This is an experiment to try to push a roll of Tri X (type) film to ISO 25600
It’s open for interpretation.
Equipment and settings:
- Camera: Nikon F4 with DP20 on Tripod and Cable Release with the eye-piece covered. AIS Nikkor 28mm f3.5 without any filter.
- Film: Arista Premium 400 ( Tri X Type film)
- Developer: Eco Pro Ascorbic Acid Developer (Stock Dilution) (XTOL Type developer) at 20 degrees Celsius for 20 minutes.
- Developing Method: Rotary via Unicolor Motorbase. Switch directions every 5 minutes.
- Scanner: Epson Perfection 4490 Photo at 2400dpi with 48bit color initially, AE at 75%., sharpen on low.
Developing time explained:
According to the Kodak tech pub J109. For Tri X and XTOL Stock at 20C Rotary:
- ISO 800 – 8 minutes.
- ISO 1600 – 9.75 minutes.
- ISO 3200 – 11.5 minutes.
It is roughly a 20% time increase at each stop. With that rule I estimated the following:
- ISO 6400 = 11.5 + 20% = 13.842 minutes.
- ISO 12800 = 13.842 + 20% = 16.5888
- ISO 25600 = 16.5888 + 20% = 19.90656 minutes.
- Lets round it up and call it 20 minutes flat. Now IF this is correct.
Notes: Severin Koller suggested that this time is no where near sufficient to push the film to ISO 25600.
First Scene – Indoor, Workshop.
- Close up Spot metered on the piece of white paper.
- Meter on the F4 reads ISO6400 f/8 1/500.
- Translate that into Zone 7 will make it f8 1/125
- Translate that into ISO 25600 will make it f/8 1/500 which is the value we will will start from, and stop down the shutter speed as we go.
- >Matrix reference1/250 f8 ISO 6400 = 1/1000 f8 ISO 25600
- Ron suggested that “the fluorescent light used which has a discontinuous spectrum and is thus difficult to meter and difficult to expose”
- The paper image on the negative indeed does not have the density of what zone 7 supposed to have.
Second Scene – outdoor , overcast day light.
- Same Method as above.
- Final starting point ISO25600 1/2000 f8
- >Matrix reference 1/3000 f8 ISO 6400 = 1/12000 f8 ISO 25600
- Severin suggested that judging by the results here, I am developing at about ISO6400 Instead.
Third Scene – Shade
- Same Method as above.
- Final starting point ISO25600 1/1000 f5.6
- > Matrix reference 1/6000 f5.6 ISO 25600
- Nikon F4 , Matrix Metering, Aperture Priority
- 1/180 f3.5 ISO 6400 EV-2 = ISO 25600
Causal use with Matrix Metering gives Unusable results. You will be a lot better off with Heavy Center Weight or Spot Metering. Extra attention to metering is required when pushing to such high ISO.
- ISO 25,000 is about the theoretical limit for any film. – Ron
- Push processing for a given film does not increase the true speed, merely the contrast, and it does increase fog. – Ron
- Also, ISO 25600 is an estimate, as No ISO speeds greater than 10000 have been assigned by the International Organization for Standardization as of July 2011.
Please remember film tests are subject to Film Developer, Agitation Methods and other variables.