Gast
Hello,
Can anyone confirm my suspicion that Rodinal causes a ‘desensitisation’ effect with certain films?
When I perform the development of films – with the sole exception of Agfa and Ilford – I almost always end up with greens that look like blacks and skies lacking detail.
It’s not that the contrast itself is too high; with subjects lacking blue, everything returns to normal.
Specifically, this happens with Fortepan and Kodak, where the effect is as described.
In any case, my images end up consisting mostly of dark grey tones and bright highlights, with the mid-tones missing.
Otto
RomanJRohleder
Otto,
How is that supposed to work?
Sensitisation takes place during exposure – by adjusting the emulsion with additives, we determine how the film reacts to a particular spectrum; the developer then only reacts to ‘exposed’ and ‘unexposed’ areas and reduces the exposed silver halide.
I’ve never heard of anything like that, never seen anything like it, and I can’t make sense of it either.
cfb_de
Hello Otto,
From a purely physicochemical point of view, Roman is absolutely right. As a blue-coloured, autocatalytic reducing agent, the developer only acts on what it can attack. In other words, on exposed silver ions where a few developed silver clusters have already been ‘created’ physically (by exposure to light).
By its very nature (and for once, the manufacturers haven’t left any room for interpretation over and above the science), a developer is “colour-blind”. Either the film is blind, or it has been over-developed. Could it be that you’re simply leaving your films in the bath for too long, causing them to become too steep, and that’s why you’re missing the famous “tonal range”? "The mid-tones are missing" points precisely to that.
Incidentally – unless you’ve got a relatively red-blind Efke/ADOX in the unit – the orange filter is quite suitable now and then for bringing out detail in the sky. Or the very classic "post-exposure" in the darkroom.
Best regards,
Franz
Gast
Franz, Roman,
I’m no chemist, but I see it differently, because the different sensitising dyes might well react differently to various developing agents.
I certainly don’t doubt your expertise in chemistry.
When you analyse a pack of Efke 50, Efke actually specifies different speeds for artificial and daylight depending on the developer.
In some cases, it has the same speed under artificial light as under daylight, and in others it doesn’t; to me, that seems to indicate a certain influence on the chroma.
Roland
Gast
One more thing
Franz,
I like using Efke and orange filters; no problem with +1.5 to 2 stops. I think you use Rodinal, I use ID 11 – perhaps it’s true that Rodinal shifts the film towards orthochromatic or desensitised behaviour.
Roland
cfb_de
Hello Roland,
This is solely down to the film’s sensitisation. There is *no* developer that can influence this. How could there be?
A developer is a reducing agent with a specific redox potential, which is set so that silver ions are reduced through the catalysis of physically developed silver nuclei (= latent image). That’s all it does, and it doesn’t even notice sensitising dyes.
The sensitisation is made particularly clear with Efke films: a lower speed is specified for warmer artificial light, precisely because the film isn’t quite as sensitive to red. I think that’s very fair and honest of the manufacturer. I also use orange filters now and then, but that slows the 50 down so much that it’s no longer any fun for me. You quickly end up with an extra second or two.
But that has absolutely nothing to do with the developer. Whether it’s Rodinal, ID11 or Nescafé, it makes no difference whatsoever as far as sensitisation is concerned.
Best regards,
Franz
Gast
Franz,
I’ve opened a box of KB 50, and it says
FR3 daylight 50/18 artificial light 50/18
FR14 80/20 50/18
FR16 50/18 50/18
FRE24 160/23 100/21
That surprises me – not the difference between artificial light and daylight, but the deviation.
Gast
Let’s assume the following: we’re dealing with a two-layer film, and both emulations have different sensitivities. It’s clear, then, that both emulations will react differently to the developer, resulting in a different image.
I can’t say for certain how this would work with a film that is – supposedly – single-layered but contains different colorants, but it does seem conceivable to me.
Roland
Gast
Roland,
That sounds like a good idea.
Otto
andreasbrigachtal
Hi Franz
I’m finally back online, and now this!
Nescafé! So far I’ve always used Rodinal in all its variations, and now this!
Give me the times. My films at the moment are Kodak Trix 320, HP5+, Acros, Techpan, Ilford and Kodak 3200.
I’m curious to see how it goes!
Andreas :D
I’m so small and always will be
RomanJRohleder
Roland,
The films Otto mentioned in the broadest sense – categorised solely by manufacturer – are not, however, multilayer films in the sense of having ‘layers’ with different sensitivities; here, ‘multilayer’ refers to the application of a wide variety of functional layers, such as binder, filter and protective layers.
You cannot specifically ‘target’ these with the developer.
Multilayer films in the sense you mean have not been in mass use for 40 years (and I include the current, still hotly debated version ‘from German shores’ in that). And even there, the whole business of specifically ‘targeting’ them is a bit of a grey area...
“As is the case with a / supposedly / single-layer film containing different colorants,”
Nothing “supposedly” about it. There is usually a homogeneously sensitised emulsion – take a look, for example, at a cross-section of an APX100.
And as for the various speeds achievable with Efke developers – these always depend on exposure and development time.
Have a look at the basics of sensitometry, then it’ll become clearer to you. A good place to start is a little booklet from Agfa-Gevaert from the 1970s, “Sensitometry”. It explains everything in about 15 short pages...
No, really, Otto either had poor exposure and/or developed it incorrectly.
cfb_de
Hello Roland,
Hmm. Which Roland should I reply to now?
The one who asked about different development times, or the one who replied with “two-layer film”?
Very well. I’ll reply to both, and I’ll start with the first one (the “development times Roland”).
The effects you describe are nothing out of the ordinary. Film manufacturers have always simply provided development recommendations adjusted towards “generous” exposure for artificial light (i.e. insufficient sensitisation).
To the second Roland (“the two-layer one”), I’d like to offer a very simple piece of advice: take a film of this type, put it in paper developer for about 5 minutes. See what happens.
Take a second film. 5 mins in paper developer, but this time *beforehand* add something like Ultrafin/A49/DS12.
Hmm. You won’t see any difference. And that would be the “ideal” development for a truly two-layer emulsion. Soft pre-rinse and finally a hard final bake. However, there are no longer any two-layer glass plates with a half-millimetre-thick coating.
Right. End of the debate.
In reality, it’s about applying a reducing agent to a silver halide emulsion. Ideally, it’s even about ensuring that this only acts where it’s desired. That is, where partial reduction has already taken place through “exposure” and consequently a “latent image” is present. It is precisely this that is then refreshed via catalysis so that it becomes “visible” to the eye and the photographic paper beneath.
That’s all that happens. And because we’re all too daft as lab technicians to get this process right every time... That’s why films aren’t fully developed, but papers or slides are in the second development. That’s the human crutch for applying proper science.
Fascinating, somehow. Chemistry that produces images as a result.
Best regards,
Franz
ChristianKolinski
I’m finally back online, and now this!
Nescafé!
Yeah, sure. It works. It’s actually really good for Imagelink & Co.
So far I’ve always used Rodinal in all its variations, and now this!
Let me know the times. My films at the moment are Kodak Trix 320, HP5+, Acros, Techpan, Ilford and Kodak 3200.
I’m curious to see how it goes!
I’m not Franz, but I can at least give you some pointers for the Techpan and the Kodak microfilms:
3 teaspoons of instant coffee and 3 teaspoons of washing soda
to 250ml of hot water. 45 minutes, shaking once every 5 minutes.
This makes all films really soft. For normal films, double the coffee
(it works as a hardener).
I’ve tried it with Lidl instant, not Nescafé, though...
No, no smileys. Seriously.
andreasbrigachtal
Hi Christian
You’re not actually joking, are you? :huh:
Please clarify! I’ll give it a go too! :D
Although I can’t quite believe it. :unsure:
I’ll probably even pop into Lidl this weekend! I recently managed to pick up a few expired Techpan films at a bargain price. I’m sure I can spare one for this! :D
I hope the coffee’s drinkable if it comes to it!
Good light
Andreas
I’m so small and always will be
RomanJRohleder
Andreas,
No joke.
Have a go at Googling "Caffeenol" (or "Coffeenol"), "Folgernol" and "Use for the last cup of coffee".
ChristianKolinski
Hi Christian
You’re not joking, are you?
No, it’s not a joke.
Have a look:
http://www.blafh.de/caffenol1.jpg
(Yeah, I really must do something about the dust. And why the Japanese had to turn the lovely Rokkor into a fixed-focus lens is beyond me too...).
Kodak Imagelink FS in the above recipe, ISO 100. Camera: Revue 16KB (aka Minolta 16MG). Negative format 10x14mm,
print on Fomaspeed Varian III, grade 2.
Please clarify! I’ll give it a go too!
Go ahead...
I recently managed to pick up a few expired TechPan rolls cheaply. I’m sure I can spare one for that!
Cut it up. So split it into streaks about 15cm long, then you’ll have more material to experiment with; as with any ‘rule of thumb’ homemade solution, you’ll have to tweak it a bit. I haven’t tested the original TechPan; it was always too expensive for me...
BTW: Development temperature 20°C, and decaf won’t do the trick – it seems something else besides the caffeine gets extracted.
Gast
Franz,
but,
if the film is always 18 DIN on Efke FR3, why does it show 20 at daylight and 18 under artificial light on FR 14?
Either Efke is giving the wrong information, or you’re overlooking something here; I can’t judge, I’ll admit that.
Roland
andreasbrigachtal
Hi Christian and Roman,
I’ll give that a go! I’ll try just about anything! Does it actually work with filter coffee as well?
I’m curious to see. I’ll put it on my website or post the link here. In future, a few friends and I will also be appearing on positivwelten.de. It’s still under construction at the moment, though, so there’s nothing to see yet. Maybe there’ll be a special feature in my planned lab section.
Oh, and a question for Franz: can the chemist explain the coffee bit?
I can hardly wait for the weekend!
Andreas :D
cfb_de
Hello Roland,
It’s quite simple. You’re dealing with two separate things. I’ll try to explain.
- The developer. A reducing agent that doesn’t care at all about the film’s sensitisation, because the chemical process can’t know which photons the film is particularly sensitive to at any given moment. Whatever exists as a latent image is amplified through catalytic reduction. This sometimes works better with one developer than with another, hence the ‘differences in sensitivity’. But that has nothing to do with sensitisation.
- Sensitisation. By design, a film emulsion is less sensitive at the red end of the spectrum. This is helped along by ‘sensitising dyes’. However, this only works to a limited extent (and is then referred to as “ortho”/“pan”/“superpan” sensitisation) and sometimes results in a lower speed being specified under artificial light (i.e. longer-wavelength radiation, where the film is less sensitive). This has absolutely nothing to do with the developer, however.
I think Efke’s statement regarding lower speed under artificial light is very fair, as this material is indeed less sensitised in the red region. Regarding the misleading information in the datasheet: you could always give it a try. There should also be a noticeable difference with FR3. Unfortunately, datasheet specifications are not gospel truth and depend heavily on the effort that has been put into them.
Best regards,
Franz
cfb_de
Hello Andreas,
There’s bound to be some reducing agent with the right potential in there. Which one? I’ve no idea. I’m not really familiar with natural product chemistry.
In principle, you can develop a latent image using any reducing agent (with the right potential). Even with horse p*** – there’s something suitable in there too (a pyrocatechol derivative, which humans lack :-)).
That’s probably where all the fun comes from:
http://www.photo.net/bboard/q-and-a-fetch-...g?msg_id=003aPB
Best regards,
Franz
