Any 'acutance enhancing agents' besides potassium iodide?

Athiril · Feb 19, 2015

Is there anything in the literature said to increase acutance besides potassium iodide? Also excluding any kind of agitation induced 'edge effect' (such as stand which I've seen in some cases to actually be worse) and tanning/staining properties.

pdeeh · Feb 19, 2015

Is KI acutance enhancing?
It's known as quite a potent restrainer.
I think it was added to some old acutance-type formulas (by Crawley maybe?) but that it was irrelevant to the type of films we use today for that purpose?

Patrick Robert James · Feb 19, 2015

Pinocryptol (sp?) yellow was a constituent in a developer, maybe FX-2? It was supposed to enhance acutance somehow. Have no idea if it does or not.

I always thought the lack of sulfite was the best way to acutance but I ain't no expert.

Athiril · Feb 19, 2015

KI increases both resolution and acutance, especially in combination with potassium thiocyanate. I've tested that combo on a number of films, most of them work with it, including T-Max.

gone · Feb 19, 2015

I would think the simplest thing would be to switch developers. Some are known for that. Acufine is a really sharp developer, at least w/ my negs.

Athiril · Feb 19, 2015

Haven't tried acufine. I've found Rodinal 1+25 and Xtol Replenished to have the same detail level on all the films I've tried. Detail level in both can be drastically boosted.

Rudeofus · Feb 19, 2015

If the balance of powerful restrainer and solvent increases sharpness, then any such combo should do the trick. There are several organic restrainers comparable to Iodide, and there are solvents comparable to Thiocyanate, so you have plenty of variables to play around with.

Alan Johnson · Feb 19, 2015

Crawley, BJP Dec 1960 p651:
"By 1954-55 it was obvious that the thin coated, compact, high acutance film was to be the next fashion..."
That type of film I believe is discontinued. It had low iodide content (there may still be such films but I don't know of them). When I wrote to him, Crawley replied " There is indeed no point in adding the iodide to FX-1 with modern films....this developer was designed for the era of 'acutance' films."
BJP Jan 1961 p10:
"...FX-2...a dye restrainer is used to ensure clarity of fine detail.....Dye restraint...can give a faintly higher image to fog level."
I see no obvious reason why this should not work with modern films.

dpurdy · Feb 19, 2015

Coincidentally I just tested Beutlers with and without Potassium Iodide about 2 weeks ago. I have used Beutlers for many years and always included the iodide. I have read that modern films are supposed to have Potassium iodide already in them so it is not necessary to use it anymore. I finally got around to making a side by side comparison on my film of choice (120 Acros) shooting a subject meant to make edge affect easily noticeable and I cut the roll in half and processed it with and without the iodide. I was somewhat surprised that it made no difference in density and it seemed like there might have been a very slight increase in edge affect but it was so slight it might have been my imagination wanting to see it.
Dennis

Athiril · Feb 19, 2015

Resolution and acutance increase, even on T-Max in a solvent developer (Xtol) without an increase in graininess, and in Rodinal, grain impoves with the solvent addition. I'll put up some comparisons later. It is incorrect that modern films do not improve or are worse off without it.

Only one film so far I've used hasn't worked with it and that was GP3, I couldn't find any change to image structure, it was identical, odd. Might have to retry it.

I did my tests on resolution charts to make sure.

Haven't tried Acros.

Ian Grant · Feb 19, 2015

Athiril said:
Haven't tried acufine. I've found Rodinal 1+25 and Xtol Replenished to have the same detail level on all the films I've tried. Detail level in both can be drastically boosted.

I'd agree with that although I only used 1+25 for N+2 development, I preferred 3+100. Replenished developer do give better result than the same developer FS or dilute this is due to the bromide and iodide build up.

Ian

Alan Johnson · Feb 19, 2015

In "Controls in Black and White Photography" p234 ,R. Henry discusses the effect of potassium iodide addition to D-76 1+1 and Panatomic-X.Using a microdensitometer he found iodide addition made no difference to the acutance or the height of the border effect.He used 5ml/L of 0.001% iodide.
Not all Henry's results are in line with later opinion,for instance he found diluting Microdol-X had little affect on acutance.

Photo Engineer · Feb 19, 2015

Iodide only works in films with relatively low iodide content. As AgI goes up, KI effect goes down. This is due to the lower adsorption of the KI from solution and the greater contribution of Iodide as the AgI develops.

Early films had about 1% or maybe even 3% Iodide, but today can have up to 10%. This may be why, in an earlier post, several people had trouble getting the KI effect from Crawleys.

And yes, there are other chemicals that act as edge effect enhancers but they are generally very expensive organic chemicals.

PE

Athiril · Feb 19, 2015

May have to click to open, and then click again to see full version.

Top chart is Rodinal 1+25, bottom is Rodinal 1+25 with KI and KSCN. Film is T-Max 100. T-Max seems to respond reasonably well to this treatment. I haven't tried KI on it's own in the same tests.

Photo Engineer · Feb 19, 2015

Dan, overall density and contrast are much lower in the bottom sample and thus IMHO, it is impossible to make a concrete statement on the changes you made.

PE

Athiril · Feb 19, 2015

PE they look very close on the monitor I'm using. Perhaps you're seeing the overall graininess of the top sample contributing to making it look a bit darker in the white area? They were both just quickly levelled scans. Negative density and contrast is very similar.

Regardless no amount of contrast adjustment, sharpening or other things will increase the top samples resolution to match the bottom and reduce grain to match as well.

Photo Engineer said:
And yes, there are other chemicals that act as edge effect enhancers but they are generally very expensive organic chemicals.

PE

Is there anywhere I can read up about these?

dwross · Feb 19, 2015

Athiril said:
May have to click to open, and then click again to see full version.

Top chart is Rodinal 1+25, bottom is Rodinal 1+25 with KI and KSCN. Film is T-Max 100. T-Max seems to respond reasonably well to this treatment. I haven't tried KI on it's own in the same tests.

How much do you add? I'd love to give it a try. Thanks.

Athiril · Feb 19, 2015

dwross said:
How much do you add? I'd love to give it a try. Thanks.

1.4g/L of KSCN to working developer
10mg/L of KI to working developer (I make up a 1mg/mL stock solution of KI for this purpose)

In a high sulphite developer like full strength/replenished Xtol some films have dichroic fogging - T-Max 100 didn't iirc. But FP4+ did which was easily wiped off while still wet. Retro 80S was hard to notice the fogging and harder to wipe off.

Didn't see any on any film in Rodinal though. It also works with stand developing.

If you're scanning negs directly rather than wet printing you may not notice a difference unless you have something that has decent resolving power (no flatbeds do iirc). The one I use can resolve 130+ lp/mm in a single pass.

Ftr I haven't tried all films I know so far if works well with T-Max 100, Retro 80S and FP4+ with some limited success on Delta 3200 in xtol (think I need go change amounts), and failure on GP3 in Xtol (no detectable change to image structure).

dwross · Feb 19, 2015

Well, that's easy enough! I will try it with Rodinal for sure. Love the stuff, but a little less grain would make it even better.

dwross · Feb 19, 2015

Second question, if I may. Where did you get your resolution target? It's a dandy.

Athiril · Feb 19, 2015

Report back on how it works out for you

Athiril · Feb 19, 2015

dwross said:
Second question, if I may. Where did you get your resolution target? It's a dandy.

Modified and printed my own from http://www.graphics.cornell.edu/~westin/misc/ISO_12233-reschart.pdf

It's vector so you can import any resolution into photoshop etc, and I set the black to full black.

Here's my modifications, made my own contrast based one, and colour/saturation based one

Photo Engineer · Feb 19, 2015

Dan, thanks for the reference. I have the Edmond Scientific metal on glass charts plus a set from my EK days. I'll have to give this a try.

But, although I see a big grain difference, I see little difference in sharpness. Also, due to the apparent density and contrast difference (and both are being viewed on the same monitor remember), I cannot judge these well.

A step wedge plot would solve the problem easily enough. Did you run one?

PE

Athiril · Feb 19, 2015

No, I would have to shoot a reflective chart to make a plot, I have access to an X-Rite 820 Densitometer, but not a sensitometer. There is a film recorder for writing images, but probably not suitable for the task.

Digitally enlarged one section 200%

Photo Engineer · Feb 19, 2015

I see pretty bad pixelization on the top image here. It does look worse for sharpness now, but I am hard pressed to say that about the first sample you put up.

I am using a geoforce EVGA at the highest resolution and 2 monitors, so I can check this pretty thoroughly now.

PE

Any 'acutance enhancing agents' besides potassium iodide?

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