Shooting with my 24-105 on each camera: with the 40D I get negligible-to-zero CA or fringing in high contrast scenes. With the 50D, same lens and settings, I'm getting noticeable CA and color (green) fringing.

What's your opinion on this?

- Steve

Had both (+the same lens) and can't say I noticed any different. But are you veiwng both at 100%? the higher mp sensor will magnify any problems more so could be more noticable

Ian.Dobinson wrote:
Had both (+the same lens) and can't say I noticed any different. But are you veiwng both at 100%? the higher mp sensor will magnify any problems more so could be more noticable
Thanks for the reply.

I took the higher MP count of the 50D into consideration. I viewed those files at 50% while viewing the 40D files at 100%. The CA/fringing from the 50D is still noticeable. It's also small enough to be correctable. Still, I can't figure out why one camera would bring this out in such a dramatic way compared to the other.

- Steve

Perhaps the higher density pixel count records more detail you don't notice in larger pixel size cameras. As I recall when I used a 40D/5D combo, I always saw more color fringing on the 40D. When I went to a 7D/5D2 combo, color fringing on the 7D was much more pronounced in high contrast areas than both the 40D and 5D2. My old 10D (6MP) rarely had any fringing as did my 5D.

A slight focus shift in either camera will cause this. Perhaps micro adjustment on the 50D could solve this problem?

saxoniv wrote:
A slight focus shift in either camera will cause this. Perhaps micro adjustment on the 50D could solve this problem?
Not sure I understand what you mean by "focus shift." While there's CA/fringing in high contrast scenes with the 50D, the images are otherwise sharply in focus and spot-on when I view the "AF Point" via DPP. In fact, the overall sharpness coming from the 50D/24-105 lens combo is simply excellent.
- Steve

I've had a 50mm f/1.8 mkI that wouldn't focus on a body very accurately. Many of the photos would be sharp but had purple fringing. Went ahead and tried it out on another body and turns out it was a problem with that body. Swapped it out and the problem went away. While the photos were sharp, they were just not spot on.

veroman wrote:
Still, I can't figure out why one camera would bring this out in such a dramatic way compared to the other.


I have a 50D, having upgraded from the 20D. Canon changed the design of the sensor wells on the 50D to pack more of them on the sensor which changed the micro-lens design. From http://www.canon.com/camera-museum/tech/report/200809/report.html


"We were able to build more pixels into the sensor without reducing the size of individual pixels by using a new photodiode construction, a new microfabrication process, and gapless microlenses. "

The CA difference between 40D and 50D is discussed here: http://www.luminous-landscape.com/reviews/cameras/50d.shtml

We had two 40D's and two 50D's and with the 24-105,they both showed CA which is easily corrected PP.

Wide open there was more CA on the 40D,stopped down more on the 50D.

Stopping down reduced the CA on both the 40D and the 50D...more so on the 40D.

Other then wide open there was less CA on the 40D.

cgardner wrote:
veroman wrote:
Still, I can't figure out why one camera would bring this out in such a dramatic way compared to the other.


I have a 50D, having upgraded from the 20D. Canon changed the design of the sensor wells on the 50D to pack more of them on the sensor which changed the micro-lens design. From http://www.canon.com/camera-museum/tech/report/200809/report.html
"We were able to build more pixels into the sensor without reducing the size of individual pixels by using a new photodiode construction, a new microfabrication process, and gapless microlenses. "
The CA difference between 40D and 50D is discussed here: http://www.luminous-landscape.com/reviews/cameras/50d.shtml


Thanks for the links, particularly to Luminous Landscape. That article pretty explains things. To consider that the sensor in the 50D would translate to 39MP if it were full frame really puts this camera in perspective. Thanks again.
- Steve

I also notice much more CA wide open on my 24-105 and 85mm with my 50d than with either of my 40d or 5d.

I've conducted a few more tests using a different lens (my old 28-105) on my 50D, 40D and 5D. I also compared results of my 24-105 on the 50D, 40D and 5D using a controlled lighting situation.

In a nutshell: the CA/fringing is entirely dependent on the situation, lighting, flash/no flash, strong vs. weak back lighting, etc. It really has little or nothing to do with the camera itself but, rather, the interaction of lens, high density sensor and lighting conditions.

Once I realized which combination produce which result, I was actually able to generate CA/fringing when ever I wanted to and ... conversely ... I was able to reduce or eliminate CA/fringing whenever I wanted to.

FYI: my 28-105 is tack sharp on the 50D ... amazingly so ... and is equally sharp on the 5D, but the 50D renders slightly more detail. At the widest angles, the 28-105 produces LESS CA/fringing (width-wise) than the 24-105 on all 3 cameras. The least CA/fringing was, perhaps predictably, was with the 5D.

When I have the time I'm going to do some more tests using my 1Ds II ... though I imagine the results will be similar to the results from the 5D.

Thank you all for your comments.

- Steve

From my experience with the 24-105 on the 40D the CA was most noticeable at 24mm and wide open when there was high contrast background. On the 50D at all focal lengths the CA was easiest to replicate with a high contrast background,but not as bad as the 40D at 24mm wide open.I think you'll find harsh contrast transitions would attribute the most to noticeable CA.