Doesnt blow the highlights

[swmcl]

If I may be so straightforward ...

The idea of a sensitometry curve that is exponentially curved upward makes absolutely no sense to me from a chemistry or film structure perspective. What kind of developers would have a warning on their labels to give a time limit before completely blacked out negatives ?!! It is absolutely incomprehensible that a film could sit in a developer and be developing nicely and then after a longer period of time start to really become very black and dense. Sorry but I cannot accept an exponential curve but I guess stranger things do happen.

Michael, I think your first paragraph indicates a shoulder condition where highlight details are all mushed together on the horizontal section of a curve. The density at which this is happening is extremely low if I may say so. Probably needing to start at 1.1 or 1.2 or so.

The second paragraph might be something similar in that a weak developing solution doesn't get to create dense areas on the film. Perhaps when people speak of Pyrocat-HD not blowing the highlights it is only so at the weak concentration of 1:1:100. The contrast index of their process would be very low.

ic-racer isn't what you describe a situation where you have developed a negative such that your negative density range is beyond what the paper can reproduce ? If so then pull the development, yes ? If Pyrocat-HD was to not 'blow your highlights' then wouldn't it just be developing to a lower contrast index ? A flatter curve ? Perhaps other developers can't be diluted as much as Pyrocat-HD ...

I can say I am not liking one bit the idea of flat negatives.

Thank you all for your thoughts.

[IanG]

It's the staining properties that are important, think of a negative that's partly silver and partly dye it's a feature of any staining developer not just Pyrocat, it's the extreme highlights that don't block up to the same extent as they would with a non staining developer (at the same contrast).

At 1+1 to 100 Pyrocat isn't particularly dilute, it's on a par with Rodinal and some other developers.

Ian

[Drew Wiley]

Something extreme can exist on a negative or transparency, yet be difficult to recover from a practical standpoint. Conversely, certain things difficult to distinguish
over a lightbox might print relatively easily. It takes some experience printing; but after enough frustration, it becomes quite apparent what "blown highlights"
mean. They're just too dense in the negative to print by conventional methods, at least in relation to the balance of the image. Sometimes later, after one has learned a lot of new tricks, or perhaps some dramatically more appropriate paper or developer arises, some of these difficult negs can be resolved. Otherwise,
one quickly learns not to overdevelop. One such dramatic improvement for me was when I learned the benefits of staining pyro developers.

[swmcl]

IanG I hear that the staining is 'proportional'. It could be something more exponential perhaps. This would support your argument. As far as I know, this is either very difficult to measure or is impossible to measure which leaves us at the doors of a little magic.

I'm going to assume the stain would be proportional to concentration. A more dilute developer would take longer to achieve the staining but the shape of its curve would be similar to the more concentrated developer. Then there is the general stain -vs- image stain ...

[Bruce Watson]

My definition of a blown highlight is a printing problem.

Yes, this. The idea that a negative can have blocked highlights is a non sequitur.

As always, the old rule still applies: Expose for the shadows and develop for the highlights. You do this to make it easier to use the negative for what you want, be that printing silver gelatin prints in the darkroom, alternative processes like Platinum printing which want more highlight density, or scanning which wants less.

Development of the negative is a tool. Use it wisely.

If you don't use it wisely, your prints may end up with blocked highlights. But that's a printing problem.

[IanG]

IanG I hear that the staining is 'proportional'. It could be something more exponential perhaps. This would support your argument. As far as I know, this is either very difficult to measure or is impossible to measure which leaves us at the doors of a little magic.

I'm going to assume the stain would be proportional to concentration. A more dilute developer would take longer to achieve the staining but the shape of its curve would be similar to the more concentrated developer. Then there is the general stain -vs- image stain ...

It probably is Unlike the US there's not an obsession with densitometers in the UK and the rest of Europe. We have one photographer, John Blakemore who makes Ansel Adams use of the X=Zone System look decidedly amateur, but then so does Thomas Joshua Cooper and he's American

Ironically I have a good densitometer but as my negatives print so well with Pyrocat HD it's a waste of my time measuring why

Ian

If we go back a stage to well before WWII Pyro staining developers were once the norm, the stain was far greater than with Pyrocat HD, and we need to really be comparing these negative/developer combinations to using Chromogenic films like XP1 & XP2