Color Negatives From Slides
Misc. Notes...
I have to say off the bat that I don’t recommend balancing color internegatives the way that Kodak taught me. Their way didn’t work too well, and everyone knew it and complained about it. That was why I came up with my own way to do it and eventually put it on a computer and sold it as “P.S. One.” It was the first software program that my brothers and I sold from our new company which we called “Photographic Software.” That was what PS stood for. “One” was our first program and we followed with “Two” and “Three” and then the “QC” and finally the “Analyser.”
But first let me tell you how Kodak recommended you do it (balance color internegatives). The 21 Silver step tablet that they sold was their gray scale offering for this purpose. It covered a density range of 3.15 and it was used to contact print onto the internegative material. Kodak, in fact, did this themselves and they published “ideal” curves made in this manner. We, as lab technicians, were to contact print the same 21 silver step tablet onto their internegative material and then match their curves.
Now the curves are derived from making densitometer readings off of the 21 steps on the processed internegative. You have to make three readings for each step. You read through a Red filter, Green filter and a Blue filter, hence you get 63 readings. You then go onto graph paper and using a red, green and blue ball point pen, you place a dot on the graph paper in the manner of a HD curve. Basically the bottom part of the graph paper indicates the amount of exposure the film received. The darkest part of the 21 silver step tablet blocked most of the light (representing the black of a transparency scene) and so it would produce the minimum amount of processed density in the internegative material. If the red density measured .21 you would place a red dot on the left side of the graph paper going up .21 in increments. In this way you would get 21 dots of red, 21 dots of green and 21 dots of blue. You take a French curve and connect these dots to draw your graphs.
By placing Kodak’s ideal curves on a light table you can now place your curves on top and compare them. You are not to “turn” the sheets to make them fit. Instead you can slide the sheets left and right to get a better fit. Depending on how much you slide to the left or right you would then know how much to adjust your filter pack in order to get a better fit. Moving the sheet to the right by ½ stop (.15 points) would basically equate with one step of the 21 silver step tablet.
The red curve is adjusted by overall exposure. So in order to move the red curve to the right by ½ stop you’ll need to increase the overall exposure by ½ stop. That means opening up your f stop by ½ stop or by increasing your exposure by 41%. If you want to move your blue curve to the right by ½ stop you need to subtract 15 points of yellow from your color head.
Makes sense? It’s a bit of work and it’s well worth it if this produces a good color interneg. You can’t beat a good color neg, believe me. All the dodging and burning in the world will not produce a better color print than one made from a really good color negative.
Problem is, it didn’t work all that well. So after all this work of getting the curves to fit as best they can why didn’t it work? Mainly you couldn’t get your curves to look like Kodak’s. If you did then you got a decent interneg from an Ektachrome original. Even when matching Kodak’s curves exactly it wouldn’t produce a good neg from a Kodachrome original. And Kodachromes were the bulk of what we got from customers back in the day.
What was the difference? When you measure a gray patch on an Ektachrome original you’ll get a reading of Red = .90, Green = .90 and Blue = .90. A great “looking” gray patch on a Kodachrome original (to the human eye) would result in a reading of Red = 1.15, Green = .85 and Blue = .92 (or something like that, like I said I don’t have my data from those days anymore).
But what this means is that although we see gray the internegative is receiving an exposure that is basically cyan/blue colorwise. In fact this is also an issue when making color internegatives from Fujichromes as compared to Ektachrome because Fujichrome cannot hold a decent gray scale from white to black. This is a fact that I knew because I ran my own tests again and again over many years. That’s why I always said that Kodak make the best materials. Now their fade characteristics took a long time to improve but that’s another matter.