I finished running my tests. I have no reason not to like this film. In fact, I find it very easy (and pleasant) to work with. It has exceptionally low B+F density (for a 35 mm film) and it dries super flat. It also
seems to resist drying marks rather nicely. The grain is fine and tight. I would imagine this film would scan really easily. I discovered no emulsion flaws, whatsoever. One interesting bit is the fact that on all three 35 mm cassettes I bought, the DX code was covered with a piece of black electrical tape. Finally, as there's been some speculation as to the film's origin, in my experience, the film does not resemble any of the current 35 mm films by Harman (including Kentmere), Foma, or Kodak. The film base, is similar to that of the Rollei Retro 80s, but I make
no claim that the film is made by the same manufacturer as the Rollei Retro 80s.
I encourage you guys to try to find flaws in my methodology, especially if they would help account for the results. I do not claim to be an expert sensitometrist!
I have tried to run the tests using as rigorous a process as I could within my modest home setup. My results
DO NOT include any real-world photography, so they are probably completely useless to most photographers. I simply exposed the film using a calibrated and certified sensitometer at 3.68 Log Millilux Seconds, processed four film strips for 4, 5:40, 8, and 12 minutes in D76 1+1 at 20C using continuous agitation in a rotary processor. I then computed all the usual parameters, such as Gamma, G, CI, film speed, fractional gradient, etc., and I am reporting my findings below. Please, refer to my previous post in this thread for more details.
As promised earlier in this thread, I ran my film test twice, just to be sure I didn't botch the first attempt completely. The results are very much the same, e.g., the "speed point" differs by 0.01 Log Exposure and the CI by 0.02 between the two runs (comparing 8 min. in D76 1+1 at 20C with continuous agitation), so within the margin of error. Compared to expired Fujifilm Neopan 400 and expired 400TX, the Catlabs 320 Pro, when processed to approximately the same CI (or G), using the ISO standard, as described in Davis (1993), Eggleston (1984), and elsewhere)
appears about 3 stops slower. In essence, when exposed and developed according to the manufacturer's film box recommendations, the film has the property of being significantly underexposed and overdeveloped, or "pushed."
I computed film speed by two different general methods: (1) the ISO standard method, using absolute log exposure values, and (2) the BTZS method, using relative log exposure values. I obtained speed point densities by means of the commonly used 0.1 over B+F method, as well as the fractional gradient (Nelson and Simonds, 1955), and approximate CI (Phil Davis, 1993) methods, all yielding consistent results. Admittedly, there is some, small, gain in speed when developed for the manufacturer's recommended time, but then you're getting the CI of 0.72-0.74, which some photographers will love, but others will hate.
. Perhaps this is the "street film" look that Catlabs refer to on their website. I can totally see this film being very popular because of that look!
The results are somewhat troubling to me. The Catlabs 320 Pro does appear significantly slower than advertised. However, different manufacturers have different methodologies of computing their "box speed," so I don't really worry about the actual ISO 320 value per se, as most photographers run their own tests anyway. What's more significant, though, is the fact that the Catlabs Pro 320 appears to be much slower than (expired) 400TX and (expired) Neopan 400. It's a pity I did not have any fresh 400-speed film to compare the 320 Pro against.
Still, I want to take the Catlabs advertised film speed and development time in good faith, so it's possible, maybe even likely, that there are flaws in my methodology. If I were to try to poke holes in my testing process. I could easily find at least two possible sources of variability (or error). One, Catlabs 320 Pro has a much different reciprocity failure property than 400TX and Neopan 400. The sensitometer exposure was 1.068 seconds. Not ideal, but that's the only option I had (I was aiming for an ISO 200 exposure). Two, Catlabs 320 Pro has a very different spectral response, which resulted in a significant dip in sensitivity, particularly, around the peak of 530 nm. I am sure I am missing something. I welcome your comments and criticism.