Can someone explain the meaning of "orthopanchromatic" (Acros)?

NortheastPhotographic · Dec 22, 2016

I haven't gotten a clear answer, but I have read alot of about how Acros is orthopanchromatic? Does this simulate some kind of filtration by increasing or decreasing sensitivity to a particular spectrum? My rudimentary understanding would have been that something is either ortho or panchromatic, but not both?

Lastly, what filter would simulate Acros on a regular film? ...Considering I don't think Fuji will make the stuff forever.

Anon Ymous · Dec 22, 2016

It simply means that it's spectral sensitivity doesn't go very far towards the red end of the spectrum. It is something between orthochromatic (red blind) and panchromatic.

NortheastPhotographic · Dec 22, 2016

So it could be simulated via a light red or orange filter?

Anon Ymous · Dec 22, 2016

Sperdynamite said:
So it could be simulated via a light red or orange filter?

None of these. I don't know what filter would give a similar result, but its colour would be what you get if you subtract quite a bit of red from white light.

NortheastPhotographic · Dec 22, 2016

I don't get it...wouldn't a red filter be doing just that?

removed account4 · Dec 22, 2016

here's a thread that might be helpful
(there was a url link here which no longer exists)

Ian Grant · Dec 22, 2016

Sperdynamite said:
So it could be simulated via a light red or orange filter?

No a blue/green filter.

Ian

AgX · Dec 22, 2016

Sperdynamite said:
So it could be simulated via a light red or orange filter?

To the contrary, you need a less-red filter.
Thus a cyan filter.

These designations are neither well-defined, nor are there standard spectral sensitations. These varied over their whole spectrum over time.
To be scientifically correct one would need the spectral sensitization curves of the old and the current film and the spectral transmission curves of some filters. Then one only needs to calculate those curves to one standard and then to choose the most apt filter (-combination)...

NortheastPhotographic · Dec 22, 2016

Ok cool! I'm starting to get it. On a related note I did just order a Lee #47 Blue filter to add to my collection.

Anon Ymous · Dec 22, 2016

Sperdynamite said:
Ok cool! I'm starting to get it. On a related note I did just order a Lee #47 Blue filter to add to my collection.

Perhaps you meant a 47B? If so, that's a tricolour blue, a filter used for colour separation work. It will only pass blue wavelengths, much narrower than what a cyan filter would pass.

NortheastPhotographic · Dec 22, 2016

Haha yes I meant 47B. As part of an unrelated project I'm trying to accentuate skin blemishes in some portraiture I'll be doing with my Pentax 67.

Neal · Dec 22, 2016

Dear Sperdynamite,

Based on the published curves, Acros is at least as sensitive to red as other films. I would say even more so. According to the Merriam-Webster site:

Definition of orthopanchromatic
of a panchromatic material

: having a color sensitivity most nearly matching that of the eye

Neal Wydra

Gerald C Koch · Dec 22, 2016

I am not surprised that the OP is confused. Orthopanchromatic is a very dumb term that unfortunately has caught on. The prefixes ortho and pan are contradictory. Putting them together is nonsensical. Something like the expression "military intelligence."

AgX · Dec 22, 2016

Likely we are getting philosophical now, but "right" ("ortho") is a relative term, it depends on circumstance, on point of view.

Why shoul it be different in photo technics?

Leigh B · Dec 22, 2016

Having shot about 87 Million sheets and rolls of Acros, I don't notice any diminished sensitivity at the long end of the spectrum.

The nominal response would be that bright red subject areas would not appear as "bright" as one would expect.
But based on proper sensitometric measurements, our expectations are likely too "bright".

- Leigh

tedr1 · Dec 22, 2016

As many already know in the beginning first came blue sensitive materials, truly monochromatic. Then we invented stuff that was also sensitive to green, which was called "orthochromatic" because it was slightly less "monochromatic" than what came before. Ortho means true or correct but photography businesses exaggerate like so many fields of commerce, but blue+green material was far from being orthochromatic so the term was abused by incorrect use, for about fifty years. Eventually red sensitivity was figured out and this new material might have been named "orthochromatic" material, which would have been true. Unfortunately this accurate name could not be used because it had already been "abused" to promote blue+green material. So blue+green+red was named "panchromatic" which means "all colors". It seems history mocks the exaggerations of salesmen.

I can't imagine why a technically savvy company like Fuji would name Acros in such a confusing fashion.

Gerald C Koch · Dec 22, 2016

I was a bit slow getting to the gate and tedr1 beat me to it. There is a German expression that fits the pseudo technical expression orthopanchromatic very well. I learned it when I was young. It is "Qvatsch mit sosse", nonsense with gravy on it!

Sirius Glass · Dec 22, 2016

Gerald C Koch said:
I am not surprised that the OP is confused. Orthopanchromatic is a very dumb term that unfortunately has caught on. The prefixes ortho and pan are contradictory. Putting them together is nonsensical. Something like the expression "military intelligence."

This is the common result when marketing people attempt original thinking. As an engineer I have had to reign in marketing people occasionally.

Leigh B · Dec 22, 2016

Sirius Glass said:
As an engineer I have had to reign in marketing people occasionally.

Same here.

- Leigh

HiHoSilver · Dec 22, 2016

'This thread is helpful for me - I appreciate each of you weighing in.

Gerald & Sirius - is that ever true about marketing language!

Gerald C Koch · Dec 23, 2016

Truth in marketing? Probably not since the serpent sold Eve on the idea of eating the apple.

AgX · Dec 23, 2016

"Quatsch mit Soße"

Well said, Gerald.
(Though I have not heard this expression for years. I made me smile.)

removed account4 · Dec 23, 2016

Sperdynamite
do an internet search using efke 25 as a search string
it was also a orthopanchromatic film, extended red sensitivity.
you can see what sort of portriats it made.
you might also think about using washi film
it is hand coated photo paper that is spooled and used in cameras.
photo paper as you know enhances blemishes as well.

good luck !

Leigh B · Dec 23, 2016

jnanian said:
it was also a orthopanchromatic film, extended red sensitivity.

Huh?

Ortho pan has reduced sensitivity to red, not extended sensitivity.

- Leigh

Bill Burk · Dec 23, 2016

I've got a book which shows typical spectral response curves exposed to daylight quality light... for color-blind, Orthochromatic, and so-called "Type A", "Type B" and "Type C" panchromatic films.

I think it's right to classify **Acros as "Type A", *TMAX as "Type B" and Tri-X as "Type C"...

So even though it has the moniker "Orthopanchomatic", there's plenty of both red and blue sensitivity in a Type A film.

*Actually I'm not sure, seems to me TMAX drops off more sharply in red (sharp drop at around 650) than this graph of a "Type B" emulsion.

**michael_r gave reference link to graph that reveals it's NOT Type A.

The book goes on and explains how to subtract the curve of the filter from the curve of the films response to a source for example the X2 filter with Type C pan film under a Tungsten light source matches approximately the response of the human eye.

Principles of Photographic Reproduction, Carl W. Miller, Ph.D.,A.R.P.S., New York, The Macmillan Company, 1942.

Can someone explain the meaning of "orthopanchromatic" (Acros)?

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