OT. but Zildjian cymbals were fantastic!
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OT. but Zildjian cymbals were fantastic!
Mustafa, that French company, if they were successful, should have paid you for your expertise. :)
I did not see this post when it went up over a month ago. I was in Montana at the Formulary.
I can say that Kodak did develop some products for Polaroid, because even though Land was a genius at inventing, his engineers did not have production coating machines nor did they have emulsion formulas and so Kodak developed a series of products for him including some B&W and color products. I do not know which ones.
The pod contains either KOH or NaOH as alkali along with restrainer and carboxymethyl cellulose (Unflavored Citrucel to US people :D ). There are also some developers and silver halide solvents. The film sheet is a film sheet but the reciever sheet is a special thing which forms the positive print. The whole thing is like a monobath.
In addition, the package contains rails to keep the distribution of pod goo even over the width and length of film, and the pod has dividers to promote even spread and burst when pressure is applied.
Filling a pod is a very exact and complex process and assmbling a pack is very expensive with some rather complex equipment involved.
Hope this helps.
PE
Take a look at US Patent 3615438. It's a Polaroid patent with a lot of discussion of monobath developer recipes and various negative films (Kodak and other).
It doesn't seem to address Type 55 specifically, but the information covers a good bit of what I think you're interested in.
Murray
pssst - still are ...Quote:
Originally Posted by Dinesh
Polaroid T-55 data sheet is still available here:
http://www.polaroid.com/service/film.../4_5/55fds.pdf
You want a fine grain film with a similar HD curve.
Of Kodak films presently available, it looks a lot like Tri-X Pan Professional (TXP320). Long toe, long straight line section, no shoulder. Very much like the classic (but discontinued) portrait films like Ektapan and Royal Pan. Or even like Verichrome Pan.
Ilford's Delta 100 is very straight line, no shoulder, but but as much toe.
The Polaroid film shown has poor red sensitivity and almost resembles a Tungsten film in speed distribution. The dmax is very low and the latitude only covers about 1/2 of that seen in most modern films.
Try here: http://kodak.com/global/en/professio...17.16.14&lc=en
About half way down the page they show the technical specifications of a typical Kodak B&W film and you see that this film has about 2x the latitude and a lot more red sensitivity. This is typical of Kodak films and is quite different than the T-55 data in the Polaroid link.
PE
The MTF falls off impressively fast on T-55.
The sensitivity curve of another film could be adjusted by a color balancing filter, like a blue one meant for shooting daylight film under tungsten light.
Yes, that MTF has been what makes me suspect it was none of the earlier Kodak emulsions. IIRC, they were better, unless the MTF was ruined by something done in coating, again something Kodak would not do.
PE
Well, how would one measure MTF in the case of T55? Seems to me the most honest way to do it would be to shoot a chart, pod-process the sheet and then take measurements off the cleared neg. Is that what they'd do? If so, then it seems to me that this could account for some deviations between T55 and panatomic x. I would expect pod processing to introduce a sort of Gaussian falloff in MTF simply because of the way the components mix and are distributed. Only the centermost regions of the film see truly optimal development, I'd suspect.
Make any sense?