Would be interesting to do the same test with Ilford's Ilfotech HC, supposedly similar to the original HC-110 formula.
Could this be due to HC-110 itself going through several reformulations in recent years?
Ilford says that their development times are published for, quoting: "The times in bold will produce negatives of normal contrast (G0.62)". Elsewhere they say: "0.62 is suitable for printing on grade 2 or 3 photographic paper under typical darkroom conditions."
I do not know why you're getting the results you're getting, but it seems to me that Ilford clearly cares about contrast.
Could this be due to HC-110 itself going through several reformulations in recent years?
Would be interesting to do the same test with Ilford's Ilfotech HC, supposedly similar to the original HC-110 formula.
View attachment 405200
This is a screenshot from the ISO:6 for the determination of film speed. My understanding is that not only the speed point must be met, but also the general curve steepness. My assumption would be that Ilford, in their data sheet , does not care about curve form, but only about point m (speed point). This is only an assumption though and might very well be a misunderstanding of the matter on my side.
As mentioned in my latest post in this thread. My assumption got confirmed by Ilford directly, about 5 hours ago. They care about a correct slope but only for one specific curve in ID-11 the rest of the data is only meant to produce box speed, in disregard of contrast. Direct quote from the Email:
"
We supply the information on our tables to give speeds using different developers but these are more accurately described as EI values (Exposure Index). The contrast at the particular speeds with particular developers will be variable and not something we have ever quoted. This data is supplied as an aid to customers, to give an indication of how to achieve the effective speed so that users can calculate exposures appropriately. It would be possible to give a defined ISO speed for each developer, but most would give a different speed under the ISO contrast conditions."
-David Abberley, technical services
"Product technologist". Working at Harman/Ilford for 42 years, 9 months.Either way I'm betting he wasn't from R&D.
Exactly. IMO Ilford's message is quite clear in this regard and despite (or perhaps, I'm starting to wonder, 'thanks to') the language barrier, it seems that @reneboehmer, you and me managed to figure out its meaning.Ilford gives times to achieve boxspeed but not (neccessarily?) normal contrast?
I'm going to be pedantic. The speed point doesn't need to be met, but is determined. You're not aiming for a speed but determining speed under the stated conditions.
You maybe reacting to a poorly worded response from Ilford. First speed is a product of the inherent qualities for the film and the specifics of development. Not the other way around. You don't process for a given speed, so the Ilford representative's response was clumsy at best. Was he unknowingly wrong or or just patronizing? Either way I'm betting he wasn't from R&D.
I wrote a post explaining my position twice, but it keeps coming out preachy.
While the data sheet on Ilford developers does give a Gbar for what they consider average processing, the film data sheets I've checked don't, but they do say, "These times will produce negative of average contrast suitable for printing in all enlargers." They also include a statement about other manufacturers' developers, "Development times in other manufacturers' developers are included for you convenience and are only a general guide. Other manufacturers can and do change their product specifications from time to time, and the development times may change as a result."
Very interesting! That means, you are completely on the safe side, if you manage to comply with Ilfords directions for development AND use ID11 (stock?). With any other developer: Contrast is a variable the user has to get right on his own. This explains a lot of my frustration over the years, until I started doing my own sensitometry. (Typo edited)Here is a full quote of the total email:
Very interesting! That means, you are completely on the safe side, if you manage to comply with Ilfords directions for development AND use ID11 (stock?). With any other developer: Contrast is a variable the user has to get it right on his own. This explains a lot of my frustration over the years, until I started doing my own sensitometry.
"These times will produce negative of average contrast suitable for printing in all enlargers." They also include a statement about other manufacturers' developers, "Development times in other manufacturers' developers are included for you convenience and are only a general guide. Other manufacturers can and do change their product specifications from time to time, and the development times may change as a result."
"Product technologist". Working at Harman/Ilford for 42 years, 9 months.
But what you can also see in the data sheet is that Ilford does only state EI and not ISO, making it not needed to conform to ISO conditions with each developerT
Dear Stephen, I think I understand that Delta X testing is a more accurate way of determining speed and is preferred over the simple .10 over base fog method, because it takes the curve toe length into account. As far as I can tell from the paper, it was discovered that Delta X was a more consistent factor to obtain proper exposure for good prints. (Please correct me if my understanding is wrong).The ISO standard is about determining film speed. It's not a standard for development. The ISO contrast parameters are defined so that there is a consistent relationship between the fixed density speed point of 0.10 over film base plus fog and the fractional gradient speed point. When ΔD is 0.80 at Δ1.30 log-H, ΔX always equals 0.296 log-H. This brings into agreement the fixed density method with the fractional gradient method. It's called The Delta-X Criterion. Delta-X Criterion paper
View attachment 405320 View attachment 405321
The average gradient of the tested film under the Δ1.30 log-H, ΔD 0.80 conditions is only 0.62 when the curve has a short toe. Long toed films have a higher average gradient. Using CI, it can be around 0.67. What they both have is a gradient of 0.3x the average gradient at Δ0.296 log-X below the fixed density speed point
Do I understand this correctly, I'm not a native speaker and the above mumbo-jumbo seems easy to get wrong: Ilford gives times to achieve boxspeed but not (neccessarily?) normal contrast? For all or only for films from different brands? Because that is what users assume when setting exposure: Boxspeed? If this is the case, it's not quite what I would wish for. Time to get my broken densitometer up and running again.
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