I decided to play around with some Lucky Color 200 for a few reasons.
I wanted something cheap and somewhat grainy to test C-41 developer modifications with, in order to see how much one can influence characteristics through development changes.
The first roll I shot normally, I achieved about 50 lp/mm from 80:1 to 4:1 contrast, though that may need re-testing to confirm it is that low normally at the high contrast side. The other thing that cropped up was that it appeared faster than it’s 200 rated speed. Probably a 400 film.
Lucky 200 @ 1600 (no push)
1600 (no push)
3200 (no push)
The first developer modification didn’t turn out great, the second one was a lot better, it involved adding 7.2g/L of Potassium Bromide to normal C-41 developer and processing at a time of 4 minutes 15 seconds, which is normally a 2 stop push.
In this case, I want to lose speed while increasing processing time. Less development with more exposure to improve grain, but with a longer time with restrainer instead of a simple pull process in order to increase contrast rather than decrease it, hopefully in order to pull a bit more detail than normal. The is idea is to suppress the larger grains of the emulsion from contributing to the image.
In this case I got 70 lp/mm @ 80:1 contrast, 62 lp/mm @ 4:1 contrast, and 45 lp/mm @ 1.6:1 contrast at an exposed ISO of 50 and 100, my chart went down to about 15 lp/mm at the distance I used it at, and could not resolve any of the 1.23:1 contrast patterns.
Now, I also got about 90-100 lp/mm @ 80:1 and 4:1 contrast with this same lens at the same aperture (f/5.6) on Agfa Precisa CT 100 (the stuff produced for Agfa by Fuji), I’ve seen it elsewhere stated to get 120-135 lp/mm at 4:1 contrast.
At f/5.6, I managed about 150 lp/mm at 80:1 out of Adox CMS 20. Excessively sharp on CMS 20, but my lens (Canon FD 28mm f/2.8) isn’t to the same standard as used for those tests that got much higher detail on Precisa.
So my results have greater loss then theirs does. Where as due to CMS’s extreme resolution and being very thin, there’ll be minimal loss.
Now considering, Precisa is allegedly Sensia, or at least close to it, Fuji rates Sensia at 55 lp/mm @ 1.6:1 and 135 lp/mm @ 1000:1, although it’s stated these are often conservative, as excellent lenses show what they can put on these films at low contrast.
So let’s assume the peak is 135 lp/mm for Precisa (Even though their lens should also have loss on it), and 150 lp/mm peak at f/5.6 for my lens, applying the resolution formula, where lens is the lens resolution, film is the film resolution, and r is the resolution of what gets put on the film:
1/lens^2 + 1/film^2 = 1/r^2
Then, using this, 1/150^2 + 1/140^2 = ~9.9314×10^-5
Or r = 100.3 lp/mm, which matches my results.
Now if I use this to work out the peak film resolution in the developer modification, what I -might- get with a much more excellent lens
1/r^2 – 1/lens^2 = 1/film^2
1/70^2 – 1/150^2 = 1.5964×10^-4
Or about 80 lp/mm, which compared to 50 lp/mm (which only goes up to 53 lp/mm with this formula) is a significant improvement. It is a 51% increase from 53 lp/mm.
Showing this technique does have some merit.
Now I suspect this film is actually a 400 speed film repackaged as 200. So if I were to use this on Ektar, I would probably rate it at 25. Though first roll.. bracket exposure tests to find an ideal exposure.
I think this can be further improved even more by tweaking, greater amount of Potassium Bromide for example. A small amount of Potassium Thiocyanate to give finer grain (Though not needed on Ektar, but would be good to experiment).
The application of this would to get essentially, a much slower speed Ektar (or other 100 speed colour negative) without having to overexpose a few stops and compromise contrast, saturation and resolution, but actually give a resolution benefit.
This same source holds that Ektar gets a 105 lp/mm peak, this would put it at almost 160 lp/mm if that 51% improvement figure would hold (and that 50 lp/mm was correct for normal processing of Lucky 200). With my lens that would allow me to hit that figure they achieved. O something like 150 lp/mm with something like the Biogon 25.
Now if we still had Ektar 25, which was rated at 200 lp/mm, that would be an excellent landscape colour negative film at the right speed without resorting to funny processing.
I should mention, that these figures are barely-resolved, they’re there, they are just barely visible, soft, but there. The higher you can push this resolution, the better the image will be at a lower resolution, ie: being able to resolve 120 lp/mm will give superior spatial frequencies at 80 lp/mm then something only just hitting 80 lp/mm @ peak. They will be cleaner, clearer, and more well defined. And 80 lp/mm is excellent definition when it is very well defined, rather than only just barely visible.
One of the sharpest colour negatives I have personally used has been Konica Centuria Super 100 in 120, although I shot it at 50 and pulled it 1 stop. It was ridiculously good for nature images, not so good for portraits (just looked odd).
I managed to get 77 lp/mm out of Lucky 200 @ 50 and 100 this time round.
Using the same process time of 4m 15s, but with 10g/L of KBr added and 300mg/L of Potassium Thiocyanate added.
This pushes the film resolution to 90 lp/mm assuming 150 lp/mm is the peak resolution of my lens.
Even with the large potassium bromide increase, 50 and 100 still looked like very good speeds, this would be attributable to the speed increasing effect of potassium thiocyanate that would help uncover more developing sites as it’s a powerful solvent.
Perhaps there is again a little more wiggle room with more KBr and a longer time again.
But this now represents a +80% increase. If this works just as well on Ektar, that’d shift it up to 190 lp/mm.
I am guessing at this point, with this amount of additives and processing time, a good exposure index for Ektar would be 25.