Quick & easy film test question

[Alex Benjamin]

Plotting my first film curves. Got my film, got my step wedge, got my enlarger (Durst CLS 501 color head), borrowed a densitometer. Going to test T-Max 100 in Rodinal (I'm crazy that way).

Question: do I need an 80A filter under the enlarger lens? Kodak Basic Photographic Sensitometry Workbook says yes, I've read elsewhere that with modern film, not so much.

Follow up: if I don't put one (as I don't have one), how far off are my numbers going to be.

Thanks.

 

[Terrence Brennan]

They may be off a bit. You will probably be using a lamp with a colour temperature of 2800-3200K, which would be closer to available light, in terms of spectral response.

When I make sensitometric exposures, using a modified B-22 enlarger, with the said modificiation being a small electronic flash in place of the regular lamphouse, I use a filter pack consisting of a Wratten 2B filter, a Wratten 81A filter and the appropriate Wratten ND filter to give an exposure of a single "pop" of the flash, with a 50mm lens set at f/8.

The flash is enclosed in a simple lamphouse, made of the same sheet metal used for heating ductwork, and it is constructed using the thin silver duct tape used to seal ductwork.