pre flashing paper

[salan]

All,
I have heard this mentioned, but have never done it. Could someone enlighten me please and give me some 'starters' as to what light and how much?
Thanks
Alan

[Thomas Bertilsson]

Make a series of exposures with no negative, like a test strip, but maybe with 1 second bursts at a small aperture. Develop the paper and see at which exposure you start to see tone (just off paper white).
Pick the exposure time just before the one you get tone, if you need a lot of help with density in your highlights, or if you just need a little boost pick a smaller amount of time.

[salan]

Can you explain the reasoning behind it please? as in how does it work?
Alan

[brian steinberger]

Alan, I leave the negative in the enlarger and put two clear plastic cups over the lens. This diffuses the light nicely. As Thomas said, find the time just before that which gives you tone. If using FB paper you will need to dry the test strip first before you make your judgement. Pre-flashing is for negatives with stubborn dense highlights or highlights which are too hard to burn in. Results with pre-flashing are normally much better than burning in however. A great example of a neg that would benefit from pre-flashing would be an well exposed interior near a window. Pre-flashing would bring detail back into the window panes, items sitting on the window sill, etc.

[brian steinberger]

Can you explain the reasoning behind it please? as in how does it work?
Alan

Pre-flashing eliminates the papers inertia. So any light to hit the paper after pre-flashing will produce a tone.

[Michael R 1974]

Not sure if Thomas is already typing as I'm responding here but what he said is right on. I'd add two more points:

1. Dry the paper before looking at the test strip
2. Once you've got the flash time figured out, you must flash the paper before you do all your further test strips, work prints etc with the negative.

There is a certain minimum threshold exposure required to overcome the "inertia" of the emulsion in the paper before any tone is produced. Pre-flashing is generally used to give the paper just enough pre-exposure to get to that threshold. The idea here is that any additional exposure when printing the negative will produce tone. This can make it a little easier to get some tone in dense highlights without having much effect on the darker tones. It is sometimes useful, although less useful than it once was given current variable contrast papers. Note a few things:

1. Pre-flashing WILL reduce local contrast in highlights

2. Pre-flashing WILL have a subtle local contrast effect extending further down into the midtones than often expected. This can be mitigated to some extent by backing off a little on the flash exposure instead of using the maximum time indicated by your pre-flash test strip.

[Thomas Bertilsson]

Pre-flashing eliminates the papers inertia. So any light to hit the paper after pre-flashing will produce a tone.

And inertia can be described as a 'threshold' of sorts. Light can strike the paper surface, and you develop it and there is no tone. The threshold means that a certain amount of light has to strike the paper surface before the paper develops a tone in the developer. That's inertia; like pushing a square box forward on a surface - if you apply a little bit of force it may not move, but if you apply more force it will.

Edit: Michael is correct. I was typing along...

[salan]

Thank you all, I will try some soon.
Alan

[jnanian]

Can you explain the reasoning behind it please? as in how does it work?
Alan

hi alan

preflahing photo paper fogs the paper a little bit
so bright white " hot spots " are not so hot.
it tames contrast too, if you like to make paper negatives.

have fun !

[Bob Carnie]

I only use paper flashing,, hot developer application as a last resort and would not consider it part of a normal workflow.. I use these techniques 1 in 50 prints..
just my 2cents.