Sensitometry. Testing film. Help.

jejes · May 16, 2023

After a lot of readings, i have my Densitometer, and my Stouffwedge 21 step. But need to expose my 135 film with the stouffer:

Options:

1. In 4x5 camera, film holder inside stoufer sticked to the film. Problem lens flare.
2. Enlarger, problem i don't have a filter (81B i'm not sure) to convert to 5600K.
3. Sensitometer, the one i found on ebay is only G/B LED Xrite, and it supossed not to be valid to test film, due to limited of spectrum.

Any suggestion??
Sorry for my English

ic-racer · May 16, 2023

The LED sensitometers work great for process control. That is, for making your own B&W control strips.

ISO testing is a whole can of worms.

jejes · May 16, 2023

ic-racer said:
The LED sensitometers work great for process control. That is, for making your own B&W control strips.

ISO testing is a whole can of worms.

Yes, I would like all the sensitometry. This is what I want to know. I have seen the sensitometry video from the naked photographer

peoplemerge · May 16, 2023

Read Beyond the Zone System by Phil Davis. It has all the testing theory that you need to understand sensitometry.

Alan9940 · May 16, 2023

Personally, I don't use a step wedge to determine a personal EI for any film. To my mind, it's better to create an exposure series in-camera, thereby removing variables such as lens flare, camera flare, shutter speed variance, etc. There are many ways to test film, but here's what I do:

1. On a cloudless day around noon, I setup a black card in open shade (not under a tree, for example, you want shade open to the sky)

2. For a film with box speed of 100, for example, I set my meter for ISO 25, meter the card, then chose a lens/aperture combo 4 stops less exposure. What you're doing here is moving a mid-gray Zone V exposure value down to Zone 1.

3. Make an exposure, close (edit: I incorrectly wrote open initially) the lens 1/2 stop, make another exposure, open 1/2 stop, expose, etc, until you've exposed for one stop over the box speed.

4. Process the film as you normal would and, when dry, you're looking for the frame that's at or close to 0.10 over fb+f (film base + fog). You should zero out the densitometer for the fb+f on a clear area of film.

This all sounds more complicated than it is to do.

Good luck.

P.S. Not clear if you're asking about sensitometry or densitometry, since you mention both terms in your post. These are two very different things.

jejes · May 16, 2023

Alan9940 said:
Personally, I don't use a step wedge to determine a personal EI for any film. To my mind, it's better to create an exposure series in-camera, thereby removing variables such as lens flare, camera flare, shutter speed variance, etc. There are many ways to test film, but here's what I do:

1. On a cloudless day around noon, I setup a black card in open shade (not under a tree, for example, you want shade open to the sky)

2. For a film with box speed of 100, for example, I set my meter for ISO 25, meter the card, then chose a lens/aperture combo 4 stops less exposure. What you're doing here is moving a mid-gray Zone V exposure value down to Zone 1.

3. Make an exposure, open the lens 1/2 stop, make another exposure, open 1/2 stop, expose, etc, until you've exposed for one stop over the box speed.

4. Process the film as you normal would and, when dry, you're looking for the frame that's at or close to 0.10 over fb+f (film base + fog). You should zero out the densitometer for the fb+f on a clear area of film.

This all sounds more complicated than it is to do.

Good luck.

P.S. Not clear if you're asking about sensitometry or densitometry, since you mention both terms in your post. These are two very different things.

Yes, sensitometry was to create o reproduce the step wedge on my film, and of course densitometry because I want to characterize the density curve of my film.

I think your system it’s way better. Because I don’t need step wedge in film.

On your step 2. You are setting iso 25 2 stops under rated iso. And then 4 stop less. Are a total of 6 stops from base iso?

Thank you

peoplemerge · May 16, 2023

I like the step wedge film method because I like to use multiple film types, experiment with different developers, and I switch to different cameras. I like plotting film and paper curves and the math appeals to me (I’m a data engineer of sorts).

Then I follow @Alan9940 ’s process to eliminate those other variables but I only need to shoot one frame on a gray card to calibrate the camera along the curve. The drawback in my adaptation is it doesn’t correct for shutter speed inaccuracies, so instead, I use a shutter speed tester so I know what’s what. At first I made an effort to make sure all my shutters were spot on or I’d have them repaired but now I’ve given up on that because I like working with the limitations of vintage gear. Shutter slow on slower speeds? I go by ear or on bulb.

jejes · May 16, 2023

peoplemerge said:
I like the step wedge film method because I like to use multiple film types, experiment with different developers, and I switch to different cameras. I like plotting film and paper curves and the math appeals to me (I’m a data engineer of sorts).

Then I follow @Alan9940 ’s process to eliminate those other variables but I only need to shoot one frame on a gray card to calibrate the camera along the curve. The drawback in my adaptation is it doesn’t correct for shutter speed inaccuracies, so instead, I use a shutter speed tester so I know what’s what. At first I made an effort to make sure all my shutters were spot on or I’d have them repaired but now I’ve given up on that because I like working with the limitations of vintage gear. Shutter slow on slower speeds? I go by ear or on bulb.

how do you get your step wedge on your film? with camera?

Alan9940 · May 16, 2023

jejes said:
On your step 2. You are setting iso 25 2 stops under rated iso. And then 4 stop less. Are a total of 6 stops from base iso?

Thank you

After testing, I usually arrive at a personal EI below the box speed of the film. Therefore, I like to start my testing at 2 stops of over-exposure vs box rating. Therefore, if you set your meter for ISO 25 (for a 100 speed film), then make a reading the meter will give you an exposure for middle gray (Zone 5). All meters work this way. You need 4 stops less exposure from middle gray to hit Zone 1. This zone is your target for measuring with a densitometer.

Re-reading my own post, I see that I did make an error in step 3. You want to CLOSE down the aperture for each exposure after the first. The idea is the first exposure should be significantly denser than needed, followed by progressively lighter frames. At one stop over the box speed, you'll probably have only blank film. Important note: do a dry run of your apertures to ensure you don't run out before completing the series.

Does this clear things up?

jejes · May 16, 2023

Alan9940 said:
After testing, I usually arrive at a personal EI below the box speed of the film. Therefore, I like to start my testing at 2 stops of over-exposure vs box rating. Therefore, if you set your meter for ISO 25 (for a 100 speed film), then make a reading the meter will give you an exposure for middle gray (Zone 5). All meters work this way. You need 4 stops less exposure from middle gray to hit Zone 1. This zone is your target for measuring with a densitometer.

Re-reading my own post, I see that I did make an error in step 3. You want to CLOSE down the aperture for each exposure after the first. The idea is the first exposure should be significantly denser than needed, followed by progressively lighter frames. At one stop over the box speed, you'll probably have only blank film. Important note: do a dry run of your apertures to ensure you don't run out before completing the series.

Does this clear things up?

Yes, thank you. Do you use a excel sheet? Or do you use plot application

Sirius Glass · May 16, 2023

Alan9940 said:
After testing, I usually arrive at a personal EI below the box speed of the film. Therefore, I like to start my testing at 2 stops of over-exposure vs box rating. Therefore, if you set your meter for ISO 25 (for a 100 speed film), then make a reading the meter will give you an exposure for middle gray (Zone 5). All meters work this way. You need 4 stops less exposure from middle gray to hit Zone 1. This zone is your target for measuring with a densitometer.

Re-reading my own post, I see that I did make an error in step 3. You want to CLOSE down the aperture for each exposure after the first. The idea is the first exposure should be significantly denser than needed, followed by progressively lighter frames. At one stop over the box speed, you'll probably have only blank film. Important note: do a dry run of your apertures to ensure you don't run out before completing the series.

Does this clear things up?

That already biases the results. Start at box speed.

peoplemerge · May 16, 2023

jejes said:
how do you get your step wedge on your film? with camera?

I lay film emulsion side up, place the step wedge, then cover with a sheet of glass like you would for a contact print. With curly films, I tape the ends of the step wedge to the film.

I have the enlarger set up with the exact parameters concerning enlarger height, pure white color, full intensity / white (0/0/0). I use the same lens at the same distance from the (empty) film plane. I think in finding that reference point, I used a light meter to discover middle gray at iso 200. At first I used a generic timer set to 0.3 sec, then switched to a metrolux which works by measuring light emissions.

There is a Windows program Plotter that allows you to put in densities and it will plot curves and figure ASA triangle for you. Again, BTZS will familiarize you with the methodology.

Alan9940 · May 17, 2023

jejes said:
Yes, thank you. Do you use a excel sheet? Or do you use plot application

I don't plot curves like many folks. I find a personal EI for my equipment and processing, test for proper development time, then go shoot pictures. I should probably mention that I shoot mostly B & W.

Alan9940 · May 17, 2023

Sirius Glass said:
That already biases the results. Start at box speed.

Not exactly sure what you mean. The series of exposures I make are intended to provide fairly gross over-exposure through box speed to one full stop under-exposed. Personally, I've never had an EI result above box speed, but I have had it be 1 1/2 stops less than box speed.

RalphLambrecht · May 17, 2023

jejes said:
After a lot of readings, i have my Densitometer, and my Stouffwedge 21 step. But need to expose my 135 film with the stouffer:

Options:

1. In 4x5 camera, film holder inside stoufer sticked to the film. Problem lens flare.
2. Enlarger, problem i don't have a filter (81B i'm not sure) to convert to 5600K.
3. Sensitometer, the one i found on ebay is only G/B LED Xrite, and it supossed not to be valid to test film, due to limited of spectrum.

Any suggestion??
Sorry for my English

admittedly a laborious process but, I haven't found a more accurate method yet.

jejes · May 17, 2023

RalphLambrecht said:
admittedly a laborious process but, I haven't found a more accurate method yet.

I want to use the elaborate and precise, but i need two answer.

1. The best way to expose my film with my step wedge (film camera holder, enlarges or sensitometer)
2. The tool to put the data read by the densitometer (of course i have a densitometer). Need a XLS or google sheet, or use the plotter of BTZS. I have discovered this fantastic tool https://bnxvs.shinyapps.io/cc_film_plot/ i will use.

Thank You to all

Stephen Benskin · May 17, 2023

Don't worry about film speed. Unless you have a calibrated sensitometer, the best you can do is relative speed. Better to field test to find what best works for you. The reason to plot curves is to determining processing. The best method is a sensitometer , calibrated or not calibrated. The next best is contacting under an enlarger. The third is contacting in a camera. The problem with the camera is off axis light fall off. Shooting a step tablet introduces uncontrolled flare which you don't want as part of the testing process.

Don't just read up on how to expose and plot curves. To fully utilize sensitometry, you need to understand the theory too. Phil Davis does a good job of combining the two, but be wary of his idiosyncrasies.

Andrew O'Neill · May 17, 2023

I prefer contact printing a step wedge to film, under an enlarger. Then make curves to determine EI, dev times, and with this data, test a sheet or two out in the field. This method has worked well for me for years...

jejes · May 17, 2023

Stephen Benskin said:
Don't worry about film speed. Unless you have a calibrated sensitometer, the best you can do is relative speed. Better to field test to find what best works for you. The reason to plot curves is to determining processing. The best method is a sensitometer , calibrated or not calibrated. The next best is contacting under an enlarger. The third is contacting in a camera. The problem with the camera is off axis light fall off. Shooting a step tablet introduces uncontrolled flare which you don't want as part of the testing process.

Don't just read up on how to expose and plot curves. To fully utilize sensitometry, you need to understand the theory too. Phil Davis does a good job of combining the two, but be wary of his idiosyncrasies.

But to contact In an enlarger must I utilize filter to convert tungsten to Daylight. To find optimal time exposure, wich density must i read in the copy of my Stouffer? To look for a perfect exposure, for example 8 step must be 0.90 ?

jejes · May 17, 2023

Andrew O'Neill said:
I prefer contact printing a step wedge to film, under an enlarger. Then make curves to determine EI, dev times, and with this data, test a sheet or two out in the field. This method has worked well for me for years...

Please, To find Perfect time and aperture in enlarger I have a problem my enlarger doesn’t have times shorter than 1 sec.

albada · May 17, 2023

jejes said:
Please, To find Perfect time and aperture in enlarger I have a problem my enlarger doesn’t have times shorter than 1 sec.

You could remove the lens of a film-SLR camera and hold it up to the enlarger's lens. Firing the shutter with the enlarger on will produce a brief light-pulse.
Warning: I have not tried this idea.

xkaes · May 17, 2023

jejes said:
After a lot of readings, i have my Densitometer, and my Stouffwedge 21 step. But need to expose my 135 film with the stouffer:

Did all that reading include Richard Henry's "Controls in Black & White Photography"? He describes how to set up your own tests. You start with developing your paper. Exposing the film comes last.

Bill Burk · May 17, 2023

jejes said:
But to contact In an enlarger must I utilize filter to convert tungsten to Daylight. To find optimal time exposure, wich density must i read in the copy of my Stouffer? To look for a perfect exposure, for example 8 step must be 0.90 ?

Must? No. Should? Yes.

Easily you could get an 80B bluish filter to have a better chance of getting repeatable and comparable results. So you should get a filter. It can be old and scratched.

Which density to read? Honestly doesn’t matter. If you get step 21 to approach zero above base & fog then all the other steps will have a meaningful value.

peoplemerge · May 17, 2023

If your enlarger only supports 1 sec minimum, that’s fine. Position the enlarger height so after development, for a medium speed film, you get middle gray around the middle of the step.

peoplemerge · May 17, 2023

I wouldn’t bother calibrating the enlarger for white light. I’ve always set the color knobs to 0/0/0, or used a condenser that isn’t equipped with color.

Sensitometry. Testing film. Help.

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