i was talking to someone today - don't want to call him an 'olde timer', but he is much older than me and ...
he was telling me all about flashing film before you expose it.
he suggested that one could pre-flash film - close down about 5 stops, out of focus / neutral gray or overcast north sky - and then expose "normally"
you will get more details in the negative when you make your actual exposure.
it doesn't work on every subject, but it will bring out details that would be not captured if the pre-flash was not done.
i know there are people that have done all sorts of things here, anyone actively do this, or at least tried it?
yes, with sheet film and a piece of white plexiglass.
It has been awhile since i have used that technique as i don't do landscape work anymore, it was quite commone for zone work.
I can't find my copy of "the Negative" but Adams spells it out in detail.
I have used this many times in the past, although I dont seem to use it any longer with the BTZS.
Anyway, the way I did it was to measure the light through a piece of white plexiglass, I would then put the plexiglass in front of the lens, close 5 stops from the indicated metering and pre exposed the film.
Works pretty good.
I have used this and would not hesitate to use it today in high scene brightness ratios.
I don't stop my lens down five stops, however. What I do is to meter through the opaque acrylic panel and then determine a Zone III placement. I next place the acrylic panel over the camera lens and give the film the first exposure at that Zone III (through the panel) exposure. I then give the film a normal exposure for the second exposure.
This effects of preflashing film is best illustrated by the following example. If we take the premise that each zone or stop of exposure represents a doubling of light. Then we start out as Zone I having a value of one, Zone II having a value of two, Zone III having a value of four, Zone IV having a value of eight. This continues until we arrive at a number of 128 for Zone VIII.
By preflashing film in this manner we raise our Zone I exposure to a Zone III 1/3, our Zone II exposure to a Zone III 2/3, our Zone III exposure to a Zone IV, and our Zone IV exposure to IV and one half. The addition of four units of light are miniscule in relation to the 128 units that a Zone VIII would normally have. Additionally this allows us to place our low values at Zone I and compress the brightness ratio by a couple of stops. The compression of values will occur in the shadow regions as opposed to the highlight regions if we were to try to accomplish this at the printing stage by preflashing the paper.
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even though i had never done this, it made sense when i heard it.
thanks for spelling it all out for me. one of these days i'll have to give it a try.
I use it regularly - made a filter out of a lee gel holder and 2 layers of baking parchment. I do it to ensure that most negs on a roll need roughly the same development time, so i dont have to use N- times for one shot, upsetting the contrasts on all the others. It works really well.
I am so glad to hear the details of this process. I can certainly use this on high contast Texas subjects. I thought that film flashing was an out of date practice that did not benefit modern films. Actually it is even more important with coated lenses that produce so much contrast. Thanks for the valuable info.
[FONT=Century Gothic][/FONT][SIZE=7][/SIZE][COLOR=DarkOrange][/COLOR] I may be getting older, but I refuse to grow up!
I'll have to try this.
The thread reminds me of an Ebay seller who is unloading a pile of Tri-x film packs and claiming it to be pre-flashed in the ad because of the age of the film. I thought it was a pile of bull and still do, high base fog is just that and I'll bet it's not quite the same as pre flashed film in image quality.
Originally Posted by glbeas
Yes, I agree that this is entirely different. However, one could preflash a holder or two and carry them for those high contrast situations. This could be done, if one wanted, before the actual exposure. Since what we are doing is breaking the film exposure threshold with non image bearing light.
Obviously for roll film users it wouldn't work the same as sheet film users.