Hi O'Malley
Autotype, Murakami, Chromaline, and other emulsion makers provide Exposure Calculators that use a "stepped" grey density filter instead of a sliding opaque step wedge sheet.
This allows you to still shoot 5 different test exposures at once without having to intervene and move a sliding opaque cover sheet accross a target pattern.
One of the grey rectangle filters blocks half the light (.5), another blocks 30% of the light (.7), another blocks 10% of the light (.9), etc.
So, if you line up the grey filter film to the ganged test pattern film and shoot a screen at 10 min. for example,
if after washout the ".5" area looks better than the others, a suggested correct exposure time is 5 min. If the ".7" looks best, it would instead be 7 min.
Note that your calculator uses a superbly sharp and dense test pattern film; but most of our customers use their inkjet or laser quality film which may not expose the same.
We'll often then recommend that they make up and output their own test pattern gang and use the grey filter film on that to better represent the type of most common image detail and film density that you'll be doing.
For those interested, here's a link to the archtype in "step wedges" for all printing industries.
Transmission Step Wedges
Happy trails!
exposure calculator ? 
