Fanesa
My recipe for reverse development states that 5 mg of potassium iodide should be added to the first developer. Is this absolutely essential for the first developer, or would it work without it?
Many thanks!!!
WolfgangF
Hello Fanesa,
The original Agfa reversal developer formula also recommends adding potassium thiocyanate (rhodanide) instead of potassium iodide.
In his guide to the reversal processing of technical films, Moersch dispenses with these additives entirely.
http://www.moersch-photochemie.de/files/articles/FO5%20Umentwicklung.pdf
Potassium salt causes increased depth development in the primary developer
It should work without it too; perhaps the shadows won’t be quite as dense then?
Jost Marchesi’s Photokollegium, Volume 1, Lesson 14, provides some useful information
Could you please send me your formula? I’d be interested to see it.
Many thanks and best regards
Wolfgang
Wolfgg
Hello Fanesa!
Potassium thiocyanate ensures that the highlights are fully developed during the initial development stage, meaning they will be properly clear in the slide afterwards, as fog robs the slide of its brilliance. It also makes the film more contrasty overall. Around 3g (not mg) per litre of ready-to-use developer solution is standard. Alternatively, the slide could be clarified in Farmer’s solution as a final step, but this does not work with all films, so test it first on test shots.
Regards, Wolfgang
Fanesa
Thanks, Wolfgg!
For first-time developers:
Top up 900 ml of water with 100 ml of Dokumol to make 1000 ml. Add 5 g of potassium thiocyanate and stir in. Then add 50 mg (not grams!) of potassium iodide. Store in a light-proof, airtight container.
That is the recipe from Schmalfilm.
So it could be omitted. The result would just not be quite as clear...
Wolfgg
Hello Fanesa,
Let me explain in a bit more detail:
When it comes to reversal processing, three things are crucial: firstly, the slide must be sufficiently transparent in the highlights (technically: the minimum density must be sufficiently low); secondly, the deepest shadows must be sufficiently dense (technically: the maximum density must be sufficiently high); and thirdly, the contrast must be suitable for projection (technically: the gamma should be around 1.5). Since ‘print films’ – that is, films designed for producing paper prints – are not primarily designed for reversal processing, a bit of tweaking is required during development to reconcile these three objectives, and not all films are suitable for this. My last test was a few years ago, but it showed that low-speed, silver-rich film types such as Ilford PanF worked best at the time.
To start with, simply find a suitable test subject (something with contrast, i.e. very bright areas as well as deep shadows), take a series of exposures (4 shots, each 1/2 stop apart), cut off a section of film and simply process it using the reverse process without any additives in the primary developer, check the result and only then decide whether the primary developer needs to be ‘doped’. Perhaps simply extending the primary development time, e.g. by 20%, will suffice. It also depends on your own standards as to how much effort you’re willing to put in.
Regards, Wolfgang
Fanesa
It’s a reversal film. Not 35mm, though, but Super 8, so the base shouldn’t be much of a problem. I’ll give it a go as you suggested.
Thank you very much!
