Adventures in film characteristic analysis

Nodda Duma · Feb 19, 2022

On the topic of flare (or veiling glare, depending on who you talk to), and since I’m testing a prototype lens build in a couple weeks for veiling glare, the standards are fresh in my memory:

For industry-accepted testing of veiling glare or lens flare, we use these standards

For characterizing lenses that can be removed from the camera body, ISO 9358

For characterizing lenses integral to the camera body (ie a cell phone camera), refer to ISO 18844.

radiant · Feb 26, 2022

Ok, new tests.

This time my main purpose was to check if my HP5 time for pushing it to 1600 is fine for next developments. But then I got idea that hey, lets add some Foma to the same batch. So everything here exposed + developed the same. I changed the exposure scheme on my device so that bottom half is exposed with half stop interval and upper part is as previously, one stop apart. That is 0.15 and 0.3 for you logaritmic lunatics

All are exposed at same EI 400. That is the step 8 is at 18%. Yes I know Foma 100 isn't ISO 400 film. (neither is Foma 400)

Developed XT-3, time 20 minutes (I know) and agitation every 30 seconds.

The results again look a bit strange. Foma 400 seem to be behaving very badly, could this be correct? I haven't done any other analysis because I (again) start to question my measuring methods

Data attached.

radiant · Feb 26, 2022

I remind separtely: all strips exposed at EI 400.

This causes Foma 100 to have more longer shoulder previous graph because it is getting two stops more exposure. That is wrong. I feel a bit bad for Foma 100. So that is why I corrected just not to bash Foma 100 too much.

And of course Foma 100's contrast is increased quite a bit because of that excessive development.

This graph is for entertainment purposes only!

Adrian Bacon · Feb 26, 2022

radiant said:
Ok, new tests.

This time my main purpose was to check if my HP5 time for pushing it to 1600 is fine for next developments. But then I got idea that hey, lets add some Foma to the same batch. So everything here exposed + developed the same. I changed the exposure scheme on my device so that bottom half is exposed with half stop interval and upper part is as previously, one stop apart. That is 0.15 and 0.3 for you logaritmic lunatics

All are exposed at same EI 400. That is the step 8 is at 18%. Yes I know Foma 100 isn't ISO 400 film. (neither is Foma 400)

Developed XT-3, time 20 minutes (I know) and agitation every 30 seconds.

The results again look a bit strange. Foma 400 seem to be behaving very badly, could this be correct? I haven't done any other analysis because I (again) start to question my measuring methods

View attachment 299342

Data attached.

Foma films in general aren't particularly good with Ascorbic Acid based developers. For your purposes, I'd ignore your Foma results and concentrate on the HP5 results.

radiant · Feb 26, 2022

Adrian Bacon said:
Foma films in general aren't particularly good with Ascorbic Acid based developers. For your purposes, I'd ignore your Foma results and concentrate on the HP5 results.

Ok, I didn't know that! I also learned today that HP5 isn't that good with Rodinal, a bit horrible. I probably messed up very good shots because of this. Damn.

The Foma results were just for fun, just to see what happens.

Adrian Bacon · Feb 26, 2022

radiant said:
Ok, I didn't know that! I also learned today that HP5 isn't that good with Rodinal, a bit horrible. I probably messed up very good shots because of this. Damn.

The Foma results were just for fun, just to see what happens.

Yeah, my experience has been with XTOL. You get a reasonable amount of toe speed, and the grain doesn't look bad, but from the midtones to the highlights, it tends to just keel over and get flat. It's nowhere near straight and a wonky looking curve, as you're seeing in your results.

radiant · Feb 26, 2022

Adrian Bacon said:
Yeah, my experience has been with XTOL. You get a reasonable amount of toe speed, and the grain doesn't look bad, but from the midtones to the highlights, it tends to just keel over and get flat. It's nowhere near straight and a wonky looking curve, as you're seeing in your results.

Sorry if I get lost in translation but do you mean XTOL + HP5 is bad combo too? Or were you talking about Foma?

Adrian Bacon · Feb 26, 2022

radiant said:
Sorry if I get lost in translation but do you mean XTOL + HP5 is bad combo too? Or were you talking about Foma?

Just Foma 100 and 400. Foma 200 renders pretty good in XTOL. HP5 doesn't really exhibit any undesirable traits in XTOL.

radiant · Feb 26, 2022

Adrian Bacon said:
Just Foma 100 and 400. Foma 200 renders pretty good in XTOL. HP5 doesn't really exhibit any undesirable traits in XTOL.

Ok, that is what I have understood in general.

Yes one can see Foma 400 + XT combo awfulness in my graph without any number crunching. Low contrast in genral and highlight compression kicks pretty early.

Is such small difference in my graphs (between Foma 100 and 400) because there is actually just 60-80 ISO difference (0.7 to 0.85 stops) to Foma 100 in real ISO?

Adrian Bacon · Feb 26, 2022

radiant said:
Is such small difference in my graphs (between Foma 100 and 400) because there is actually just 60-80 ISO difference (0.7 to 0.85 stops) to Foma 100 in real ISO?

Foma 100 tends to actually be closer to 125/160 in XTOL, and 400 tends to be more like 200-250 in XTOL. Others have speculated that they're actually the same film. I don't think that's the case, but they are very similar in a lot of other aspects.

radiant · Feb 27, 2022

Adrian Bacon said:
Others have speculated that they're actually the same film. I don't think that's the case, but they are very similar in a lot of other aspects.

Well, from my (single) test you can see answers to both; not the same film but very similar. I mean amazingly similar. I really expected they are more different.

Bill Burk · Feb 27, 2022

I’ll take a look this looks like fun.

Please do a series of same film same exposure series and different development times. Just stick your fingers in the tank pull out the reel, rip off a foot of film and drop it in the stop/fix at intervals until the last strip gets the longest time. The exact series of time is not critical. You just want meaningful results from barely developed through developed more than usually necessary.

Then a time-contrast curve may be derived.

I have marked strips by slitting a nick with scissors as I made the exposures. It was painfully awkward loading the reel as you can imagine film kept jumping the track at each slit. But it was easy pulling and tearing a strip at a time.

radiant · Feb 27, 2022

Bill Burk said:
I’ll take a look this looks like fun.

Please do a series of same film same exposure series and different development times. Just stick your fingers in the tank pull out the reel, rip off a foot of film and drop it in the stop/fix at intervals until the last strip gets the longest time. The exact series of time is not critical. You just want meaningful results from barely developed through developed more than usually necessary.

Then a time-contrast curve may be derived.

I have marked strips by slitting a nick with scissors as I made the exposures. It was painfully awkward loading the reel as you can imagine film kept jumping the track at each slit. But it was easy pulling and tearing a strip at a time.

I haven't forgotten that you want the development time series! Marking the strips by scissors is a good idea, otherwise it could be difficult to cut from correct position.

I will do that test some day for sure, however I believe there isn't any big surprises (HP5 + Xtol isn't that rare combo )

Bill Burk · Feb 27, 2022

Maybe tabs of tape instead of scissors cuts as you make your way. Like I say it is really hard to get slit-up film onto a reel. Then as you process feel out the tape and cut there with wet scissors, and clean off the scissors later.

radiant · Feb 27, 2022

I forgot to write down base + fog for previous Xtol tests:

HP5 0.35
Foma 100 0.32
Foma 400 0.45

I had to run the density mappings again so I hope I didn't mess anything.

radiant · Feb 27, 2022

Bill Burk said:
Maybe tabs of tape instead of scissors cuts as you make your way. Like I say it is really hard to get slit-up film onto a reel. Then as you process feel out the tape and cut there with wet scissors, and clean off the scissors later.

The previous test was three strips taped together, got those on reel fine. I've been doing double 120 films for years so it seems to come out fine. Maybe cutting + taping together isn't that bad idea. How to get those strips one by one off the plastic reels is probably the hardest and most annoying part..

Craig · Feb 27, 2022

radiant said:
I forgot to write down base + fog for previous Xtol tests:
HP5 0.35

When I did my testing the film base +fog for that combo at normal developing time was around 0.07. Extending the developing time to 16 min it came up to 0.1.
Delta 100 in Xtol was about 0.15.

Bill Burk · Feb 27, 2022

Show of hands for those who say Foma 400 isn’t a 400 speed film. Is that everybody?

@radiant developed in XT-3 for 20 minutes. That’s the developing time which made that Foma 400 hit within tolerance of the ASA triangle.

Foma 100 and HP5+ are far overdeveloped in that same run, they reached CI at or above 0.80

You are seeing the correct normal developing time for Foma 400 and time for pushing Foma 100 and HP5+

I don’t specialize in analyzing speed you get by pushing, so I am not sure what you got there, but they are pushed for sure.

Bill Burk · Feb 27, 2022

Adrian Bacon said:
Foma 100 tends to actually be closer to 125/160 in XTOL, and 400 tends to be more like 200-250 in XTOL. Others have speculated that they're actually the same film. I don't think that's the case, but they are very similar in a lot of other aspects.

@radiant showed that the time to develop Foma 400 to ASA specifications is the same as the time to push Foma 100 to practically 400.

radiant · Feb 28, 2022

Craig said:
When I did my testing the film base +fog for that combo at normal developing time was around 0.07. Extending the developing time to 16 min it came up to 0.1.
Delta 100 in Xtol was about 0.15.

I probably need to cross-check my data. I forgot to take base+fog readings at first time and needed to re-do everything so there is possibility that I messed something up. I'm using stouffer scanned at the same time with the strip as measurement tool so it is a bit more complex system

radiant · Feb 28, 2022

Bill Burk said:
Show of hands for those who say Foma 400 isn’t a 400 speed film. Is that everybody?
@radiant developed in XT-3 for 20 minutes. That’s the developing time which made that Foma 400 hit within tolerance of the ASA triangle.
Foma 100 and HP5+ are far overdeveloped in that same run, they reached CI at or above 0.80
You are seeing the correct normal developing time for Foma 400 and time for pushing Foma 100 and HP5+
I don’t specialize in analyzing speed you get by pushing, so I am not sure what you got there, but they are pushed for sure.

Thanks again Bill for plotting it out. I need to learn do the same, I was thinking of some javascript-tool which would do that from the data. Your graph is a bit low on the resolution btw, it is just about readable of course.

Foma 400 at ASA triangle with that time? Wow, that wasn't anything I expected. I'm glad I added some Foma in the same batch! Now we know how to develop Foma 400 in Xtol

I'm not really trying to gain speed by "pushing" HP5 - I've done it for the style; deep shadows mainly. I've tried to aim for really contrasty negatives really. So basically I'm overdeveloping to gain the normal contrast. Could the analyze be done by just shifting the data by 0.6 (or two stops)? I mean my aim for this test is to confirm that my development time fixes the contrast back to ASA triangle, or a bit over.

Adrian Bacon · Feb 28, 2022

Bill Burk said:
@radiant showed that the time to develop Foma 400 to ASA specifications is the same as the time to push Foma 100 to practically 400.

i can’t see which is which on your graph. I’ll have to look again when I’m on a device with a bigger higher resolution screen.

Adrian Bacon · Feb 28, 2022

radiant said:
Foma 400 at ASA triangle with that time? Wow, that wasn't anything I expected. I'm glad I added some Foma in the same batch! Now we know how to develop Foma 400 in Xtol

yes, you get decent toe speed, but the highlights keel over and get flat. I couldn’t get Foma 400 to go much over 2.0 density, and I was blasting it with so much light it was piping light into adjacent frames

radiant · Feb 28, 2022

Adrian Bacon said:
yes, you get decent toe speed, but the highlights keel over and get flat. I couldn’t get Foma 400 to go much over 2.0 density, and I was blasting it with so much light it was piping light into adjacent frames

That is the "feature" on Foma 400. Nice flat and contrast free highlights! Very good for dull sky photography

radiant · Feb 28, 2022

I made this kind of graph tool which could be extended for characteristic plotting / analysis. All code done by me so easy to add features. Any ideas?

Try clicking on the graph, you get the line tool. It shows some data below the graph.

https://jouni.kapsi.fi/filmgraph/

Adventures in film characteristic analysis

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