I don’t think it’s worth getting into a whole argument over this but you’ve got your color theory 101 wrong, and it’s really about light more than color theory. I’ll yield at this point.
You clearly do not understand the significant difference, Milpool. Take any two true RGB color separation filters and put them together, viewing a strong light source, natural or artificial full-spectrum, and the result is almost black. I've even viewed solar eclipses that way. But take the strongest magenta and yellow filters you can find, do the same thing, and you'll see that a fair amount of residual white light still gets through.
Do the same thing looking a something bright red. With either a nearly pure green 61 filter of 47 or 47B blue, that red object will look black. But if you look at it with either a yellow or magenta filter, you'll still discern the red color. One catergory of filters is truly sharp-cutting; the other is not. No, VC papers are not sensitive to red light, but this does prove how some white light is getting through in
either case subtractively, whether Y or M, containing some of both blue and green as well as red.
Yes, you can go either way in terms of VC paper printing. Magenta subtracts green light, while yellow subtracts blue; but the effect can never be as downright intense as full true green versus full true blue. Color theory 101.
I don't want to press this fact too hard in the present context, because one rarely needs to go to those extremes with today's excellent VC papers unless they're dealing with really bad negatives to begin with, needing a lot of "salvage" printing. But there is a significant difference between additive and subtractive light in principle per se.
And there are times one basically just wants to print VC using ordinary enlarger light, but then add a little selective punch to one of the extremes exclusively. True additive G versus B filters do a better job of that.
Thanks for that proof, The algebraic notation made my head spin a bit and I am not sure if I understood all of it so I need to ask some questions:
What does d represent and likewise what is tb'? Clearly in your proof intensity of the green and blue are important as well green exposure, Am I correct in assuming that the effect of blue exposure on the print is the sum of tb+ib and likewise that of the effect of green exposure is tg + ig?
If you've seen the video what I am about to say is redundant but if not then between mins 16-17 he states that his single grade print was grade 3 which he had produced in his previous video. So might half a grade to 3.5 made it the same as his split grade?
@pentaxuser it's the difference between what people think they should use in terms of grade/ exposure and what they should actually use.
There's not a single mention on there of FX-21 having development inhibition effects, and its formulae suggests that its chances of meaningfully delivering any are very slight, compared to developers that were meaningfully designed to do so (or that did so by initial accident of their design and subsequent emulsion research/ engineering - D-76 and modern emulsion designs will produce an intentional degree of inhibition effects - but not as strongly as some other formulae). There is good evidence that Ilford and Kodak (and likely everyone else too) had both tested & outflanked Crawley's various formulae and didn't find them worth pursuing. As a matter of fact, there is also a fair bit of solid evidence that shows Ilford (for example) was well aware that developers that did not act on the emulsion with a degree of solvency did not produce as good a balance of granularity and sharpness as those that did.
There is a photographer near to where I live who has photographed rural life in the county of Devon starting from around the mid 1970s to recently.Wrongo! Crawley's formulas are for "perfectionists", as he himself told me when I wrote to him back in the 1980s. I have read about and experimented with many of his developers. They do not rely solely on "inhibition effects", but also on "chemical means". FX-14 (Acutol) was engineered to provide superior sharpness, and compensation mostly for the highlights, without adversely affecting mid-tone gradation. FX-21 (Acuspeciaal) was engineered to produce extra sharpness even beyond that produced by Acutol, but at the sacrifice of some mid-tone gradation, and was intended for slow, fine-grain films. I have found that FX-21 produces extraordinary results with T-Max 400, which behaves very much like slow-fine-grain films. You really need to learn more about this.
"
ACUTOL FX-14 DEVELOPER
Acutol gives maximum definition on films ISO 5-200 by increasing the apparent sharpness at the edges of fine detail.
It achieves this effect chemically, so allowing normal agitation and giving negatives of excellent gradation. There is only the slightest compression of the middle tones, more than compensated for by the brilliance of detail within the picture. The edge effect is most marked on high acutance films, which are generally 35mm films of speed rating ISO 5-200. As these slower films usually have quite high contrast, Acutol suits them very well and will produce impressive results on subjects containing textures.
Films faster than ISO 200 and most roll films do not give the extreme sharpness of which this developer is capable. Acutol is a medium fine grain developer and while it will give good results with fast films and roll films it is normally preferable to use Aculux and so ensure the finest grain and longest tonal range.
Acutol gives a ½stop speed increase, useful with the slower films and is well suited to pictorial photography.
Acuspecial FX-21 appeared by autumn 1969
A new type of soft working 'surface' developer invented by Geoffrey Crawley. "It is designed to give a special result with modern high performance slow and medium speed miniature films 5-200 ASA but may also be used with higher speed films. Acuspecial produces a negative of 'engraving' type sharpness and definition, coupled with extremely fine grain. The emphasis on this type of definition is obtained with a minimum reduction in continuous tonal gradation, and this is offset by exceptional separation of tones on fine detail. The disadvantages of streaking and inconsistency of action, usual to surface developers, have been overcome. There is an effective film speed increase of a half-stop.
Acuspecial does not replace Acutol which continues to give the optimum balance of tonal gradation, sharpness and definition. But the 'engraving' type negative given by the new developer, and the control of contrast which its soft working action provides, make it an important new tool for the knowledgeable photographer in the miniature and sub-miniature fields. Acuspecial is available as a highly concentrated liquid which is normally diluted 1:29 for use. Full instructions are supplied.
If you have a densitometer, and know how to use it responsibly, split grade printing is essentially pointless. You have the correct tool to be able to define the optimal grade to start from & judge how you want to tackle areas you might want or need to dodge and burn at other grades. All of the various split-grade methodologies are workarounds for lack of a densitometer or trying to make enlargers essentially stepless in contrast grade. That's about all there is to it.
There's not a single mention on there of FX-21 having development inhibition effects, and its formulae suggests that its chances of meaningfully delivering any are very slight, compared to developers that were meaningfully designed to do so (or that did so by initial accident of their design and subsequent emulsion research/ engineering - D-76 and modern emulsion designs will produce an intentional degree of inhibition effects - but not as strongly as some other formulae). There is good evidence that Ilford and Kodak (and likely everyone else too) had both tested & outflanked Crawley's various formulae and didn't find them worth pursuing. As a matter of fact, there is also a fair bit of solid evidence that shows Ilford (for example) was well aware that developers that did not act on the emulsion with a degree of solvency did not produce as good a balance of granularity and sharpness as those that did - i.e. a balance of physical and chemical, rather than purely chemical development (or 'surface development' in Crawley's words).
@Lachlan Young , I have been suspicious of some of Crawley's formulas. For example, some employ two buffers though most developers have only one. Also, I have heard doubts expressed about some of Crawley's work from a couple of people. Could you post links or quotes? You mention "good evidence" and "a fair bit of solid evidence".
I have a densitometer, so an experiment I'd like to do someday is modify a Crawley two-buffer developer to use one stronger buffer, and determine whether image quality or curves became worse.
Mark
Why? Do you think you know more than he did? He revised and replaced several of them over the years.@Lachlan Young , I have been suspicious of some of Crawley's formulas. For example, some employ two buffers though most developers have only one. Also, I have heard doubts expressed about some of Crawley's work from a couple of people. Could you post links or quotes? You mention "good evidence" and "a fair bit of solid evidence".
I have a densitometer, so an experiment I'd like to do someday is modify a Crawley two-buffer developer to use one stronger buffer, and determine whether image quality or curves became worse.
Mark
I have tried several of them, but Acutol remains the best I ever used. FX-21 (Acuspacial) works amazingly well with T-Max 400. Just try it!Ian Grant has posted on here about his discussion of Crawley's developers with chemists from Ilford in the early 1980s - Ilford had apparently at one time been the contract manufacturer for the range - and the Ilford scientists' skepticism of the claims. The obvious subtext is that Ilford had gone through the range of formulae to check they hadn't missed something worth utilising themselves (all the major manufacturers had units whose job was to essentially dismantle the others products and see how they worked, then try to work round the patents - or to see who was infringing whose patent). Secondary to that however, is published material from Kodak researchers of the same time period where some of Crawley's formulae are pretty clearly outflanked - and there is microdensitometric data, which is really where key linkages to perceptual image quality come about. The third thing of note is that somewhere between 1980-1990 Crawley's commercially manufactured developers all seem to get revised and some withdrawn (I would not be entirely surprised if his contacts in the industry had quietly persuaded him that some of the formulae weren't really doing what they were supposed to). At the end of the day, essentially all of Crawley's formulae will develop film competently, it's more the question of if they deliver optimal image structure/ image content transmission etc. There's also the problem that as the editor of the British Journal of Photography, Crawley had a level of cultural influence across the practices of a large swathe of photographers in the UK and wider afield, and there was what looks like a tendency amongst the readership - and those influenced by that readership - to trust his formulae more than that of the manufacturers - never mind the obvious conflicts of interest.
FWIW, I consider that latter example to be split-grade printing - more limited than applying the full technique, but still split-grade.
I think Ilford felt that many of his formulas were over complicated rather than being skeptical of how they performed.Ian Grant has posted on here about his discussion of Crawley's developers with chemists from Ilford in the early 1980s - Ilford had apparently at one time been the contract manufacturer for the range - and the Ilford scientists' skepticism of the claims.
I think Ilford felt that many of his formulas were over complicated rather than being skeptical of how they performed.
They reckoned that the same end results could be obtained with simpler formulations.
Could you elaborate on a procedure on how to do this? I have a dentistometer but I have no idea of how to use it to determine a paper grade I would need or an optimal exposure for making a print.
I also have an RH designs Zonemaster, is that something similar to what you are thinking of? It does suggest a paper grade after metering different parts of the negative when projected onto the baseboard.
I have seen some excellent prints from that combination when I started getting interested in photography and began seeing print exhibitions.. The commercial Paterson developers were the best I have ever used. FP4 in Acutol was simply stunning!
Either way, it's clear that this thread has been derailed by one of Ornello/ Michael Scarpitti's socks feeling a need to once again force us to listen to his obsessions with Geoffrey Crawley's developer formulae. It was old 20 years ago, and hasn't improved with time.
I use Ye Olde D76 and I don't think that has improved with time either, but it gives me negatives that I like.
That's what I don't know. So I measure a shadow and a highlight on the negative and get some values of density. Then what do I do with those numbers? I have no idea how that would translate to what filter out of the Multigrade set to use.As it is, I'll give you a hint: let's say the number you end up with is 0.7 - what grade of Ilford MG FB cooltone would be a likely starting point to use?
Then what do I do with those numbers? I have no idea how that would translate to what filter out of the Multigrade set to use.
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