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Processing Time vs. Developer Concentration


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#1 Marc Roessler

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Posted 01 October 2007 - 04:26 AM

Hi..

To my understanding, for lower processing solution concenrations a longer processing time is
necessary for the negative development process.

I have the following questions:

1. surely, there are some side effects. How will a negative developed for a longer time in a lower concentration look compared to a negative developed in a higher concentration bath for a shorter time?

2. how do the paremeters "processing time" and "developer concentration" relate? Is there a linear
relationship, i.e. halve the concentration, double the processing time? Or is this a curve?

The background of my question is that I have a 1,8 Liter processing tank, but processing solution
for only 1,6 Liters, so i would have to add slightly more water. Of course i would like to compensate
for this by processing for a longer time.

Are there any isses with the fixer, the bleach bath and the clearing solution being slightly
thinned from 1,6 Liters to 1,8 Liters?

Greetings,
Marc
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#2 Brian Pritchard

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Posted 01 October 2007 - 08:08 AM

There is not a lot of information in the literature about developer dilution. The development rate compared to the dilution does vary according to the developer composition. Metol/Hydroquinone developers do not have a linear response; you require proportionally more time as you dilute.

The other thing is that as the developer concentration is reduced the maximum contrast obtainable is reduced even with increased time. You do tend to get finer grain and increased edge effects from a dilute developer. In the stills world some developers are used very dilute in order to get the highest definition from edge effects..

You are suggesting a dilution of around 12.5%. My guess would be that you should increase the time by about 15%. I would do the same for the clearing bath, bleach and fix. These baths are not terribly critical as long as you give sufficient time so perhaps 20% would be safe.

As always you should do a test to be sure but, of course, that is not always possible. If you are not worried about a bit of extra contrast you could increase the development a little more, remembering that if the first development produces a heavy image your final image will be thinner. You didn't say but I have assumed that you are B/W reversal processing.

Brian
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#3 Nick Mulder

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Posted 01 October 2007 - 03:33 PM

You could also try to offset time with increased temperature - or even increased exposure ...

Its like playing 3D chess with Spock

yikes... test to be sure


I have the 100ft Lomo tank which takes about just under 2 litres - and the standard Kodak mixtures make about 3.8litres - 3.8/2 = 1.6L
---- do we have the same set up ?? If so, I simply tested development times as I was using odd film/developer mixtures and there was no recommendation anyway ...
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#4 Marc Roessler

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Posted 01 October 2007 - 04:24 PM

Hi,

thanks for your suggestions, Brian! I used a 12% increase in development time, worked like a charm.
Beautiful images. Won't be able to really judge it until i see them projected tomorrow. This was
Fomapan 100R and the Foma Reversal Kit, by the way.

May be of interest: I found that the permanganate bleach bath can be replenished. I used a mine, let it sit for
about 1.5 hours, then added another 4 Grams of KMnO4 for replenishing, no further filtration. Worked just
fine. I developed another film and a snippet of the film most of which i had developed with the first
processing, no visible difference.

Yes, i use the 100 feet Lomo tank.

Despite the very nice lomo tank, still quite a mess though and takes lots and lots of time. Makes you really
appreciate what the labs are doing for you...

This was the test roll shot with the Keystone A3 16mm camera. Will try to put some images/video on
youtube when i get the chance to.

Greetings,
Marc
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#5 David Mullen ASC

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Posted 01 October 2007 - 04:42 PM

Marc R., since you joined in 2005, there was a rule change requiring people's User/Display Names be a real first and last name, so please go to My Controls and edit your Display Name. Thanks!
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#6 K Borowski

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Posted 01 October 2007 - 07:00 PM

Mark, I understand that you are probably just an interested hobbyist from your post, but please follow my recommendations here:

1. Do NOT play around with developer concentrations and processing times, especially with important, one time only family footage or footage for a film project you are working on.

2. If you are working with color, do NOT play around with anything; follow the instructions to the letter. Just remember than many many fine minds, most of them with masters and PhD degrees, designed the color film processes and color films used today.

3. Do NOT try to over-concentrate developer to shorten processing time. That is not the way that the system works.

From working with B&W paper developers, you can get quicker times with higher concentrations, but the overconcentrations also alters the shape of the characteristic curve, in effect rendering much higher contrast and a much steeper "slope" between highlight and shadow. Highlights get denser (dark areas on a negative), which would hide detail in an MP process.

I haven't read the specifics of your post (sorry, don't have the time), but if you cannot temper your tank to the proper temperature, I'd suggest getting some sort of fish tank heater and a tupperware tanks to hold the whole Lomo and thereby keep your temperatures in spec.

Do not play with the chemistries of processing solutions unless you are going for a special effect, and in that case you need to read up on and acquire a sensitometer and learn sensitometry to really understand what you are doing. Even with a good knowledge of film behaviour and sensitometry, you will need to run extensive tests to achieve the proper gamma (contrast).

This really is a highly complicated intricate science, that most cinematographers haven't the faintest grasp of, so there's no real way I can explain alterantive processing effects to you until you are fully versed with the workings of standard ECN-2 and D-96 film processes.

But again, with all of the different developers out there for B&W, which is what it appears you are doing, you really have no need to tailor a formula to your own usage. There are at least five hundred commonly known B&W film developer formulae floating around out there, with different variations on the reducer, preservative, restrainer, and other chemical type whose name I can't remember mixed together to produce a specific result.

D-76, the old Kodak standby developer has history as an MP developer from the 1920s, and it is still a stnadby, so I doubt that through dilution or time variation you will chance upon something better than an 80--yo tried-and-true formula.

About the only time you'll want to mess with concentration is when you are making a replenishment sollution to keep a used developer mix fresh, adding over-concentrated replenisher at a certain rate per square foot of film. Even here, I probably wouldn't mess around, as B&W replenishers were always shirked by my professors of photography in college.

YOu sound like you are small-volume enough that you shouldn't really need to worry about it.

- - - - - - - - -

My advice to you is to keep it simple and not develop your own film until you can shoot tests, send half to a lab, and process half yourself and get as-good-as or better results than the lab.

The cost savings of DIY film processing is tempting, as I can attest to having tried doing my own C-41 for a while (color negative stills), but the hastles involved were far greater than I anticipated, so I am back to using a lab now for a lot of my work.

How about the hastles of drying 100 feet of film without kinks and cinches? Again, this is a huge hastle. I had a hard enough time with 5-foot lengths of 220 film, whereas the few times I processes 50-foot rolls of DR8 in HS I don't think Ihad a single roll that escaped some sort of physical damage during drying.


Regards,

~Karl Borowski
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#7 Marc Roessler

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Posted 02 October 2007 - 04:51 AM

Karl,

of course all the procedures I described above I did purely for hobbyist use. It's quite clear that this is nothing to
do on a film project... I'd even strongly suggest against home processing in general on projects, as the
lomo tanks sometimes have a tendency to "skip" a few revolutions if you are not very careful (difficult
as you can't feel it in the lower section, and can't see it of course...)... which then means that not the whole
film will fit onto the reels, so you only notice the film has not loaded properly after finishing loading!

To me home processing is interesting mostly from a learning standpoint. But this also means that you
have to ask some "evil" questions ;) .. staying perfectly within the specified procedure without looking
left or right ("so now what would happen if I...") does not teach you a lot about how all of this works.
To be able to really understand what is happening, you have to also tackle the critical edges. (This bascially
is the same with all technology, if you really want to grasp it.. I experienced this again and again)
That's the background of my questions, not the "I want to develop my feature film at home".. :rolleyes:

I don't find the cost very tempting, considering all the hassle it comes along with and the time it takes.
Maybe it's cheap if you buy all the chemistry in bulk and mix it yourself, but thanks to all the current
hysteria e.g. permanganate is basically impossible to obtain around here.

I did not find it difficult to dry 100 feet of film... I used paper clips (the plastic coated type, for chemical
inertness) bent open hung to my halogen lamp wire system. The clips are bent so the film is lying on a
horizontally oriented part of the clip. The clip fits perfectly into 16mm perforation, so the film won't slip away.
You need two clips per support, so you only have 90 degree bents (vs. 180 degree bents with just one
clip).
For the basic experiements I was doing, this was totally sufficient, it worked much better than I expected.
Of course you have to have some experience with film handling ("by the edge") for doing all of this,
but I'd expect that from anyone attempting to process film on his own.

Greetings,
Marc
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#8 Marc Roessler

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Posted 02 October 2007 - 04:52 AM

Karl,

of course all the procedures I described above I did purely for hobbyist use. It's quite clear that this is nothing to
do on a film project... I'd even strongly suggest against home processing in general on projects, as the
lomo tanks sometimes have a tendency to "skip" a few revolutions if you are not very careful (difficult
as you can't feel it in the lower section, and can't see it of course...)... which then means that not the whole
film will fit onto the reels, so you only notice the film has not loaded properly after finishing loading!

To me home processing is interesting mostly from a learning standpoint. But this also means that you
have to ask some "evil" questions ;) .. staying perfectly within the specified procedure without looking
left or right ("so now what would happen if I...") does not teach you a lot about how all of this works.
To be able to really understand what is happening, you have to also tackle the critical edges. (This bascially
is the same with all technology, if you really want to grasp it.. I experienced this again and again)
That's the background of my questions, not the "I want to develop my feature film at home".. :rolleyes:

I don't find the cost very tempting, considering all the hassle it comes along with and the time it takes.
Maybe it's cheap if you buy all the chemistry in bulk and mix it yourself, but thanks to all the current
hysteria e.g. permanganate is basically impossible to obtain around here.

I did not find it difficult to dry 100 feet of film... I used paper clips (the plastic coated type, for chemical
inertness) bent open hung to my halogen lamp wire system. The clips are bent so the film is lying on a
horizontally oriented part of the clip. The clip fits perfectly into 16mm perforation, so the film won't slip away.
You need two clips per support, so you only have 90 degree bents (vs. 180 degree bents with just one
clip).
For the basic experiements I was doing, this was totally sufficient, it worked much better than I expected.
Of course you have to have some experience with film handling ("by the edge") for doing all of this,
but I'd expect that from anyone attempting to process film on his own.

Greetings,
Marc
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#9 Dominic Case

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Posted 02 October 2007 - 08:16 AM

Nick Mulder calculates:-

standard Kodak mixtures make about 3.8litres - 3.8/2 = 1.6L


I'd say this arithmetic is indeed like playing 3D chess with Mr Spock - or possibly around 2.8D chess. ;)

BTW, buried in Karl's responses is one point worth making again - while you might get a good and alomst predictable result with non-standard times, temperatures, dilutions etc in a black and white process - and there's nothing wrong with experimenting - anything you discover will NOT be applicable to colour processing. Each layer reacts at a different rate, and things like dilution are particularly discrimatory between the layers - it's all about the time that the chemicals take to permeate the upper layers to start workon the layers underneath, among other factors.

Other than that, good luck in the darkroom.
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#10 Marc Roessler

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Posted 02 October 2007 - 08:51 AM

Dominic, I fully agree concerning color processing. Also temperatures are much more critical there.
I was referring to b/w reversal processing only, I think i missed to make that clear. Color reversal is not
something I want to try at home...

Greetings,
Marc

Edited by Marc Roessler, 02 October 2007 - 08:52 AM.

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#11 Charles MacDonald

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Posted 02 October 2007 - 08:15 PM

One kinda off the wall sugestion is that if you do want to play with developers to see what is happening.. Why not look for a Minolta 16 Still Camera? YOu can use 12 inch lenths of any 16mm Movie film and process then in 8 oz of soultion in a Jobo or Yankee (or other) still film tank. The camera and a tank would be probably under 30 dollars all together on the great auction site. A quick look shows someone with 20 NOS Yankee tanks at $6, but which seem to have high shipping to canada, but perhaps are OK to the USA. The minolta 16 Cameras start at 10 bucks.

If you find something that works (or is SO bad that you can't resist trying it as a movie) it probaly will scaleup with the SAME film to your lomo.
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