Light set-up for film EI testing...

[Photopathe]

Hi! I am starting to perform film tests to establish personnal/optimal exposure index with both color (negative and reversal) and b&w films. If I usually shoot outside should I perform the tests outdoors or is it perfectly fine to do the tests inside with a flash and flash meter? I read some places that it does matter. I find it more convenient to perform those tests inside with stable controllable light (and comfortable temperatures...).
Thanks!

 

[Paul Howell]

I've read methods for both, as I don't have a densitometer test in open shade with a 18% gray card to find zone V, and then a ring around using a black and white cloth, my wife for skin tone and a gray card, between the 2 I can find a workable E.I. What I've notice is that my newer cameras with electronic shutter and accurate meters usually test at box speed. The only noticeable exception was Ultrafine Xtreme. With aged older mechanical shutters and hearing batters, all over the map.

 

[Mr Bill]

Hi, to just get a usable speed rating I would tend toward testing in the situation where you actually take your photos.

But if you want to make critical comparisons between different materials then probably a controlled (and thus repeatable) setup is better.

Things that might affect your results include the spectral makeup, loosely color, of the light. If the exposure meter doesn't have the same spectral sensitivity as the film then... well, you can probably see where this is going.

In the case of a color film, something that may not be obvious is that there are basically three different color-sensitive layers, and that each layer needs to be more or less "correctly" exposed. These films are generally "balanced" for "daylight," which is considered to have a color temperature of about 5500K. At any other color temperature there will be a tendency for the three layers to become "unbalanced" exposure-wise. So unless you thoroughly understand these effects, and perhaps use color-balancing filters on the camera, you may possibly end up having one of the color layers being underexposed. An actual shooting test under those conditions should show up such a potential problem.

Fwiw an electronic flash typically has a color temperature of about 5500 to 6000K, pretty close to "daylight," so the flash should be a good testing substitute. Assuming the same meter, etc.

If you are shooting color film outdoors, but in the shade, most likely the light will have a higher color temperature, perhaps 8000 to 10000K as an example. This means that bluish light is a larger proportion of the total. So you expect to get a healthy amounts of exposure in the blue-sensitive layer of the film, but... you may be underexposed in the red-sensitive layer. Or if the light has a lower color temperature then the situation is reversed - the blue-sensitive layer would tend to be underexposed.

Anyway, there is a lot to be said for doing the test under your actual shooting conditions.

 

[Bill Burk]

An electronic flash, or an enlarger can make a suitable sensitometer. I would recommend setting up a 'permanent' rigging so that your time spent testing doesn't require inconveniences like reconfiguring your main enlarger.

Definitely the first purchase towards testing should be a Stouffer transmission scale.

This thread tells you all you need to know:
https://www.photrio.com/forum/threads/enlarger-sensitometer.92518/

 

[Photopathe]

Thanks for the replies! All very helpful. Will read the complete thread Bill pointed out tomorrow. Paul's comment made me remember that recommendation to test for each shutter. It makes sense but it feels overwhelming, even discouraging. I shoot 6x6 with a Hasselblad 500 and 3 lenses, 4x5, and 35mm (Rollei 35 and a Chinon). Also after trying quite a few films I finally settled on few ones, but I still intend to use 3 different b&w films.

 

[Photopathe]

Another question: testing using half-stops increments shoudl be good enough (as opposed to thirds)?

 

[Bill Burk]

Half stop increments for the exposure series is fine, then when you interpret you will get your results in third-stops. Third stops are necessary because that's what film speed numbers increment by.

If you want to experience traditional Zone System, then you would test by well-documented methods and the results are only good for that camera, lens, film and paper.

But I think testing shutters should be done separately from testing film.

 

[Photopathe]

If all shutters are recently serviced and reasonably close to each other. Is it good enough to do the film tests with one camera and consider the results good for all cameras and shutters? I assume the answer is not realy...

 

[Bill Burk]

Try a test shutter speed of a half second more or less. This is something you should be able to check with an app based shutter checker. And it’s close to what you would be doing. One consistent test setup is best because it rules out variables.

Then test the shutters later and if they are very far off, mark their actual speeds on a note. When figuring out the f/stop and shutter speed, you often get readings that don’t match the camera marked speed. But they might match the note.

 

[Photopathe]

BTW I should have mentionned that I kind of have a densitometer. I recently got an Analyser 500 for my Ilford Multigrade 500 head and it has a densitometer mode.
For color film I'll do the tests outside on a clear day between 10am and 2pm to get the light those films were balanced for. Will use color-balancing filters later on if I notice a shift in colors when shooting during the golden hour or in shade...
Will report back if you are interested.

 

[RalphLambrecht]

Hi! I am starting to perform film tests to establish personnal/optimal exposure index with both color (negative and reversal) and b&w films. If I usually shoot outside should I perform the tests outdoors or is it perfectly fine to do the tests inside with a flash and flash meter? I read some places that it does matter. I find it more convenient to perform those tests inside with stable controllable light (and comfortable temperatures...).
Thanks!

both work fine but it is preferable to do it in the light you are typically shooting. I shoot in daylight or studio.So, I shoot a Stouffer step wedge taped to a window pointing north; this way, all exposures are done in one shot and I don't have to worry about shutter or aperture variations.

 

[Photopathe]

That's interesting. I didn't think about that. I was going to use a method I read several places on the internet: shooting zone I on a dark target for maximum density... Zone VII to find optimal developping time... and so on... I was planning to use one speed and change the aperture.
One problem I can think of is that I was about to use 35mm film (already bought all the film I need for that) so I don't know if shooting the step wedge on film that small will give me enough surface to mesure each step with the probe. I guess the step wedge method would work better with 4x5 and the appropriately sized step wedge.

 

[Bill Burk]

That's interesting. I didn't think about that. I was going to use a method I read several places on the internet: shooting zone I on a dark target for maximum density... Zone VII to find optimal developping time... and so on... I was planning to use one speed and change the aperture.
One problem I can think of is that I was about to use 35mm film (already bought all the film I need for that) so I don't know if shooting the step wedge on film that small will give me enough surface to mesure each step with the probe. I guess the step wedge method would work better with 4x5 and the appropriately sized step wedge.

That's where the enlarger-sensitometer thread comes in. You can lay the step wedge directly on the film in the dark as if you are making a contact print. Then your enlarger or flash provides the light. Electronic flash if you want to simulate daylight (or an 80B filter with tungsten light on an enlarger).

 

[Andrew O'Neill]

I always start my tests under the enlarger with a step wedge, to generate curves, then test that data in the field.

 

[RalphLambrecht]

That's interesting. I didn't think about that. I was going to use a method I read several places on the internet: shooting zone I on a dark target for maximum density... Zone VII to find optimal developping time... and so on... I was planning to use one speed and change the aperture.
One problem I can think of is that I was about to use 35mm film (already bought all the film I need for that) so I don't know if shooting the step wedge on film that small will give me enough surface to mesure each step with the probe. I guess the step wedge method would work better with 4x5 and the appropriately sized step wedge.

Yes, a close-up of a large step-wedge test target would work best and avoids an unpredictable change in aperture. You can never change the aperture as precisely as Stouffer can on their stepwedges

 

[RalphLambrecht]

Another question: testing using half-stops increments should be good enough (as opposed to thirds)?

half stops are good enough but, the Stouffer gives you thirds without extra effort.