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05-22-2008, 12:16 AM   #1
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From-Green-to-Purple gradient on K10D

Hi, all!
Has anybody seen the subj on K10D?
Lets see



K10D, 1s, F8, ISO1600

Left part of the frame has green, and right part has purple.
Whats up?

05-22-2008, 12:26 AM   #2
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I bought my k10d a couple of months ago so I haven´t used it much yet. I have experienced the same effect on a video camera though as a tv photographer. I got similar color shades if the sun or another strong light source stroke the lens from the side - obviously from an angle where the lens hood wasn´t enough. Was there a sun or a lamp post near where you shot the image?
05-22-2008, 12:39 AM   #3
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no sun and no lamp. This Effect appears even in ISO800 and a long exposure.

PS It is the subject of wide speculation on Russian Penta-club.
05-22-2008, 01:08 AM   #4
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I have never seen that on my K10 nor on my new K20, both havig served easily many thousand images by now.

Is this the only image with the strange gradient? Or do you have more examples of that behaviour? As KungKrille wrote, this is a fault, that can occur, when light goes through the optics (lens) via an oblique angle. Obviously, as the sensor has a microlens array in front, this could occur either in the camera lens or in the micro lens array. In the latter case it might be a relict caused by an inferior or unsuitable camera lens, like an old uncoated modell (or a lens with a antique coating, even SMC coating changed massively over the years).

Theoreticaly it could be an electric fault, too. But whatever I have seen from CCDs looks quite different. Usually you have a much stronger hot spot instead of that smooth gradient.

Ben

05-22-2008, 01:25 AM   #5
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yeah! I have more examples. Not my.

one:


two:


three:


four:


and many others...

But this artefact is not appearing at K100D. So I think it is electrical fault. Probably thermal.
and if you shoud increase aperture or decrease ISO or exposure time this fault is going to dissappear...
For examples:
ISO800, F6.3, 1.3s


ISO400, F6.3, 3s

Last edited by kulmann; 05-22-2008 at 01:35 AM.
05-22-2008, 02:19 AM   #6
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Hi kulman

Thanks for the additional examples. These look bad! But the direction of the gradient changes, sometimes (from left to right) from magenta to green, sometimes vice versa. That makes me think, that it is not caused by the electronics. All of the images look as whether they where taken with a wide angle lens (at least the kit lens in WA position) and most samples were made under artificial lighting, which could be a contributing factor. (Especially as these seem to be mostly sodium/mercury lights ith a discontinual spectrum.)

It think, that it is some artefact caused by an interaction of the lens coating and the incident angle of the light onto the micro lens array. As you know, current lenses have a special coating on the rear element to reduce reflections between the lens and the sensor. The colour cast/gradient your images show, might just be severe examples of why these new coatings make sense... But this is pure speculation, as one would need the exact image data to delve deeper in to this (lenses, apertures, post-processing like colour/saturation enhancement etc.)

Ben
05-22-2008, 03:23 AM   #7
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BUT, why this effect depends on exposure and ISO?
And why it NOT appears on lower-body K100D with the same lens?

BTW, the lens which used to take this picture was DA40mm/2.8 ltd. Not WA.
05-22-2008, 03:30 AM   #8
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here it is:
daylight (no aditional light), f22, ISO1600. It's white ceiling.


Nice gradient!

05-22-2008, 03:35 AM   #9
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So you mean that you can reproduce the gradient whenever you want just by setting the "correct" exposure?
05-22-2008, 03:44 AM   #10
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Yes.
Try this: Mode -Av, ISO1600, Aperture F11-F22...
05-22-2008, 04:13 AM   #11
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I tried all aperatures between f11 to f22 but didn´t get the effect. I also changed between jpeg and raw but nothing.
05-22-2008, 04:23 AM   #12
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ISO1600 and low light.
NR enabled?

P.S. Could you post the photo here?

Last edited by kulmann; 05-22-2008 at 04:33 AM.
05-22-2008, 05:11 AM   #13
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Yepp, here is one. I have noise reduction on. I took several shots with different aperature on a white paper on our toilet at work with light leaking through the door opening. Lucky me that my boss isn´t here today :P I haven´t edited the image other than converting it from RAW to jpeg. The only gradient I can see here is the bad vingetting.
05-22-2008, 05:18 AM   #14
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Well. I haven't see the Gradient when NR is on!
Ex:
ISO1600, F13, 3s, NR on


however, when NR is off...
05-22-2008, 05:38 AM   #15
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Ok, with noise reduction of I get some gradient. Well, I can´t explain this for you

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