Grade change time

bwrules · Apr 28, 2011

Hi.

I am wondering if there is a rule of thumb for time to step between grades. Roughly how much time do I need to go between grade 2 and 3 for example when printing? I am guessing 1/3 of established time, but not sure.

Thanks.

polyglot · Apr 28, 2011

With the Ilford paper+filters, the exposure times are meant to be approximately the same (for a constant midtone I think) for all grades except #5. Or if you're talking about split-grade printing, you would typically use #1 and #4, the ratio thereof depending on what actual contrast you wanted.

2F/2F · Apr 28, 2011

Are you talking about graded paper or VC paper?

With VC paper there is usually a big increase in exposure time when jumping up to grade 4. I am not sure if it can be boiled down into a more specific rule of thumb than that, but maybe. It will be different for each individual paper. In the little paper that comes in the box, there should be some info about this.

Nicholas Lindan · Apr 28, 2011

It depends on what tone you want to remain constant. Look at the family of HD curves for MGIV RC.

If you want to hold a ~0.6 od tone (a wee bit lighter than 18% gray / ZV) then there is no change required. If you want to hold a ZII 1.6 OD tone then you need to increase exposure by around 0.6 stops.

Darkroom Automation supplies HD graphs and speed charts for common Ilford papers. See the support files page http://www.darkroomautomation.com/support/index.htm

David Brown · Apr 28, 2011

bwrules said:
I am wondering if there is a rule of thumb for time to step between grades.

Yes. Make a new test strip. Because ...

Nicholas Lindan said:
It depends ...

bwrules · Apr 28, 2011

Arista.edu FB VC Paper. It really does look like there is no way around a test strip, is there? So far it looks like 1/3 of time to go to 3 from 2. Thanks.

hoffy · Apr 28, 2011

David Brown said:
Yes. Make a new test strip. Because ...

What he said!

Jeff Kubach · Apr 28, 2011

I agree use a test strip!

Jeff

phelger · May 1, 2011

I recently bought some equipment which solves the problem once and for all : A 'StopClock Professional' and a 'ZoneMaster II', both from RH Designs. here's the link :
http://www.rhdesigns.co.uk/darkroom/index.html
True, it comes at a price but the time and the photographic paper saved by using it is convince me it is worthwile
peter

R gould · May 1, 2011

As a rule of thumb with ilford filters it is the same time for filters 00 to 3 1/2 and double the time for filters 4 to 5, It always worked for me in my pre analyser/pro days,
Richard

RalphLambrecht · May 1, 2011

As Nicholas said, it depends on the print tone that you want to keep constant. Filter kits are typically calibrated to give the same exposure for the ISO speed point; a tonality too dark for calibration across paper grades in my opinion (see 1st attachment). You have to pick a tone, because the characteristic curves between grades differ (otherwise it would make no sense to switch grades). I advocate to expose prints for the highlights, so I pick a lighter tone (Zone VII or VIII). As others said, yes, it's best to test for your conditions.

However, you don't have to make a test strip every time. You can conduct one test and make yourself a table (see 2nd attachment), which is good for one particular paper/developer combination. Once you have the table at hand, you can convert a proper highlight exposure of one grade into another for another grade with ease.

bwrules · May 1, 2011

Thanks all. Really appreciate the information.

BetterSense · May 1, 2011

This is part of the reason that I used to use split-grade printing with only 00 and 5 filters. I've kind of stopped doing that because #2 just works for most of my negatives, but any time I need to make a contrast adjustment, I always wish I had started with the 00 and 5 split grade technique, because it's easier to vary the proportions of exposure without changing the actual filters you are using. By the way, is there any H&D curve difference between using 00 and 5 filters versus using the equivalent single exposure with an intermediate filter?

RalphLambrecht · May 1, 2011

BetterSense said:
... By the way, is there any H&D curve difference between using 00 and 5 filters versus using the equivalent single exposure with an intermediate filter?

By using the two filter extremes for split-grade printing, you can produce the same characteristics curve as any intermediate filter. There is absolutely no tonal advantage to split-grade printing if you simply add the two exposures. You will, however, get a benefit if you dodge and burn differently with both filters.

Grade change time

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