Thread Up's In Developing Machines

Mike Panczenko · September 5, 2009

I was reading a manual on lab procedures on the Kodak website, and it mentioned that to ensure the proper run-time in the developer, to ensure that the processing time is the same "when a machine uses different thread ups for different film stocks."

Why would different film stocks require different threading paths in the machine? Aren't all ECN-2 stocks standardized to the same times, developers, fixers, etc?

What would the purpose be to having dedicated threading paths for particular stocks?

Mike Panczenko · September 5, 2009

Here is the direct quote:

"Machine speed is checked by carefully measuring the time it takes for a given length of film to pass a specific point. Knowing it is possible to use an incorrect processing time when a machine uses different thread-ups for different film stocks, the careful laboratory checks the solution times every time there is a threading change."

My question is: why different threading paths for different film stocks?

Thanks!

Brian Pritchard · September 5, 2009

Here is the direct quote:

"Machine speed is checked by carefully measuring the time it takes for a given length of film to pass a specific point. Knowing it is possible to use an incorrect processing time when a machine uses different thread-ups for different film stocks, the careful laboratory checks the solution times every time there is a threading change."

My question is: why different threading paths for different film stocks?

Thanks!

You are right that in normal circumstances ECN2 is a standardised process; however if you want to push or pull the film you have to change the development time. Most labs would do this by changing the running speed of the machine. This does mean that when you change the machine speed all the other baths will change as well. Theoretically when pushing or pulling you would add or remove strands in the developer so that you are only changing the development time and not all the other baths.

Brian

Robert Houllahan · September 5, 2009

Theoretically when pushing or pulling you would add or remove strands in the developer so that you are only changing the development time and not all the other baths.

Brian

While this is theoretically true it would be impractical from a workflow standpoint, ecn-2 machines are designed with more bleach/fix than is actually necessary to do the job and these steps are not critical in terms of time like the developer is. The real gauge of what happens in the processor is the sensiometric test and a lab will run a sensi after setting the machine up for Push/Pull to verify the results. ECN machines are usually qualified once in house and then checked from time to time but calibrating times before each run is unnecessary and impractical.

-Rob-

Brian Pritchard · September 5, 2009

While this is theoretically true it would be impractical from a workflow standpoint, ecn-2 machines are designed with more bleach/fix than is actually necessary to do the job and these steps are not critical in terms of time like the developer is. The real gauge of what happens in the processor is the sensiometric test and a lab will run a sensi after setting the machine up for Push/Pull to verify the results. ECN machines are usually qualified once in house and then checked from time to time but calibrating times before each run is unnecessary and impractical.

-Rob-

Of course it is impractical; I was just explaining what the Kodak information meant. I don't know of any lab that would carry out this procedure but an explanation was asked for and that is what I gave.

Brian

Robert Houllahan · September 5, 2009

Of course it is impractical; I was just explaining what the Kodak information meant. I don't know of any lab that would carry out this procedure but an explanation was asked for and that is what I gave.
Brian

Yeah I don't know why that would have been in the kodak lit, someone mentioned B&W in reference to this on the CML but even then you process to a gamma that is determined by the sensi... It must be an arcane reference. We have run a partial bleach bypass in the past (it was a real pain to setup removing a few racks and testing to get what they wanted) and full bypass is really the only time pulling racks seems necessary.

-Rob-

K Borowski · September 6, 2009

I agree with Rob.

The only problem you might run into is with a pull or double pull, where the bleach and fix steps don't go to completion by speeding the machine up.

I don't know if you have any darkroom experience but think of it like developing an 8x10" glossy print in a tray; it basically develops to completion and that is it.

Same is true with the "secondaries" (bleach, fix, stabilizer) in the ECN or ECP processes.

Too much is time/temperature is fine (as long as there is extra water wash time at the end); too little is the only time they are problematic.

Mike Panczenko · September 6, 2009

Hey guys, thanks for all the responses. I posted this on CML as well, and everyone really pitched in. I appreciate it.

I am going to ask the same followup here that I did on CML, please forgive me for copying and pasting!

As an assistant, you never really get to see or understand lab procedures in depth. It's a bit of black magic in terms of the specifics of labs. The reason I asked is I recently acquired some shortends of what I thought was '19 off of eBay, and I had them clip tested. It turns out they were actually '29- revealed after the test. Reading that quote about different threading paths for different stocks concerned me that 19 would be developed differently than 29. Am I correct in reading your responses that all ECN2 stocks are processed for the same amount of time in the same loop in the same bath? It seems one could write on the cans, reports, and PO any arbitrary stock number as long as they exposed correctly up front; ie sending in a roll of 5205

exposed properly at 250asa, but in paperwork calling it 5201, and still getting the exact same neg as if you had identified it correctly as 05. Am I correct in thinking this? Does the same apply in b&w or does target gamma throw that processing uniformity out the window?

Thanks!

Dominic Case · September 6, 2009

All ECN2 negative stocks have exactly the same processing specifications. There is no need to change the dev time for any of them.

Kodak tends to offer precise but not entirely practical advice in its processing manuals. You will never ever go wrong if you follow their procedures - but you might neve actually get the film processed in reasonable time either.

While it's true that bleach, fix etc can all accomodate reasonable changes in machine running speed, the drying cabinet can sometimes be a problem. Some film emulsions carry more water than others, and so take longer to dry. This is usually OK for most stocks and for normal processing but can become a problem with faster-running pull-processing. It's easy to turn the temperature up, but this merely bakes the emulsion. It comes out dry on the surface but takes longer to "cure". More airflow is also needed and this isn't always so easy to provide. This is one reason why Kodak is cautious about recommending running speed changes.

However this is also a good reason NOT to mislabel your stock, as labs may sometimes need to make fine adjustments to drying temperature or airflow, air-knife or squeegee settings for different emulsions.

Black and white neg is a different kettle of fish. Every emulsion type requires a different dev time to achieve the required gamma. There are also more developer formulas in use, with different times and temperatures for each one.

Mike Panczenko · September 6, 2009

Would the drying ever be a problem in normal processing or is it only in special processing where the time is shortened? Would you trust the results of my clip test considering it was misidentifed and only discovered to be 29 after processing?

Edited September 7, 2009 by Mike Panczenko

Charles MacDonald · September 7, 2009

Would the drying ever be a problem in normal processing or is it only in special processing where the time is shortened? Would you trust the results of my clip test considering it was misidentifed and only discovered to be 29 after processing?

the clip test is normal processing, even if they lab might have changed their drying settings for the given stock - once it is dry it is dry. on a clip test they are just looking at the d-min to ensure the stock has not picked up too much age fog (or X_ray fog ) so the clip test should be vailid.

Now that you know what stock you have you should of course list that on your order when you have the REAL work done.

Mike Panczenko · September 7, 2009

the clip test is normal processing, even if they lab might have changed their drying settings for the given stock - once it is dry it is dry. on a clip test they are just looking at the d-min to ensure the stock has not picked up too much age fog (or X_ray fog ) so the clip test should be vailid.

Now that you know what stock you have you should of course list that on your order when you have the REAL work done.

Now as far as drying goes, if a stock is not dry when it should be, due to whatever factor- liquid retention, structural damage, etc, is the lab aware and can they continue to dry it until it is fully dry, or will they take the neg out of the drying racks, and end up with a soaking wet neg that is subject to warping and distortion? Basically, would they be aware it is still wet and be able to give it extra time and TLC to remedy that, or will it be screwed once it's out of the drying racks?

I really appreciate all the insight into lab procedures. I've been an assistant for 6 years, and when it comes down to it, there is almost nothing I know about true lab procedures. Of course we all know the basics and the theory, but just as a lab tech wouldn't necessarily know how to lace up a Panaflex, what happens once the film actually goes into the bath is such a mystery! I am loving learning about this. Also, can anyone recommend any good books on lab procedural techniques that would cover other similar areas in depth?

Mike Panczenko · September 7, 2009

Also, would the drying cabinet settings ever need to be varied for normal processing, even slightly, for whatever reason (including different stocks), or is that only when you are pushing or pulling? Will all stocks be dry before exiting the cabinet in normal processing, or do you need to finesse the settings even in normal processing?

I think a tour of my local lab is in order. Thank you all for shedding light on this shadowy area for me!

Charles MacDonald · September 7, 2009

Now as far as drying goes, if a stock is not dry when it should be, due to whatever factor- liquid retention, structural damage, etc, is the lab aware and can they continue to dry it until it is fully dry

the film is wound on a take up once it gets out of the drying section. the lab techs will no doubt be watching it at that point to ensure the whole process is behaving.

if the film is not 100% dry they have some problem with the equipment or settings.. The film is actually supposed to be not only dry but also in equilibrium with a specified relative humidity. Also don't be surprised at the camera loading abilites of Lab workers. Many are also filmakers. They actually have to know the insides of a lot of cameras so they can analyse any defects to see if they are camera faults.

Robert Houllahan · September 7, 2009

the film is wound on a take up once it gets out of the drying section. the lab techs will no doubt be watching it at that point to ensure the whole process is behaving.

if the film is not 100% dry they have some problem with the equipment or settings...

99.9999% of the time the film is dry (to the touch) 1/3 of the way through the dry-box of the processor. Serious problems have to have happened for this not to be the case. See the attached photo of the drybox on our Treise Ecn machine to get an idea of the machine.

Dominic Case · September 7, 2009

Also, can anyone recommend any good books on lab procedural techniques that would cover other similar areas in depth?

Oh all right, I'll go ahead and take this one ;)

Film Technology in Post Production, 2nd edition - Dominic Case, Focal Press. Has quite a lot about lab processing and all the rest.

My earlier book, Motion Picture Film Processing - Dominic Case, also Focal Press, has been out of print since the other book was published, but there are occasional 2nd hand copies on Amazon. It has even more detail on the intricacies of film developing and printing. It's over 20 years old, but really, not much has changed with film processing except the numbers of the stocks.