Test procedure for even development?

[laser]

Keep it simple.


A lens formed image like one produced by an enlarger or camera will have Cosine to the 4th falloff.

An easy technique that is free of the optics problems is to use low wattage incandescent lamp i.e. 7.5 watt, four or more feet from the film. A dimer is useful to lower the output. Control the time with an electric timer.

A density of 1 to 1.2 will make it easy to see the differences.




Expose to a mid-scale density.

 

[ic-racer]

I was going to say that is awful - makes using an enlarger for sensitometer look like a bad idea.

Until I realized. I keep the enlarger locked at the height to make an 11x14 print from 4x5 neg. So I am only using the sweet spot near the middle.

I placed the film squarely under the lens, but positioned the test strip on the left-hand side - so maybe I fortunately avoided the hot-spot at dead center.

And I am using a grid light source, not condenser.

What is your light source (does the lens really have a hot spot in the middle or do condensers play into it)?

The example shown is a cold cathode source originally used for graphic arts printing. I subsequently modified it somewhat for continuous tone printing, though, I keep it only as a spare. One modification was to use that piece of film shown (exposed under the enlarger) as a center filter above the negative to even out the light. Other modifications involved mounting the cold cathode closer to the negative and enlarging the orifice of the mounting plate.