Need Guidance on Getting a Sensitometer

[Tin Can]

I have been busy, but just tested the 1996 X-RITE 331C DENSITOMETER in like new condition, all documentation included with the very handy AC charger adapter Looks like original rechargeable batteries

First null or zero unit, push a button labeled NULL !

Then using the original included step wedge with OE calibration readings from 1996 in ink pen, my reading today match

Next to check if X-RITE 383 SENSITOMETER works, which is less a concern as I have a Stouffer Step wedge and could burn my my own

All made in USA

Great pickup.

What I do is to test all my 'working' film/developer combinations for baseline. Then, when some "unknown to me" film or developer comes along I can compare the new stuff to the known stuff in the comfort my darkroom (with the sensitometer/densitometer) before going outside to do the in-camera tests.

https://www.largeformatphotography.i...light=shanghai

[ic-racer]

[ic-racer]

Next to check if X-RITE 383 SENSITOMETER works, which is less a concern as I have a Stouffer Step wedge and could burn my my own

To plot the results from the sensitometer, you will need to know the values of the step wedge. Is it built-in to the 383? If so you will need to remove it to measure it with your densitometer. I had to do that with my EISCO and Wejex. The EG&G does not have a built-in step wedge. You can use any step wedge you have on the film stage.

[Tin Can]

Found this in old thread

Download it now, before the end...

Basic Photographic Sensitometry by Kodak 2006

https://www.kodak.com/uploadedfiles/...y_workbook.pdf

[ic-racer]

If using that workbook (everyone should read it), it assumes you will know the output of the sensitometer. One can find that, using the principle in post #42 above.

By definition the exposure to produce 0.1 density on a H&D curve for ISO 100 film will always be 8.0 millilux seconds.

Since Logs let us add and subtract, we can change that to the Log of 8 which is 0.9, now that can be subtracted from sensitometer light intensity in log units.

Log of Light Source millulux seconds = 0.9 (by definition for 100 film) + Step Wedge Density that produced 0.1 on the film.

So if you plotted Ilford Delta 100 and find which step of the step wedge in your sensitometer gave you the 0.1.

Say it is step 6, so you have already disassembled the sensitometer and measured step six and got a step wedge density of 2.0

Sensitomter Log Millilux seconds = 0.9 + 2.0 = 2.9 = 800 millilux-seconds

[Jim Noel]

I'm not sure if the original responder really wants a sensitometer,or a densitometer.

[ic-racer]

Sensitometer. Confirmed with PM.

[Bill Burk]

Wow fun thread. Use a sensitometer to find things out about fresh film: your development time. The test you do that results in an ASA parameter match, with fresh film in a standard developer, logically gives you (by trusting the manufacturer) the amount of light which struck the film. So when you meet the parameters then you have calibrated the sensitometer.

Then when you test an unknown film in an unknown developer. I have a roll of 1940’s Super-XX that was nominally 200 (100 old ASA but 200 new ASA). It would have been 200 at the time but depending on fog (If I develop in D-76 1:1), or if I add Benzotriazole to the developer), I expect it to test out as 50 or 100.

The “speed point of a 200 speed film will shift to the right on my graph one stop (0.3 log units) compared to TRI-X, but since the film is unknown due to age, it may shift significantly more.

[Tin Can]

Bill, you have solidified my thoughts on how to use my new gear

This is all new to me and I am an old dog

Thank you!

Set my own standard with new film, then compare and contrast is my understanding

Wow fun thread. Use a sensitometer to find things out about fresh film: your development time. The test you do that results in an ASA parameter match, with fresh film in a standard developer, logically gives you (by trusting the manufacturer) the amount of light which struck the film. So when you meet the parameters then you have calibrated the sensitometer.

Then when you test an unknown film in an unknown developer. I have a roll of 1940’s Super-XX that was nominally 200 (100 old ASA but 200 new ASA). It would have been 200 at the time but depending on fog (If I develop in D-76 1:1), or if I add Benzotriazole to the developer), I expect it to test out as 50 or 100.

The “speed point of a 200 speed film will shift to the right on my graph one stop (0.3 log units) compared to TRI-X, but since the film is unknown due to age, it may shift significantly more.