Southwest Summer Colors, July 2014 - Canon Powershot A4000 IS.

Summer Rain Began, July 2014 - Canon Powershot A4000 IS

The Rainy Season Arrived, July 2014 - Canon Powershot A4000 IS

My Lovebird b. 1996 - Kodak EasyShare Z1485 IS. He’s 18 yrs old.

Big Evening Sky - June 2014 - Kodak EasyShare Z1485 IS

Anonymous said: Very sorry for the loss of your kitty.

Thank you! How sweet and I appreciate your thoughts. Take care

Jock - RIP May 14 1995-May 16 2014 - IPad Air.  An amazing creature and incredible buddy. He loved all humans. I and many others will miss him.

Room And The View, Kodak Easyshare Z1485 IS - HDR photo

Kat Kounting, Winter 2014 - Canon GIII Q17 35mm on Agfa Vista 100. 16 years of pennies.

Fall Mobile Dream 2013 - Canon GIII Q17 35mm film.

Java Cup Fall 2013 - Canon Powershot A4000 IS

Sunset El Paso, Feb 2014 - Kodak Easyshare Z1485 IS

Pho Noir, El Paso, TX 2014 - Kodak Z1485 IS

Dove In The Tree, Feb 2014 - Kodak Easyshare Z1485 IS

The Prokudin-Gorskii Archive: Fixing Color Casting Using GIMP 2.8

The Prokudin-Gorskii Archive: Fixing Color Casting Using GIMP 2.8
If you haven’t read my first article you should read it first:
Restoring the Prokudin-Gorskii Archive using GIMP 2.8. Specific steps at the beginning and end of this article will assume you have read it.

A Brief Word About GIMP 2.8
If you tried GIMP in the past and found it frustrating then try it again with this version. Many of the User Interface annoyances have been fixed and it’s now much better and easier to navigate.

Color casting…
One of the more common problems with the Prokudin archive are weird color casts. This is generally caused by the emulsion on one or more of the separations having badly faded over the years and in this case it’s a red color cast. A good example is the following glass plate composite from the Library of Congress.

In the courtyard of a Sart home. On the outskirts of Samarkand
image

You can see right away that the color has ‘shifted’ away from what it was intended to be.

You might spend quite a bit of time using Curves or Color Balance in GIMP to fix it but it would take quite a bit of fudging around. However, the separations for this photo reveals the true problem with the above photo and it’s easy to fix too…
image
The emulsion on the red separation on the bottom has faded/deteriorated quite a bit. The red separation appears to be 2 EVs overexposed than the blue separation. To a much lesser extent so has the green separation in the middle and possibly 1 EV overexposed/faded. It’s apparent in the bottom right hand corner of the separation where the steps are. 

  • Start GIMP 2.8

  • Crop out each individual separation (see my first article).

  • Open As Layers all 3 of the separations

  • With all 3 separations visible set the Mode to RGB. (Important).

  • Make sure all separations are visible.

To confirm the fact that most of the color cast is coming from the red separation you can turn on the histogram tool. Colors=>Info=>Histogram.

Now one at a time, look at the histogram of each separation by clicking on the filenames of each of the separations. You’ll see in the histogram that the blue and green separations are fairly flat and spread out. However the red separation is skewed all the way to the right third of the histogram and starts coming close to being clipped. We’ll come back to the histogram in a minute, it will be our friend.

Time to fix it…
What may first seem like an extremely tedious or hopeless operation is really quite simple and quick to do. Hopefully, you have not forgotten to change the Mode earlier to RGB. Now you can…

  • Right click=>Colors=>Levels

This will bring up the Levels panel with a histogram. Underneath the histogram are 3 upward pointing arrows, the black point, mid point and white point. What you want to do is reset each of these points. When you do, it will flatten out on the histogram and thereby get rid of the color cast. Here’s how to fix it and it’s quite simple once you get the hang of it. It will take a little practice but not much.

  • Go to the far left of the histogram. The up arrow there is your black point. You want to set it right on the end of the tail of the histogram on the left. Just before all the light falls off completely.

  • Next go to the far right of the histogram. The up arrow there is the white point on the histogram. Again move it to just before the light ends, the far right tail.

  • Finally, go to the middle up arrow under the histogram. Find the tallest ‘hump’ and move the arrow to the top of that hump.

  • Click OK

  • Follow the same procedure above for the green separation.

The color cast has been mostly eliminated. You can now go through the procedures described in my previous article. After you have created a composite you can further saturate, adjust curves and otherwise post process to your liking.

Below is the Library of Congress version and my version which is post processed in GIMP 2.8 and minimally restored.

Library of Congress version straight from the glass plateimage

My restored version using GIMP 2.8
image

From here you can further make sharpening, cropping, corrections and restorations now that you know how to get rid of the color cast. Prokudin’s ingenious, 100 year old process is timeless, artistic and scientific.

Prokudin’s method has stood the test of time for creating some of the most beautiful Technicolor photographs made then and now. I personally love the extremely high dynamic range he was able to achieve bringing out incredible depth and color that can’t be easily duplicated with digital cameras. I always ask myself, How will digital photos fare 100 years from now?

If there is an interest here in restoring the Prokudin-Gorskii photographs using GIMP 2.8 then let me know and I’ll write up more howto’s. In particular, how to restore severely damaged and broken glass plates of Prokudin-Gorskii using GIMP 2.8. It’s not nearly as difficult as it might first seem.