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Author Topic: Blue fringing on fine branches against sky  (Read 4297 times)
plinden
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« on: November 24, 2006, 12:36:53 PM »
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Hi, I am wondering if anyone reading these messages can tell me your experience with a situation I encounter often.

I do fine-art landscape work and I just upgraded my back from a Kodak Proback to a 39 mpixel Imacon back for my H system.

One reason was the terrible blue color fringing around bare branch detail, presumable due to the de-mosaicing process used, that I often encountered with the Proback.

I'm now using the Imacon back, and while the frequency of this problem happening is MUCH less, and the appearance less obvious, still the sensor seems unable to descriminate between very fine structures (branches) and the surrounding color (sky). Please see the two examples posted.

Is this just a fact of life with bayer pattern sensors, or is the Phase One or Leaf backs not prone to this?

Thanks for any feedback about your experience.

Peter Linden

[attachment=1214:attachment]

[attachment=1215:attachment]
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damien
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« Reply #1 on: November 24, 2006, 02:15:58 PM »
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Hi Peter,

It may be an artifact of image sharpening in the raw conversion. I have not suffered with this fringing using my P25 on my H1 with my 35mm lens at all. Other users have been less impressed with the 35mm lens for chromatic aberration but I believe the 'error' you describe is in the way the image is built from the pixel data. I saw a Kodak DCS camera produce magenta edges like this once and it was a processing bug not a lens or ccd fault.

Damien.
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« Reply #2 on: November 24, 2006, 03:13:25 PM »
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Quote
Hi, I am wondering if anyone reading these messages can tell me your experience with a situation I encounter often.

I do fine-art landscape work and I just upgraded my back from a Kodak Proback to a 39 mpixel Imacon back for my H system.

One reason was the terrible blue color fringing around bare branch detail, presumable due to the de-mosaicing process used, that I often encountered with the Proback.

I'm now using the Imacon back, and while the frequency of this problem happening is MUCH less, and the appearance less obvious, still the sensor seems unable to descriminate between very fine structures (branches) and the surrounding color (sky). Please see the two examples posted.

Is this just a fact of life with bayer pattern sensors, or is the Phase One or Leaf backs not prone to this?

Thanks for any feedback about your experience.

Peter Linden

[attachment=1214:attachment]

[attachment=1215:attachment]
[a href=\"index.php?act=findpost&pid=86884\"][{POST_SNAPBACK}][/a]

Try turning off all sharpening in Flexcolor for the raw conversion and use Smart Sharpen in PS.
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rainer_v
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« Reply #3 on: November 24, 2006, 03:29:26 PM »
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Try turning off all sharpening in Flexcolor for the raw conversion and use Smart Sharpen in PS.
[a href=\"index.php?act=findpost&pid=86906\"][{POST_SNAPBACK}][/a]

i know this effect from color noise reduction, which is even at default setting in many raw converters working at some level. this blurs the color channels, and so little artefacts disappear as well as fine color structures as you describe them cannot longer be reproduced.
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rainer viertlböck
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plinden
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« Reply #4 on: November 24, 2006, 07:08:23 PM »
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Thanks for the thoughts. The image was processed in Flexcolor with NO sharpening and NO color noise reduction. The only sharpening was done in Photoshop and the problem was clearly evident before.

So it must come from something else?

Peter
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Graham Mitchell
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« Reply #5 on: November 24, 2006, 09:13:01 PM »
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I don't see anything untoward in the supplied images...
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« Reply #6 on: November 24, 2006, 11:51:32 PM »
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I don't see anything untoward in the supplied images...
[a href=\"index.php?act=findpost&pid=86932\"][{POST_SNAPBACK}][/a]
post a 100% crop.
i was working longer time also with kodak chip in the slr, which showed the same in fine branches. here it was the NR. Off doesnt mean often Off.
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rainer viertlböck
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khwanaon
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« Reply #7 on: November 25, 2006, 06:45:45 AM »
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Hi, I am wondering if anyone reading these messages can tell me your experience with a situation I encounter often.

I do fine-art landscape work and I just upgraded my back from a Kodak Proback to a 39 mpixel Imacon back for my H system.

One reason was the terrible blue color fringing around bare branch detail, presumable due to the de-mosaicing process used, that I often encountered with the Proback.

I'm now using the Imacon back, and while the frequency of this problem happening is MUCH less, and the appearance less obvious, still the sensor seems unable to descriminate between very fine structures (branches) and the surrounding color (sky). Please see the two examples posted.

Is this just a fact of life with bayer pattern sensors, or is the Phase One or Leaf backs not prone to this?

Thanks for any feedback about your experience.

Peter Linden

[attachment=1214:attachment]

[attachment=1215:attachment]
[a href=\"index.php?act=findpost&pid=86884\"][{POST_SNAPBACK}][/a]

hi Peter,

this is most probably the noise filter which is at tha same time filtering details away.

aon
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kolyasik
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« Reply #8 on: November 25, 2006, 01:00:27 PM »
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I found same issue , leaf aptus 65 / mamiya 645 afd.
lens 55 mm
iso 200, exposure 1/125, f/6.7
onened in ps2 settings:
sharpening 0
noise reduction 0
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plinden
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« Reply #9 on: November 26, 2006, 04:50:16 PM »
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Thanks again for the comments. The images posted WERE 100% crops. I'm adding another 100% crop but of an uprezed version to make the problem easier to see.

kolyasik, you clearly have the same problem.

I'll investigate the noise filter hypothesis, but I thought off meant none.

I appreciate your giving this problem your consideration.

Peter
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Graham Mitchell
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« Reply #10 on: November 26, 2006, 04:53:44 PM »
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Peter, it doesn;t look so bad to me. If the image cast by the branches becomes less than a pixel wide then of course the resulting colour should be a mixture of the blue sky and the black branch.

Kolyasik's images are much more severe. That looks like a limitation of the lens to me. Could be wrong
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« Reply #11 on: November 26, 2006, 05:31:27 PM »
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I will try to explain what I think is happening here.

Here is a quick masterpiece I came up with in Photoshop. The lines are all pure black. Thick ones are 13px, thin ones are 1px.



Then I reduced the file to 25% using bicubic interpolation. Suddenly the fine lines appear blue not black due to their sub-pixel width:

« Last Edit: November 26, 2006, 05:37:28 PM by foto-z » Logged

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BernardLanguillier
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« Reply #12 on: November 26, 2006, 10:52:13 PM »
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If this can be of any help, I have seen similar problems with Mamiya ZD files converted using Silkypix 3.0.

The good news is that the same file converted using Raw Developper 1.6 shows a lot less, if any, of these issues.

The setting controlling this is called "color smoothing".

The Iridient Digital site lists the Hassy backs as being supported:

http://www.iridientdigital.com/products/ra...er_cameras.html

Cheers,
Bernard
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A few images online here!
plinden
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« Reply #13 on: November 27, 2006, 10:58:19 AM »
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Graham, thank you so much for doing that test. I think that explains WHY.

As far as what to do about it, I fiddled with the color noise filter, in flexcolor, as per someone's suggestion. While the filter was not exacerbating the problem (because it was off) I found that USING it tended to desaturate the problem areas to the extent that through masks I can blend in corrections in photoshop.

Attached is an example of the effect of the filter. Disregard the difference in overall color as I was experimenting with other settings changes at the same time!

While this filtering doesn't solve the problem it reduces the effect to a workable level...at least for this image.

Thanks all for your help

Peter
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