Got Stouffer Step Wedge - Now What Do I Do With It?

[Alex Hawley]

Got a Stouffer transmission step wedge. Though this was the hot thing for film testing but there's no directions with it and the ones on their website talk about exposing film from and enlarger? How the heck do you do film development testing with this thing?

 

[Photo Engineer]

Alex, I wrestled with this problem for quite a while!

Start with some Ilford MGIV paper and make an exposure at each grade and watch how the scale changes just like in Cteins "Post Exposure".

An ISO 160 film will take about 1/2 " - 2" at f22 - f32 depending on reciprocity with my enlarger. You might want to start there. You can then compare films by reading density, but the reciprocity will affect the results.

With film, it is best to take pictures of the MacBeth color checker at normal camera speeds. And, you can use Ilford MGIV for this too, at ISO 25.

PE

 

[Alex Hawley]

I'm still missing something Ron, like where to start? Expose a film sheet to a standard gray card, then develop for the assumed "N" time, then expose that negative on paper with the step wedge laying on the paper like you say?

 

[Photo Engineer]

The step wedge is essentially an expanded zone system chart with more than 2x the number of 'zones'. You can read the chart and use it to construct a curve of the film and determine where to place the optimum 'zone' on it.

PE

 

[Alex Hawley]

Think I'm staring to get it through my dense head. Thanks Ron. Anyone else have any sage advice on doing this?

 

[jgjbowen]

Alex,

I use mine with the BTZS manual to do the film and paper curves. Phil Davis' book tells you how to do it.

 

[Bruce Osgood]

step wedge test

Hopefully attached in PDF format is an article written by APUG's noseoil back in '06 on "how to" do simple step wedge testing.

If it's not attached let me know and I'll try again.

 

[Bruce Osgood]

Geeez, I'm getting good, it appears to be attached.

However, I had intended to PM it to you.

 

[Mahler_one]

Alex: I agree with the suggestion about Phil Davis's BTZS book. In addition, I believe that The View Camera Store has an inexpensive DVD which will explain the entire process using a step wedge to derive film and paper speeds. Finally, if you want to short circuit the entire process, call the VCStore and speak with Fred Newman. He can do your film tests inexpensively, and return the data in a graph form that is very simply to understand and apply. Best of luck.

Ed

 

[Alex Hawley]

WOO-HOO. Thanks everyone! Bruce, that pdf was what I was thinking of. Thanks everyone for all the good advice.