Utilisation of speed - Beginner's question

biskardi · 2007-06-14T09:40:07+00:00

Hallo, ich bin neu hier im Forum, mache grade eine Versuchsreihe mit allen SW-Filmen, in der zweiten Phase jeweils ein Film + verschiedene Entwickler Es h...

biskardi

Hello, I’m new to the forum. I’m currently running a series of tests with all the SW films; in the second phase, I’m testing one film with various developers. People always say that some developers make good use of the film’s speed, some reduce it (fine-grain developers, Perceptol), whilst others (Microphen) increase it. That’s all well and good; I’ve read a lot about pushing and pulling, but I don’t understand what actually happens at a chemical level? Question: Is it the case that a fine-grain developer breaks down the crystals through semi-physical development, making them finer and thereby reducing sensitivity, whereas a push developer enlarges the grain (???) and thus increases sensitivity? Is the latent image developed more weakly or more strongly in these two cases? And does that actually mean that a (normally exposed!) ISO 400 film in Perceptol (for example) will have fine grain but less detail in the shadows, whereas the same film in Mikrophen will have a bloated grain and more detail in the shadows? I read somewhere that the shadow detail lost through underexposure when pushing the film cannot be restored; only the contrast would increase. So why ‘higher speed’? Perhaps in the mid-tones or highlights? I’d be grateful for any information! Regards Maciej

Otto

With black-and-white film, the development process is not standardised in the same way as it is for colour film. In colour photography, there is the C41 process for negative film and the E6 process for transparency film. These processes are standardised worldwide, and no one would think of using different processes or developers. With black-and-white film, in principle every film/developer combination has its own development time and its own speed. The speed stated on the film box refers to a process and developer specified in the standard. If a different developer is used, a different effective speed is achieved. As there are many films and even more different developers, it is easy to work out how many combinations are possible. Therefore, a good development chart should include not only the development time but also other parameters (such as effective speed) to provide more accurate values for one’s own work. Before any comparative results can be evaluated, one must first determine the correct development time and the effective speed. And that is precisely what makes meaningful tests so time-consuming. What question are the tests outlined above intended to answer? Best regards, Otto Beyer! http://www.ottobausw.de/

biskardi

What exactly are the tests outlined above intended to answer? Best regards, Otto Beyer! Hello, Thank you very much for your post! Unfortunately, this doesn’t answer my questions... I know that ISO speed is tested under standardised conditions, with a specific developer, in relation to a specific contrast, etc., and that a film-developer combination yields a different, effective speed (EI), or rather that you can also test and adjust it yourself to achieve the desired results. My question was twofold: In practical terms – does a loss of sensitivity(e.g. correctly exposed 400 ISO film in Perceptol, or Delta 3200 in ADX A+B – effective sensitivity should be approx. 400) simply mean a loss of detail in the shadows or overall, i.e. shadows, mid-tones, highlights – because reduced speed should surely mean less density at the same exposure, and increased speedshould correspondingly mean more detail in the shadows/in shadows, mid-tones and highlights – because increased speed should surely mean stronger density?? All in comparison with a developer where the speed is fully utilised; and theoretically: What is happening here? See my original question – how can a loss of speed occur? Speed – determined by grain size – is, after all, a given. According to Steven Anchell’s ‘Darkroom Cookbook’, grain size can only be altered to a very limited extent. So I have the latent image, distributed within grains of a certain size, and now what? If a fine-grain developer breaks the grains apart (through sulphite and physical development), doesn’t that result in finer grain? But why does it lead to a loss of speed?? Is less silver simply reduced from the latent image, resulting in less density and fewer details??? And with a sensitivity-enhancing developer? Does that perhaps enlarge the grain???? I don’t understand what’s supposed to be happening chemically here..... As I said, I’d be grateful for any literature recommendations or a detailed explanation. Many thanks in advance! Maciej PS – I’m just doing these tests to find the right combination for my purposes.

Otto

A film has a different nominal speed when used with different developers. This means that a particular film has a different nominal speed in D76 than, for example, in Perceptol. If you expose a film at a speed that differs from the developer-specific nominal speed, this usually results in a loss of quality in the print. It is up to each individual to decide what level of quality loss is acceptable, and this will likely depend on the intended use and size of the planned images. This means that when setting the exposure, you should already know which developer you intend to use. This has nothing to do with a loss of sensitivity. With a developer, you achieve the developer-specific nominal sensitivity; and that is all there is to it. There are probably no tricks involved. The effects of under- or over-development in combination with under- or overexposure can be seen, for example, here: http://www.fotokollegium.ch/Lektionen/Lektionen.html Specifically, see Lesson 10. Unfortunately, the images are quite small, but they certainly give an initial impression of how it works. What happens photochemically there is a matter in itself. There are a large number of different developing agents. And these are combined in commercially available developers and optimised with further substances. I think that borders a bit on alchemy. Perhaps I’ve been of some help. Best regards, Otto Beyer! PS: You can study the effect of different developers in various dilutions on the same film here: http://www.inficad.com/~gstewart/filmtest.htm

biskardi

Hello, and thanks again for your reply. It’s certainly helped, thank you very much; the links in particular are really useful... I’ll just carry on with my tests now, then I’ll see the differences, and as for the alchemy, I’ll just have to work my way through Marchesi and Anchell, or perhaps someone else will get in touch – knowledge is just a matter of putting in the effort... Best regards from Luxembourg! Maciej

Otto

Hello Maciej, Here’s another link that’s already been helpful to me: http://www.imx.nl/photosite/technical/indextech.html . You’ll find several articles there that are relevant to the topic. Best regards, Otto Beyer!

Hoddy

Best regards, Otto Beyer! Hello, Thank you very much for your post! Unfortunately, that doesn’t answer my questions... As I said, I’d be grateful for any book recommendations or a detailed explanation. Many thanks in advance! Maciej PS – I just want to use the tests to find the right combination for my needs. Have a go here http://www.foto.unibas.ch/SKRIPTEN/ReseauC...e_Chromogen.pdf Regards, Horst

piu58

I don’t know why, as a beginner, you’re so keen to experiment. I’d recommend you pick a fairly standard film (e.g. FP4+ or HP5+) and a standard developer with a specified development time, such as ID11. Then increase the exposure by half a stop and perform the development for 20% less time than stated in the instructions. That’s a good starting point. If the shadows are too thin, the film has underexposure, so use more light next time (half a stop). If the density is too high overall and the shadows are well covered: use less light. If the prints become too harsh at gradient 2, the film is overdeveloped – next time, develop for 10% less time. If the print is too soft, develop for longer. After 2 or 3 rolls of film, you’ll have found a good combination for normal lighting conditions.