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chromatic aberrations (color fringing) EX1
I noticed that when I attempt to produce a good depth of field where my subject is sharp and my background and foreground is soft, I get a magenta hue that glows and outlines bright objects at sharply focused edges. Sometimes a green hue will also appear as well at the edge of sharply focused lines.
I uploaded a clip to the Sony Products Operation Support Center and after reviewing the clip, a specialist there authorized a repair and directed me to send my EX1 to Sony Repair in LA. A repair technician was able to reproduce my issue. I told him that it helps to be zoomed all the way in on an item that is midway between other objects that are further away, and be focused sharply on the midway item. He adjusted my EX1 and updated the firmware, but stated that it is operating in normal acceptable range and two other EX1 he tested all produce what I am seeing.
I was a little amazed because the Product Operations Support Center authorized the repair in the first place, after concluding that there was an issue.
The specialist at Product Operations Support Center called the issue “Color Fringing”. It reminded me of a CRT projector that was poorly converged. My cousin is an amazing photographer, and he noticed that I used the terms DOF; Depth of Field and Depth of Focus together, and he pointed out to me that Depth of Field happens in front of the lens, and that depth of focus occurs behind the lens! And then I realized what may be happening.
When the depth of focus (behind the lens inside the camera) is so narrowed by the result of zooming all the way in, the image is arrested at the focus plane, which in the case of the EX1 is three CMOS sensors. If they are like a very thin sandwich, one in front of the next, Red, Blue, and Green, then the image can only be in complete focus at one finite physical place because I’m zoomed at the end of the lens, and in my case, the red sensor and green sensor is getting the image out of focus and therefor not sharp or perfectly aligned to the single sensor that is sitting at the true plane of focus. When I’m not zoomed in, the plane of absolute focus opens up to include a wider space, just like on the other side of the lens, where more things are in focus for a longer distance than when you are zoomed in. The obvious difference is that inside the camera the difference measures in sub-millimeters, and in front of the lens the distance can be measured in centimeters, inches, of even feet! If there were only a single chip or sensor, there wouldn’t be any issue regarding separation of color!
A video clip at studiodaily featuring David Leitner speaking on the EX1 and he states that Sony uses software called Chromatic Aberration Correction (CAC) to adjust the image upon zooming. If you look up the word Aberration, where it applies to color it states the following:
• Optics the failure of rays to converge at one focus because of limitations or defects in a lens or mirror
But again, I am wondering if this is a result of the fact that three sensors cannot occupy the same space as they have some measurable thickness, enough to miss the extremely small acceptable focal plane inside the EX1. Here’s the link on David Leitner speaking on the EX1:
https://studiodaily.com/main/training/9334.html
After that I searched the web for Chromatic Aberration, and learned that it occurs often in digital photography, and software such as Picture Window Pro, or even Photoshop CS3 can remove most of the issue. I posted an exported frame of my EX1 clip that features some serious chromatic aberration or color fringing, and one of the people I found on the web who deals with the issue in digital photography cleaned up the image almost completely! I am wondering if there is some type of filter that could be applied to the entire clip that would clean up the chromatic aberration as well.
-stephen
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4 Replies
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This is probably a real long shot but did you make sure that wide angle CAC is turned off in your EX menu?
Thanks for posting the Studio Daily link. I found the article and companion video clips quite interesting.
– Don
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Thanks Don – I’ll look into it. Presently, my EX1 is still in LA at Sony Repair. My initial reaction to learning about the Sony Chromatic Aberration Correction (CAC) kicking in upon zooms, was a little unsettling. Blue sky is not to have your image digitally altered, but if it corrects Chromatic Aberration, great.
Most of what I read at this forum on the EX1 is centered around image issues that are associated with the Long GOP, and slanted and/or soft images during a pan or quick movement of the subject, etc. I have not really witnessed that to a degree that has my attention like the issue that I am trying to explain and get to the bottom of. I’d be interested to know what the factory default is for CAC; on or off? Thank you for replying to this post. -s
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[stephen may] “I’d be interested to know what the factory default is for CAC; on or off?”
The default factory setting is W/A CAC off.
– Don
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I’m interested to know if your color fringing problem was fixed after the repair?
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