TriX and HP5+ time difference in processing time with D76

[Wanderer]

Hello,

I am going to process some HP5+ (exposed for 400 ISO) with D76 at 1:1, 20°C in a SP 445 tank.
Looking in the Massive Dev Chart, it is recommended 13 minutes.
I have only been processing TriX yet, with a developing time of 9 minutes (D76 1:1, 20°C with continuous agitation for 1 minutes and then 10 seconds of agitations every minutes) as per indicated on the same site. And as far as I can see (I still have to scan the negs), the result seems satisfying.
I am very surprised to have such big difference of time (4 minutes, almost 50% more for the HP5) between this 2 films, I thought those films were quite similar.
What would be the reason for it?

Oh, and as per Ilford recommandation, it should be 11 minutes.https://www.ilfordphoto.com/amfile/f...roduct_id/695/
I am a bit confused now, I don't understand how Massive Dev Chart gives 13 minutes?

Thank you for answers
Regards

Alain

[Bernard_L]

I am very surprised to have such big difference of time
I don't understand how Massive Dev Chart gives 13 minutes?

The "information" in the MDC is of unspecified and uncontrolled origin. Even without definite proof, I tend to believe that the manufacturer supplied information is based on systematic testing. With the exception of the big hiccup from Kodak when they updated HC-110 dil.B for 400TX.

[Huub]

Checking the Ilford datasheet on HP5+, it states 13 min for 1+1 ID-11. Because D76 and ID11 are more or less the same developer, I would use this time.

A few factors also to consider are subject contrast - when high contrast you might want to develop a bit less and when low contrast you might want to add a bit of devloping time - and what you want to with the negatives after development: scanning and printing in a condensor enlarger demand for negatives that are a bit softer then those to be printed with an enlarger with a difusor head. Keep notes and evaluate the results and work from there for the next batch of negatives.

[Wanderer]

Thank you very much for your answer and all the advices, much appreciated.
I will go for 13 minutes then, and see what it brings.

[koraks]

I am very surprised to have such big difference of time (4 minutes, almost 50% more for the HP5) between this 2 films, I thought those films were quite similar.
What would be the reason for it?

While these films serve similar purposes, they are of course completely different products from different manufacturers. There is no hard relationship between film ISO and development time, although higher ISOs tend to require longer development times - but this is not a hard and specific rule that can be applied linearly across individual films, let alone products from different manufacturers. There are many variables that determine the required development, such as grain geometry and surface, degree of hardening (permeability) of the emulsion, thickness of the emulsion, chemical composition of the silver halide mix, presence or absence of development accelerating or inhibiting compounds, etc. etc. etc.

[Pere Casals]

I am very surprised to have such big difference of time (4 minutes, almost 50% more for the HP5) between this 2 films, I thought those films were quite similar.
What would be the reason for it?

There are several reasons explaining development time difference.

One is crystal shape, cubic crystals (HP5) expose less surface to chem for the same amount of silver than T-Grains (tabular), so things may happen faster. In theory TX/TXP are classic films but they were modified to include a T-Grain share. HP5+ was also modified (delivering less fog), but it remains less changed, I guess.

D100 (Delta grain) develops slower than FP4, what may be strange, but D100 is not Tabular but "epitaxial growth".

It is usual that (with the same kind of emulsions) the slower film develops faster, (see D100 vs D400 and PANF vs FP4) in that case the slower film has smaller crystals, having more surface than larger crystals for the same silver.

Of course there are other factors I don't know or even undisclosed...

[Wanderer]

koraks and Pere Casals thank you very much for your answers, the time difference makes more sense to me now.
I must confess, I have been using TriX for many years and HP5+ from time to time, but i actually never bother to really dig into the technicalities of the films, wrongly assuming they were not that different.
Glad I learned something today. Thanks again!

[koraks]

i actually never bother to really dig into the technicalities of the films

I think there's nothing wrong with that. Every minute spent on digging into technical details is a minute not spent on making images. I know, because I read and think on technicalities way too much to be an actual photographer. You may notice that the vast majority of people who are very knowledgeable on the technical aspects of photography have very little (if any) impact in artistic terms. There are, of course, exceptions to inspire us all.

[Pere Casals]

they were not that different.

let me add that a main aesthetic difference of hp vs tx/txp is grain structure, while hp has the peak graininess in the mid grays tx/txp has more in the shadows, this is harder to be seen in LF... but it can be very well seen in a 30" or 40" print (from 4x5" negative) at close distance. In smaller formats this has been exploited a lot, to extenuation...

This is how a grain simulation softaware replicates the grain nature of both, see that tx has peak grain at left, in the darker greys:



Of course the grain perception also depends on microcontrast, contrasty textures mask grains... so to compare well see washed areas, it is shown it better.

[Fred L]

I used to refer to the MDC but found it all over the map imo. I'd sooner trust (and actually use) Freestyle's dev charts if not the manufacturer's times. Not sure if it's still mentioned or not in the charts, but times, as mentioned before, were for a certain contrast index. Some testing would be prudent to find times that work for your regimen