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Author Topic: Image degradation issues  (Read 2948 times)
2jbourret
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« on: August 23, 2010, 04:36:17 PM »
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I am experiencing  image quality degradation  using certain LR3 develop module settings in images with a broad range of tonal value.

Certain images that I have worked on recently have developed pixellation, banding and chromatic aberration issues that I have not experienced before. My issues seem to arise mostly when using the HSL color adjustments (especially luminosity) and the GND tool to achieve graduated darkening and saturation of bright sky areas, particularly around the bright edges of backlit clouds.  I am also having difficulty controlling  C.A. along the skyline profile edges of the same images. I am admittedly trying to achieve fairly strong luminosity adjustments, but I have never had these kinds of issues before. If I back off on the intensity of the adjustments being applied, the issues diminish, but then I do not achieve the result I intend.

I am wondering if my LR skills are not up to snuff, or if I'd be better off trying to make these adjustments in PS, or if I'm simply trying to go too far with these files. I've stopped using Capture One as my raw processor given that LR3 has, up until now, seemed to do a great job, but maybe I need to go back to that? (Until LR3 came out I was an Aperture user, and used C1/5 as my raw processor prior to importing files into Aperture.)

I am shooting 16bit raw files (Phase One P30 back, Mamiya 645 AFD3), and importing directly into LR3 for raw conversion, using 64bit mode. Images were shot at ISO 100, f16, with a Mamiya MF 35mm lens and 3 and 5 stop Galen Rowell soft GND filters.

Can anyone provide help with any of this?

Thanks!
Other images from this group that I have had trouble with can be seen at:
http://jamesbourret.photoshelter.com/gallery/Sawtooth-Range-Idaho/G0000.z2dveewazs/P00005Dv5c42raL4
Specifically images 2,3,14
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Lost
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« Reply #1 on: August 23, 2010, 05:38:57 PM »
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I am not sure that I could tell from the (downsized) photographs.

However, Mac LR3 seems to take some performance related shortcuts when rendering in the library and develop modules. Frequently I see apparent artifacts with the image zoomed at 'fit' scale, but these dissapear when viewed at a different scaling.  If you are reviewing the photographs within Lightroom perhaps this is the problem?
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2jbourret
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« Reply #2 on: August 23, 2010, 05:55:27 PM »
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You are right, the problems I am seeing won't be visible in the web or screen sized images here. They are hardly visible in Full size preview mode, but plainly visible at 1:1 and in larger prints. (20 x 30in). I 'll try to find out how to post a large enough file to zoom to 1:1, or a segment at 1:1 to show the problems I am having.

Thanks
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photopianeil
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« Reply #3 on: August 23, 2010, 07:14:29 PM »
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I have seen all the problems you have described since HSL first came out, both in Camera Raw as well as LR.  I see it a lot in my Photography I class when students make huge leaps  (of faith) with their early attempts to pull their under/overexposed image into submision.  I was very surprised to hear you got similar results with your high quality everything.  I have to assume that your exposures are ample without clipping.  I don't get to see that high end capture except once a year when I bring my advanced class to an advertising shooter who uses the best LEAF sensor.  However, the answer is simple. Look at the corrections at 100%, you can see when it sours.  Both saturation and luminance can create those artifacts.  And you are right, you may have to go back to the HSL settings after any local correction.  Don't worry, just do it up to the point before it goes over the edge.  I have to believe that this also enhances the CA.  You should also be able to relieve this problem with the local tools, just as it can make the problems worse.  This may sound simplistic, but give it a try.  Without seeing exactly what you are, I could be way off base.  You could send me a one inch square portion at 100% as a full rez jpeg.  That should show the problem.  I am looking at it on a NEC 2690 internally calibrated high gamut display (not an Eizo CG but close).
Neil
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2jbourret
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« Reply #4 on: August 23, 2010, 10:46:05 PM »
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Neil,
Thanks, and I suspect that you are right, I am just trying to pull a little too much out of the hi end of the Tonal range. A good argument for exposing to the left, I suppose, but the areas I'm having trouble with are really not over exposed. Neither the back histogram nor the LR histogram are showing clipping. It is only after reducing the luminosity of adjacent (blue)sky areas that trouble begins to show up, in the form of pixellation of the boundary between blue sky and cloud, and in the (previously) subtle gradations of the cloud areas, and in the CA issues I referred to previously. CA becomes almost completely unresponsive to adjustments applied in the CA  tool.

I'll post a 1:1 image segment tomorrow when I'm back at my computer.

Jamie 
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stamper
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« Reply #5 on: August 24, 2010, 02:54:33 AM »
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If you are using filters - I assume to tame highlights - why then are you having to make massive shifts to them in post processing? For the type of image that you posted then a subtle HDR might help or two images shot 2 stops apart and blended in Photoshop?
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Mark D Segal
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« Reply #6 on: August 27, 2010, 10:14:57 PM »
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I am experiencing  image quality degradation  using certain LR3 develop module settings in images with a broad range of tonal value.


I am shooting 16bit raw files (Phase One P30 back, Mamiya 645 AFD3), and importing directly into LR3 for raw conversion, using 64bit mode. Images were shot at ISO 100, f16, with a Mamiya MF 35mm lens and 3 and 5 stop Galen Rowell soft GND filters.



It's best to process these files in C1. Once they are rendered, import them into LR as TIFFs for further processing.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
JeffKohn
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« Reply #7 on: August 27, 2010, 10:41:59 PM »
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Quote
or if I'm simply trying to go too far with these files.
Yep. Any tool that works like the HSL tool in LR/ACR is going to have those artifacts when you push too far (such as trying to darken down a blue sky too much). These tools try to "select" what pixels they affect based on color, and are going to be imperfect along the edges of the implicit selection. For more modest adjustments, you usually won't see it; but when pushed too far, things can get pretty ugly.

You'll also see the same thing in B/W conversions if you use the LR/PS B&W conversion tool and push the color sliders too far (although sometimes it isn't as noticeable in the monochrome result).

You might have a little more success doing this type of adjustment in Photoshop proper, where you can do it on a layer and use blend-if or careful masking to limit the artifacts.

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2jbourret
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« Reply #8 on: August 28, 2010, 06:53:10 PM »
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Thanks for your comments.  I may return to doing raw conversion in C1, but I'm also finding that with wide dynamic range images in LR it seems to work best to make global exposure adjustments weighted toward good sky and cloud values, and then selectively lighten the areas below the horizon, rather than the other way around. It has also been suggested that CA should be corrected early in the adjustment sequence, and then micro-adjusted later as local adjustments are added, rather than waiting until late in the sequence, as is commonly suggested. This seems to help to keep CA more controllable. I am also thinking a better performing wide angle lens might be in order, as mine is an older Mamiya 35mm 3.5 with fairly poor edge sharpness and CA characteristics.
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