How do I calculate the right push developing time?

[Twan]

Dear analog enthousiasts,

I'm have a question regarding finding the right developing time / formula the info cannot be found on Massive Dev Chart.

I have two roles of B&W film that I want to develop and both push one stop. One roll of IMAGO 320 (ARS) and one roll of 400 TMAX (Kodak).

1) My first question relates to finding the right developing time. I am using Ilfotec DD-X developer, but since Imago 320 is a rare film I imagine, there are no results for this combination on Massive Dev Chart. How should I go about this? The only developing times in MDC that show up from Ilford are done with ID-11 developer.

2) How do I calculate the right push-processing time based on the standard developing times? Doing a quick Google I found here that usually a 1-stop push can be achieved by using 1,5 times the standard developing time. But I'm confused as it also says that for TMax film a 1-stop does not have a longer developing time as an exception.

Why is this the case? How do I push-process for Tmax 400 and how would I go about it for Imago 320?

3) Sometimes on Massive Dev Chart I find two different results on the same stock / developer combo. Is that just because two different people uploaded this that have a different preference?

I am fairly new to the whole process of developing my own black & white film, my apologies if I am asking very simple questions but I'm very keen on understanding how this all works.

Warm Regards,
Twan (Film Student)

 

[compur]

Here is the data sheet for DD-X:
https://www.ilfordphoto.com/wp/wp-content/uploads/2019/08/ILFOTEC-DDX-AUG19.pdf

It gives times for pushing TMax 400. (Manufacturer's data trumps internet advice.)

To push the Imago one stop w/out specific data, I would add a minute or so as a guestimate.

 

[jcdeboever]

Tmax...The answer is probably in the data sheet. I never liked it all that much unless I used tmax developer, it definitely is weird with HC110 which is my main developer.

1 to 1.5 is a good starting point for pushing, mileage will vary on film stock and dilution. A small reason why I stick to only a couple of film stocks. I don't push a whole lot, i did it only to experiment. Pushing really messes up darkroom print quality. Pushing is way over rated imo. I rhink pushing film is more a byproduct of software editing because it doesn't work that way in the darkroom in my experience.

As far as 320 film maybe look at the data sheet and compare times between another common film stock and your developer and do the math?

 

[Twan]

Here is the data sheet for DD-X:
https://www.ilfordphoto.com/wp/wp-content/uploads/2019/08/ILFOTEC-DDX-AUG19.pdf

It gives times for pushing TMax 400. (Manufacturer's data trumps internet advice.)

To push the Imago one stop w/out specific data, I would add a minute or so as a guestimate.

Thank you Compur, I did realise all of this information actually can be found in the developer manual. Very helpful!

As for jcdeboever: what I did now is to reference how the ID-11 developer in TMax developing times relates to the one I have and make a calculation based on that for the Imago 320 filmstock.

TMAX 400 (non pushed based on manual)
ID-11 - 7:00 in 20c (stock) (420s) (pushed time 9:30)
DDX - 8:00 in 20c (1+4) (480s) (pushed time 10:00)

Imago 320 (non pushed based on manual)
ID-11 - 7:00 in 20c (stock) (420s)
DD-X estimate: 8:00 in 20c (1+4) (480s) (pushed time 480s x1,5 = 720s = 12:00) does this push time seem excessive or should it be alright?

 

[compur]

Imago 320 (non pushed based on manual)
ID-11 - 7:00 in 20c (stock) (420s)
DD-X estimate: 8:00 in 20c (1+4) (480s) (pushed time 480s x1,5 = 720s = 12:00) does this push time seem excessive or should it be alright?

I would have tried 10:00 just based on the Imago data sheet but I have no experience with that film so it would just be my guesstimate.