Ortho film is film that is sensitive only to blue light, so you can expose it like photographic paper using a red safelight with an enlarger. You could also use regular panchromatic sheet film, but the exposure times will be much shorter, and you have to work in the dark. You could also make enlarged paper negatives, but the paper base will make exposure times long for albumen printing.
There are a few different approaches to enlarging negatives. One is to make a small print and photograph the print with a big camera, if you have a big camera.
The internegative approach usually involves making an enlarged positive transparency (actually an "interpositive") on ortho film (or conventional film) and then contact printing that to another sheet of ortho film to make the enlarged negative. I know one photographer who enlarges in stages, making a 4x5" positive from the smaller negative and enlarging that onto a larger sheet of film to make the enlarged negative.
There are some direct positive methods, such as using a direct positive film used in the graphic arts, which is available from Ultrafine and other sources, or using reversal processing, where you use the method for making a B&W slide to duplicate the negative in a larger format. dr5 is a lab that specializes in B&W slides, and they can make enlarged negatives in this way for alternative processes. The advantage of a direct positive method is that it cuts out one generation. The main disadvantage is that it is generally harder to control contrast with reversal processes.
thanks a lot david,
from what i found so far, looks like the most obvious path is the ortho film, as it is the easiest (to obtain i mean)
but after reading some archive on x ray duplicating film as ic-racer suggested, i became curious, how is it when compared to ortho film?
based on this thread: http://www.apug.org/forums/forum42/6...negatives.html i gather that it looks like the better choice is the x ray duplicating film?
as i'm betting it will be easier to get those x ray films here in Indonesia than ortho film.
The X-ray dup film can be exposed under an enlarger and processed with Dektol under a safelight just like conventional enlarging paper. This one-step process yields a giant negative, which can be used directly for your big alternative contact process under UV light.
The LF forum has already been corrupted with so many people making digital internegatives that I suspect they are ignorant of how easy it is to do it the 'correct' analog way. Photoshop can only hope to approximate the analog artist's dodging and burning and development control to make the perfect large-scale internegative
Contrast control is a non-issue. Three generations of photographers have been matching camera negative contrast to graded silver paper with various permutations of "N" development and there is no reason why your camera negatives can't be processed to fit the internegative materials sensitometric characteristics.
Last edited by ic-racer; 01-27-2011 at 05:51 PM. Click to view previous post history.
But since this is not Pan film, it cannot be used to make a separation from a slide image? Do I understand that correctly? So a separation would require pan film?
Originally Posted by ic-racer
Is this double coated? I picked up a pack of regular blue sensitive x-ray film off eBay some time back, and it is double coated. I use chlorine bleach to remove one side of coating, but it's a lot of work.
How about the effect of a lack of an anti-halation layer? Is that important?
I'm pretty sure the positive dupe film is single sided. I don't know if it has an anti-halation layer or not. I suspect you are correct about the inability to make a good separation negative.
Originally Posted by michaelbsc
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