Re: [APML] recommendations for development of tech pan

[Chuck Vaughn <aa6g@aa6g.org>]

Richard,

> what is the consensus around here about how to develop tech pan 2415?
>  
> I am guessing nearly everyone does their own, but which developer, 
> what temp and for how long for the develop etc?

D19 is the standard for TP astrophotos. I develop for 10 minutes. I 
consider 10 minutes to be a compromise between grain and density. Less 
time means finer grain but less density and longer time means more 
grain but more density.

Considering negative density only, 10 minutes in HC-110 Dil B will 
require 1.5 times the exposure to equal the density of D19. I believe 
Brad Wallis says you can develop in HC-110 for about 16 minutes to 
compensate for density but you get more grain. D76 can also be used and 
has a very nice tonal range but will require 2 times the exposure to 
begin the reach the density of of D19 when developed for 10 minutes. 
Technidol liquid can also be used but requires very long exposures and 
gives you a negative similar to color film, i.e., very thin but nothing 
burns out.

Although Jim has a valid point about TP negatives being too dense for 
some scanners, I would not recommend developing in HC-110 to solve that 
problem. My approach is to adjust hypering and/or exposure time to 
control the density. My experience is that most objects are too faint 
to turn out well with HC-110 unless you're willing to expose longer.

Also, on Jim's comment on stop bath, it definitely contributes to 
emulsion flake-off which is a problem only with hypered TP. I have not 
used stop bath for at least 10 years now and I cannot note a problem on 
any negative. I cannot detect any degradation on any negative.

Chuck <aa6g@aa6g.org>

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