The ACUROL-N Thread

[lawrence]

Several points spring to mind when viewing these negatives:

• They are very over developed. Reducing the time by about 10% to 10min as you plan will not be sufficient, you will need a bigger reduction than this probably to about 8min.
• The increase in grain is not simply to do with the scanner, over development always leads to an increase in grain even with wet printing.
• Foma 200 has a true film speed of about 125 EI, therefore this part of the instructions is correct.
• There isn't excessive detail in the shadows, in fact only just enough, which indicates that the film has not been over exposed i.e. the excessive density in the highlights is not caused by an exposure issue and is clearly a development issue.

Hope this helps
Lawrence

 

[albireo]

Thank you both - that's extremely helpful.

Sounds like the best way forward is to reduce development. I will try a couple of rolls at 8 and 9 minutes respectively and report back.

Only a minor point, Lawrence. Based on foma's official data sheets, I was under the impression that the true film speed was a variable associated with the developer.

If we look here

https://www.foma.cz/en/fomapan-200

The plots on page 2 indicate (unless I'm misunderstanding the plot) that this film can be a 160/200 true iso film, depending on the developer.

Indeed, my experience with Fomadon LQN (4th graph, bottom) seem to suggest that good results can be had exposing at 160 and developing for 6-7 minutes.

Again - I'm only just starting with this, so I might be completely wrong, happy to stand corrected.

 

[lawrence]

I'll run through the charts supplied by Foma. First thing you need to decide is what gamma (contrast) you're going to develop to and IMHO 0.6 is about right and approximately where ISO speed is measured (many people suggest less contrast than this but personally I haven't found much advantage in it).

Starting with Ilford Microphen, shown in the first chart, you can see that at gamma 0.6 (the lower curve) you are getting EI 160 (the upper curve). So what this tells you is that with Microphen you're not getting as much as EI 200. The speed point for Fomadon LQN and Excel is approximately the same and all three of these developers give a slight boost to film speed (Microphen, Ilford's speed increasing developer, giving a little bit more than the other two).

The chart for D76/ID11 tells you that you're going to get a very contrasty result with undiluted developer at normal development times but if you extend the curves leftwards you can extrapolate that at gamma 0.6 your EI will be about 125. Since ISO film speeds are determined when using MQ developers such as D76, the true speed of this film is close to 125 EI.

 

[albireo]

Fantastic explanation - thank you very much!