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Old Apr 1, 2003, 7:20 PM   #1
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Default 10D chromatic aberration?

I noticed quite a bit of CA in the photos posted on Phils and some other places. Has anyone else noticed this in their photos? Could it be the different processor used? I have never noticed this with my D30
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Old Apr 1, 2003, 7:59 PM   #2
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Isn't this more characteristic of the lens used rather the body? After all CA doesn't come film (or CCD), especially when this camera is not a full frame...
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Old Apr 1, 2003, 9:28 PM   #3
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Hi Sarah,

The 10D and D60 are more sensitive to CA than the D30, but it's not caused by the sensor itself. There are two facets to aberrations. True chromatic aberration results from differential refraction of the light spectrum through glass. Specialized lenses of various names such a "apochromatic (APO), ED, LD, etc., made with special glass and coatings are ways of describing what's commonly called "low dispersion" glass which work to focus the dispersed frequencies back within specific tolerances. The second type of aberration is more properly called "blooming" and results from close proximity of photodiodes which tend to leak voltage between adjacent sampling sites at points of extreme contrast such as where a green vegetation might meet a very bright, white sky. This aberration is usually blue/purple in shade and can most frequently be seen in these areas of high contrast.

Because the pixel density is greater in the D60/10D vis a vis the D30 where they share a common frame size, the possibility is greater in the six megapixel sensor for this type aberration, but special care is taken in the manufacturing process and the firmware to minimize the probability of this happening.

If what you are seeing is red/green fringe, it most likely is caused by the use of wide angle lenses. The higher the resolution of the sensor, the greater the likelihood that you will see this characteristic, especially in the periphery. It's not that it isn't there with the D30, it's just that the lower resolution doesn't make it nearly as evident. It's found on nearly every shot with some of even the "L" class zooms which have extreme wide angle capabilities, and seen most often with the ultra high resolution "top-of-the-line" EOS-1DS.

Fortunately, using a good CA control software such as Picture Window Pro 3.1 will result in minimizing or completely removing this annoying aberration. On the other hand, if you are seeing blue/purple fringing, it's likely that it has resulted from overexposure at high contrast areas, and the only way to deal with this issue post capture is selective desaturation.

Bottom line is that CA is not a serious issue with the 10D or D60, especially if you stick to top quality glass.

Lin
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Old Apr 2, 2003, 9:51 AM   #4
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Thats interesting Lin. I saw both CA and blooming in Phils pics, really bad blooming on tree branches against white sky. I didnt want to post there as I would probably be labeled an unpatriotic troll terrorist LOL Did you get the Sigma Foveon camera? How is that for these problems?
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Old Apr 2, 2003, 12:25 PM   #5
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Hi Sarah,

You're chasing a ghost here, hon. The CA/blooming problem you are seeing is a result of the 17-35mm L Canon lens, a known "felon" :-)

If you look carefully at every instance where you see this problem, you will see that the 17-35mm lens was being used. In the D30 review, Phil never used that lens. Every time he has used it, it results in significant aberrations. Even when he tested the 1DS - probably the best digital camera ever built - the problem was identical.

I sold my SD9 to a friend in Switzerland, who dearly loves it. But he is a professional who understands both the power AND limitations of the camera. It's not a good all-around choice because it absolutely must have good light to perform. It also has its own share of problems. I would be remiss if I recommended it for general all-purpose photography. It's definitely a specialist camera and for those cases where it works, it works wonderfully - but when it fails, it's just as spectacular.

I decided to take a shot for you of branches against a bright sky with my 10D so you can see how it performs with proper exposure and with a known "good" lens - the 100-400L IS. Click on the link below the 800x600 to bring up the full sized image with EXIF.

Best regards,

Lin


http://www.lin-evans.com/samples/IMG_0207.jpg
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Old Apr 2, 2003, 2:13 PM   #6
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Also blooming is proportional with the amount of incident light and can be corrected (ie less light less blooming) whereas CA in lenses is inherently constant and more noticeable with color. A non-full frame camera, like the 10D, usually helps in the CA department since it does not cover all the way to the edges 8)
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Old Apr 4, 2003, 11:41 AM   #7
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Well part of my problem also is that my new monitor has terrible convergence problem. There is no way to set it to get rid of it. Not only is it off horizontal and verticle, which can be set, but diagonal. Its a Viewsonic P95F+. I sent back the first two because of even more problems and finally gave up and kept this. I have to move a pic around so that I view the part i want to check out in the middle 9 square inches.

I didnt notice or know about the lens Phil used. anyhow i was just curious and now have learned some more stuff from you
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