Changing Dilution for N+1

[sterioma]

Hi all,

I am using some of my time in lockdown to do some (more or less) rigourous film testing, with my newly acquired transmission densitometer. As an engineer, I am finding this a lot of fun.

I have almost nailed my times for N and N-1 development for HP5 (120), developed in HC-110 dil H. I have found that my EI, for this film and developer, is 160 and I need 15 minutes for N development (Zone VIII having 1.30 density) and 10 minutes for N-1 (Zone IX also having 1.30 density).

I am now looking to do my expansion (N+1) tests. However, 15 minutes for "normal" development is already on the long side, and certainly to achieve N+1 the developing times could easily land around the 20 minutes.

So I am considering using HC-110 at dilution B (which I believe it's twice as strong as Dil H) to expand my negative scale with reasonable develpment times (maybe around 10 minutes or so). Do you guys see anything wrong with this? Could using a stronger dilution move my speed point in a significant way (say, more than 1/3 stop), so potentially requiring a new film speed test?

 

[bernard_L]

Do you guys see anything wrong with this?

No, to the contrary.

Could using a stronger dilution move my speed point in a significant way (say, more than 1/3 stop),

Even if it would move by 2/3 stop or 1 stop, that would not be a catastrophy. Include a few calibration frames (blank, Z1, Z2, Z5, Z8) next time you dev at N1.

• You will now for sure how much it moved
• If it turns out you exposed at 160 and your actual speed was ISO250, enjoy the nice separation in the shadows. No harm done.

 

[ic-racer]

Best speed point for pictorial photography is based on fractional gradient that would not change with changes in development. But "Zone Systems" can be made as complicated as one wants; BTZS.
I might suggest using a range of graded papers or multigrade paper instead of standardizing on a single grade by altering negative development.