Acutance: Good thing or bad?

[Ed Bray]

Since reading about acutance and it's effect on sharpness I have been pleasantly pleased with using a Caffenol CL formula in a semi-stand manner. I have found that this has given me nice crisp negatives that scan very nicely. Whilst working on an image taken yesterday of Venford Dam spilling water I was surprised when spotting to notice what has actually happenned to my negatives which were processed to acheive the increased acutance effect. I was a bit unsure at first, but have since looked at some other negatives which have similar high contrast situations and the result is much the same. I then looked at some of my recent 5x7 negatives (these are constant rotation processed due to their size) and these do not exhibit this effect.

So, the questions are, is high acutance a good thing or bad? As an effect, can it be overdone to the detriment of the image?

This is a 100% crop of the high contrast edge of my Dam image here (http://www.largeformatphotography.info/forum/showthread.php?46577-What-did-you-compose-at-Water’s-Edge&p=917241&viewfull=1#post917241)

http://i332.photobucket.com/albums/m338/EdBray/100cropAcutance.jpg

[E. von Hoegh]

That's not acutance per se, it's edge effect from the stand developing. Stll can be a good effect, though.

[MDR]

It depends

Too much accutance can look just as bad as too much HDR processing.

Dominik

[Ivan J. Eberle]

Didn't the need for this technique originate in the wet darkroom to counteract enlarger lens induced diffraction? It would seem to me that if you're hybrid printing it's unneeded, and unlike oversharpening, sort of irreversible. Might make a flatbed scanner seem better than it is ( say, if printing to small)?

[Ed Bray]

I shall be ceasing the semi-stand technique for a while as I've just ordered all the chemicals needed to make pyrocat HD so by the time my new 5x7 camera arrives I shall be able to process the film from it.

[sanking]

Acutance results from microcontrast caused by edge effects. How much is desirable depends on film, format, and degree of enlargement, and can be enhanced by choice of developer, dilution and type of agitation. There is no one size fits all since acutance is only one component of sharpness, and sharpness itself is subjective.

In hybrid printing edge effects on film, unless very gross, are too narrow to be captured by consumer flatbed scanners. To capture fine edge effects the scanner needs to be able to capture an effective resolution of about 4000 dpi, a figure only obtainable with drum and professional flatbed scanners.

Sandy

[Ed Bray]

Acutance results from microcontrast caused by edge effects. How much is desirable depends on film, format, and degree of enlargement, and can be enhanced by choice of developer, dilution and type of agitation. There is no one size fits all since acutance is only one component of sharpness, and sharpness itself is subjective.

In hybrid printing edge effects on film, unless very gross, are too narrow to be captured by consumer flatbed scanners. To capture fine edge effects the scanner needs to be able to capture an effective resolution of about 4000 dpi, a figure only obtainable with drum and professional flatbed scanners.

Sandy

Hi Sandy, thanks for the reply. I'm just about to make my first batch of Pyrocat HD in a short while as the chemicals for part A arrived today, but I will be using the Sodium Carbonate (anhydrous) version of part B as I have an almost unlimited supply of it. Now my silly question, I have ordered a couple of Vacuum Pumps and special stoppers, but will the parts A & B be okay if stored in plastic bottles for a while?

I only plan to make up 500mls of each concentrate initially.

[sanking]

Hi Ed,

No problem with sodium carbonate so long as you use it in the right amount. I would recommend a 20% stock solution of sodium carbonate and then mix 1 part A + 5 parts B +95 parts water.

Storage in plastic containers for a few weeks is fine. But for long term storage glass is best.

Sandy




Hi Sandy, thanks for the reply. I'm just about to make my first batch of Pyrocat HD in a short while as the chemicals for part A arrived today, but I will be using the Sodium Carbonate (anhydrous) version of part B as I have an almost unlimited supply of it. Now my silly question, I have ordered a couple of Vacuum Pumps and special stoppers, but will the parts A & B be okay if stored in plastic bottles for a while?

I only plan to make up 500mls of each concentrate initially.

[Ed Bray]

Thanks Sandy, that is good to know. One of my sites uses 40x 25kg bags of Sodium Carbonate (anyhdrous) a week.