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Author Topic: Epson V700 Blown Highlights on Reflective Scans with Silverfast AI 8 Studio  (Read 9317 times)
Stephen G
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« Reply #40 on: November 13, 2012, 03:12:52 AM »
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Thank you all for helping me challenge my thinking and workflow. Too easy sometimes to just plod on with something that works, but may not be the best approach.

OK, refining things a bit: here are the tiffs from which I created the jpegs above. Should have done this in the first place. Except for the linear source file they are all in ProStarRGB, which is another thing I'm playing with at the moment. In this situation it's just a container - I've performed no adjustments after conversion from the scanner profile so it should not be influencing these results.

The LR downsample+jpeg+AdobeRGB process contributed to the clipping and obscured the actual results I got. I also capture sharpened the files, 0.6 87 Smart sharpen, which probably added a little clipping too as I did not protect the highlights. lazy.

Yes I do have clipping at the upper limits. No it's not clipping that  I'm worried about as the files print fine. It's mostly in the paper colour background, touching on the brighter colours in the drawing. The approach I used in the end was what similar I described a few posts above: CoCa DCSG profile extended by setting the whitepoint at 1.1. This gave me a slightly compressed masterfile that I then brought back to the exposure I wanted, while trying to avoid clipping. It's a controlled approach: I can apply as much compression/extension as is necessary to capture a given original. The Silverfast output is definitely safe, but will create unnecessary correction work if the gamut of an original fits well within that of my target.

A gap in my understanding: I'm not sure what you mean, Mark, by 'the gamma factor used in my profiling and scans'. I'm not applying any gamma adjustments to my scans. I'm relying on the profile to restore correct exposure to the linear source file.  I output 16-bit linear, assign the profile, convert to working space and the exposure and colour are 95% of the way there. The Silverfast and Epson scans have been gamma adjusted, but out of my control.

I tried what Dean suggested: use LR to bring the HCT Extended sample close to the look of the 'final colour' sample. It came up nicely, retaining good variation in the oranges that is a little lacking the CoCa-based final. I suppose the measure of a good profile is not just how close it gets you when you assign it, but how well the resultant file responds to adjustments. How robust it is. HCT-based profiles yield very robust files, for reflective and film work.

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Mark D Segal
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« Reply #41 on: November 13, 2012, 05:56:55 PM »
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Stephen, I may have been a bit cryptic in that one phrase - sorry. Of course a profile describes device behaviour, so that isn't where the gamma issue comes in. It comes in at the image interpretation stage - whether the default interpretation has gamma = 1.0 (linear) or some higher gamma which increases brightness and contrast, and along with that higher risk of clipping. The fact that you output 16-bit linear is great. SilverFast by the way does allow you to control the gamma in Preferences. The profile wouldn't have much impact on how well the file responds to adjustments unless it is so bad that the ensuing corrections could exceed the capabilities of the image editing software. Bit depth and gamma would have a bigger impact on how well the file responds to adjustments.
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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
Stephen G
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« Reply #42 on: November 14, 2012, 09:03:41 AM »
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OK gotcha now. You were referring to the brightness/contrast adjustments made to a file after applying the scanner profile, yes? If so then in most of my samples there have been no adjustments. Only the 'final colour' sample had a (slight) exposure lift to bring it up to match the original. The others were just assign, convert to working space and save, with Epson Scan and Silverfast taking care of these steps for me.

'quality' of profile makes a big impact, particularly when scanning film. Slides are often underexposed and being able to restore them and maintain good colour is very important. When scanning bright artworks it's not such a big deal. You don't need to push exposure up by 1-1.5 stops, small tweaks are all that's needed. The are examples of this on the HCT site, but I'm going to try and make my own, if only to justify the purchase of my HCT transmissive target. :-)
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Mark D Segal
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« Reply #43 on: November 14, 2012, 09:24:33 AM »
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'quality' of profile makes a big impact, particularly when scanning film. Slides are often underexposed and being able to restore them and maintain good colour is very important.

Stephen, As you may know, I've been doing this for years and a whole chapter of my book is devoted to the subject of colour managing scans and post-scan workflows, including the importance of correct profiling. Yes, if you use the wrong profile or a really crap profile it can make a big difference to the range of risks, time and trouble encountered in a post-scan workflow, but as long as the profile is the correct one for the scanner model and made with reasonably decent profiling software so that neither blacks nor whites are clipped, there are a number of effective techniques that will reveal underexposed detail that exists in the original media, often to surprising effectiveness, given how dismal the original media may appear to be. I have also dealt with that subject in my scanning articles here on LULA and in the book. Of course I agree the better the profile the less work this involves, but my experience is that no matter how *accurate* the profile, these heavily under-exposed areas do need a fair bit of user intervention regardless. So yes, a decent profile is necessary, but not sufficient.
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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
Stephen G
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« Reply #44 on: November 14, 2012, 10:25:22 AM »
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no matter how *accurate* the profile, these heavily under-exposed areas do need a fair bit of user intervention regardless. So yes, a decent profile is necessary, but not sufficient.

I'm going to test how 'decent' the profiles I have available to me are, with respect to restoring underexposure. For reflective I've got profiles from HCT, DCSG, Epson, Silverfast, CC24 and QPcard. For transmissive I've got profiles from HCT, Epson and Silverfast.

I don't when I'll get to this, or how exhaustively I'll do this, but it'll be fun and I'll bring the results here (probably a new thread) when I've got some.

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Mark D Segal
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« Reply #45 on: November 14, 2012, 10:56:02 AM »
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That's great Stephen, it will make a useful contribution.
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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
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