sensor dump or full resolution. I am not sure if reviewing pictures after they are taken is done with the full image or a reduced resolution image.

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