Loris,
My print flash (I use post exposure flash, and have no idea if pre-flash is the same) exposure is typically 3-4 seconds under a typical bank ov UV lights. Negative exposure is 2 minutes, but could be as long as 3 minutes for negatives printed on transparencies with almost no base density. Exposures are much longer for pictorico based negatives.
When flashing the print I almast always use chlorox bleach development, or it would take forever t develop.
Marek
> Date: Tue, 13 Oct 2009 09:08:18 +0300
> From: mail@loris.medici.name
> Subject: RE: Gum tonal range and linear response
> To: alt-photo-process-l@usask.ca
>
> Marek, I think you had mentioned that before, but I somehow forgot about
> it...
>
> Thanks again for another useful tip; I will definitely try this if I come to
> a situation that calls it. I use digital negatives (but the curve is from
> cyanotype) and I usually don't have any problem with highlights, only
> occasional underexposure which is pseudo-fixed by developing less (I don't
> like this but will do it if I need). May switch to give short flash
> exposures in future prints; I can certainly use more robust (but not
> stubborn!) layers in development, especially if I plan to intervene by hand.
>
> What is your upper and lower limits for flash exposure? (Please include info
> about the base exposure too, to let me compare.)
>
> Thanks again & regards,
> Loris.
>
>
> ________________________________
>
> From: Marek Matusz [mailto:marekmatusz@hotmail.com]
> Sent: Tuesday, October 13, 2009 4:43 AM
> To: alt-photo-process-l@usask.ca
> Subject: RE: Gum tonal range and linear response
>
> etienne,
> I just thought about the whole linear/non-linear response of gum and now I
> think that my method of exposing gum for some time and then flasing it with
> straigh UL light (no negative) for a short time period (seconds) which
> results in a very nice extension of highlight detail, is an old-fashined way
> of curving otherwise linear Stouffer step tablet. Maybe somebody saavy in
> Potoshop could work out a curve that corresponds to this physical
> manipulation. It really works miracles to reveal highlight detail of dense
> negatives. It adds little exposure to shadows that have already been exposed
> a lot, but changes highliths a lot, since it adds a significant exposure
> there. Great for those palladium negatives that you never though could be
> printed in gum.
> Marek
>
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