Simulating Orthochromatic film

AgX · Jul 27, 2007

Harrigan,

I don’t understand your argument.

It is `just´ a question of filtration or rather filters. If you have sharp cuttting filters with several cutting frequencies at hand, you can choose the one apt to cut off the spectrum you like. (Actually, as stated above, our choice of filters in practice is somewhat limited.)

(Might be that your idea was based on the spectral sensitation on the very layers of colour films where an overlapping of the sensitation spectra is essential to render any colour hue.)

MarkS · Jul 27, 2007

One thing to remember is that there are varying levels of orthochromatic respsonse. Until 1991 or so, EK made a "Tri-X Ortho 4163" sheet film. It was a continuous-tone film, advertised for portraits of men. Its 'look' was quite different than the higher-contrast, graphic-arts type ortho films still available.
So if you're trying to replicate an old-time look, there are many of those, and no one way to get them all.
That said, I have tried the #44 filter on Tri-X 4164, as a means to the 'ortho' look. The test subject was my red car in front of foliage, with a blue north sky behind it. The filter did indeed darken the car, and lighten the sky and foliage. It gave a quite different look from an unfiltered shot of the same scene- which of course varied from the same scene photographed with a #12 yellow and a #25 red. However, the effects with the #44 were not extreme- the car didn't reproduce as black, nor was the sky white. An interesting experiment- although I haven't found a use for the #44 filter since.

David A. Goldfarb · Jul 27, 2007

No two films look alike, so I'm not sure it makes sense to worry too much about whether filtration will reproduce the exact look of "ortho film" since ortho films don't all look like each other for reasons other than spectral sensitivity (i.e., characteristic curve, grain size and pattern, etc.). On top of this, many who use ortho film today are looking to reproduce a certain historic look, and there is usually much more to that look than the spectral sensitivity of the film (i.e., historic format, lenses, slow film speeds and long exposure times, retouching and historic lighting techniques in the case of portraits, plates vs. film, etc.), and these other differences will be much more important to the overall feel of the image than small differences in spectral sensitivity.

[MarkS and I were posting at the same time.]

AgX · Jul 27, 2007

In order to exactly emulate the spectral response of a certain ortho-film with a certain panchro-film, those two films must coincide within that ortho part of the sensitation (or there must be filters which enable for tiny changes within that spectrum) and the two cut-off flanks of that cyan filter must resemble those side parts of the ortho sensitation in question. But all that would be twisting hairs I guess…

panastasia · Jul 27, 2007

MarkS said:
...there are varying levels of orthochromatic respsonse....

This is true!

The process has infinite variability throughout, the outcome (the look) is subjective - based on method. The uncertainty and the surprizes is what makes it all interesting.

Where are the rules and who is making them?

Have fun,
Paul

Photo Engineer · Jul 27, 2007

panastasia said:
QUOTE: "It should be noted that a panchromatic film can be used to simulate orthochromatic or blue-sensitive rendering using filters."
Ansel Adams, THE NEGATIVE, pg. 25, subject: Spectral Sensitivity.

Was Mr. Adams incorrect?

This statement is correct. It can be simulated by filtration.

The problem is that earlier in this thread, someone said that Adams had said just the opposite. That earlier comment was incorrect. The person misquoted Adams.

PE

keithwms · Jul 27, 2007

You can most definitely simulate ortho sensitivity with filters.

If you want to be really fancy, you could browse over to Edmund Scientific and decide which Schott glass you need...

referrign to these charts, you see that the filtering method is much more flexible than using an old-style ortho film: you can go for only blue, or only green, or blue+green or UV sensitivity.... whatever.

The obvious issues that arise are that (a) you could have deleterious effects from the filter, (b) if the ratio of the transmission maximum to the minimum isn't high enough then you could get a little bit of mixed sensitivity.

And just to restate the obvious: filtered pan film is not the same thing as ortho when you step into the darkroom... ortho can be treated like paper in terms of safelights, but pan film of course cannot! So what? Well, actually the only time I shoot ortho film in LF is when I want to work on something that will require inspection as I develop, i.e. when duping or whatever.

gainer · Jul 27, 2007

One also wonders if the eye can tell enough difference between a rendering that simulates every jot and tittle of some orthochromatic film and a minus red color separation filter's rendering to make one artistically preferable.

Edmund Scientific has some subtractive filters with quite sharp cutoffs. They are quite expensive. I personally would not invest in them unless I had other uses for them. My 2001 catalog shows about $80 for a set.

gainer · Jul 27, 2007

The filters I was thinking of are dichroic.
Schott has a factory at Parkersburg, WV, about 50 miles from here. I tried to take my physicist-astronomer brother on a tour, but couldn't get in. His latest book, by the way, is "Real Astronomy with Small Telescopes" by Michael K. Gainer.

AgX · Jul 27, 2007

Yes, there are interesting filters around. But if you look at those catalogues you'll find that many are offered in diameters not really practical as camera filter. That was one issue I referred to by saying "in practice".

gainer · Jul 27, 2007

AgX said:
Yes, there are interesting filters around. But if you look at those catalogues you'll find that many are offered in diameters not really practical as camera filter. That was one issue I referred to by saying "in practice".

I would find a way to use either the 50 mm round or the 50 mm square size. The 2001 price at Edmund Scientific for the set of three was $72.10 + shipping.

nworth · Jul 28, 2007

A number 44 filter would probably do an excellent job of simulating orthochromatic sensitivity. But if you don't have one, you might try an 80A color conversion filter. It corrects 3200K lighting for daylight color film. You will still get some red sensitivity, but mostly it will be blue and green. My filters manual shows a density of about .78 at 700 nm, .75 at 600 nm, and .27 at 500 nm, tapering to low densities in the blue. Many older ortho films had somewhat low sensitivity to green, so this may emulate that pretty well. The red sensitivity is well down but still significant. That may not be a problem.

Rolleijoe · Aug 5, 2007

Tim Gray said:
I understand there were films like Tri-X ortho available in days past, but no longer.

Efke 25 is an ortho-panchromatic, but Rollei Ortho 25 is a full ortho film, and in MF with Rodinal 1:50 gives beautiful results.

Both available from Freestyle.

Ole · Aug 5, 2007

Somewhere I have a nice little book - "arbeiten mit farben-empfindliche Filme" - which gives the spectral sensitivity for a wide range of sensitising dyes in use 90 years ago.

Maybe I should get it out and scan a couple of pages...

Photo Engineer · Aug 5, 2007

I posted a scan of a page of the Eastman Organic Chemical catalog in which they listed about 15 sensitizing dyes usable with photographic emulsions.

PE

keithwms · Aug 5, 2007

Ole, PE, wouldn't it be nice if we had a way to catalogue all the spectral sensitivity curves and reciprocity info somewhere on this site.
Okay, I am not volunteering. (at least not now!)

Simulating Orthochromatic film

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AgX

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nworth

Rolleijoe

Ole

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keithwms

Simulating Orthochromatic film

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