How was Tech Pan emulsion different?

[rmazzullo]

Hello everyone,

I wanted to know if anyone knows how (without venturing too far over the "proprietary information" line) Kodak's Tech Pan emulsion construction / formulation / etc., differs from other B&W films, and if there is any patent discussing the Tech Pan emulsion.

Also, being new to the forums, I see references to books mentioned on this forum by the author(s) last name(s), but no titles. I would guess this is because these books are well known to the list members. Is there a post on this forum or some other source which gives details of the book titles and their respective authors?

Thank you,

Bob Mazzullo

[David A. Goldfarb]

Hmmm...a traditional photo bibliography with complete citations on APUG--that wouldn't be a bad idea, but meanwhile there's the search engine, and that might help you track things down. And if you don't find what you're looking for, you might just ask in the thread that mentions the source that you're interested in.

[Photo Engineer]

Here are two very good textbooks:

Mees and James "The Theory of the Photographic Process"

Haist "Modern Photographic Processing"

Tech Pan was a very fine grained sharp rather slow film. That is about all I know about it. I never did any work with it at all.

PE

[rmazzullo]

Thanks David, and PE for the information,

Bob Mazzullo

[Peter Black]

There's some information on the Kodak website if you haven't already seen it.

http://www.kodak.com/global/en/profe...255/p255.jhtml

[Maine-iac]

Originally Posted by rmazzullo

Hello everyone,

I wanted to know if anyone knows how (without venturing too far over the "proprietary information" line) Kodak's Tech Pan emulsion construction / formulation / etc., differs from other B&W films, and if there is any patent discussing the Tech Pan emulsion.

Also, being new to the forums, I see references to books mentioned on this forum by the author(s) last name(s), but no titles. I would guess this is because these books are well known to the list members. Is there a post on this forum or some other source which gives details of the book titles and their respective authors?

Thank you,

Bob Mazzullo

I'm out of my depth in this forum; my high school chemistry class was light-years ago. So I can't give you the technical details about Tech Pan. I did, however, have a several-year-long fascination with it back in the 80's. I believe it was originally designed for high contrast lithographic work. With many conventional developers, it gave very, very high contrast results--almost just pure blacks and whites.

However, in a POTA-style low-contrast developer, it gave a normal range of tones. It had a variable film speed, depending on the developer being used, and was super-fine grain, much finer than Panatomic-X or T-Max 100. Mostly I shot it at around ISO 25.

What was interesting about it was that it had a built-in red sensitivity (orthochromatic), so that it gave results similar to using a light orange filter over the lens with a normal panchromatic film. This intrigued me, because I normally shoot B & W with a yellow filter over the lens at all times anyway. (T-Max films have something of this red-sensitive quality also), and it was nice to not mess with filters, but get the darker sky effects anyway.

I began using it because, at the time, I couldn't afford a medium format or large format outfit, and I was stuck with my 35mm and wanted to get my photos to look as sharp and grainless as those done on 4X5. Tech Pan did that admirably, once I got the hang of correctly developing it. I did 11X14 blowups that look as though they were done with 4X5--absolutely smooth tones and no visible grain. Eventually, I found the slow speed limiting and was able to acquire a medium format outfit, and well, I just never went back. But it was definitely an interesting film.

Larry

[jnanian]

hi bob

i loved using tech pan at high speeds ( like asa 100 and 200 ) and processing the film in print developer to give a higher contrast and no grain negative.
unlike lith film, there were always mid-tones ... great stuff!

john

[Ryuji]

Originally Posted by rmazzullo

Also, being new to the forums, I see references to books mentioned on this forum by the author(s) last name(s), but no titles. I would guess this is because these books are well known to the list members. Is there a post on this forum or some other source which gives details of the book titles and their respective authors?

If it's my post, I can supply those info. If you are seriously interested, feel free to write me but please include your email address.

Also, check this out:

http://wiki.silvergrain.org/wiki/ind...tle=Literature

I wanted to know if anyone knows how (without venturing too far over the "proprietary information" line) Kodak's Tech Pan emulsion construction / formulation / etc., differs from other B&W films, and if there is any patent discussing the Tech Pan emulsion.

I still have quite a bit of Tech Pan (they are for sale too!) so I could analyze the emulsion for some basic parameters...

The Tech Pan is most different from pictorial negative films in (1) extended red sensitivity, (2) inherently higher emulsion contrast and much narrower exposure latitude, (3) finer crystal size.

The extended red sensitivity is due to a different sensitizing dye. The higher emulsion contrast is due to more uniform crystal sizes in very narrow size distribution (many negative emulsions use multiple emulsions of different grain sizes to increase latitude and decrease contrast).

Tech Pan was introduced in late 1970s. Considering the emulsion making technology of that time, and the required specification for Tech Pan, I think the most likely choice would be cubic AgBrI crystals of edge size about 0.1 to 0.2 micron. Well, the right answer can be found easily by dissolving a bit of emulsion off the film and looking at the crystals under electron microscope.

This type of emulsion was most commonly made with a conventional double jet system. Most likely with a reaction vessel with a premixing chamber, a pair of electrodes to monitor pAg, pH, and temperature, with automatic feedback control system. The flow control of both jets (silver jet and halide jet) is very critical to maintain a certain target pAg value, or the emulsion won't be as high contrast. And the target pAg ideal for high contrast emulsions will most naturally make cubic AgBr crystals, unless the crystal habit is chemically modified, but at that time this technology wasn't developed yet.

In order to make a high resolution emulsion, you must design the crystal size very carefully. Emulsions with crystal sizes in 0.2 to 0.5 micron range is not very easy to use for very high resolution applications because of large scattering of light caused by the crystals themselves. Tabular grain emulsions have a definite advantage here.

Incidentally, many paper emulsions are in the size of 0.2 to 0.5 microns. They are also coated on reflective paper. So they have terrible resolution although the emulsion is very slow compared to the negative emulsions.

Also, Technical Pan is not a lith film, as users of both types of film can tell. Lith films are usually AgClBr emulsions, possibly with a very small amount of iodide. Bromide emulsions don't develop very well in classic lith developers that was in active use at the time of Tech Pan's introduction to the market.

[Keith Tapscott.]

Originally Posted by rmazzullo

Hello everyone,

I wanted to know if anyone knows how (without venturing too far over the "proprietary information" line) Kodak's Tech Pan emulsion construction / formulation / etc., differs from other B&W films, and if there is any patent discussing the Tech Pan emulsion.

Also, being new to the forums, I see references to books mentioned on this forum by the author(s) last name(s), but no titles. I would guess this is because these books are well known to the list members. Is there a post on this forum or some other source which gives details of the book titles and their respective authors?

Thank you,

Bob Mazzullo

You could contact Michael Maunder about this film, which he has used from it`s name as SO-115 through to 2415 Technical Pan for astronomy.
This he has developed in a wide variety of developers such as Kodak D-19, P.O.T.A, D-23, C-41 through to his own formulated processes such as Celer-Stellar and Celer-Reverser.

http://www.speedibrews.free-online.co.uk/

[Emile de Leon]

Tech Pan is great stuff. I used to use it with a very high resolution Leica DR Summicron and the results were astounding. I got good results with Photographers formulary TD3 and sometimes good results with Kodak technodol. I wish it was still made, a great portrait film as well. Emile/www.deleon-ulf.com.