Using the New PCC Tool

[Robert Q. Kimball]

In the past, color calibration was a two step process ( Background Neutralization and Color Calibration).  Is it now a ONE step process, or does Background Neutralization still need to be performed prior to PCC?

[Alejandro Tombolini]

Hi Robert,
You can do one step process checking Background Neutralization in PhotometricColorCalibration tool and selecting a Region of Interest of the image as reference of the background or you can do a two steps process by unchecking Background Neutralization in PhotometricColorCalibration tool and using Background Neutralization before PhotometricColorCalibration tool.
To be sure your background is correctly neutralized, use STF tool linking the channels and aplying autoSTF. You have to see a neutral background. If you see a predominance in one or other color, something was wrong. 
Saludos, Alejandro.

[Robert Q. Kimball]

Thank you!  What a great new tool.

[javajunkie2121]

Hi Robert,
You can do one step process checking Background Neutralization in PhotometricColorCalibration tool and selecting a Region of Interest of the image as reference of the background or you can do a two steps process by unchecking Background Neutralization in PhotometricColorCalibration tool and using Background Neutralization before PhotometricColorCalibration tool.
To be sure your background is correctly neutralized, use STF tool linking the channels and aplying autoSTF. You have to see a neutral background. If you see a predominance in one or other color, something was wrong. 
Saludos, Alejandro.

Hi:  I tried using PCC both ways.  When used as a sinfgle step with Background Neutralization box checked, works fine..but when I used PCC on the same image that had BN previously applied, I got a horrible green cast.  Not sure what I am doing wrong?
jeff

[bob_franke]

Hi:  I tried using PCC both ways.  When used as a sinfgle step with Background Neutralization box checked, works fine..but when I used PCC on the same image that had BN previously applied, I got a horrible green cast.  Not sure what I am doing wrong?
jeff

Hi Jeff,

You are not doing anything wrong. After running PCC, you always have to reset the background. PCC uses multiplication against the three color channels and this introduces a color bias to the background. Background neutralization uses addition/subtraction. Because the background level is so much lower than the rest of the image, this has no effect on the overall color.

I suggest starting with a flat neutral background. Then let PCC do the background neutralization and everything will look fine. Personally, I leave "background neutralization" unchecked and do it myself. I usually set the background with HistogramTransformation.

Cheers,
Bob

[javajunkie2121]

Hi Bob:  I have tried to reset the STF after using PCC, but can't get rid of the green background.  So, if I do PCC single step with BN checked within the process, I got a good result, but if I run PCC on a file that had BN previously, it looks awful...nmot sure what I'm doing wrong, but the background won't reset.

I was starting with a master sub that had DBE and BN applied...so no significant gradient and neutral background

jeff

[bob_franke]

Hi Jeff,

After PCC adjusts the color, the background ALWAYS needs to be neutralized. This can be done by PCC or you can do it yourself with the BackgroundNeutralization tool, HistogramTransformation or by subtracting a background model created by DBE or ABE. If you want to let PCC do it, you should start with a flat neutral background. You cannot do it with the ScreenTransferFunction.

Bob