Perceptol and Speed Loss

I'm trying to understand about Perceptol and speed loss. I'm shooting Acros. Both the Acros and Perceptol data sheets recommend 12.5 minutes of development in Perceptol stock solution at box speed (100). However I keep reading that I should rate it at 50 or 64 otherwise I will lose shadow detail. To further complicate matters, the Massive Dev Chart says that 12.5 minutes is good for either 50 or 100 (unless I'm reading it wrong: http://www.digitaltruth.com/devchar...os&Developer=Perceptol&mdc=Search&TempUnits=C).

What's this all about?

usual in-accuracies posted on internet.

Halving film speed is needed if you want to have 5 stops from a spot metered value to black (zone zero). You would only need that if your subject brightness range is 10 stops from black to white.

The average subject is 7 1/3 stops range and that is what manuafcturers film speed and dev is based on.

So the question becomes, what is YOUR typical subject brighness range? If its 10 stops then you should halve film speed. But if its close to average or less than average then don't halve film speed.

Most of the people advising halving film speed are following a general rule of thumb which applies to the zone system and they are landscape photographers. If you are photographing in the studio or subjects which don't have sky and/or bright clouds or white water in sun, then using manufacturers ISO speed and dev should be fine assuming you are metering correctly.

Interesting. I've read about downrating film, but it usually calls for a corresponding decrease in development time (N-1 or N-2). MDC has Acros/Perceptol at 12.5 minutes for "50-100" which doesn't make sense to me.

In practical terms, there was a period of time when I was exposing Acros at 50 or 64, as I had planned to develop it in Perceptol and read that it was "the thing to do." So I have a handful of rolls from late last year exposed as such, and I'm trying to decide what to do with them.

Both Fuji and Ilford say:

EI 100 12.30 @ 20 degC using Perceptol Stock.

until you have found that to be producing results you don't like, then I would go with it.

exposing at 64 or 50 will just push everything up the curve without casuing any problems unless you have long SBR and push highlights too far onto film shoulder.

diluting and/or reducing dev time will lower the negative contrast. Overexposing just pushes everything up the curve which gives better shadow separation but may reduce highlight separation if exposure is pushed onto shoulder.

So 50 or 100 will both work. But you only need to use the slower speed if you really do need to. I can't say what will be acceptable to you but if you don't need the extra shadow separation because its OK at 100 then why do it.

I would add that Perceptol tends towards a medium to longish toe. With T-Grain films Perceptol produces a long toe.
I don't think Across is a T-Grain film but others may know better than me on that.

I have done very little testing with Acros and Perceptol a long time ago.

The only suggested dev times I can give you you are

EI 60, Perceptol Stock 7.5 minutes @ 20deC.

Continuous agitation first 30 seconds and then 2 inversions every minute.

That will produce a CI of around .5 and will print a 10 stop range from black to white on G2 paper.

That may be too soft for your typical subject matter, I don't know. Others prefer more normal negative contrast which the manufacturer recommended EI, times and temps will give you.

This is a topic that fits in with my work at the moment. I mixed a batch of "homemade" Perceptol on Friday just before I left for the cottage. I like it to settle for a few days before I use it. I'm going to be using it at 1:2 with Ilford PanF+ that I have loaded in a couple of old Rollei cameras. But I have used it with Fuji Acros with great results. With Acros I went with 1:3 and it was a fine combo. The only thing you must watch when diluting Perceptol is the strength of the developer. If I'm going to develop one roll of 120 film I always use a two roll tank to make sure the developer doesn't poop out before the developing time ends and those times are long when diluting. I don't have my times at hand, but I think my Perceptol 1:3/Acros times were in the 18 minute bracket. Also, when you dilute the negatives are not only slightly sharper, but they have less speed loss too. As for the Massive Development Chart? I take it with a grain of salt. I think these times are entered by different folks and that's why you see things like you are seeing. Same times, different ISO??? John W

bvy said:

I'm trying to understand about Perceptol and speed loss. I'm shooting Acros. Both the Acros and Perceptol data sheets recommend 12.5 minutes of development in Perceptol stock solution at box speed (100). However I keep reading that I should rate it at 50 or 64 otherwise I will lose shadow detail. To further complicate matters, the Massive Dev Chart says that 12.5 minutes is good for either 50 or 100 (unless I'm reading it wrong: http://www.digitaltruth.com/devchar...os&Developer=Perceptol&mdc=Search&TempUnits=C).

What's this all about?

Click to expand...

Just try it once,cutting film speed by 2/3 stops will do wonders for yor image quality and your friends will wonder what your secret is

Ralph,

I think you're right about the secret.

But I don't think speed loss is a myth. We're talking relative speed loss of the same film compared to a standard developer.

I found an old "How to Use" Kodak Microdol Developer technical booklet...

If Perceptol is anything like Microdol then this logic might pertain.

"Since Kodak Microdol is an effective fine grain developer, however it does not bring out the inherent maximum speed of the photographic material. Therefore, under conditions where it is not possible to give normal exposure but it is necessary to come close to the underexposure border line, it may be preferable to employ Kodak Developer D-76..."

JW PHOTO said:

I don't have my times at hand, but I think my Perceptol 1:3/Acros times were in the 18 minute bracket. Also, when you dilute the negatives are not only slightly sharper, but they have less speed loss too.

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Less speed loss than what? You seem to be suggesting that 1:3 will give better speed than stock. I don't believe that. As far as I'm aware, diluting a developer such as perceptol to 1:3 removes so much sulphite from the brew that its silver reduction is massively reduced. The net result is apprent increase in sharpness and contrast which you may be mistaking for speed increase.

RobC said:

Less speed loss than what? You seem to be suggesting that 1:3 will give better speed than stock. I don't believe that. As far as I'm aware, diluting a developer such as perceptol to 1:3 removes so much sulphite from the brew that its silver reduction is massively reduced. The net result is apprent increase in sharpness and contrast which you may be mistaking for speed increase.

Click to expand...

That might be exactly what I'm seeing, but I'm seeing it just the same. As far as the sulfite reduction goes I think slightly over 30g per-liter is all that's needed. If you read any of Barry Thornton's writing you'll see he cuts sulfite for a gain in sharpness/acutance and doesn't indicate a speed loss with dilution. Now, to be honest I have never used Perceptol full strength. I've only really used it at 1:1 and higher dilutions, but there is even a difference between 1:1 and 1:3. I rate my Acros at ISO 80 for 1:3 and ISO 64 for 1:2. I almost never use 1:1 anymore. That's just me of course. My developing time and temp, my metering, my agitation, but I'm very, very happy with my silly method and rating. Yes, slight speed drop, but not as much as some folks think. John W

RobC said:

Both Fuji and Ilford say:

EI 100 12.30 @ 20 degC using Perceptol Stock.

until you have found that to be producing results you don't like, then I would go with it.

Click to expand...

I haven't looked the Fuji instructions but I wonder why there are no times for Fuji Acros at 1+1 on the Ilford site? As far as I recall Ilford gives 1+1 times for other films. It may not have tested Acros at 1+1 of course but given how many other films it has tested at 1+1 it just seems strange

pentaxuser

pentaxuser said:

I haven't looked the Fuji instructions but I wonder why there are no times for Fuji Acros at 1+1 on the Ilford site? As far as I recall Ilford gives 1+1 times for other films. It may not have tested Acros at 1+1 of course but given how many other films it has tested at 1+1 it just seems strange

pentaxuser

Click to expand...

I'm pretty sure its becasue diluting perceptol tends to put a long shallow toe into the curve and if you want to take that out you lose effective film speed. You need to use stock to keep the toe as short as possible.

Thanks RobC.

pentaxuser

Modest loss of film speed with high sulfite - low alkalinity developers like Perceptol, Microdol-X, or even for that matter good ole D-23 is to be expected. It is the price one pays for finer grain. Diluting the developer reduces the proportion of sulfite in the developer and hence reduces the amount of halide solvency. Effective film speed increases closer to box speed and there is also an increase the grain sharpness. So one has a choice use Perceptol FS, 1+1 or 1+3 depending one what you want.

Jerry,
Thanks for clearing that up and it makes me feel better knowing what I'm seeing isn't a mirage. I wasn't saying I get box speed with 1+3, but it's not far off. I shoot 120 so the moderate increase in grain is no problem either. As I said before, I have two Rollei's loaded with PanF+ and will be using a 1+2 dilution with the ISO set at 32 with my incident meter. I'll post some shots from the "Duel of the Rollei's" and then folks can decide if there is enough sharpness, grain or film speed/shadow detail. John W