Pre-flashing RA-4

Hi guys, I have some questions abou pre-flashing RA-4 paper. Hopefully you can enlighten me as I've not done this yet:

- I've seen it done in B&W, but what is best technique in colour - especially with regards to colour cast?

- Is it common to use filters artistically to put a bit of colour into it?

- Other than the impact on changing the print exposure and recovering highlights, does it have any impact on the look? I've noticed some prints that I believe may be pre-flashed have a sort of glow to them around areas with contrasting colours but I'm not sure what's behin this

I'd ideally like to use my enlarger and in a systematic fashion, but realise that this might require moving the head and changing settings which could end up being inconsistent.

Thanks!

It works just like B&W to contract the curve. Use a blank piece of C41 film (preferably of the same roll as the actual negative) in place of the negative and filtering in accordance with the determined filter pack for the negative itself for neutral results. Changes in filtration may induce a subtle or even pronounced crossover as the difference in filtration will be disproportional to negative density. Hence, maybe there could be a way to get a sort of 'split toning' in color, if that makes sense, but I haven't tried that. I did try normal pre-flashing with 'proper' filtration and that worked quite well. There is a subtle difference in the effect depending on pre- or post-flashing - I cannot explain it, but I did witness it. I did not notice any kind of glow and I don't see how it could emerge other than due to (non-preflash associated) optical problems in printing setup. No changes to the head or its position itself are required for pre/post flashing other than obviously replacing the negative with a suitable blank piece of film. Since this contains no detail, it won't result in loss of detail etc.

Thanks @koraks - lots of useful info there!

koraks said:

contract the curve

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I understand what you mean but can't visualise the curve or how it would change - I'd be interested to see a visual example

koraks said:

I did not notice any kind of glow

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See image below for an example of what I meant - I've seen it a few times and know that is intentional, but the cause escapes me

koraks said:

No changes to the head or its position itself are required for pre/post flashing other than obviously replacing the negative with a suitable blank piece of film

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This plus using the blank neg are super helpful, thank you

Mike Chalmers said:

Thanks @koraks
I understand what you mean but can't visualise the curve or how it would change - I'd be interested to see a visual example

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I'd have to do some digging or make one, but the effect isn't all that difficult to imagine. Think of a print from a color negative in which the bright highlights are blown out. In the pre-flashed version, the brightest highlights are brought back so that they exhibit visible density - i.e. they become something darker than pure white, and color and tonal separation becomes visible. The effect is less apparent in the higher midtones and becomes virtually negligible in the midtones and shadows.

See image below for an example of what I meant - I've seen it a few times and know that is intentional, but the cause escapes me

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Looks like either two exposures onto the same paper, one in proper focus and one significantly misfocused, or (perhaps more likely) the old trick of putting gauze over the lens or smearing some vaseline on the front lens element. It has nothing to do with preflashing as far as I'm aware.