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Author Topic: Seriously bad reflective Epson V850 scans  (Read 1121 times)

donbga

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Re: Seriously bad reflective Epson V850 scans
« Reply #20 on: June 12, 2018, 04:54:29 PM »

You nerds are making this difficult. Blur each patch and then read the values. That is of course assuming you are scanning properly. Just use the Epson software in Pro mode and set your white and black points properly.

Once that is done select a patch with the select tool of your choice and give it a Gaussian blur. Read the value 0 to 255. The use of layers is recommended.

Mark Nelson has a good explanation for this method in his Precision Digital Negatives software for the Mac. Worth every penny. Don't re-invent the wheel. Life is too short.

Don Bryant
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Doug Gray

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Re: Seriously bad reflective Epson V850 scans
« Reply #21 on: June 12, 2018, 07:14:23 PM »

The best term for this seems to be "spatial crosstalk." I've found some discussion of this in sensor arrays and camera imaging systems where aperture, lens diffraction, and glare are the culprits. There are even specialized charts  for quantifying it. It's apparently long been known and pretty much ignored.

ISO 12641 specs the IT8 targets and usage. One problem with IT8 targets, is that they are for scanning traditional (chemical) photographs. More and more photos are not on film but digital. Arguably the original digital images never need scanning but as digital prints get older and the originals are lost, there will be a shift towards scanning inkjet prints. For those it's best to use targets made for the inkjet inks. This substantially reduces metameric shift errors since scanners are no where near L/I.

IEC 61966-8 provides lots of characterization methodology for scanners and is nearing two decades old. Section 13.1-13.4 focuses on scanner "Large area spatial crosstalk."
https://webstore.iec.ch/preview/info_iec61966-8%7Bed1.0%7Den.pdf

Running scannerreflfix.exe even improves the IT8 profile generating accuracy.

« Last Edit: June 13, 2018, 11:44:41 AM by Doug Gray »
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nirpat89

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Re: Seriously bad reflective Epson V850 scans
« Reply #22 on: June 13, 2018, 12:27:49 PM »

You nerds are making this difficult. Blur each patch and then read the values. That is of course assuming you are scanning properly. Just use the Epson software in Pro mode and set your white and black points properly.

Once that is done select a patch with the select tool of your choice and give it a Gaussian blur. Read the value 0 to 255. The use of layers is recommended.

Mark Nelson has a good explanation for this method in his Precision Digital Negatives software for the Mac. Worth every penny. Don't re-invent the wheel. Life is too short.


Don Bryant

Didn't realize PDN has solved all problems that were to be solved.
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donbga

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Re: Seriously bad reflective Epson V850 scans
« Reply #23 on: June 13, 2018, 02:39:56 PM »

For what it costs the customer it's worth every cent. Mark has developed a very sophisticated package. Epson scanners have issues and the reflective glass isn't usually one of those unless the inside of the scanner needs to cleaner from out gassing.

Ik you want Lab values just pick up a spectro. Less expensive than the 850 scanner.

IT8 reflection targets for profiling the scanner isn't a bad investment either.
Mark's ebook provides an education on many levels for about the cost of a package of premiun inkjet paper.
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nirpat89

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Re: Seriously bad reflective Epson V850 scans
« Reply #24 on: June 13, 2018, 04:24:29 PM »

For what it costs the customer it's worth every cent. Mark has developed a very sophisticated package. Epson scanners have issues and the reflective glass isn't usually one of those unless the inside of the scanner needs to cleaner from out gassing.

Ik you want Lab values just pick up a spectro. Less expensive than the 850 scanner.

IT8 reflection targets for profiling the scanner isn't a bad investment either.
Mark's ebook provides an education on many levels for about the cost of a package of premiun inkjet paper.

Hi, Don:

Not sure you are following the main thrust of Doug's work.  It is nothing to do with digital negatives, nor does it have to do with un-clean glass - Doug's scanner is brand new.  The phenomenon is related to the way a scanner gathers data from a given area which would be applicable, in general, to all scanners.  I joined in the discussion since I had seen a similar phenomenon while calibrating for digital negatives.

I do have a spectro now (ColorMunki Photo) which I plan to use in future.  The good thing about the scanner is being able to collect all the data in one shot.  Also have an it8 target.  I am fairly happy with the system I have developed for myself and the level of understanding on what is going on in making of digital negatives.  What I don't know, these forums have been excellent source of knowledge from experts like Doug Gray and others.  Specially if one knows the right question to ask.  I have nothing against the PDN system and it is not about the cost, it is about the satisfaction and fun of figuring things out yourself (that's the geek in me. :))

:Niranjan.
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