PM-Scanner can't read Target Image File

Moderator: jsachs

jjones
Posts: 4
Joined: August 30th, 2009, 3:38 pm

PM-Scanner can't read Target Image File

Postby jjones » August 31st, 2009, 6:53 pm

Hello,
I'm using Profile Mechanic Scanner (1.003) under WinXP-Pro (latest SP) and I'm trying to make a profile for my Epson V750-Pro scanner. Using the EPSON Scan program that came with my scanner, I scan my IT8 target with all of the scanner-generated color/corrections disabled, and then I save the scan as a TIF-file. Pretty simple, cut and dry operation. Then, I open Profile Mechanic, but when I select that same TIF file as the Target Image File, I get an error-dialog saying "Cannot read target file: ..."

Well, PWP (4.0113) can read it okay, so I opened it with PWP and then immediately saved it again, overwriting the original. Now Profile Mechanic can read the file and I can successfully generate the Scanner's Profile. But now I question the validity of the profile because of issue #2 below.

1 - The obvious question is why can't Profile Mechanic read the TIF file unless some other program has "touched" it first? I can also open it with IrfanView (4.00) and resave it with the same result that PM can read it. Is there something missing from the original Epson Scan TIF file that PWP/IrfanView is applying, thus enabling Profile Mechanic to read it? It shouldn't be profile data it's looking for because I've turned that off as per the explicit instructions in Profile Mechanic.

2 - The first question leads to this one... Doesn't the Color Management of PWP modify the image when it reads the file and/or writes it back to disk, thus destroying the viability of the image for profile generation by Profile Mechanic?

Admittedly, I am a beginner at Color Managed Workflows, and I am struggling a bit, so I am still somewhat confused by what's happening to the raw image-data out of the scanner. Maybe you could clarify the "life of an RGB value" for me. The following is my weak understanding:

I assume the scanner generates an RGB value, optionally pushes it through a profile (which I disabled) to get a new RGB value, which it then writes to disk? Or does it write the original RGB value to disk and just record the profile LUT (assuming I didn't disable it) as supplemental data in the file (in which case I would think it wouldn't matter if I disabled the scanner's color management or not because the raw data is present and unmodified)?

Obviously, something Profile Mechanic wants is not in the original scan-file, which seems pretty odd to me.

Any advice and guidance is greatly appreciated.

Jeff

jsachs
Posts: 776
Joined: January 22nd, 2009, 11:03 pm

Re: PM-Scanner can't read Target Image File

Postby jsachs » August 31st, 2009, 9:44 pm

There are many different variations of TIFF. PWP has been updated to support more of these variants than PM so the older code in PM is probably having a problem with the type of TIFF file Epson Scan is writing. You may get PWP to read Epson Scan's TIFF files if there are various options for saving the file from Epson Scan. You should also be able to use Epson Scan as a TWAIN driver via PWP's File Select Source/File Acquire command and import the files directly into PWP without saving them as TIFF first.

As long as you do not set up PWP to convert files on open to the working color space (File/Color Management/On Profile Mismatch), it should be OK to run files through PWP. If you have it set up to ask, then don't convert.
Jonathan Sachs
Digital Light & Color


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