Bad Bokeh - not the lens

Started Feb 8, 2008 | Discussions thread
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orbmansony
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Bad Bokeh - not the lens
Feb 8, 2008

Hi,

Last month I started a thread on the bad bokeh I was seeing in my new XTi and Canon 100-400mm zoom lens. The problem was multiple ghost images of linear features in the near and far just-out-of-focus areas.

http://forums.dpreview.com/forums/read.asp?forum=1031&message=26278988

After much discussion on this forum and on the Canon Lens forum, and with the recommendation from the Canon Tech support folks to return the lens, I did just that, but opted for a 400mm f/5.6 prime lens and a 200mmf/2.8 prime lens (for lower light situations and casual walks), rather than getting another 100-400mm zoom lens.

The two new lenses arrived yesterday. Much to my surprise, the same multi-ghost images appear using these lenses as well, although not quite as evident as with the 100-400mm lens. Here are some test shots with both lenses - cropped, sharpened, and contrast enhanced to bring out the multiple images of blades of grass in the foreground and background.

200mm lens:

400mm lens:

Thus, it was not the lens causing the bad bokeh. I suspect that it may have something to do with secondary and tertiary lobes of the point spread function of the image diffraction pattern combined with the sensor pixels and internal processing s/w. I know that some other forum members have seen this same effect, but do not know if it is just with the XTi, or perhaps with other Canon models as well??

I don't plan on returning my XTi - will just deal with it. I am happy with my new lenses though. It is a bit harder to use the 400mm without IS, even shooting at 1/1250 sec - I need to concentrate harder on keeping the camera steady. Also see at bit more color fringing on the 400mm prime than I did with the 100-400mm at 400mm - perhaps this is because of sharper edges??

But when it is on, it's on!

Here are a few images I took today with my new lenses, and I am just learning the best way to use them.

400mm lens, ISO 200, 1/1250 sec, f/5.6, manual mode

200mm lens, ISO 100, 1/500 sec, f/3.2, shutter priority

Orb . . .

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