Ilford Delta 100 processing conundrum

dkonigs · Jan 17, 2020

So today I went out and shot some Delta 100 in my 4x5" camera. I accidentally metered the scene at ISO 50. This gave me an exposure time of 80s, which with reciprocity became an actual exposure of 2m19s or 4m10s (depending on whose formula you use). I actually decided to shoot at both, so I could compare later (since I'm new to long exposures on Delta).

I'm planning to process the film in DD-X (1:4), and need to decide what processing time to use.

First question... Do I process with the time for ISO 100 (and hope for the best), or the time for ISO 50?

Second question, who do I trust for processing times?
At ISO 100, Ilford's datasheets say 10:30. Meanwhile, Ilford's product page and the Massive Dev Chart say 12:00.
At ISO 50, Ilford's datasheets say 8:00. Meanwhile, the Massive Dev Chart says 9:30.
(Or do I use a different time entirely, perhaps somewhere in the middle?)

adelorenzo · Jan 17, 2020

I always use Ilford's information. The massive development chart is unverified information and it's related to one individual's particular process.

I normally shoot Delta 100 at ISO 50 and develop for 8 minutes in DDX, it works well. If you developed it for 9:30 you'd get good results as well I am sure just a bit more contrast. It's less than a 20% increase in development time.

adelorenzo · Jan 17, 2020

Ilford has recently published specific reciprocity data for their various films, the factor is 1.26 for Delta 100 so the 4:10 exposure should be the correct one.

dkonigs · Jan 17, 2020

adelorenzo said:
I always use Ilford's information. The massive development chart is unverified information and it's related to one individual's particular process.

Yeah, I'm usually suspect of that chart when I see conflicting numbers from more "official" sources. This happens more often than I'd expect, and gets tricky when the official sources "feel" off or incomplete.

adelorenzo said:
I normally shoot Delta 100 at ISO 50 and develop for 8 minutes in DDX, it works well. If you developed it for 9:30 you'd get good results as well I am sure just a bit more contrast. It's less than a 20% increase in development time.

What are your thoughts on shooting Delta 100 at ISO 50 vs 100? I'm also wondering if I should treat this as an isolated screwup (and just develop these sheets by themselves), or if I should shoot more at ISO 50 on-purpose so I can process in a larger batch. (Though I do have other exposed-at-100 sheets to process, so I'm wasting a little bit of chemistry either way.)

adelorenzo · Jan 17, 2020

dkonigs said:
What are your thoughts on shooting Delta 100 at ISO 50 vs 100? I'm also wondering if I should treat this as an isolated screwup (and just develop these sheets by themselves), or if I should shoot more at ISO 50 on-purpose so I can process in a larger batch. (Though I do have other exposed-at-100 sheets to process, so I'm wasting a little bit of chemistry either way.)

Well it's negative film so it has a ton of latitude. If it was me I'd just throw everything in the tank and develop it as if it was for 100. You'll still be able to get a good print or scan from it.

When I'm shooting Delta 100 (or FP4+) I am usually on a tripod anyway, so I figure ISO 50 for the extra stop of shadow detail and slightly less contrast gives an easier negative to work with. Plus I'll take an overexposed negative vs. underexposed any day.

I've not done film testing or anything like that, just going with what works for me. YMMV.

dkonigs · Jan 18, 2020

adelorenzo said:
Well it's negative film so it has a ton of latitude. If it was me I'd just throw everything in the tank and develop it as if it was for 100. You'll still be able to get a good print or scan from it.

When I'm shooting Delta 100 (or FP4+) I am usually on a tripod anyway, so I figure ISO 50 for the extra stop of shadow detail and slightly less contrast gives an easier negative to work with. Plus I'll take an overexposed negative vs. underexposed any day.

I've not done film testing or anything like that, just going with what works for me. YMMV.

So you're suggesting to just throw it all in the tank, process for 10:30 in DD-X, and I'll probably be just fine?

cowanw · Jan 18, 2020

You are stressing about one stop in ASA but are quite OK with an alteration of one stop in shutter speed. If the longer shutter speed is correct you are really back to an ASA of 100 with the shorter shutter speed. In effect you have bracketed one way; you just don't know which way.

Bikerider · Jan 18, 2020

Yes, use the Ilford processing information, but only off the website. Sometimes the formulas for the emulsion change without warming and the developing times can also be different. In the case of roll and 35mm film the times are printed on the inside of the box, but these too can be incorrect. Boxed are printed in their many thousands and before they are all used the formulas can change. These are Ilford's words not mine.

dkonigs · Jan 18, 2020

Bikerider said:
Yes, use the Ilford processing information, but only off the website. Sometimes the formulas for the emulsion change without warming and the developing times can also be different. In the case of roll and 35mm film the times are printed on the inside of the box, but these too can be incorrect. Boxed are printed in their many thousands and before they are all used the formulas can change. These are Ilford's words not mine.

The box the film came in doesn't even list a time for DD-X, surprisingly enough, so its not even a factor here. However, it is interesting that the product page gives a different time (12m) from their Delta 100 datasheet (dated Nov 2018), their DD-X datasheet (dated Aug 2019), and their downloadable chart (dated Oct 2019), all of which give 10:30.

I think I'm probably just going to throw this in with my other Delta 100 shots, process in DD-X for 10:30, and hope for the best. As already pointed out, I've sort-of bracketed and its only one stop, and a little overexposure on negative film isn't necessarily a bad thing either (and might even benefit this particular scene).

dkonigs · Jan 19, 2020

So this afternoon, I went ahead and processed the film for 10:30 in DD-X. While its still hanging to dry, I did look at it and crunched some numbers that are probably worth sharing.
First, there were two sheets I actually exposed correctly (using strobes). Those look perfectly fine.
Now onto the sheets I opened this discussion with...
So there are two different reciprocity formulas out there for Delta 100. There's the formula specified in the Ilford datasheet, and the formula in an article by Howard Bond. Since this was my first time dealing with this situation, metered the scene and exposed one sheet adjusted with each formula. As my meter was set to the wrong ISO, I think this actually saved me.

If we assume the Ilford formula is the correct one, and I do some math to determine how far off I was from the actual correct exposure, it looks like one sheet is 1/4 stop over and another sheet is 1 stop over. Visually, this seems to be in the ballpark. As such, I now have at least one sheet that looks pretty good.

From these results, next time I'm going to meter correctly and use the Ilford formula.

John Wiegerink · Jan 20, 2020

dkonigs said:
So this afternoon, I went ahead and processed the film for 10:30 in DD-X. While its still hanging to dry, I did look at it and crunched some numbers that are probably worth sharing.
First, there were two sheets I actually exposed correctly (using strobes). Those look perfectly fine.
Now onto the sheets I opened this discussion with...
So there are two different reciprocity formulas out there for Delta 100. There's the formula specified in the Ilford datasheet, and the formula in an article by Howard Bond. Since this was my first time dealing with this situation, metered the scene and exposed one sheet adjusted with each formula. As my meter was set to the wrong ISO, I think this actually saved me.

If we assume the Ilford formula is the correct one, and I do some math to determine how far off I was from the actual correct exposure, it looks like one sheet is 1/4 stop over and another sheet is 1 stop over. Visually, this seems to be in the ballpark. As such, I now have at least one sheet that looks pretty good.

From these results, next time I'm going to meter correctly and use the Ilford formula.

Are you using a darkroom and enlarger for printing? If not you'll probably like the thinner negative a little better. Maybe even a little thinner than what you have now. My scanner likes thinner rather than thicker negatives. If you are enlarging either one of your negatives should print OK. Have fun! JohnW

Harman Tech Service · Jan 20, 2020

We changed the recommended times to 8/10.5/12 mins for EI 50/100/200 with D100 in DDX a while ago. Our Film processing chart and the Tech Sheet for the film were updated fairly soon afterwards. The DDX tech sheet was updated in Aug last year with the new time (among other changes). Incidentally, it was a customer who pointed out over-development at the original time so we retested it and came up with the new times (thanks Andrew). I'm sorry if we have left the old dev time(s) somewhere. Please let us know where you found them.

David

Ilford Delta 100 processing conundrum

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