Paper Flashing

21 May 2010

Often times, burning in a small spot or an area with lots of different tones can be very difficult. You could burn it in, but you run the risk of letting your shadows go too dark, and not getting enough in the highlights, especially in very bright highlights such as skys, near lights, and other problematic spaces. Paper flashing is a really good way of dealing with this.

Paper needs a certain amount of light before it will start to show tone. Flashing is a method of providing not quite enough light to provide tone on the paper, but as soon as you expose your negative, the little bit of light in the highlight will be enough to cause the area in question show some detail.

Properties of Flashed Prints

Flashing also has some other properties that may be beneficial.

  • It will shift the exposure levels from the toe of the papers sensitivity curve further up the curve, providing detail where detail previously didn’t exist on paper (but did on the negative).
  • making further burning easier, as the paper is already close to it’s “darkening” point.
  • increasing the amount of detail visible on the paper in highlight areas.
  • extending the tonal range of graded or VC papers.
  • decreasing the overall contrast of a print.

How To: Flash Paper

  1. A test strip will need to be done to determine the maximum flash before the paper starts taking on tone.

    1. Set your enlarger at it’s maximum height, or a consistent height that you can easily remember. The best is maximum height as you need a very dim light for this test.
    2. Set your lens at it’s smallest aperture, and make sure no filters are in the filter head. This test should be done with pure white light.
    3. Mark several 6+ marks on your paper with a pencil or waterproof marker. You’ll use these to determine where each step in the test is.
    4. Place a 10cm wide piece of paper in your easel, covering the bottom 1/3 of the paper with an easel blade. This will make your life easier later.
    5. Expose each test section for a period of time. Depending on your paper, this could be anywhere beteween 1/10 of a second to 3 seconds each. I usually start at 1 second each.
    6. Develop normally and dry. Yes, dry. You cannot do this test from wet paper due to dry down.
    7. Determine which test zone is the first to show any kind of tone; your maximum flash point is the one before the one that shows any tone. For example, if you see tone on the 4th test zone, and each zone was 1 second, your maximum flash point is 3 seconds. Use the bit that was covered to compare against. If you’re not 100% sure which one shows a tone, cover all other zones and look again with out the other zones trying playing with your eye.
  2. Now that you’ve found the maximum flash point, expose several pieces of paper to the maximum flash point.
  3. Make a normal print, including a test strip on a piece of the flashed paper. Remember, you may have to increase your contrast level.

Notes on paper flashing

  • Flashing the paper will decrease your contrast, so you may need to up your contrast on a flashed print by 1/2 a point.
  • Emulsions change paper to paper. You must redo this test for each different box of paper, and each time your flash device changes. Thus, if you’re working in a communal dark room, you’ll need to do it at the start of each printing session. Or, if you’ve got your own dark room, but only one device to flash paper, you should check each and every time!
  • Sometimes, going beyond the maximum flash can be beneficial and you shouldn’t be afraid of it. It can help in troublesome areas such as sky’s, and such. It’s also useful it you will be toning the print later and want to have some ‘tone’ in that area.
  • Flashing can be done before or after the print has been exposed on the paper. In either event, it should be done with no negative in the enlarger, and no filter in the filter head.

The ‘Science’ Behind Flashing

The best way to describe this involves a bit of the zone system, so if you aren’t familiar with the zone system, this may not make too much sense, but hopefully it’ll get you started. Photographic paper responds in a S curve. It takes a certain amount of light for the start of the tone to appear, and once DMax (maximum black) has been reached, the paper cannot get any darker.

For example, say a paper starts taking on tone at 50 units of light, and hits DMax at 1200 units. (These are magic numbers designed to explain how this all works, the units are imaginary).

Zone 0 - 1200+ units

Zone 1 - 1100 units

Zone 2 - 1000 units

Zone 3 - 800 units

Zone 4 - 600 units

Zone 5 - 400 units

Zone 8 - 200 units

Zone 9 - 100 units

Zone 10 - 0 units

Now figure, I’ve got an area on my film that registers as a zone 9.7, but I want it to show up on my paper. It’s got 40 units of light, so it’s not going to show up, as we already know the paper requires at least 50 units before it will register anything. Okay, so lets add units of light to the paper by flashing it with our maximum flash (the point right before it shows detail). That will give it 49 units of light.

Now we’ve got 49 units of light all over the paper, and we expose our negative.

Our troublesome highlight that only had 40 units before, well, now it has 49+40=89 units. Woo Hoo, it’s now going to show up, it’ll be hight than a zone 9, but we’re going to at least have some hints of details!

What about that great shadow detail that I have at zone 2 that I have? Well, we’re only adding 40 units, so we’re not really going to shift it all that much.