Diagonal Streaks?

[sjt1]

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Anybody seen this before? I am getting diagonal streaks sort of coming out of the top left corner. Any ideas what it could be?

 

These streaks do not appear to be dependent on where the light is coming from, and they appear on DNG files, and jpegs coming out of the camera. For this picture I used a 35 f2 asph lens without coding and lens recognition was off. The pic was shot at iso 160 on a bright sunny day.

 

The pic is a DNG converted to black and white using Photoshop CS3's Black and white layer. The DNG was imported with slightly lower exposure than usual, actually in an attempt to reduce the noise. (The exposure was -0.85, the blacks were 35, the brightness was +70 and the contrast was +76). I have tried other pictures using the auto setting in ACR, and the streaks are less evident but the can be clearly seen.

 

My camera is one that was a replacement for another, and I have looked at the files from the original camera, and cannot find any evidence of streaking like this, when applying the same sort of processing. So it looks like the streaking is a feature of the camera I have now, and not something general with the camera or software. The camera is at version 1.107

 

Don't worry about the spots. I know they are there and they are easy to fix. Streaks are much more difficult! I have also looked at the DNGs from the first few shots with this camera, and the streaking is present, so it has always been there. Hence I don't think this is a sensor cleaning issue.

 

I am just about to send the camera off for repair and if there is an easy fix I would rather know about it beforehand. Leica UK are claiming a 3 week turnaround.

 

 

Thanks in advance for any help on this. I am emotionally preparing myself from a long separation from the camera and a return to film!

 

Steve Taylor

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[jaapv]

Try converting in C1 and exporting to PS in 16 bits TIFF. We have seen this before. It is posterizing in the postprocessing, depending on the RAW converter and/or 8-bits processing. I don't think it is a camera issue.

This thread:

http://www.l-camera-forum.com/leica-forum/leica-m8-forum/33589-strips.html

 

adresses exactly the same issue, and C1 cleared it up.Unfortunately the last post reporting that seems to have disappeared from the thread.

[Shootist]

While you're at it try cleaning the sensor, especially the bottom half (Top of the image).

I also see something in the upper right of the image (Bottom left of the sensor that looks like dried liquid which can be caused by a very wet cleaning and it dried on the sensor.

[sjt1]

Try converting in C1 and exporting to PS in 16 bits TIFF. We have seen this before. It is posterizing in the postprocessing, depending on the RAW converter and/or 8-bits processing. I don't think it is a camera issue.

This thread:

http://www.l-camera-forum.com/leica-forum/leica-m8-forum/33589-strips.html

 

adresses exactly the same issue, and C1 cleared it up.Unfortunately the last post reporting that seems to have disappeared from the thread.

 

Thanks for this. I have just tried it, and I am afraid that in C1 16 bit it left similar streaks. I was using ACR in 16 bit anyway. However, in some cases, C1 does appear to produce less pronounced streaking.

 

To me it doesn't look regular enough to be posterisation, as the streaks are of different thicknesses and some don't go all the way across.

 

Thanks again. I will keep trying.

[jaapv]

That is a pity. Somehow I feel it must be a postprocessing problem; it has never been reported yet as a hardware issue. Still, you could be unlucky enough to discover a first. I hope you solve the issue soon. Let us know.

[sjt1]

OK I am replying to my post with a update. The camera (sent to leica Sept 19) returned yesterday with a letter I am quoting the body of the letter verbatim:

 

"I have checked your M8 and found, that the mentioned streaks occur only when you heighten the contrast of parts of the image. I have seen that you have done this in some of your images to get more contrast in the sky. The clouds are getting shinier, but the sky changes to a more unnatural colour.

 

However, in that case slightly non-uniform sensor sensitivity gets visible. We have changed the CCD sensor of your camera and I have made a special check to secure that the sensor meets the specification."

 

It doesn't sound like an cheap repair. The camera was returned in first class condition, and they even threw in a couple of screen protectors.

 

I haven't had a chance to test it in bright sunny conditions (I live in the UK!!!), but I have repeated a test I did before the camera went off - I shot a lightbox with the camera and looked at the blue channel (where it was worst) and increased the contrast until the histogram filled a good proportion of the space. I did the same for both before and after pictures. The picture from the camera before it went off to leica had the streaks very clearly. After it came back, there were still some streaks, but much reduced and much less noticeable. They are also in different positions - this time they are on the lower right of the frame. I think this is the nature of the sensor.

 

I stress that I think the test is a very tough one indeed.

 

Overall, I am pleased with leica's customer service. They replaced an expensive part and conducted tests, and on the basis of the tests I have been able to conduct so far, the situation is much improved.

 

I will suspend final judgement until I get a sunny day to photgraph, but the inital results look very promising.

 

Hope this is useful

 

Steve

[Baxter]

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Cyan drift of sorts? It might be the absence of using fimware with lens coding, but am surprised since you were using a 35mm lens. I got some posterisation in the corners on sunny day (in UK!) when using an uncoded Zeiss 21mm f4.5 in colour images. Using Cornerfix removed the problem. Then able to convert to B+W using LR.

 

Might be worth downloading Cornerfix, generating a profile, correcting the file, converting to B+W and then seeing if it alleviates the problem. Alternatively look at controlling the cyan channel in your conversion.