Illford has something called Core-Shell Crystal Technology for their Delta 100 film introduced aprox 1990 or so. Ive never used Delta, anyone have any info on this technology and how it compares to other grain structures?
Im also looking at Berger 400 pan with its duel emulsion technology... any comments on its grain structure in comparison to other films? What advantage does a duel emulsion have over other films?
In essence, Ilford's terms refers to how they grow & control the growth of the grains in the emulsions during manufacture. Delta films use tabular crystals as part of their structure & they are, funnily enough, triangular. Grain is well behaved, very sharp in just about everything.
Bergger's is likely referring to the use of two discrete coated layers (like every 200+ speed film since the 50's...) each with different emulsion component (s) & the use of the relationship of those layers to optimise behaviour. It may also refer to emulsions being blended together, again to improve latitude, contrast etc with cubic grain construction.
If you want to know more about emulsion design/ technology I'd suggest going to Photrio & asking/ looking there - there is an emulsion making subforum & people who had extensive emulsion research & design experience at Kodak etc contribute.
Very different films. Ilford Delta 100 is a T-grain film similar to Kodak TMax 100, but a tad grainier, with a bit more of a toe to the characteristic curve, equating to about one less stop of crisp deep shadow separation. Both Delta and TMax can be developed to a relatively high gamma, or degree of negative contrast, and are very fine grained. Bergger 200 was an old-school relatively thick emulsion film with an extremely long straight line similar to Kodak Super-XX, but not quite as grainy. These kinds of films could handle high contrast superbly, but were also used for tricolor separation negatives in dye transfer color printing; they were distinctly grainy, though I loved them for 8x10 work, which does not need the same degree of enlargement as 4x5. The present Bergger Pan 400 is related to neither of these categories, but perhaps to a former Foma 400 product (not Fomapan 200) that employed a dual emulsion as alternate path to a long scale, but with peculiarities I personally found disappointing. I can't comment on the technical issues of manufacture, but do know that the manufacture of highly predictable specialized films like TMax, Delta, and Super-XX are as much art as science, just like making a fine wine, and that once the original continuity of technicians and maintained equipment, and specialized supplies are no longer around, they might be hard if not impossible to replicate. These are not do-it-yourself kinds of emulsions.
Im tossing the coin for either delta or tmax. Ive used Tmax since it hit the streets in all formats n love the results I get. Delta just has a nice catch phrase... core crystal technology... a nice ring to it. n got my attention.
I recently was using up some arista 100 4x5 and 9x12 fomapan 100 (same stuff) I got it free with something I bought, Im not very happy with them. The Tmax will more than likely be my choice. I considered trying the Berger and just may buy a box just for giggles.
Photrio (APUG) has been a long time reference for me. I'll be asking the chemist over there now that I have an idea whats what.
Thanks for the heads up.
While delta 100 is a fine product, I've always liked tmax100 more. There's something to the grain structure of delta100 that I never quite liked. But it's a nitpicking exercise really. Both excellent films.
thanks koraks.
I can't see the grain in my LF prints.
As a footnote I recently developed one sheet of Acros and one sheet of Delta together in a Jobo 3005 tank on a CPA processor with Xtol 1:1 for 21 minutes. Both sheets were shot sequentially with the same lens and given the same exposure time. The Acros sheet had the better Dmax but 21 minutes is my time for Acros and 22.5 minutes is my time for Delta. But Delta's Dmax maxes out at 1.6 IIRC while Acros's Dmax continues to increase with time. It would be an interesting experiment to see if Delta's Dmax at 22.5 minutes of development would equal Acros's Dmax at 21 minutes.
Thomas
Acros cannot be developed to nearly as high a gamma as Delta or TMax. But it has other special characteristics which make it highly appealing, namely orthopan sensitivity, almost no recip correction factor needed, and very fine grain combined with excellent edge effect. It has more of a toe at the bottom than TMX or TMY, similar in that respect to Delta: you surrender at least a full zone of shadow separation. Therefore, in high contrast situations, I rate both Delta and Acros at 50, whereas I never need to do that with TMax films, and use full box speed under all conditions. Sadly, Acros is officially discontinued in all sizes, so if you like it, buy up what you can, while you still can.
I think Fomapan 200 is worth a closer look as well. Unlike Fomapan 100 and 400, it is not a classic/cubic-grain emulsion. It is a variation of the tabular grain structure like TMax or Delta (they also use the "core-shell" term on their website) or perhaps a mix of tabular and cubic crystals.
Foma 200 seems to be underappreciated for two reasons. First, people often try the 100 first and then assume the 200 would have mostly the same look with slightly more speed and grain. Second, (as with all Foma films, more or less) the box speed of ISO 200 is only reached with a speed-enchancing developer. In common stuff like Rodinal or D-76 it is closer to ISO 125. So metering for 200 is not going to give optimum results and pushing it to 400 is not a good idea.
You can think of Fomapan 200 as an FP4+ replacement in some ways. It's not as fine-grained as Delta 100 or TMX and it doesn't have any special advantage in the reciprocity failure department. But you can develop it to a look that is somewhere between the clean look of Delta or TMax and classic stuff like Tri-X @ 250.
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