I just use an old Kodak exposure guide. I think Delta makes them nowadays.
Always good to compare methods, but there are reports about some film holders not able to take film and step tablet (too thick). Also, the OP has one of the following step wedges, and I don't know if they fit into the film holder.
Originally Posted by CPorter
Anyway, I think it may be more realistic to actually photograph the tablet. This way you get the 'real' workflow with meter and camera flare and the difference between meter and the actual exposure, which is a mixture of image-forming and non-image-forming light.
A further method is to do it all in the darkroom, using the enlarger. After fitting a large-format lens to the enlarger, this works well, but it has the same advantage or disadvantage as placing the tablet into the film holder.
I use a Stouffer 4x5 inch 31 step transmission wedge in the following way.
First, I place the wedge in a negative carrier and backlight it with evenly diffused light, with all stray light around it blocked off to prevent excessive flare. Then I photograph the step wedge with the film and camera I'm testing, using only the central portion of the negative, regardless of format. Since the Stouffer wedges are 10 stops, I meter the backlight without the wedge in place, and then set the exposure at 5 stops greater exposure than the backlight. This places the middle step(s) of the Stouffer wedge at medium gray, or what a Zone System user would call Zone V. It also gives a scale that reaches +/- 5 stops from middle gray, enough to cover 99% of shooting situations. I bracket if I feel I need more than the 10 stop range to test for unknown film speed or other factors.
I develop the film and then place it in the enlarger I use for printing. I project the negative of the step wedge onto the baseboard and focus, then read the steps with a Darkroom Automation Enlarging Meter. This gives me relative readings in stops (to 0.01 stop resolution) for each wedge, which is easily converted in a spreadsheet to optical density by multiplying by 0.30. The reason I use only the central 1/3 or so of the negative is to minimize light falloff in the enlarger. With the spreadsheet it's very easy to calculate fb+f and find where the Zone I density falls. The spreadsheet can draw a graph and calculate your choice of contrast indicators.
As Ralph indicates, this is a real end-to-end test of the process. It's also a very quick and easy way to add a one frame process control strip to any single sheet or single frame of roll film.
I have a Stouffer 4x5 21 step tablet and the film and the tablet fits my Fidelity Deluxe holders just fine--those are the only holders I have so I can't speak for any other holders.
Originally Posted by RalphLambrecht
I understand fully there is a difference of opinion in how the wedge should be exposed. I can only say that I have enjoyed very fine negatives with this testing procedure and I can't honestly say the arguments I have seen (we have seen in other threads) are compelling enough to redo my tests. My negatives I'm producing just do not indicate a need for change.
Thanks for your input though, always appreciated.