ISO 6 + 0 Stops

Once upon a time, I got myself a few rolls of obscure motion picture film stock. With “a few rolls”, I mean 8 rolls of 609 meters (2000 feet) each. That is 4876.8 meters (3.03 miles) when laid out end-to-end. Imagine that. What a waste of money. With “obscure”, I mean Fuji Eterna RDI and Fuji Eterna CI. Both of these films are meant to be used for creating intermediate copies of motion picture film that was shot on location. It is not meant to be taken out and be shot in normal daylight, but to be processed in some presumably very expensive machines in some kind of lab. So why did I shell out money for those rolls? Simple: I had a hunch that this film might be usable for stills photography.

ISO 6 + 1 Stops (ISO 3 effectively)

You may have noticed the lack of ISO speed information in the names of the film stock. I did not find any ISO speed on the internet or in spec sheets, either. For the film stock that I have experimented with for this entry, it isn’t unexpected at all: Fuji Eterna RDI is a “digital intermediate” film stock that is usually exposed by an Arrilaser. Thus, the spec sheets speak about wavelengths and laser strength instead of ISO speeds. This leads us to the “experiments”: Figuring out what ISO speeds to use with RDI on location in a normal 35mm camera.

ISO 6 + 2 Stops (ISO 1.5 effectively)

I started off with a set of exposures in a controlled lighting situation. I used the ISO setting of the camera and changed that through the range that is supported by the camera. After development, I could see on the film strip that the first faint images were starting to appear at around ISO 50. I scanned the film with the Nikon Super Coolscan 9000 and confirmed that the first usable image actually was at ISO 6. Unfortunately, that was the end of the exposure set, as this was the lowest ISO that the camera (Nikon F6) supported.

ISO 6 + 3 Stops (ISO 0.75 effectively)

I decided to give it another go, using the exposure compensation setting on the camera. The images you see in this entry are from this round, with the camera set to ISO 6 and going from 0 to +5 stops of additional exposure. The lens was initially set to f/8 for maximum sharpness.  Given that ISO 6 is already a stretch in daylight at f/8, exposure times reached 20+ seconds quickly, forcing me to open the lens up further. That, and the long exposure times, lead to the loss in sharpness in the higher range of additional stops.

ISO 6 + 4 Stops (ISO 0.375 effectively)

The images were scanned as is in VueScan and converted to in DxO PhotoLab. The only conversions made were an inversion of the tone RGB tone curve, exposure correction by 2 stops (the same I would do to other film stock), and white balance to the bottom right square of the color chart.

ISO 6 + 5 Stops (ISO 0.1875 effectively)

Looking at the results of this experiment, I think I will shoot Fuji Eterna RDI at ISO 6 or ISO 3 (I.e. ISO 6 + 1 stop).

Amendment: I have taken Fuji Eterna RDI out for a “real world” shoot by now (picture will be shown in a future blog post). I noticed a strong, yellow color cast in the images, which I found hard to correct in post-processing in DxO PhotoLab 3 and Skylum Luminar 4. Only a few images looked good-ish right from the start. They all had a somewhat brighter scene in common, and I was able to improve them somewhat in post. With that hint in mind, I went back to the scans for this post and did a re-edit:

• Center the histogram.
• Level out the luminance histogram.
• Look at the R, G, and B histograms.

As the scene in these test images is mostly white with some black from the color chart, it was easy to spot which exposures exhibited color casts, and by how much. The “real world” pictures were shot at ISO 3. For a new test in the real world, I would at least go down to ISO 1.5. Maybe even ISO 0.75.