20 stop dynamic range

20 Stop Dynamic Range Technique

by EveNSteve

Here is a quick technique I use from time to time to get the maximum usable dynamic range out of film on a contrasty scene.

  • Film: Kodak TMAX 400 (TMY-2)
  • Developer: PMK 1:2:100 @70 F (Mixed with Distilled H2O)

Please note: If you have never used PMK developer understand that it requires careful handling… always wear gloves and use safe chemical handling techniques as it can be quite toxic. Also with T Grain films the temperature is important so use a water bath to maintain 70 F during processing.

Exposure:

Expose the scene for the shadows… if you have a spot meter make sure you have a solid Zone III…. don’t worry about the highlights as they will be just fine. (Stay tuned for my review of the new spot meter by Metered Light!)

Once you have your exposure figured out overexpose by 3 stops. You could always just set your meter to an EI of 50 instead of the normal 400 for TMY-2 (this is what I do). In simplest terms we are overexposing by 3 stops and developing for 50% of our normal time. The developing procedure listed below represents a 50% reduction in development time from my normal with this film / developer combination. This technique will work for different films with PMK as long as you follow the simple rule…. overexpose by 3 stops and reduce your development time by 50%.

Processing:

1. Pre-wet- 1 minute at 70F, constant agitation (distilled H2O).

2. Developer: PMK for 7.5 minutes (1+2+100). Continuous agitation for the first 30 seconds then one inversion every 15 seconds till completed time. Save the used developer as you will use it again in the after bath.

3. Stop: Tap water, 2 minutes fill and dump with agitation. Do not use anything but water!

4. Fixer: TF-4 for 5 minutes, follow package directions. Only use TF-4 fixer!

5. After Bath: For those of you not use to using PMK you reuse the saved exhausted developer by dumping it into the tank for a second time after the fixer which will increase the image stain. 2 minutes with standard agitation. There are schools of thought that suggest that the after-bath is not important… with some films like 400TX I would agree but with this technique and film it is a good thing in my opinion.

6. Wash for 30 minutes.

7. Wetting Agent.

8. Dry.

Note: This technique as outlined here is for scanning purposes and I have not tested it for wet darkroom usage so I do not know how well it would work, BUT- for scanning it is fantastic. I would only use this technique for situations where the contrast / dynamic range is well beyond “normal”… this plus a bit of pre-exposure goes a long ways (no pre-exposure was used on this image but I will write an article on this technique very soon)! I have tested it on “normal” scenes with success, but it does require a bit more work in Photoshop to correct for the huge expressive shadows and somewhat flattened highlights, so it is best to use this for high contrast scenes.

So the results….drumroll please…

Inside Indian Hill Imageworks

In the image above the shadows (Zone III) were placed on the dark barn board above the windows… the snow outside which was in direct sunlight was 17 stops brighter… this is a straight scan on our Imacon… no dodging or burning! There were no lights on inside the building so it was quite dark. In Photoshop I added a minor “S” curve but nothing else. The grain is very nice and controlled for 35mm. The snow outside the window has nice detail (not sure how well that reads in the online image)… nothing is lost on either end.

Camera: Leica MP with a 28mm lens.

Chemical resources:

I chose TMY-2 for this test as it is box speed in PMK and it is a film I really like… another good choice would be TMAX 100 which is also box speed but with the 3 stop overexposure you have a working film speed of 12… time to break out the tripod!

Viva la Revolution-
Stephen