Graininess with Pt/Pd

[clay]

I think this may be the explanation for any difference you see.

Another thing is that it is almost impossible to judge just from prints when you are doing the propeller head stuff. The reason is that all these combinations have an effect on the speed of the print too. So it is quite easy to mistake what is really a speed change for a contrast change.

For instance, if whatever mix you use slows the print speed, the highlights will be lighter, naturally, and what was 100% black in the shadow areas will still be dark and probably appear black, and the almost-dark areas will be slightly lighter. This may appear to be a contrast change, but it is really a speed change. It is very difficult to judge from a print alone because there are too many 'moving parts'.

For those so inclined, the only really accurate way to do this is to spend a Saturday morning printing some step wedges and then slapping them on a reflection densitometer.

Perhaps the discernible difference you are noticing in the two prints you are referencing is the greater pt ratio to pd ratio... not the chemical characteristic of the Na2 contrast method, but the chemical contrast characteristic of pt to pd
EG: 7 drops of pt (6 drops of normal pt and 1 drop of Na2 pt) to 6 drops of pd ... vs ... 6 drops pt to 6 drops of pd.

 

[RobertP]

Ahhh yes... the old speed vs. contrast variable. Everytime I try a new paper I have to keep that in mind. Thanks for pointing that out Clay. Robert

 

[Kerik]

The Turnip speaks The Truth. Listen my friends and make your lives easier!

 

[Dan Dozer]

Since a couple of more questions have come my way - my light box has (7) 24" UV tubes in it and my exposures run about 5 - 6 minutes. I don't have a fan in the box, but maybe I need to put one in.

This is all great - thanks everyone. I've concluded that the more I learn, the less I know.

Dan

 

[scootermm]

Since a couple of more questions have come my way - my light box has (7) 24" UV tubes in it and my exposures run about 5 - 6 minutes. I don't have a fan in the box, but maybe I need to put one in.

Dan, I bought this tiny little 6" oscilating fan (was about $4 at Target) that plugs into the same Gralab timer as my UV bank is plugged into. So it comes on high whenever the UV bulbs are on. Perhaps unnecessary since my exposure times are about the same as you (5-10mins) but figured it was a good habit. Also, a big discernable difference I experienced was in humidifying the paper right prior to exposing the print. Helped alot and gave noticeably better blacks etc. Good luck.

This is all great - thanks everyone. I've concluded that the more I learn, the less I know.

Dan

How true this is, I've found the same.