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Old Apr 19, 2004, 3:42 PM   #1
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Default purple fringing on the F828

HI all

We used to have a DSC-F717 camera which we now have sold on in order to by
the new DSC-F828. As the F717 was an excellent camera we were looking
forward to the F828 as this should have been even better.
Well I must admit the new F838 is better in some respect But I'm very
disappointed on the purple fringing that comes out from this camera.

So we sent an email to sony and this is the repliy they sent back
We are pleased to read you are the owner of a Sony DSC-F828 and wish to
assure you that your set is functioning correctly and that the problem you
desribe is not technically caused.
Colour fringing may be observed in images recorded by the DSC-F828 digital
camera. This phenomenon of colour fringing may occur when shooting subjects
with high contrast or extreme variation in light levels. It is seen as a
colour "fringe" in the image where bright light is immediately adjacent to
dark. Colour fringing results from the difference of refractive index
caused by different light wavelengths as they pass through the lens. The
phenomenon may be more likely to occur when shooting strongly backlit
subjects or reflective surfaces with flash while using wide aperture. Under
these conditions, colour fringing is a normal characteristic of images
recorded by digital camera technology.
When shooting strongly backlit subjects or reflective surfaces with flash,
the likeliness of colour fringing may be reduced by selecting a narrower
aperture (f4-f8, for instance) or avoiding such conditions. The likeliness
of this phenomenon may also be reduced by reducing the overall exposure

Hope this might be of some usefull info to others who have, or are going to by this camera ops:
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Old Apr 19, 2004, 10:27 PM   #2
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That response from Sony certainly assuaged my concerns!

I am pleased that the Sony PR team didn't weigh in and insist that the purple fringing was a unique Sony feature that is included in the 828 to highlight the portions of the image that had high contrast or had extreme back lighting.
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Old May 5, 2004, 2:00 PM   #3
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The f828, like many of the new high resolution cameras has more purple fringe in high contrast areas, especially if you shoot wide open. But take note that this is certainly not limited to the f828 though it's one of the worst offenders.

If you don't mind sacrificing a little image quality and resolution, you can get the Minolta A2 which has apparently some internal filtering to ameliorate this issue and has considerably less than other 8 megapixel variants using the Sony sensor.

Having shot way over 10,000 images with the F828 I can say that PF is a minor issue which I've learned to avoid in the vast majority of cases and eliminate in software for those few cases where it still is problematic.

In the vast majority of cases, even if it appears at 100% magnification on screen, it's of no consequence in even 8x10 prints. It would be nice if there were no problem at all with it, but aside from the Minolta A2, all of the new 8 megapixel cameras have it in various degrees.

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Old May 5, 2004, 10:04 PM   #4
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The 828 and the A2 use the same [Sony] imaging sensor; and the 828 Zeiss lens and the Minolta GT lens are each paragons of optical engineering excellence. Yet there is this disparity in this one area of performance. I'm still baffled as to why the 828 seems to exhibit the PF as much as it does [compared to its peer group].

There was a suggestion that I saw on some other forum that the 828 PF problem may relate to the optical system integration [i.e., the chain of primary lens/UV band stop filter/Super HAD lens layer/Sensor array/read-out structure] that is uniquely sensitive to the UV portion of the spectrum coupled with overdrive (blooming); which becomes acute with the 828 since the 828's design allows sufficient UV band pass to support the Night Framing/Night focus feature(s) that are unique to Sony cameras.
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Old May 5, 2004, 10:20 PM   #5
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My best guess (strictly speculation) is that it may have more to do with the new 4 color filter array on the Sony (unique to the Sony). I'm also wondering if it could be physically different (microlens design, etc.) compared to the CCD Sony is marketing to the others.

As far as UV, I've still got some Hot Mirror Filters that I bought for older digicams with CA. They were a waste of money, and did zero to help with the PF.

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Old May 8, 2004, 10:42 PM   #6
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jawz wrote:
I'm still baffled as to why the 828 seems to exhibit the PF as much as it does [compared to its peer group].

I think it is strictly optics--the lens on the 828 is a full stop faster than its competitors. This much wider aperture has to have some sort of tradeoff, and in the 828 I think it manifests as fringing. I'm sure the engineers were fully aware of this during development, and chose to accept the tradeoffs. There is no perfect camera!
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