Sensitometer Calibration: Synchronizing In Camera Data with Sensitometer Data

ic-racer · Mar 22, 2025

So, to test the Matrix cameras in Matrix mode (F100, F6, N80, N75, N55) which are not expecting all the zones to be equally illuminated with a test source, I made up some DX cassettes of varying exposure index and just took pictures (about 200ft HP5 over a couple years).

Indeed the 250 negatives look a little too dense to my eye with HP5 on these cameras in Matrix mode.

It is not hard to imagine what happend next, I just started using 400 on all cameras, irrespective of metering mode, even though for 40 years I NEVER exposed ISO 400 film with a 400 EI.

ic-racer · Mar 22, 2025

So, this will bring it full circle.

One might think if I like, say EI250 for HP5 (2/3 over exposure) can't I just add the 2/3 exposure to any other unknown film?

What about the SVEMA film? It is billed as 800. So just exposue at 500 and be happy?

That didn't work. Because the 800 rating of SVEMA is likely based on ISO 7892:1986.

Also, the SVEMA was purchased to make 72 exposure loads for my Rolleiflex SL3003 with it's 72 exposure film back. That is the camera from the Zone I test from 1987 shown in post #15 above.

Everything is all set up to go. All is in place to just make a step wedge exposure on the SVEMA, plot it on the shifted baseline spreadsheet from post #5 above and I will instantly have an exposure index comparable to what I was doing with that Rolleiflex back in the 1980s and 1990s. I have not had time to do the test yet.

Bill Burk · Mar 22, 2025

ic-racer said:
The story is a little more convoluted too, because near that same time I got a bunch of late-model Nikons with Matrix metering. That 'black box' system appears to add extra exposure in difficult situations. This DOES seem to give good negatives in my darkroom with HP5 at 400.

So, nothing to suggest the ISO rating is wrong, just with the new added features of my spreadsheet, (shifting the curve) turned out to be a very easy way to calibrate the system to match my old negatives and allow for similar interpretations of unknown films (specifically 200ft of Svema I just got) without any in-camera testing. I see nothing wrong with the mathematic provisions suggested by Stephen above, just that my spreasheet isn't configured to shift things that way.

Those are limitations from doing my spreadsheet in Apple Numbers. Which brings up another part of the back story: What ever happend to Aparat's software? I actually had given up on my own spreadsheet a few years ago, waiting for his software to appear. When I got the 200ft of Svema I needed to evaluate it and had to re-created my spreadsheet from scratch in Apple Numbers.

I'm trying to solve my problem with Adobe software, I had CS and designed my graphs in InDesign. Now can't install CS because they turned off the phone registration system. They want something like $1,000 a year for subscription and I don't use it often enough to justify. Next time I design some graphs I think I'll use TeX. Anyway they're all PDF so I can print out as many as I want.

Let me know your raw numbers and I can try to graph it in pencil.

Of course! Matrix metering is going to work perfectly with ISO. I play with EI all the time. You probably saw lots of my blather about how my ES-II always gets tricked by a catchlight in the frame. I rely on downrating to avoid underexposure with that camera.

Anyway it's important to have your sensitometry for your unknown film arrive at the actual film speed (the speed that would work for Matrix), then shift EI according to the project de jur.

Bill Burk · Mar 22, 2025

Last Sunday a friend from Threads mentioned he'd be in town, so we met up at a coffee shop.

His specialty is intentional camera movement (ICM). His abstractions of California's famous scenery reminds me of the impressions that I feel after looking at some of my own slide shows. Even though my photos are sharp, after you see them the mental image isn't sharp.

I brought Super-XX expired November 1952 which I have tested with the EG&G to be EI between 2 and 4. I knew this would be the right film for the day.

I was shooting ES-II at the lowest possible setting (speed 20 and 4X compensation) with a yellow filter. Getting speeds like 1/2 second f/16 with shutter speed varying dramatically as I aimed northward vs southerly across the beach, or as more or less sky was included.

Wanted speeds like 5 seconds. I forgot about the "Pedestrian's Foot" experiment. I could've used B.

Bill Burk · Mar 22, 2025

May I suggest you label the column headers "ZS W-Speed" and "ZS Delta-X Speed"? That would encapsulate your intentions.

Bill Burk · Mar 22, 2025

ic-racer said:
So, to test the Matrix cameras in Matrix mode (F100, F6, N80, N75, N55) which are not expecting all the zones to be equally illuminated with a test source, I made up some DX cassettes of varying exposure index and just took pictures (about 200ft HP5 over a couple years).

Indeed the 250 negatives look a little too dense to my eye with HP5 on these cameras in Matrix mode.

It is not hard to imagine what happend next, I just started using 400 on all cameras, irrespective of metering mode, even though for 40 years I NEVER exposed ISO 400 film with a 400 EI.

It's so funny that you went the opposite way from me but arrived at the same point. I was so disappointed with thin negatives at 400 in the ES-II and OM-4 that I got into all this sensitometry and put the cameras at 250 based on the convoluted stories we've told each other.

And it's not just that ZS is 2/3 stop less than ISO.

I set the camera to 250 for intentionally denser average negatives, insurance so to speak.

ic-racer · Mar 22, 2025

Bill Burk said:
May I suggest you label the column headers "ZS W-Speed" and "ZS Delta-X Speed"? That would encapsulate your intentions.

Good idea.

Sensitometer Calibration: Synchronizing In Camera Data with Sensitometer Data

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