XSI & Zion Underground

Started Apr 29, 2008 | Discussions thread
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CityLights OP Forum Pro • Posts: 12,545
Re: Very nice as always! Question ....

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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