Thanks to CHDK and this thread on POTN:
I have never done this type of "hack" before, but it took me all of 3 minutes and worked
perfectly the first time I tried it. Spot metering is a very nice addition, and YES it does
work as it should (metered exposure differs from other metering settings).
A while ago I did "push" the ISO on the XTI up to 3200 (and even 6400), in post
processing (Photoshop curves adjustment). I thought the results were pretty good for
the XTI, but now that the option is available in-camera (push processed, just like the "H"
or 3200 setting on the 40D), I thought it would be worthwhile to compare the two
cameras. Here is the XTI pushed ISO thread:
The following shots were taken with the self timer, but the aim was off slightly when I
switched bodies. When I took the 100% crops I attempted to crop to the same area.
The shots were taken with the 17-55 2.8 IS stopped down to f/5.6 and set to the 17mm
focal length. ISO 800, 1600, and 3200 settings were used with corresponding shutter
speeds of 1/25 sec, 1/50 sec, and 1/100 sec.
First are the full images, resized for web. At this size very little noise is noticeable.
Original size images can be viewed at this link, and 100% crops will be in the post
following this one. Also at the SmugMug link you can hover over the image and click on
the "i" logo to view the EXIF data.
XTI, ISO 800
40D, ISO 800
XTI, ISO 1600
40D, ISO 1600
XTI, ISO 3200
40D, ISO 3200