Pyrocat stain on low values (ie Zone I)

[Marco Buonocore]

Does pyro - Pyrocat HD specifically - stain low values? I'm testing film speeds, and looking at my Zone I threshold. I'm curious whether or not there is stain there, or if it occurs higher up the the scale. I would like to base my Zone I / threshold on a densitometer reading, and dial in the contrast according to the look I prefer in actual prints.

Thanks!

 

[Marco Buonocore]

Thank you Michael for your explanation.

I was under the impression that stain was only apparent in the higher values. I was hoping to use densitometry to establish an EI, and that's about it. I may have a colleague with a densitometer with a blue channel I could borrow.

Probably when it's all said and done I'll go back to doing things visually.

I appreciate your help!

 

[john_s]

I've used PMK and PMC (an earlier developer of Sandy King) and Pyrocat-HD, and it is obvious to me that there is some noticeable stain even in FB+Fog judging by looking at the colour of the negatives. I would guess that the difference in stain between FB+F and Zone I or II would be very small. And more to the point in relation to the OP's question, I consider the colour in FB+F with Pyrocat to be noticeably less than with the other two that I've used. This is just judging by eye.

As Michael states above, if I may paraphrase him, a value of Zone I really has to be ascertained by its effect on the paper (assuming that you're wet printing).

 

[dpgoldenberg]

Here are curves measured for Ilford Delta 400 developed in Pyrocat-HD, comparing the overall density and that for the blue channel only (using a X-rite 810 densitometer).

The data show that both densities increase with exposure, but the difference between them also increases markedly. So, practically, it probably is true that the stain only contributes significantly at higher negative densities.

Hope this helps.

David