thoughts on TransAm's landscapes

For me, the most relevant sample photos from the EF-S 17-55mm f/2.8 IS so far are the landscape shots from TransAm. Unfortunately, the RAW files are still not available for these, but there are still a number of conclusions I can draw from them.

1. Vignetting (light falloff) at f/2.8 is noticeable throughout the zoom range, particularly at 17mm, but mostly limited to the corners. Thus, it'll probably be possibly to compensate for this in Photoshop without artifacts becoming distracting for most pictures. I don't expect to make many (or even any) 17mm f/2.8 shots against uniform, bright backgrounds.



2. Contrast and color are significantly better at f/8 than f/2.8, even for the in-focus central parts of the scene. This could be due to a slightly different exposure, but the histograms seem to indicate a redistribution of light values, not a shift. Either Klaus is right and the 2-3% difference in the contrast lines of Canon's MTF charts really is noticeable, or I'm seeing veiling lens flare let in by the wide aperture. For the sake of landscape photography, I hope it's the first.



3. The sides are a little softer than the center; the left side a little bit softer than the right. It doesn't look to be a focus issue because the background trees in the center are sharp, and because the sides are just as soft at f/8 as f/2.8. On the one hand, the fact that stopping down doesn't help is disturbing (but expected from the MTF charts). On the other hand, the dropoff only happens more than 2/3rds of the way to the corner, and it is not nearly as bad as the sharpness dropoff of the EF-S 18-55mm f/3.5-5.6 or EF-S 10-22mm f/3.5-4.5 (again, all of this squares with Canon's MTF charts). I doubt it will be noticeable at 8"x12" without squinting - it would be almost entirely cropped out of a (center-cropped) 8"x10" print.



4. Center resolution matches a good prime of similar focal length.