Development compensation for Foma 200 reciprocity?

[Shen45]

Does anyone have approximate % figures (not zones) to reduce development with Foma 200 5x4?

By way of example:
Normal development is 8 minutes
Metered exposure is 10 seconds
Corrected for reciprocity is 90 seconds.

To my mind some reduction in development time seems required to control highlight development but I'm not sure how much.
If you need to explain in terms of zone reduction can you indicate what that is in percentage terms.

Thanks Steve

[Pere Casals]

Does anyone have approximate % figures (not zones) to reduce development with Foma 200 5x4?

See development times N, N-1 for the percentages.





By way of example:
Normal development is 8 minutes
Metered exposure is 10 seconds
Corrected for reciprocity is 90 seconds.

To my mind some reduction in development time seems required to control highlight development but I'm not sure how much.
If you need to explain in terms of zone reduction can you indicate what that is in percentage terms.


Still I've a lot to learn regarding night photography, but let me explain how I face that situation.

First you may need not only a compression but also a compensation. Highlights have less failure than shadows, so the compensation will selectivelly decrease development in the highlights, this is obtained with a diluted developer and low agitation, in that case developer is "exhausted" sooner in the highlights which will have an smaller effective development time. In fact that developer "exhaustion" is more provocated by bromide presence (a development byproduct) than from true developer exhaustion.

If you check the LIRF table compensation for 10s is 90s, this is x9 more exposure time, but highlights at +3 overexposure have a nominal exposure of 1s and the table says the compensated time is 3s, just 3x.

So your good exposure compensation is different depending on shadows, mids, highlights. This ends in a deformation of the curve and a decreased film latitude...


The tools you have to face this problem is compression and compensation, for best results you may want to combine both. From the 9x to the 3x you will have highlights overexposed by 1.5stops more than expected.

Me, I still would expose a bit more than the table says, to have better shadows, so at least I'd have to fight a 2 or 3 stops additional overexposure in the highlights, say that we have 2 stops, I'd decrease development time to N-1 for all the negative, and I'd decrease agitation to decrease one additional stop effective selectively in the highlights.

So I'd use Xtol 1:3 for Foma 200 rated at ISO 100 (N-1), this would be around 12min(I guess), and reduced agitation (each 3 or 5 min) to cut some 1 stop development selectively in the highlights. To prevent bromide streaks I'd do it with tray development, inside a paper safe so I can open lights.

in practice:

> Overexpose a bit more than recommended if wanting better shadows.

> Use development time for N-1 or (N-2) with diluted developer, so time for Foma 200 rated at 100 at 1:3 or 1:2 dilution, the one you use.

> Practice with reduced agitation. This will reduce develoment in the highlights while not messing much in the rest, this will reduce the deformation of the curve provocated by LIRF.


__________________-


Note that I use "compensation" term for 2 different concepts, time compensation in the exposure, and development compensation to selectively develop less the highlights from developer dilution combined with low agitation.

[Shen45]

Great answer and information. Thanks for taking the time to share your knowledge.

Steve

[Pere Casals]

My pleasure

[koraks]

In my experience, while the fomapan reciprocity characteristics are quite challenging, they're not as severe as the datasheet suggests. At 10 seconds, I'd go for about 1-1.5 stops additional exposure and normal development. The additional contrast will still be within the comfortable range of variable contrast papers and shadow detail will be still good.

[Pere Casals]

while the fomapan reciprocity characteristics are quite challenging, they're not as severe as the datasheet suggests.

Also IMHO recommendations in datasheets are a bit conservative, and this is not bad for the starting point.

With LIRF compensation tables we have several problems. First metering style has a lot of influence, some use personal film speeds, and the right factor is different for shadows, mids and highlights. At the end we can do two things, one is experimenting to know the film behaviour under our metering style, the second thing we can do is calibrating film in LIRF conditions, this is making the Stouffer's contact copy with long exposures, drawing the film curves, and comparing with a LIRF free curve.

[Drew Wiley]

My normal for PMK was only 6 min. The recip characteristics are downright awful. And the real speed for me was around 100. But I gave up on it due to quality control issues - lots of coating zits and thin cracks. Those issues were small enough where a contact printer of 8x10 film might be able to tolerate them; but they show up on even modest enlargement, and very thin long lines are among the hardest things to cleanly retouch in a print. If I had to do some serious minus development, I'd probably use a high dilution of HC110 to prolong the processing time. But someone else might have a better idea.