Looping - Intensification

[Ian Grant]

In astro-photography before they went digital there was a technique called "Looping"

Shoot your images on a C41 film, develop in C41 dev but instead of Bleach Fix wash and just bleach in a ferricyanide-bromide bleach . Then re-expose to light and redevelop in C41 dev, this cycle can go on for a few times.

This also works with normal B&W films. Bleach in a re-halogonating bleach, wash redevelop in a C41 or other colour developer with an apprpriate colour coupler. In theopry you can do this as many times as you want, but in practice I found once is enough. Then bleach & redevelop in a print developer.

Ian

 

[Claire Senft]

The technique is very useful for increasing the contrast in both color negatives and prints. The first time I ran into it the techniqye was referred to as the Anderson Method,

 

[Photo Engineer]

I have posted this both here and on PN. I have referred to it using the Kodak name, or rehalogenization bleaching. It is also Rehal processing.

Another way to increase contrast is by using catalytic imaging by means of adding either peroxide or cobalt hexammine chloride to the color developer. This directly increases contrast with no need to rehal bleach.

Catalytic processing or imaging and rehal processing are published here and on PN with complete process cycles for both types of process.

Both processes are nice in that the final color imaging can be done in the daylight by inspection which is a big plus. The minus is that often all 3 layers don't react the same and you can get color casts, and the dmin comes up with contrast, which can be objectionable.

Using this process, I have gotten good 2400 speed images from 400 speed negative film by amplifying the faint image there from a 'normal' C41 process.

It does work but is not perfect.

PE