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Message: <blockquote data-quote="tdodd" data-source="post: 1216894" data-attributes="member: 55450">I just shot a series of three test shots with my 100-400 at 400mm, 1/1600 and f/5.6 on a tripod. Subject distance was approx 10m - a realistic working distance for this lens. I used Live View and focused manually to get the best focus I could and, using the 10 second timer, fired a shot with no filter. Without changing any of the setup I then screwed on my Hoya Pro 1 Digital UV filter and fired off another shot. I compared results on my laptop and saw a distinct deterioration in IQ with the filter attached. Wondering whether the filter might have caused a focus shift I tried refocusing manually with Live View and 10X magnification, and fired off a third shot, again with the 10 second timer. I have attached 100% crops of the raw files with no sharpening at all. These were shot in neutral picture style, with camera sharpening parameter set to 0, and these are straight crop and convert jpegs. If you look at the fine text of the password "WINEBANK" I think the deterioration is quite evident. The fourth image is the bare lens without filter, but with sharpening set to 3 in DPP and picture style changed to Standard. The fifth image is the shot with the filter attached and manually refocused and again sharpened and with Standard Picture Style. Image 1 - no filter, unsharpenedImage 2 - filter added, not refocused, unsharpenedImage 3 - filter added, refocused, unsharpenedImage 4 - as image 1 but sharpenedImage 5 - as image 3 but sharpened</blockquote>

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