How to measure approximate film speed with a step wedge?

MCB18 said:

I’d love to make H&D curves for each developer with some films, but unfortunately I don’t have a densitomiter to do it.

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There are plenty of alternatives to a densitometer -- and you might already have one. If you have a hand-held meter it might have an enlarger attachment. Since you have an enlarger, do you have an enlarger meter? If not, these start at around $10. Color analyzers can also be used. Some of these are more fine-tuned than others -- hand-held meters are usually in 1/3 increments -- but that should work fine for your purposes, just like your step table.

Might want to check this out.


or this

Using just eyedropper tool with the photo you uploaded, this is what the graph looks like to me.

You might get better estimates looking at the negative and original scale by eye.

If you have an enlarging meter such as Ilford EM-10 or Omega CS-10 you could read a null on the scales for better comparison.

But it looks like very contrasty, you might cut down development time next time.

Bill Burk said:

Using just eyedropper tool with the photo you uploaded, this is what the graph looks like to me.

You might get better estimates looking at the negative and original scale by eye.

Click to expand...

That's what I'd also do, BUT make sure to make a photo or scan that doesn't suffer from strong flare and reflections, like the photo posted earlier in the thread.

Hi all,
Thanks for your generous attention and time!

(And thanks/sorry to OP for letting me dip into your thread. It seems we are benefiting from similar questions/stages of development, and the generous community here!)

I intend to do the test again when I am organized for my next film development, and do it more carefully.

I scanned this on the Epson V500. I was tempted to adjust settings to make the whole strip more visible. I am afraid that the Epson software may have made the adjustments anyway, given the image that was included.

I do have an X-rite 331 densitometer that produces somewhat erratic and inconsistent readings, but if I make a series of readings on I can eliminate some of the errata and inconsistent readings from.

I don't have photoshop, but the Epson-scan software does have a preview eyedropper ("densitometer") tool.

Here are some of the uncorrupted and readable ("before") values from use of that tool: (Are these reliable densitometer readings?)

19: 129
18: 138
17: 149
16: 161
15: 173
14: 182
13: 192
12: 200
11: 207
10: 213
9: 220
8: 223
7: 226
6: 229
5: 231
4: 232

The film base has a reading of 236