Good darkroom work revealed

[Craig Swensson]

subscribed to thread and website saved to fav.thank you

[Bruce Robbins]

Ok going to sound stupid but what the difference between preflashing then exposing to just exposing for a longer time? Especially considering the above post which says you can do preflashing with negative in place.

That's a good question. All papers require a little bit of exposure before they will start to record any tones at all. This exposure just takes the paper to the point where tones start to appear. (The effects of flashing are more evident in highlights than shadows.) Where there are very bright highlights the negative is so "dense" that not enough light gets through onto the paper to push it up beyond this threshold level, leaving those areas blank in the print. Pre-flashing lifts the whole sheet (if it's all exposed to the flashing light - you can pre-flash selected areas) up to that level so that all tones record with any subsequent exposure.

If you don't pre-flash but expose for a longer time then you end up with a print that is too dark. Imagine that you've made a print where all the tones, except for the brightest highlights, look perfect. The brightest highlights were too dense on the negative to reach the threshold level and are a blank white in the developed print. If you give these highlights enough exposure so that you get a tone on the paper, all the other tones that were perfect also get this additional exposure and become too dark.

I suspect you were asking about giving extra exposure by just burning in the very light area rather than exposing the whole sheet? This is possible but there's always the chance that the burning in will be evident in the final print as a "halo" unless done very skillfully. You can mitigate this possibility by burning in at a low contrast grade if you're using variable contrast paper. Not all areas that require burning in are OK with the low-contrast look, however. Burning in at a normal or higher contrast grade is much more obvious and has to be done very well if there's to be no tell-tale halo. In batwister's print above, it would be quite straightforward to burn in at a soft grade. Since distant scenes are often of lower contrast because of atmospheric haze, this would look OK in batwister's print. If you saw Omar's pic, even though a low contrast look would be OK for the blank areas of the print, you can see how much more difficult it would be to burn in the windows. That would require some accurate masking. Definitely easier just to flash the paper.

[Arctic amateur]

Does the order of events matter? Would you get the same result if you first pre-flashed and then exposed as if you first exposed and then post-flashed?

[SMBooth]

Thanks Bruce.

[Bruce Robbins]

Does the order of events matter? Would you get the same result if you first pre-flashed and then exposed as if you first exposed and then post-flashed?

Order of events doesn't matter. It's probably easier, though, to pre-flash and then make the print. The other thing with pre-flashing is that if you always do it the same way then the necessary pre-flash exposure will be the same for that grade and type of paper. For instance, if you put the enlarger head at the top of the column and stick with, say, f16, with no negative in the carrier, you'll only need to work out the flashing exposure once.

[Bob Carnie]

Using a pre flash and lower grade burn is helpful, but for my money burning in with grade 5 over top of flash and low grade burn, really makes the highlights work.
In all highlight areas, or most, I am not talking about open areas of bright white with no detail, but highlight areas with detail, using the 5 will darken any lower tones within and greatly give the eye more to look at.

[batwister]

Order of events doesn't matter. It's probably easier, though, to pre-flash and then make the print.

I've been using a square piece of frosted glass just below the lens. Of course, most of the light is absorbed (no negative detail passes through) so there's no need to take the negative out. I can also stick appropriately cut pieces of card on the top side of the glass to flash selected areas - something you wouldn't be able to do with pre-flashing.

[Michael R 1974]

A careful flashing test is important whether the flashing is non-localized, localized, masked, etc, but particularly if it is non-localized (ie the entire sheet of paper). Flashing WILL decrease local contrast - and that effect will extend downward further into the midtones and darker values than most people assume it will. It is often helpful in the initial flashing test, to back off slightly from the maximum exposure that appears to generate no tone. This depends on the type of highlight one is attempting to bring in, and also on the overall tonality of the image (ie is it mostly dark tones with some tricky highlights, or is there a substantial light area etc).