 Re: Exposing problems
Hi Lance
There are some situations with screen handling and film-to-emulsion contact issues that can pose goofy results in a step-wedge test.
Since you know that your previous Diazo emulsion was good at 14.5m on a 156t, the Ulano Dual-cure should fall in somewhere around 8-12 minutes on the same mesh.
Your 305 yellow is a finer mesh (thinner emulsion/faster than 156), but is also dyed (filtered UV light/ slower than white mesh), so is a bit of a wash on time difference, but your lamp distance and halogen spectra would make the screen better at the higher time chosen.
In a nutshell, you should expose at 12-14 minutes on the 305 yellow mesh and post-expose the carefully developed image after drying so you can move on.
Once that job is done, on the next screen, I'm going to suggest to cut to the chase and do a more refined test.
(Note that step-wedge tests are best when you're not certain of where exposure time should be accross a broad range of time estimates)
Your new exposure guide should be a test film that you make:
The image should be a 1" x 8" rectangle with a continuous, graduated halftone from 0-100% at your DPI of choice.
Expose it at a time that is your best experienced guess.
If the time is good you'll get good dots from 20% to 80% evenly, for example (10%-90% is even better)
If you're slightly (+1-2 minutes) over-exposed, your dots will appear developed good from 30% to 95%, for example.
If you're slightly (-1-2 minutes) under-exposed, your dots will appear developed good from 10% to 70%, for example.
The best exposure time will be the broadest good quality dot image result from end-to-end.
This film pattern will allow a more exact refinement of time vs. image quality, and can be nested on ALL screens, positioned off to the side where it can be blocked out.
It is then an ongoing test pattern to help you QC image quality and all its variables on an ongoing basis, with no extra work.
Happy trails! | 
