In-camera half-toning

[BetterSense]

I wasn't talking about making the halftone screen using photoresist. I was talking about using photoresist as my pictorial imaging negative--in place of film. The idea would be to spin-coat photoresist onto a glass plate and then use that in-camera, develop it, and contact or enlarge it.

Since photoresist is not a continuous-tone medium, the only way that would work would be using halftone techniques.

[Bill Burk]

I get that. You will need a halftone screen.

You can buy a "contact halftone screen". Check auction site completed listings. It's like a sheet of film with a negative of a bunch of fuzzy dots. For that you will need a vacuum back.

I've never seen a glass halftone screen on an auction site, but I know they used to exist. This is what I think you can get your photolith department to conjure up. It won't be light sensitive, it will be a checkerboard.

You'll hold this glass checkerboard a very slight distance away from your sensitive plate. Just enough that the shadows don't overlap, but make a continuous pattern of dark to light. As each dot under the screen opening gets hit by more light, first a small dot forms, then it grows as more light hits it.

For now, just hold a windowscreen over a sheet of paper, you'll be able to see the effect.

[holmburgers]

I'm interested in doing something similar and have just beeen searching the archives, only to find this pretty-darn-recent post.

What I want to do is transfer a carbon-gelatin image onto copper (or other metal), and then use a patina formula to get a 'patinograph'. Again though, one would need a half-tone negative to get gradations.

There appears to be some halftone screens on eBay. They are all magenta in color, and say 'magenta'. Why is this? Do they have cyan and yellow? I don't quite get why the screen itself has to be colored, as it itself is presumably not a separation filter. Or is it?

BetterSense, have you attempted anything thus far?

[Steve Smith]

What I want to do is transfer a carbon-gelatin image onto copper (or other metal), and then use a patina formula to get a 'patinograph'. Again though, one would need a half-tone negative to get gradations.

If you use copper clad PCB material with a photo resist and etch it in ferric chloride, you basically have an etched copper plate which you can use to print with. Ink it up with a roller and press it onto paper (I don't know what a patinograph is but I'm going off to find out now!).


EDIT:

I failed!!! This is what Mr Google said:

Did you mean: pantograph
►

No standard web pages containing all your search terms were found.

Your search - patinograph - did not match any documents.

Steve.

[holmburgers]

Yeah... I made it up!

Here is the back story... electro-plating is another option. -> http://www.apug.org/forums/forum42/7...uys-think.html

[andrew.vartabedian]

I'm sure this already crossed someone's mind, but it sounds like the solarplate process is similar and could hold a solution. In it, one exposes the plate using a halftone screen and then exposes the plate to the image. Perhaps one could use a random-dot half tone (aquatint) screens to expose the photoresist plate, then remove the screen and expose the plate to the image (either through contact printing or through a camera). Depending on the nature of the photoresist plate, the half-tone prep could be done well in advance of the image exposure.

[holmburgers]

Here's a picture of one of the screens... http://www.imcclains.com/catalog/blo...ntscreens.html

Sounds promising.

I don't quite understand the double-exposure; I thought that usually they were exposed simultaneously, but even this seems fuzzy to me, as in, how does that create half-tone from continuous tone?

[glbeas]

There appears to be some halftone screens on eBay. They are all magenta in color, and say 'magenta'. Why is this? Do they have cyan and yellow? I don't quite get why the screen itself has to be colored, as it itself is presumably not a separation filter. Or is it?

The film used with the screen is blue/green sensitive so the red light that gets through a magenta screen has no effect on the image. I think the magenta was used for more speed in the exposure. I've used both magenta and grey screens and saw no real difference in how well they worked. One thing to consider is to look for an elliptical dot screen, these produce smoother gradations in the mid tones than a round dot screen.

[holmburgers]

Thanks Gary, very good to know.

[Hexavalent]

Here's a picture of one of the screens... http://www.imcclains.com/catalog/blo...ntscreens.html

Sounds promising.

I don't quite understand the double-exposure; I thought that usually they were exposed simultaneously, but even this seems fuzzy to me, as in, how does that create half-tone from continuous tone?

"Aquatint" screens are a replacement for classic technique of using rosin powder in a "dust box" with copperplate etching. Tones are reproduced by means of the ink held in the etched areas - depth and size of the etch plus the viscosity of the ink used are the major determinants of the tonal range produced.

Think of the double exposure somewhat akin to getting the image 'off the toe'.