Inspection light for BW film development......dark green?

[harlequin]

Dear APUG Members,

Was wondering if there is a particular inspection light that can be used on medium and slow speed BW films
during the last few minutes of development..?

a) I heard it was a green light, if so how many watts and how far away from film?
b) also how long can you inspect I am assuming this is brief and back in the soup pronto?
c) can if fog the film or does this require copius testing...?
d) thanks for any/all input on this
e) superior to snip test or should I do both.....

Mostly medium format 120 film...

Thanks for your feedback/responses...


Harlequin

 

[removed account4]

hello harlequin

yup a dark green filter
here's a very good article on the subject
http://michaelandpaula.com/mp/devinsp.html

 

[chris77]

hello harlequin

yup a dark green filter
here's a very good article on the subject
http://michaelandpaula.com/mp/devinsp.html

thanks john. good link this!!

 

[Peter Schrager]

Always on it john!!

 

[removed account4]

thanks chris77+peter
i try

 

[Gerald C Koch]

Back when films were slower Kodak recommended using a Brownie safe light. This was the type that had interchangeable cups for each color. The green cup is used. Cover half the cup with black electrical tape and use a 7.5 W bulb. Keep the light at least 4 feet away from the film. The light should be turned on for 2 to 3 seconds every minute. It is recommended to use a foot switch. The light will be very dim and allowing your eyes to be accustomed for 20 t0 30 minutes before use is needed. This means sitting in the dark for that time with only the safe light These directions were for older slow films rather than today's faster ones. All in all not really that useful. A bit more practical is the use of a densensitising prebath. The film is immersed briefly in a dilute solution of the dye and than transferred to the developer. The film can then be viewed by dim room illumination rather than by safe light.

Remember to look at the back side of the film rather than the emulsion side when evaluating the degree of development. .

 

[pentaxuser]

If you have developed a film at box speed for the maker of your developer's time and this is close but not quite right, how long do you have to persist with using a green light before you can actually gauge accurately when to stop development or increase it. On the first occasion of a green light's use, 10th occasion, 100th occasion?

If it's the first time of use that gets you an accurate development time then fine but at what point in getting, there such as the 10th occasion or 20th, before it will it have been quicker and easier use the film test routine?

In my early days I had a Durst tri-colour light that had a dark green filter for panchromatic film.I decided to try it first. After about 10 minutes I could just about get around the darkroom without stumbling and see a hand in front of my face but judge a film's development accurately - not in a million years! If I had tried to do so I have little doubt it might have got better but how many time would I have needed to try before I could see enough on the film to make it a worthwhile procedure - an awful lot more times than the cut film in say three and use box speed times plus and minus the usual percentage process

pentaxuser

 

[Alan9940]

I've never used an inspection light with film developed in "regular" developers, but I have when doing DBI with pyro developers. Since pyro developers harden/tan the emulsion during development, the film actually becomes less sensitive to light toward the end of development. With catechin-based formulas, it's best to use a green safelight; while pyrogallol-based formulas can use a yellow/green safelight. I use a green safelight with a 15 watt bulb at about 4 feet from the developer tray or tank. All that said, be advised that it will take repeated trials before you'll be able to accurately judge development completion in the few seconds you get to look at the negative.

Good luck!