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Tuesday, 17 November 2015

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I had to explain to my wife why Fred Mertz's tie with a lot of detail had color fringes.

Totally different process, though.

One of my favorite features in Lightroom is the ability to change the luminosity of the working space that a photo is resting on, from white to black with several grays in between. When I'm adjusting overall tonal balance and/or evaluating a composition, I like to display the photo at 25%, with a generous border around it. For composition, this allows me to take in the whole picture, while switching the luminance of the working space around it allows me to quickly assess the tonal balance. There's no such thing as perfect pitch in a visual sense. Our eyes adapt to an environment rather quickly and completely—it's important to vary that environment often.

When One of my Daughters was at University of Pennsylvania, she did a project where she printed on glass. 12" square sheets of window glass, which we coated with clear polyurathane varnish then painted on photo emulsion (Remember Liquid Light?), dried then exposed and processed in the darkroom. Her Idea was to mount the glass pictures in a shadow box frame, 3" in front of a mirror.
They were hung slightly high so that the viewer would not necessarily have to see their own reflection, but could if they chose.
I remember them as being mesmerizing creations.
The transillumination was wonderful.
Over the years they faded badly despite being fixed and washed well. You comments reminded me of the process.
It also reminded me of the wonderful H & D curve of Film, which sombody should invent for digital.......


I had cataract surgery a couple of years ago. I laid back on the reclining operation chair and tried very hard to keep my eye still, but it still moved around a little. So that the surgeon could see what they are doing, there was a very bright light shining into my eye. I couldn't blink.

After a while, the light appeared mid grey, but as my eye minutely moved around there appeared a bright white edge on one edge, and a black one on the opposite edge.

I think that this is the same effect as with the negative afterimage of the castle. The mid grey appearance of the light shows desensitivation which isn't enough to fully offset the dazzling brightness, while as the eye moves, the image of the light falls on a part of the eye that is not desensitised so looks very bright.

On the other edge the heavily desensitised part of the retina is no longer looking at the light, hence the black edge.

This video clip is a very nice demonstration of the effect, but I'd suggest that some of Edwin Land's (inventor of the Polaroid camera) experiments in colour perception are more remarkable.

In his paper 'Experiments in Color Vision' of 1959 (http://www.psy.vanderbilt.edu/courses/psy236/ColorVision/Land1959.pdf) he describes the following:

Using b&w slide film, photograph a still life once with a red filter, and again with a green filter. Use two projectors to display the slide images precisely overlapped, and put a red filter on the projector with the slide taken with the red filter.

Logically you'd expect that the resulting image would have a colour range from black to white to red, with most of the image being shades of pink-greys. What the eye and brain see is a reconstruction of the full range of colours in the original scene (although desaturated).

Land argued that this demonstrated that colour is a field phenomenon, not a point phenomenon. In other words, our perception of colour does not exclusively depend on the spectral distribution of the light arriving at a single point on the retina, but also on the 'field' of colour distributed over an area around that point.

Years ago I tried to repeat the experiment, with some success but not to the extent Land described. One day I'll get round to trying with digital projectors - I'm not sure if the pixillation and relatively poor gamut and uneven spectral output will stop it working.

Have any other TOP readers tried this?

For various reasons including clients that liked dark prints for reproduction, because the guy making the plates liked them that way, or having a really bright inspection board and the prints drying down, plus the lighter prints being sold, lost or given away I have a lot of boxes of pretty dark prints on portriga rapid which have amazing detail in the "blacks".

It turns out that's a good thing, because they reproduce digitally much better than the "good" prints do. The same is true for my slightly dark C-prints.

Pavel Kosenko talks about a similar exercise with the tube in his eBook, Lifelike. He has the viewer look down a tube at a relatively 'flat' image and note how, over a period, the vibrance and subtlety of the colors increases. Put the tube down and continue looking and you can see the those beautiful colors fade away and the image become flat again.

(The book is excellent by the way, dealing with color perception and color correction for digital photographers. Written from an artistic point of view rather than a technical one and draws from painting, as well as Kodak and Fuji's experiments with color perception. He notes that impactful and appealing color interpretation was actually the thing film emulsions productised, so there was a lot at stake in researching perceptions of colors and their relationships. It's available to here if you're interested: https://pavelkosenko.wordpress.com/2015/05/21/lifelike-a-book-on-color-in-digital-photography/)

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