Sorry if that was not clear: there is no reduction in speed from the Citric acid/EDT bleach. Fomapan 400 is not a 400 speed film (per Foma's own datasheets), so shooting it at 400 is a ~1 stop increase. Also keep in mind that the developer has much more to do with speed increase than the bleach. However, the bleach can make the speed worse by blixing too much and leaving you with a thin negative. Leaving it in the bleach too long in the acetic acid/peroxide bleach will take quite a lot away. The unpredictable nature of the bleach speed is also very annoying.
The leftover yellow "staining" from the acetic acid bleach is not actually staining, as discussed earlier in the thread. It's fine grains of silver that get evenly deposited across the film. This is why it doesn't clear with a sulfite bath. The EDTA and citric acid in the the bleach we formulated on this thread chelate that silver and prevent it from re-depositing on the film. You still need to use a sulfite bath with this bleach to get rid of the actual staining.
In your negatives you are definitely seeing some emulsion damage. But because they are so big you probably don't see it on scans. Do a detailed scan and zoom to the highest resolution and you will definitely see it. Some films do better than others. Temperature seems to have very little impact from all the testing I did. Which is further reinforced by the fact that none of the patents out there talk about temperature as a controlling factor in emulsion damage.
Yes, we did test it. No it doesn't work well. You get weird swirl lines all over the film.
If the bleach (or an additive in first developer, such as the thiosulfate I've added in the past) dissolves some of the undeveloped halide, this will lighten the final positive -- which is effectively an increase in film speed.
I am pretty sure as I said a few posts back that what you are seeing with speed gain has nothing to do with the bleach and everything to do with the very aggressive developers being used. AFAICT the only thing the bleach can do is to make the positive thinner all around…
the action of bleach/thiosulfate on the thinning of undeveloped halide resulting in a lighter final positive makes sense and in the end can really only be considered as an effect on speed. Even if it’s essentially indirectly resulting in the speed increase because of its subtractive action, the end result is still a lighter final positive when means over-exposure/speed gain.
This doesn't seem correct to me. Lightening of the final positive due to Blix action of the bleach is basically a reduction in contrast and not an increase in speed. But we don't need to argue over this as any claim on speed increase can be easily tested by those who make the claim.
Even claims of speed increase in reversal processing due to a high energy first developer are questionable.
Reversal processing is the only process in which a real and measurable speed increase can happen from an extended FD step (of an appropriate type that is able to access and develop all the available silver). The speed increase is (I recollect) however not terribly large - about 1/2 stop or so. The mechanisms are explained elsewhere on here. The problem is that the speed increase comes with a loss of Dmax.
Even that 1/2 stop increase in speed, if and when it happens, can and should be tested and confirmed. Otherwise, the very few who do reversal processing today end up building a web of myths about reversal processing.
They are well known within the literature, described by researchers who work with the processes - and obvious from manufacturers' characteristic curves if/ when push & pull effects are shown…
Even that 1/2 stop increase in speed, if and when it happens, can and should be tested and confirmed.
@Fragomeni: this could be of interest to you and others in this forum who reversal process FP4.
Quoting from the page on reversal processing by a preeminent manufacturer of films, italics mine. I believe the 'our' in the italicized sentence refers to the manufacturer's R&D team.
"For general indoor/outdoor use, first adopt the published ISO setting and vary this, by trial and error, to determine the best exposure for your particular taste. In our tests we found 1 stop over exposed to be a good starting point."
https://www.ilfordphoto.com/reversal-processing/
When you're shooting FP4 at EI:500, you're actually giving nearly 3 stops less exposure than optimal. If processed normally, that would give you very dark positives. You can increase the halide solvent (thiosulphate or thiocyanate) in the first developer and also increase the developing time to get lighter slides. However, the resulting positives will have low contrast and show significant shadow loss. Such slides might not shine when projected but can possibly give acceptable results when scanned and post-processed. If that's acceptable to you then there is nothing wrong in shooting at EI:500.
The key here is that I’m not processing these as normal negatives to make a positive print. That’s a different process altogether with different intended outcomes. This is where speaking to intended outcomes becomes important. Generalizations based on a different process has little practical use here.
The recommendation by Ilford to overexpose by a stop was specifically for reversal processing of their films including FP4+. You can check again the link I shared earlier.
@Fragomeni: English isn't my native tongue and I at times struggle to express my point of view clearly. My mere point was that in reversal processing, bleach doesn't increase the speed of a film nor does the first developer beyond a small increment. If Ilford has recommended giving additional exposure for their films, it's not because they use Permanganate bleach. If you look at major labs doing reversal processing today, DR5 and Studio 13, they too recommend EI <= 125 for FP4+ for best results and DR5 doesn't use Permanganate bleach. It doesn't mean, however, that FP4+ can't be shoot at 250 or 500. One can get acceptable results at higher EI but with significant shadow loss. So, if your process of underexposing FP4+ and bleaching with peroxide has given you acceptable results, it's fine - whatever works for you. I'll desist from commenting further on this topic as I'll be repeating myself to the boredom of many.
I had the chance to try my hand at the improved reversal formula (EDTA version) with Fomapan 400 in 120. I definitely agree with those who spoke of this combination as particularly valuable because of the transparent film base of Fomapan 400 in 120 size and the more neutral color of slides made with this improved bleach formula. I still see the slightest bit of a gold hue in my slides but a massive improvement over the almost sepia of the vinegar formula (I actually like the sepia tone as well and can see value in both). I still see a speed increase in my results, although this time 1/2 - 1 stop (compared to 2 stops with the vinegar formula. I was surprised to find any increase in speed with this based on the results others have had. Below is a quick exposure comparison (don't mind the light leak on the right edges of each frame -- thats from removing my darkslide with a slight light leak). I'm in Souther California where things are a little warmer so pretty much the only deviation from the formula as written is that my chemistry is at 28C rather than 20C. The example below is just taken with my iphone but it does a decent job of showing the exposure differences. The 0 exposure is a bit washed out where as the -1 exposure is pretty dead on (more so in real life than in this quick phone scan).
For those using this process, which of the solutions are you finding can be saved and used more than one shot? I see the bleach referenced as keeping well in brown bottles but is that keeping after being mixed and then using one-shot or keeping and being reused? Also, the sodium sulfite bath, does this keep and can it be reused? My instinct is to use everything one shot to maintain better consistency but am interested in what others have found.
Sorry for going dark on this thread for a couple of weeks. Was taking a much needed vacation!
Glad it worked out for you. @kentanghk and I spent many, many hours getting to that formula. Looks like you got very good results. And yes, the Fomapan 400 works surprisingly well considering they don't recommend it as a reversal film. Not the best Dmax in the world, but looks good.
You say you still have a bit of yellow staining. Did you use the clearing bath?
The vinegar stuff lasts for quite awhile. Note that its behavior is quite unpredictable, though, because the amount of peracetic acid formed has a big impact on speed and amount of bleaching. I found that the Citric acid/EDTA bleach will last a month or more and probably 3 rolls of film for 500ml (e.g. guessing maybe 5-6 rolls for 1L). After that it still works, but you get more staining. I never tried to exhaust it. I did let it sit for a few months and then when I went back to it it was not working any more. However, there was a fair bit of air in that particular jar.
If you don't mind one shot you will definitely get the best results.
Hope the vacation was great! I just got back myself and planned to have many rolls to process as b&w reversal...but sure enough left my bag of film on the plane. Too much plane wine I guess.
It was great, although too short. Oh, no! I hope you were able to recover the film and it's not all gone :|
Anyone have idea on how to get better Dmax in this reversal process? I’m still holding onto hope that DR5 will eventually release their process as was claimed but hasn’t happened yet. Rich Dmax is about all I long for now.
DMax is generally not an issue in reversal processes that use Dichromate or Copper Sulphate bleach in my experience. Of course DR5's DMax is at a different league altogether. BTW DR5 uses Dichromate bleach.
That being said, if your first developer is overly aggressive or contains too much sliver solvent you can cause further loss of Dmax. It's probably the place to look for better Dmax first IMO.
Have you tried reducing the bleach time? That could also help to increase Dmax, although you’ll need to find an optimal time where the highlights are clear.Anyone have idea on how to get better Dmax in this reversal process? I’m still holding onto hope that DR5 will eventually release their process as was claimed but hasn’t happened yet. Rich Dmax is about all I long for now.
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