Color separation

If I wanted to separate my color negatives into 3 B&W positives (or positives to negatives), what filters should I use? Would it be easier to do with slide film due to the lack of the orange mask? Also, how do I determine how to expose film with an enlarger?

Place the film in place of the photo paper, I assume you will be using 4x5" or 8x10" sheet film for this.

You would have to filter the light, since film is much more sensitive than paper, you got room for filtering more I reckon by logic.

I would balance the light or filtering to neutralise the orange mask first.. so probably daylight balance the backlight and then filter with the opposite of the negative mask (however you want to create that filter, or calculate it and find something appropriate).

Then add your red/green/blue filters for each exposure on top of that.

For example a 100 speed film should be 5 and 2/3rds of a stop faster than typical paper, thus I dont think that much filtering without increasing the backlight would be much of a problem

Though someone who's actually attempted this may give better advice than me.

Orange mask is compensated just by adjusting the individual R/G/B exposure times, as you have to do in any case. It's the easiest way and works for any film.

hrst said:

Orange mask is compensated just by adjusting the individual R/G/B exposure times, as you have to do in any case. It's the easiest way and works for any film.

Click to expand...

I guess that makes more sense

hrst said:

Orange mask is compensated just by adjusting the individual R/G/B exposure times, as you have to do in any case. It's the easiest way and works for any film.

Click to expand...

That makes sense. What filters should I be using, though? Will any old red, green, and blue filter work? I have a #12 (minus blue) filter; could I get a #32 and #44A (minus green and minus red) and use two at a time to get a single color?

If you have your slide, (you can do this in camera too) you simply put the slide in a duplicator attachment. You can buy color seperation filters from kodak (expensive) or you can buy giant filters for theater lights which will but much, much cheaper. You need a red green and blue filter. Simply expose one frame of black and white film through red, one frame through green, and one frame through blue. When you reverse these, you tone the red image cyan, the green magenta, and the blue yellow.

The short answer is to try filter nos. 29 red, 61 green and 47B blue. These are used in the Dye Transfer Process for making separation negatives.

RPC

Or use WR99, 98 and 70 which is the best for color reproduction.

You make negatives from Slides though, and you get positives from negatives. So, making a negative from a negative is a 2 step process.

The exposures must be adjusted such that a neutral scale is identical to each region of the spectrum so you must first calibrate your exposure by making 3 individual (R/G/B) neutral scales that match. There are several textbooks on this as well as Kodak publications that may be obtained with complete descriptions.

The most difficult part will probably be the selection of the B&W film and process that yields the best results for you.

PE

color sepearation

Color separation


Having spent over 40 years as a graphic arts color separator The information for dye transfer is correct as far as it goes. How you plan to use the separation negatives can influence the filters. For a three color system with fully balanced and corrected dyes the 29 red 61 green and 47B blue work great Photo mechanical printing uses less corrected inks and the separation have to be masked to compensate for the ink deficiencies use the broader band 25A 58 and 47.All three separations must have the same curve and end points which also require different exposure and developing times for each filter If the curves do not match you will get a condition known as cross over where balancing the highlights and shadows and neutrals are next to impossible
But fear not , ingenuity can solve anything While I was still in the Navy having too much time on our hands my buddy and I decided to do dye transfer .,Using my lab on on board we figured the exposures by trial and error and developing times by the simple process of timing them by him yelling through the door when to put the different negatives into the developing tank! The only timer on the ship was a GE clock timer. We even rigged a home made densitometer using an old GE exposure meter Actually got some decent dye transfers too.,