Film speed and development testing for DBI and Staining Developers

[jstraw]

Ok, if I'm testing for personal film speed for a given emulsion in a non-staining developer I know what to do...shoot zone III at a variety of ISO's and find the sheet with the desired density...

If I'm testing for normal dev time...Shoot a bunch of Zone VIII sheets at the personal film speed and find the dev time that gives the target density...

But lacking access to a color densitometer, how can I go about determining film speed and normal development with a staining developer?

I'm going to be using high dilutions and DBI so dev time is somewhat academic but I do need a baseline...and film speed is just as important as ever.

I'm somewhat at a loss.

 

[Tom Hoskinson]

Commercial color printing labs (including 1 hour labs) usually have a color densitometer and most are willing to make your density measurements.

Also, The View Camera Store offers film testing services.

Dead Link Removed

 

[jstraw]

Commercial color printing labs (including 1 hour labs) usually have a color densitometer and most are willing to make your density measurements.

Also, The View Camera Store offers film testing services.

Dead Link Removed

But, but...that means (oh dread) deferred gratification!

Thanks Tom, that's a good idea to consider.

 

[ZoneIII]

Why not just buy a used densitometer. They are going for incredible prices on eBay now that so many labs are closed down. In fact, even though I have had one for many years, I picked up another one on eBay just as a spare.

 

[jstraw]

I'd need a color transmission densitometer for use with stained negatives, if I understand correctly.

 

[Tom Hoskinson]

Yes, a color transmission densitometer or a UV transmission densitometer.

 

[Allen Friday]

Why don't you just do a standard zone system test without using a densitometer? Pick the paper you want to print on. Do a maximum black test with a b+f negative. Then print variously exposed negatives to find the one that gives you the first shade of grey above maximum black at the minimum print time to determine your film speed. Go to the View Camera website. Steve Simmons has an article on film testing that goes through it all step by step.

Personally, if I am going to use a densitometer, I will use BTZS as it gets you to the same result much faster and with less wasted material. If I am not using a densitometer, I use the zone system for testing.

 

[jstraw]

Thanks for the pointer Allen.

My real attraction to DBI is for expansion and contraction. I could do any of these testing methods to determine "N" development...and in fact it may prove useful...but if expansion and contraction are going to be handled subjectively then there's really no reason other than determining a baseline for "N," to use sensitometry.

 

[Allen Friday]

Jstraw,

I have done DBI, and it works well. But, I still did the BTZS (or ZS) testing to see how the materials respond to the changes. Also, I still do a ZS meter reading when taking the photo so that I have an idea of the development that is needed before going into the darkroom and so that i can adjust film speed at the time the shutter is opened. I labeled my film n, n+ or n- just as if I was going to do a time and temprature development. I would then process all the N film together, the n- film together and the n+ film together. The DBI was for making vey fine distincions on the negatives. Personally, I found it difficult to mix negatives with very different development times using DBI. I think, but you'll have to check over at the Azo website, that Michael also labels his film for + or - development, even though he uses DBI. Check out his article on DBI in the articles section.

Once you have determined your N deveopment time, you can alsways follow AA's rule of thumb on film speed compensation, which is to 1/3 to 1/2 stop increased exposure for a minus deveopment, and to give the opposite change for contraction development. Of course, it is just a rule of thumb and you will have to test to see if you need to make a different adjustment.