What Gives ACROS Its Distinctive Look?

[MaxElmar]

Other than the sharpness - a quality shared by several modern emulsions - one thing for me is way it seems to roll off to black quickly. (Not unlike its Fuji Velvia 50 cousin). But it also seems like they mess with the spectral response a bit. The word "orthopanchromatic" appears in the (B&H) description. Now this word is certainly an invention of marketing, no? It seems like an oxymoron. But there is something about the film that suggests the look of ortho to me. The spectral response curve on the data sheet has a pronounced dip at 500nm. Is that what I am seeing? Or have I been sniffing too much XTOL?

 

[Larry H-L]

I've never looked at the spectral charts, but the "ortho" would seem to indicate less sensitivity to reds.

Ilford makes an ortho B&W, and Kodak used to offer Tri-X Ortho. Both of these films render most faces slightly darker, and outdoors show more open shadows and balder white skies, indicating more blue/green sensitivity and less red.

 

[tunalegs]

I think the two things which stand out most are the lack of grain and the deep black.

The sensitivity does drop off steeply in the red spectrum, but the film is not insensitive to red, which may be why it's labelled "orthopanchromatic". The dip at 500nm is in the green spectrum. The steep drop at about 650nm is in the red.

 

[Nokton48]

It does have an "ortho" type of rendition that can be pleasing. This was a thirty second exposure and required no reciprocity correction. That is a good thing.

Orton Geological Library detail, Ohio State University Oval.

Makiflex Acros 150 SymmarS by Nokton48, on Flickr

 

[Freakscene]

The distinctive look of Acros is, in comparison to other modern films, from the film's distinctive spectral response and curve.

The spectral response is orthopanchromatic. This is used to describe a film with reduced red sensitivity compared to panchromatic film, but not as low or absent as in orthochromatic films. This colour sensitivity is sometimes supposed to match the human eye more closely than panchromatic film, but really only does so in that it is most sensitive to green.

The curve has a very short toe, and is upswept in the lower tones but straighter in the higher tones. This makes the low and lower mid tones look darker than on a film with an overall straighter initial curve and is why the tones can "fall to black" if placed well. The straight section maintains the relative separation of tones in the upper mid and highlight tones. FujidolE and Xtol give Acros a much more upswept curve than most other developers.

If you can place important midtones in the area where the curve becomes straight the separation you get is extraordinary, but if you miss it Acros can leave you with a mess.

I like the look for some subjects and where I can control exposure and development precisely, but that's relatively rare for me. Like a lot of people, the greatest utility of Acros is in its lack of reciprocity failure for long exposures.

Marty

 

[Chriscrawfordphoto]

The Orthopanchromatic label is not a marketing invention, or even a new term. Its been used for decades. The old Efke films were orthopanchromatic films, too.

I've never been a fan of Acros for anything but very low light work, where its wonderful reciprocity characteristics make it an easy film to work with. I've done shots with 5 minute exposures that required only half a stop of compensation for the long exposure.

I've never liked Acros's tonality in normal light.

 

[Skiff]

Other than the sharpness - a quality shared by several modern emulsions - one thing for me is way it seems to roll off to black quickly. (Not unlike its Fuji Velvia 50 cousin). But it also seems like they mess with the spectral response a bit. The word "orthopanchromatic" appears in the (B&H) description. Now this word is certainly an invention of marketing, no? It seems like an oxymoron. But there is something about the film that suggests the look of ortho to me. The spectral response curve on the data sheet has a pronounced dip at 500nm. Is that what I am seeing? Or have I been sniffing too much XTOL?

No, you have not been sniffing too much XTOL.
Acros is indeed an orthopanchromatic film. And this technical term is absolutely correct and used in the film industry for decades. It has absolutely nothing to do with marketing. It is a precise technical description.

An orthopanchromatic film renders red darker than a normal panchromatic film. But not completely black, as an orthochromatic film does.
Besides Acros, Adox CMS 20 II is also orthopanchromatic.

Besides this specification Acros is also the finest grain ISO 100/21° BW negative film (it is a little bit finer grained compared to TMX).
And together with Fujichrome Provia 100F it has the best and simply unique, outstanding reciprocity performance.

I like Acros very much. I prefer it developed in Adox FX-39, Rodinal 1+74, Adox ADX II or Spur HRX. It fits perfectly in these developers.

 

[SyPat]

The curve has a very short toe, and is upswept in the lower tones but straighter in the higher tones. This makes the low and lower mid tones look darker than on a film with an overall straighter initial curve and is why the tones can "fall to black" if placed well.

This explanation is correct. A picture in bright sun taken with Acros is like wearing brown sunglasses.

 

[farlymac]

I'm starting to reserve my use of Acros for cloudy days. I like what I get with Ilford Delta 100 in bright sun much better.

PF

 

[HHPhoto]

The curve has a very short toe, and is upswept in the lower tones but straighter in the higher tones.

Marty

From my own experiences and different tests with Acros in a lot of different developers I have to disagree.
I have to disagree in the following way:
The phenomenon you have discribed can be there: But only with certain developers or certain dilutions.
But it is not a general characteristic of Acros.

As with every film the results is very dependant on exposure, type of developer, dilution of developer, agitation rhythm.
The above described phenomenon is also there with Tri-X or FP4 + if you choose the"wrong" developer or dilution.

Example:
With Adox Rodinal alone I can get 4 (!!) completely different results / characteristic curves with Acros!
ISO 100/21° and dilution 1+25: Short toe, upswept curve, blocked highlights.

ISO 80/20° and dilution 1+50: Longer toe, less upswept curve, brillant highlights with good separation.

ISO 50/18° and dilution 1+75: Very good shadow detail, almost perfect linear characteristic curve. Wonderful separation of tones and perfect tonality.

ISO 40/17° and 50/18° at dilution 1+100: Very similar to the results with 1+75, but with lower density in the highlights (compensating effect).

With Acros it is exactly the same as with every other BW film:
Decisive is the right combination of film, exposure (use of real effective speed), developer, dilution, developing time an agitation rhythm.
To find these perfect film-developer combinations is essential for results in BW.
And by far the best solution to find these perfect combinations is using the perfect method BW experts are using for decades:
Use a densitometer and evaluate the characterictic curves of the film-developer combinations.
This method is
- by far the most precise
- it gives you all the information you need at once
- it is very easy
- it is very cheap.

Those who want the best BW results consistently should go this route. They will have much better results compared to their former ones, they will have much much less frustration, they will have much more fun shooting BW film.

Cheers, Jan

 

[Freakscene]

From my own experiences and different tests with Acros in a lot of different developers I have to disagree.
I have to disagree in the following way:
The phenomenon you have discribed can be there: But only with certain developers or certain dilutions.
But it is not a general characteristic of Acros.

As with every film the results is very dependant on exposure, type of developer, dilution of developer, agitation rhythm.

Sure, but the general look is there in almst all photos from Acros on the web, matches the OPs description, and is visible in all of Fuji's published curves for Acros (which none of Kodak's show for Tri-X nor Ilford's for FP4+). Rodinal type developers depress the midtones a lot with Acros, and the loss of speed isn't very appealing in an already slow film. I have graphed the curves from dozens of Acros-developer combinations from a densitometer, and most of them turned out as I described. There are even printing papers that match the odd curve fairly well.

Marty

 

[Skiff]

Sure, but the general look is there in almst all photos from Acros on the web, matches the OPs description, and is visible in all of Fuji's published curves for Acros (which none of Kodak's show for Tri-X nor Ilford's for FP4+).

Neither is there "a general look on the web" for Acros, nor are the few official curves published by Fuji confirming your statement.
On the web there are so much different looking shots for Acros: All is depending on the developer used and the developing technique (agitation and dilution). And of course lots of Acros shots on the web varies because of different scanning techniques and different electronic post-processing.

Rodinal type developers depress the midtones a lot with Acros,

No, not if you use the right dilution (higher diluted). I don't have depressed midtones with my Acros films developed in Rodinal.

It is all about the right developer and developing technique matching the film you are using.
No matter if you are using Acros, or Tri-X, FP4+ or any other BW film.