Scanner calibration

[WGPhaneuf]

It stands to reason that scanners should also be calibrated. I've
tried it with less that stellar results. Has anyone tried this with
any success?

[steve sprengel]

What method(s) have you tried for calibrating a scanner that are not working as well as you would like?

Are you suggesting using the ACRCalibrator script for calibrating a scanner?  If so, how did you create a RAW file from a scanner?

[Walter G Phaneuf]

   Jpeg’s and Tiff’s can be opened with Camera Raw, at least the lower resolution (200 or so).

 

Step 1---From Photoshop CS3 scan the ColorChecker with an HP 5550c scanner and its generic software.  I use a resolution of 200.  I’ve tried 1200 but neither the Jpeg nor the Tiff will open in Camera Raw.

 

Step 2---Rotate (if necessary) and save the image as a PSD, JPG, and TIF.

 

Step 3---Using Bridge, open the JPG (or TIF) in Camera Raw.  Confirm the ProPhoto and 8-bit color settings.

 

Step 4---“Open” the image in Photoshop.

 

Step 5---Run the AcrCalibrate script.

 

   The first time I tried this, the script took 5 hours to run and the results seemed reasonable.  The second time, the script took 50-minutes and some of the sliders were at max (±100).  I will try again but will switch off the scanner’s color correction.

 

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[Steve Sprengel]

A JPG has colors "compressed" enough to cause problems.  You might be able to get by with a TIF or PSD, but the scanner needs to be used in a consistent way between when the color-checker is scanned and the photos, themselves, are scanned. 

 

Another thing to think about is that Tom's script only uses three of the 24 color patches to compute the calibration so is unlikely to be very good for very bright and dark colors.  If you really want to use a script to calibrate your scanner, you should probably use a script more like Tindemans variation that uses all 24 color patches instead of just three:  http://www.21stCenturyShoebox.com/

 

But if you want to calibrate your scanner for use with something like Photoshop, I'd suggest using a "real" calibration process that generates ICC or ICM color-profiles that you can assign to your scans that uses a color-target like an IT8 that has many more than 24 colors covering the entire spectrum and brightness range.

 

A scanner-based printer-profiling process can generate a scanner ICM as a side-effect.

 

I use MonacoEZColor which is no longer available, to do this.

 

I think the ProfilePrism product from DDISoftware may generate scanner ICM files along with the printer-based ones, although I do not have this product so I am not sure.  The website should say one way or the other.

 

Once it is created, to use an ICM scanner profile with ACR/LR you would acquire the scanned image in Photoshop, assign the scanner-profile and then save it, then open it in ACR or Lightroom, which will take that assigned profile into account.  Depending on your scanner software, it may also allow you to assign the profile on the way into Photoshop, but mine doesn't, so I assign it, manually.

[Walter G Phaneuf]

Thanks for your time and effort!

 

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