The Backwards Method

[Joakim Målare]

Hey folks,

The main supplier of analog photographic material here in Sweden has a short tutorial on how to calibrate your exposure and developing for any chosen combination of brands and equipment. Of course it's nothing new, but I had not heard of this particular solution before.

Basically you need an even lit surface and constant light for the exposures. You shoot two blank frames (unexposed), then four underexposed frames from -4 to -2.5 in half steps and finally five overexposed frames from +2.5 to +4.5 stops. Use your regular technique for the developing.

When the negatives are dry, see which of the underexposed frames is the most similar to the two blank frames stacked (double base+fog). If the -3.5 frame seems right, keep using the EI you shot the film at, otherwise adjust appropriately.

Contact print, on your usual paper/grade, all the frames so that the underexposed frame you picked becomes almost black. Determine which of the overexposed frames is almost white. If the difference from your chosen under- and overexposed frame is seven steps, you need not change your developing time. Otherwise do so.

So...

The first question I had was why double base+fog is suitable as a blackpoint value. I was told that this is similar to 0,15D, which is where you start to see detail in the shadows. Ok, but doesn't the density of base+fog vary a lot from film to film?

Also, why should I strive to achieve seven steps, or eight stops? Is it not possible to get to eight steps, nine stops? That would be ten "tones" when you add full black and completely white, as in the zone system, no?

And, to sum it up, is it worth the hassle? Does it become that much easier to make prints from a calibrated process, or are the different light conditions you shoot in enough to break the system?

Any input appreciated!

/ Joakim

 

[charjohncarter]

These methods and I haven't used this one but others, some more complicated. They always ended up in my mind accumulating error upon error, which expands the error geometrically. But I guess I learned something from doing them.

I think the most I got out of this; was that I was in the ballpark. My tweaking from roll to roll after the testing seemed more productive. Now I just cut the ISO in half and develop not even -10% of the time. After that I do my tweaking method.

The stacking is an interesting concept, but like you I don't understand it. Maybe someone will jump in with an answer.

 

[Roger Hicks]

Although I'd not encountered it before, this sounds like one of those pseudo-scientific rules of thumb where the inventor thinks it is cleverer than it is. You're absolutely right about fb+f varying widely. I much prefer simple iteration with real-world subjects: from http://www.rogerandfrances.com/subscription/ps expo neg.html --

After full sensitometric testing and the Zone System, the third approach is simple iterative testing with real subjects. We very strongly recommend this approach as both easiest and best.

Ideally, it is done in two stages. The first stage -- as little as one roll should be enough -- consists of shooting mundane subjects that are more or less the sort of thing you normally shoot, but without trying to get Fine Pictures. This gives you your basic exposure and development time, and if the pictures are too contrasty or too flat or badly exposed or tonally nasty, you haven't lost any good images.

For the first roll, set your meter to the ISO speed; use your meter to give you a 'best guess' at the exposure (see below, Metering Technique'); and make three exposures of each subject, at the best guess and at one stop more and less. Develop as recommended by the film or developer manufacturer, or at your best guess; look at it to see which exposures give adequate shadow detail; print the ones that look best.

If you are happy with the first roll, you can go straight to the second stage, which is taking real pictures. Otherwise, shoot another roll, with a revised ISO speed as necessary, and change the development time to get more or less contrast (there is a module on developing black and white films). If there is plenty of shadow detail at the ISO rating, but only the faintest traces at the one-stop-under, by all means split the difference. Let's say it's ISO 400: you could try EI 500 or 650. Or if you prefer the tonality at a stop over, you could use EI 250 as your starting point. Bracket again, but this time by 1/2 stop or 2/3 stop (1/3 stop isn't worth bothering with when you are shooting negatives). Again, develop and print.

By now you should have a pretty good idea of the optimum exposure index (EI) and development time, but if you haven't, repeat the process until you are happy. You might also want to have a look at the module on choosing films: we firmly believe that there is no point in persisting with a film or developer that is giving you difficulty.

Then you can start shooting real pictures, using the EI and development time you have established. Do not regard either as sacred. If over the course of the next few films you find that you could do with a bit more exposure or a bit less contrast, change the EI or development time or both. This goes against the strict scientific method, where you change only one thing at a time, but to be honest, photography ain't that scientific, and you can aim off on the basis of experience: a little more development may add as much as 1/3 or even 1/2 stop, but a little less development will lose speed a lot faster.

The reason for restraining the number of steps is simply a question of what you can get into the final print. The number of zones in the Zone System has gone up over the years, but it's much easier to expose and process for fewer zones than for more. You might find it interesting to read The Zone System and Why We Avoid It, http://www.rogerandfrances.com/subscription/ps zone.html

Cheers,

R.

 

[charjohncarter]

I've read Roger's 'The Zone System And Why We Avoid It' but it has been a few years. I had forgotten the statement, a little more development may add as much as 1/3 or even 1/2 stop, but a little less development will lose speed a lot faster. That is why I didn't lower my development time as much at first. His book 'Perfect Exposure' goes through all the testing exercises, but in the end has a very good simple approach to the film speed-development time problem.

 

[Joakim Målare]

I had a feeling you would respond in a similar fashion 🙂 I appreciate your opinions, much because you both have a sound insight in photography, both theoretical and practical. I tend to fall into theory a little too often, trying to find shortcuts to minimize wasted material and gain more control. More often than not it turns out the opposite, with added frustration 😀

The reason I started looking at calibration methods is that I bought a (for me) fairly large amount of film that I haven't used before, and different chemicals as well. I have decided to stay with this combination, so I figured I might as well get the process straight from the beginning.

As usual, I guess it's better to learn from experience and have your own theory hammered out along the way, so I'll skip this issue for now and focus on the practical work instead. Just now, I came in from a few hours of shooting one camera, one lens, one filter. Two rolls are getting souped later today. Feels great 😀

Have a nice day!

 

[charjohncarter]

We've all changed films with frustration. I tried TMY years ago and just couldn't get anything like liked out of it. I revisited when TMY-2 came out and I have been happy enough to keep using it (I really don't think it is much different except for finer grain). It seemed so easy years ago in the 50s when I loaded the Brownie with Verichrome and never seemed to miss. And that was with a fix aperture and shutter speed. Now I still struggle with exposure, and development. It feels good to be confident with a film and just go shot, so I stick with a couple of films. Although I do have a few specialty films that I use, but that is just for variety.

 

[Roger Hicks]

We've all changed films with frustration. I tried TMY years ago and just couldn't get anything like liked out of it. I revisited when TMY-2 came out and I have been happy enough to keep using it (I really don't think it is much different except for finer grain). It seemed so easy years ago in the 50s when I loaded the Brownie with Verichrome and never seemed to miss. And that was with a fix aperture and shutter speed. Now I still struggle with exposure, and development. It feels good to be confident with a film and just go shot, so I stick with a couple of films. Although I do have a few specialty films that I use, but that is just for variety.

Dear John,

100% agreement except for the highlighted portion -- I think TMY-2 is MUCH more tolerant of over- and under-exposure and of over- or under-development too.

Cheers,

R.