To help identify what is paper-base and what is a tone, cover a long edge of the test-strip with the arm of the easel - it will give a direct comparison for each stage of the strip.
On multi-contrast paper, it is also possible to flash with grade-00 or grade-5, instead of white light. That can make a handy difference, as (for example) over-exposed clouds may be relatively low contrast within themselves.
Like everyone else has mentioned, this 'adds' the ineffective exposure which would otherwise be at the bottom left of the log-exposure/density curve, running pretty much along the x-axis. And no, it isn't an everyday technique unless you have very unusual negatives. EDIT: It could become more standard for you if you shoot contrasty scenes on Ilford Direct Positive paper though.
To add a more classical term than intertia, we are really talking about getting the exposure with the pre flash to push the paper response up off of the toe of it's response curve, in a classic illimination H- to Log D density plot.
It's a pretty arcane trick in this era of high-quality VC papers, but I guess everyone tries it at least
I wouldn't necessarily call it arcane if it is localized flashing. It can be useful for bringing in lightbulbs and that sort in addition to careful burning, without getting into masking etc. But I would agree in many cases it is no longer as necessary as you can accomplish virtually the same thing with low contrast burning. And I'd always prefer a localized application than doing something to the entire sheet if possible.
replacing developered paper that has been rinsed and squeegeed under the enlarger
and aligned with the negative in the easel and burning in that way can also do the trick.
it takes more effort than flashing and doesn't smell as good as warm developer ..
but t works
How do you do the localized flashing?? or better yet how do you find your position to flash small areas??
Originally Posted by Michael R 1974
There are several ways depending on what is required. Of course there is negative masking, but there are a few other more simple techniques I sometimes use (both require a second light source/enlarger and easel - I bought a small used Durst for $10 for this purpose so I can use filters etc):
1. With the flashing easel set to the same size as the print, you can tape down little markers, pointers etc so you know where to position the burning cards/holes etc during the flash exposure.
2. Make an actual scrap print, cut out the areas to be flashed, and place the print on or above the paper during the flash exposure (essentially paper plane masking). Note it is best to use RC paper for this since in addition to it being obviously easier to work with and faster to process/wash/dry, it has to be dimensionally stable paper so that "registration" at the paper plane works properly.
3. Combine (1) and (2), burning/dodging during the flash exposure with a print that has cutouts etc.
Diffusing paper can be used with any of these techniques to feather edges etc.
I originally learnt about localized flashing from John Sexton's masterful use of it in many of the powerplant, Hoover Dam and space shuttle prints in his "Places of Power" series. These prints remain my reference point for how to manage extreme contrast situations without destroying local contrast.
Preflashing is a rather specialized contrast reduction technique. Anchell gives a good discussion of it and several useful variations in "The Variable Contrast Printing Manual," and Rudman gives a detailed explanation in "The Photographer's Master Printing Course." It generally comes into play when the shadows are OK but the highlights are too dense to print properly. Contrast reduction is more pronounced in the highlights, noticeable in the midtones, and almost non-existant in the shadows when the technique is applied correctly. This comes about from the additive nature of the non-focused flashing exposure and the image exposure. You have to experiment to find the right level of flash. The idea is pretty well explained above, and generally the point just before the exposure causes any increased density is the right point, but it can vary depending on your aims. Often preflashing is combined with an increase in the contrast grade to get a balanced picture.
A very nice easy to read explanation of pre-flashing here:
Pre-flashing works with any exposure-sensitive material including film. For film one is concerned with shadow information, whereas with paper its highlight area information.
For film I use a white-balance filter (as described in Lambrecht's "Way Beyond Monochrome")
For fiber-based enlarging paper I use a flasher by RHDesign. It easily installs on the enlarger lensboard.
For silver chloride contact paper I use Besseler Audible timers that give control to 1/10 second. I pre-flash the paper prior to placing in contact printing frame.