Flexicolor Reference: b-2020-c41.pdf

[Bormental]

@Mr Bill no responses here, but I thought your comment was fantastic, thank you.

 

[Mr Bill]

Thanks, it's always nice to know if anyone is reading one's comments.

As a note, something interesting just came up on another thread. Another member, mtjade2007, seems to have already done something similar to what I suggested, testing in both the Jobo standard way, plus with a surplus amount of developer. I don't know anything further than what is stated in the link, but it seems to support my comments on something that might happen using sparse amounts of developer.

https://www.photrio.com/forum/threa...f-kodak-flexicolor.175962/page-2#post-2319869

 

[Mick Fagan]

Mr Bill, I too thank you for your input in this thread and any other thread you contribute too as well. Very much appreciated.

Mick.

 

[Mr Bill]

Thanks Mick, to a guy whom I appreciate also goes way back with color processing experience.

 

[Adrian Bacon]

The numbers are official Kodak guidance taken from Z-131. Yes, that's assuming no replenishment. @Mick Fagan there are substantial differences between Kodak's official recommendations, that tend to be conservative, and community wisdom. I have assembled only the manufacturer's data there. One area where I made an exception was "Chemical Storage Life" table.

I don't replenish the developer, and use a JOBO. For every 570ml, I process up to 4 rolls of 135 and 1 control strip in the 5 slot. My last run was less than 0.01 deviation (HD-LD) from the reference strip for the red and blue channels, and 0.04 in the green channel.

 

[Bormental]

I don't replenish the developer, and use a JOBO. For every 570ml, I process up to 4 rolls of 135 and 1 control strip in the 5 slot. My last run was less than 0.01 deviation (HD-LD) from the reference strip for the red and blue channels, and 0.04 in the green channel.

Thank you. Funny, but right now I am reading JOBO manuals and I have a question for JOBO users specifically regarding C41:

- Does it really keep the developer at 100F?

I looked at how it's constructed and I find it hard to believe that the developer doesn't lose some temperature as you pour it into the tank through the lift. Is the lift tunnel heated? I lose about 1-2F when I pour 100F developer from one pre-heated bottle to another, yet the JOBO instructions for C-41 advocate for keeping the water bath at 100F, as if nothing gets lost during pouring. True/false?

 

[Adrian Bacon]

Thank you. Funny, but right now I am reading JOBO manuals and I have a question for JOBO users specifically regarding C41:

- Does it really keep the developer at 100F?

I looked at how it's constructed and I find it hard to believe that the developer doesn't lose some temperature as you pour it into the tank through the lift. Is the lift tunnel heated? I lose about 1-2F when I pour 100F developer from one pre-heated bottle to another, yet the JOBO instructions for C-41 advocate for keeping the water bath at 100F, as if nothing gets lost during pouring. True/false?

that’s not true. You still have to account for heat loss. I pre-heat my tank for 3:15, and temper my developer at 39-40.5C depending on how many rolls and ambient room temperature. I’ve built up a little table of best temperatures based on how many rolls and temperature in my lab. I temper my bottles in a separate tempering bath from the jobo water tank. That is set to 100F.

if you get a jobo, you’ll want to work out the temperature loss for you specific setup. If I remember correctly, Kodak’s z131 has the procedure for getting and compensating for temperature loss.

 

[Bormental]

Good to know, thanks.

 

[Mr Bill]

I don't replenish the developer, and use a JOBO. For every 570ml, I process up to 4 rolls of 135 and 1 control strip in the 5 slot. My last run was less than 0.01 deviation (HD-LD) from the reference strip for the red and blue channels, and 0.04 in the green channel.

Adrian, I think this is a bit misleading. When I first read it, I'm thinking to myself, "how could this be?" Then I'm thinking, well, if the film is only lightly exposed. Then I get to thinking, I wonder how he's reading these, it it actually a Status M densitometer or is he deriving the numbers from something else? And then, I think, why does he give only the "contrast" (HD-LD in control strip nomenclature, meaning a high-density patch minus a low density patch), but not the LD value? So I'm real distrustful of the values, yet it IS what you're getting, so who can argue with that? Still, it goes counter to what I've spent a large part of my adult work life dealing with. But your next post largely answers this:

I pre-heat my tank for 3:15, and temper my developer at 39-40.5C depending on how many rolls and ambient room temperature.

Since the process is actually spec'd at 37.8 C (100 F), this means that you're actually starting out your developer above this aim by 1.2 to 2.7 C (rough 2 to 5 F), which is really quite a lot. So the fact that you are raising temperature to more or less compensate for extra rolls helps explain why the "development," more specifically the contrast values, didn't fall off.

I think this needs to be pointed out because people who are not familiar with the temperature numbers may not catch this, and rather conclude that extended use of the developer has little effect.

But... it seems odd to me that Kodak would be so free about boosting the temperature this far. Since you referred to your source, the Z-131 manual, I took a quick look. I interpret this differently than you do.

On page 3-2 (this is section 3 of the Z manual) they have a "Developer Starting Temperature..." section. (This section is actually using a so-called "sink line" rather than a rotary processor.) What Kodak seems to be saying is to actually develop at the spec temp (37.8 C, 100.0 F), but... start out with a higher developer temperature to compensate for the cooling effect of lowering a rack of film into the developer.

The rotary processor section starts on page 3-6 where they have some comments about prewarming the tube (see footnotes for table 3-5).

On page 3-7, there is a brief discussion, see "Developer Temperature and Time..." From that section, "The best way to compensate for loss of developer temperature is by increasing the developer time (from the standard time of 3:15)." As far as I see, Kodak is not specifically recommending to increase developer temperature. I can't really make a qualified opinion on this, as my experience is almost exclusively with systems that are always kept in spec (aside from periodic screwups).

I'm not trying to be nitpicky about this, and wouldn't have bothered posting had you been clear from the start that you had elevated the developer temperature. But without that you have put me in an awkward position. I had just explained how sparse use of a color developer is likely to cause problems, and then you step in to essentially say, "well, I use those quantities of developer in a Jobo and (certain parts of) my control plots are right on the money." So if I don't respond it might appear that I am conceding the argument (which I would not do). My apologies if it appears I'm overdoing it, and best wishes with your system.

 

[Bormental]

@Mr Bill I think Adrian starts with a higher temperature to compensate for the inevitable temperature drop which happens when you pour chemicals into a JOBO

 

[Adrian Bacon]

Adrian, I think this is a bit misleading. When I first read it, I'm thinking to myself, "how could this be?" Then I'm thinking, well, if the film is only lightly exposed. Then I get to thinking, I wonder how he's reading these, it it actually a Status M densitometer or is he deriving the numbers from something else? And then, I think, why does he give only the "contrast" (HD-LD in control strip nomenclature, meaning a high-density patch minus a low density patch), but not the LD value? So I'm real distrustful of the values, yet it IS what you're getting, so who can argue with that? Still, it goes counter to what I've spent a large part of my adult work life dealing with. But your next post largely answers this:



Since the process is actually spec'd at 37.8 C (100 F), this means that you're actually starting out your developer above this aim by 1.2 to 2.7 C (rough 2 to 5 F), which is really quite a lot. So the fact that you are raising temperature to more or less compensate for extra rolls helps explain why the "development," more specifically the contrast values, didn't fall off.

I think this needs to be pointed out because people who are not familiar with the temperature numbers may not catch this, and rather conclude that extended use of the developer has little effect.

But... it seems odd to me that Kodak would be so free about boosting the temperature this far. Since you referred to your source, the Z-131 manual, I took a quick look. I interpret this differently than you do.

On page 3-2 (this is section 3 of the Z manual) they have a "Developer Starting Temperature..." section. (This section is actually using a so-called "sink line" rather than a rotary processor.) What Kodak seems to be saying is to actually develop at the spec temp (37.8 C, 100.0 F), but... start out with a higher developer temperature to compensate for the cooling effect of lowering a rack of film into the developer.

The rotary processor section starts on page 3-6 where they have some comments about prewarming the tube (see footnotes for table 3-5).

On page 3-7, there is a brief discussion, see "Developer Temperature and Time..." From that section, "The best way to compensate for loss of developer temperature is by increasing the developer time (from the standard time of 3:15)." As far as I see, Kodak is not specifically recommending to increase developer temperature. I can't really make a qualified opinion on this, as my experience is almost exclusively with systems that are always kept in spec (aside from periodic screwups).

I'm not trying to be nitpicky about this, and wouldn't have bothered posting had you been clear from the start that you had elevated the developer temperature. But without that you have put me in an awkward position. I had just explained how sparse use of a color developer is likely to cause problems, and then you step in to essentially say, "well, I use those quantities of developer in a Jobo and (certain parts of) my control plots are right on the money." So if I don't respond it might appear that I am conceding the argument (which I would not do). My apologies if it appears I'm overdoing it, and best wishes with your system.

no worries. In a jobo, no matter how much you pre-warm the tank in the tempering bath, the film and reels inside the tank change temperature very little unless you also pre-wet with at temperature water. I don’t do that... so, if I just pour 100f developer in the tank and check the temperature inside the tank after 1 minute of it running on the jobo, it’s way below 100f. So, following Kodak’s procedure, I then boost the temperature of the developer before it enters the tanks so that at the 1 minute mark after the developer enters, the temperature is 100f. From there, it remains a stable 100f for the rest of the development time because the water jacket is at temperature.

where the bugaboo exists is when the number of reels and/or film surface area changes, as then the thermal mass needed to to get to 100f at the 1 minute mark changes. I’ve simplified this down to always developing with the same 5 reel tank size, and always using the same amount of developer to eliminate those two variables, then simply through testing, worked out the best starting temperature for each number of reels in the tank for a given range of ambient temperatures in my lab. In the interest in keeping my total process time down to less than 30 minutes per tank, I’ve also just standardized on 3:15 pre-heat of the tank running in the 100f water jacket, as after that, the temperature of the tank itself doesn’t change much as I just makes it easier to have a 3:15 pre-heat, then dump the developer in and hit it for 3:15 again.

in terms of results, the last few images I’ve uploaded to my gallery are Kodak color plus 200 processed with this system

 

[Adrian Bacon]

Adrian, I think this is a bit misleading. When I first read it, I'm thinking to myself, "how could this be?" Then I'm thinking, well, if the film is only lightly exposed. Then I get to thinking, I wonder how he's reading these, it it actually a Status M densitometer or is he deriving the numbers from something else? And then, I think, why does he give only the "contrast" (HD-LD in control strip nomenclature, meaning a high-density patch minus a low density patch), but not the LD value? So I'm real distrustful of the values, yet it IS what you're getting, so who can argue with that?

Here's the full reading from the last run of today:

This was with 4 rolls of 36 exposure and 1 control strip and 600ml of developer entering the tank at 39.5C. I suspect that I accidentally got an extra mL or two of part A in this particular 600mL batch, as my DMIN is right at control limits and my LD is skirting action limits. I could probably also bump an extra mL of starter in to pull the HD-LD red and blue down a smidge.

The only downside to doing things in smaller batches is you have to be a lot more precise with measuring out the parts.

 

[Mr Bill]

Here's the full reading from the last run of today:

Thanks for the full set of example data.

Adrian, when you first posted the HD-LD it didn't look right to me, knowing that that was processed with a limited amount of developer. So from my point of view, having just estimated the Br (restrainer) levels for an "average" roll, I would not expect the plot to be so close to aim. (At 0, 4, 0, they're closer than most well-controlled processes.) With the bromide levels running 15-20% high (at the tail end of processing) the control strip plots ought to be appreciably lower. But this is possibly explained by having the elevated starting temperature; even though it falls back into spec after a minute there could still be a considerable effect.

But now, seeing all the numbers, it's pretty clear that they're not Status M. (I presume you're trying to derive them from scanner data, which cannot legitimately be done, at least not without prior knowledge about the spectral characteristics of everything.)

The things that immediately stick out are the very high numbers for Dmin (clear film). A typical Kodak pro color neg film would have densities of roughly: Red = 0.20, Green = 0.65, and Blue = 0.85. Whereas yours are all substantially higher, above 1.00. Now, it's certainly possible to have something go wrong with the process, producing a high base stain level. But getting those same numbers (above 1.00) on a Kodak reference strip, the one actual processed by Kodak, is near-certain evidence of incorrect readings.

Of course you can still use the data for "process control," seeing it as a statistical process, etc. But I wouldn't be so sure that it's giving you a clear picture of Kodak spec limits; I suspect that the differences are being minimized.

 

[Tom Kershaw]

Of course you can still use the data for "process control," seeing it as a statistical process, etc. But I wouldn't be so sure that it's giving you a clear picture of Kodak spec limits; I suspect that the differences are being minimized.

In a way I find it reassuring my own experiments with Flexicolor developer in a Jobo processor match (within reason) the advice given by Kodak. I intend to stick to 4 rolls per litre of working solution.

 

[Adrian Bacon]

Thanks for the full set of example data.

Adrian, when you first posted the HD-LD it didn't look right to me, knowing that that was processed with a limited amount of developer. So from my point of view, having just estimated the Br (restrainer) levels for an "average" roll, I would not expect the plot to be so close to aim. (At 0, 4, 0, they're closer than most well-controlled processes.) With the bromide levels running 15-20% high (at the tail end of processing) the control strip plots ought to be appreciably lower. But this is possibly explained by having the elevated starting temperature; even though it falls back into spec after a minute there could still be a considerable effect.

But now, seeing all the numbers, it's pretty clear that they're not Status M. (I presume you're trying to derive them from scanner data, which cannot legitimately be done, at least not without prior knowledge about the spectral characteristics of everything.)

The things that immediately stick out are the very high numbers for Dmin (clear film). A typical Kodak pro color neg film would have densities of roughly: Red = 0.20, Green = 0.65, and Blue = 0.85. Whereas yours are all substantially higher, above 1.00. Now, it's certainly possible to have something go wrong with the process, producing a high base stain level. But getting those same numbers (above 1.00) on a Kodak reference strip, the one actual processed by Kodak, is near-certain evidence of incorrect readings.

Of course you can still use the data for "process control," seeing it as a statistical process, etc. But I wouldn't be so sure that it's giving you a clear picture of Kodak spec limits; I suspect that the differences are being minimized.

the readings are not nulled out, so the base fog is relative. That should be obvious given that the reference control strip readings (DMIN AIM) are also high. The readings that say AIM are readings from the supplied reference strip plus the correction factors supplied with that batch of control strips. Is it status M? No, it’s not. I’m working with what I’ve got. I’ve been on the hunt for a good color density meter for a while. All I can say is that the state of the film processing industry is in shambles and quality equipment is either not that abundant, or prohibitively expensive. So... I make do and work with what I’ve got. I can tell you that in an effort to validate my own process, I’ve sent very carefully constructed test rolls to a fair number of labs here in the US and can say with a pretty high level of certainty that a significant number of labs running today most certainly are not doing any monitoring of any kind as the results I got back varied wildly. I’m not going to name names as that was a snapshot in time and my intent is not to name and shame, but to just simply point out that the state of the industry is not what it was at its height.

all that aside, let’s get to the heart of the matter... I’m processing 4 rolls of film with 600ml of 1 shot developer. That gives me 150mL of developer per roll. Given that the replenishment rate per roll in a replenished system is quite a bit lower than that, I’m not sure what the source of heartburn is. Please enlighten me.

 

[Lachlan Young]

the readings are not nulled out, so the base fog is relative. That should be obvious given that the reference control strip readings (DMIN AIM) are also high. The readings that say AIM are readings from the supplied reference strip plus the correction factors supplied with that batch of control strips. Is it status M? No, it’s not. I’m working with what I’ve got. I’ve been on the hunt for a good color density meter for a while. All I can say is that the state of the film processing industry is in shambles and quality equipment is either not that abundant, or prohibitively expensive. So... I make do and work with what I’ve got. I can tell you that in an effort to validate my own process, I’ve sent very carefully constructed test rolls to a fair number of labs here in the US and can say with a pretty high level of certainty that a significant number of labs running today most certainly are not doing any monitoring of any kind as the results I got back varied wildly. I’m not going to name names as that was a snapshot in time and my intent is not to name and shame, but to just simply point out that the state of the industry is not what it was at its height.

all that aside, let’s get to the heart of the matter... I’m processing 4 rolls of film with 600ml of 1 shot developer. That gives me 150mL of developer per roll. Given that the replenishment rate per roll in a replenished system is quite a bit lower than that, I’m not sure what the source of heartburn is. Please enlighten me.

Process control/ calibration certainly isn't being helped by X-rite having decided to stop selling the requisite transmissive calibration test step tablet. And I've found that running similar quantities of film (25xx drum, 650ml chemistry) definitely gets Portra 800 more in line with where it should be than some labs (running dip/ dunk machines) that clearly aren't replenishing correctly for faster films.

I also suspect that Kodak may have built in a 100% margin of safety in their single-shot capacity recommendations - as it was probable that a great many owners/ users of rotary developing systems weren't going to be buying colour densitometers to run a process that Kodak wanted to keep relatively straightforward to do. Be careful with extrapolating minimum solution volume from replenishment rates - for example compare Xtol's replenishment rate: minimum solution per 80 sq in of film to D-76's replenishment rate: minimum solution per 80 sq in of film (note that T-Max demands a higher replenishment rate in D-76) & it rapidly becomes apparent how complex the whole replenishment thing is.

 

[Adrian Bacon]

Be careful with extrapolating minimum solution volume from replenishment rates

no argument from me there, I totally get that. I also get the minimum required chemistry needed per roll, though 1 roll per 250 mL seems very conservative. I’ve not seen a large difference between 150mL per and 200mL per roll, and even 300mL per roll, though I have in the past ran 5 whole rolls in 600mL (And 6 rolls of 120) and when the developer comes out, it looks and smells pretty used. Backing off to 4 rolls per 600mL and that doesn’t really happen. I’d be OK with 3 rolls per 600mL, but much less than that and I might as well close up shop as my throughput wouldn’t be profitable.

it’s easy enough to find an xrite 810 on eBay, though few if any come with the Calibration stuff which makes them not much better than what I’m already doing, and as you said, I can’t buy a new one any more.

 

[Mr Bill]

all that aside, let’s get to the heart of the matter... I’m processing 4 rolls of film with 600ml of 1 shot developer. That gives me 150mL of developer per roll. Given that the replenishment rate per roll in a replenished system is quite a bit lower than that, I’m not sure what the source of heartburn is. Please enlighten me.

It's mainly just an interesting puzzle to me, how your system is working. But like I said earlier you put me in an awkward position; since your earlier post seems contrary to what I had just said (~150 ml/"roll" should have a measurable reduction in developer activity), if I don't respond I may be seen as conceding the point. Now, since I have personal knowledge that C-41 developer is pretty sensitive to development byproducts I'm pretty confident in what I had posited, although it was sort of a "back of the envelope" sort of thing, and it's possible that I could have been completely off on my estimate.

Plus I was curious as to how you could possibly have control strips plotting so well, essentially right on the money. Anyway, I think that the elevated starting temperature explains a lot of this.

 

[Mr Bill]

it’s easy enough to find an xrite 810 on eBay, though few if any come with the Calibration stuff which makes them not much better than what I’m already doing...,

Well, the thing is, if you're already matching the reference control strip, not much need for this. I just suspect that the narrow spectral zone seen by the Status M response will exaggerate density variations a little more than a broader spectral zone. So you might get a little more jitter on the plots. But it's possible that your current reading system might not be hitting the right spectral areas.

Regarding calibration, there's a handful of workarounds. For film, for example, you "zero" the instrument with nothing in the gate, reading "air" as it's sometimes called. So you only need a higher density patch to set the "slope." The original check plaques look like like black & white film, so you could probably use that IF you knew the density values. You wouldn't be too far off using a step tablet from Stouffer (or however it's spelled). You could just presume that all colors get the same value; this'll to plenty close enough for most practical purposes.

 

[Adrian Bacon]

It's mainly just an interesting puzzle to me, how your system is working. But like I said earlier you put me in an awkward position; since your earlier post seems contrary to what I had just said (~150 ml/"roll" should have a measurable reduction in developer activity), if I don't respond I may be seen as conceding the point. Now, since I have personal knowledge that C-41 developer is pretty sensitive to development byproducts I'm pretty confident in what I had posited, although it was sort of a "back of the envelope" sort of thing, and it's possible that I could have been completely off on my estimate.

Plus I was curious as to how you could possibly have control strips plotting so well, essentially right on the money. Anyway, I think that the elevated starting temperature explains a lot of this.

I wouldn’t be surprised if 150mL per roll is right on the ragged edge of minimum developer for most emulsions, and potentially not enough if I had 4 rolls of 400/800 speed, or 4 rolls of heavily exposed film. I say this because I have noticed a very marked difference in appearance and smell of the used developer at the end of the run on the times I’ve done 5/6 rolls per batch.

in terms of the starting temperature, you’d be amazed how much heat you lose in a jobo through the simple act of taking the tank off the machine so you can pour in the developer, then pouring in the developer and putting the tank back on the machine. It sounds really high at first blush, but a lot of that heat is totally sucked out just by doing that alone. It’s even worse if you have a jobo with a lift system as none of the channels that you pour the chemistry through are heated, so you lose a huge amount of heat just getting the chemistry through the channels in the lift before it’s even entered the tank. In terms of temperature management, using a jobo is nothing like processing with other systems. The number one problem is making sure you have enough heat going in as you lose a lot of it just getting the chemistry into the tank.

 

[Adrian Bacon]

Well, the thing is, if you're already matching the reference control strip, not much need for this. I just suspect that the narrow spectral zone seen by the Status M response will exaggerate density variations a little more than a broader spectral zone. So you might get a little more jitter on the plots. But it's possible that your current reading system might not be hitting the right spectral areas.

Regarding calibration, there's a handful of workarounds. For film, for example, you "zero" the instrument with nothing in the gate, reading "air" as it's sometimes called. So you only need a higher density patch to set the "slope." The original check plaques look like like black & white film, so you could probably use that IF you knew the density values. You wouldn't be too far off using a step tablet from Stouffer (or however it's spelled). You could just presume that all colors get the same value; this'll to plenty close enough for most practical purposes.

hmm... interesting... my current system uses a strobe for the light, so it’s about as wideband as it’s going to get, and is sensitive enough that I can see differences in the readings from run to run when I tweak the mix of chemistry at the mL level. All that said, I’d still prefer to use an actual densitometer, but have been very cautious about actually picking one up, as most of the time the seller doesn’t even know what they’re selling and respond to most questions with a generic “it turns on”. Not very confidence inspiring, given the point of having one.

 

[Mr Bill]

Just as a point of reference the attached image shows how Status M spectral sensitivity fits onto the spectral dye density of a given film.

The base image is taken from a Portra 160 data sheet. The only change I made was to add the three colored bars to indicate what a Status M response is "looking" at, spectrally. (The height of bars doesn't mean anything, only it's position on the "wavelength" axis.)

The base image shows, spectrally, what Portra film looks like for both the Dmin (clear base), and what a "neutral" exposure, for example, a photo of a gray card under daylight, would look like.

My added-on color bars are about 10 nm wide, more or less centered on the peak sensitivity range. If you were to extend by a bar's width on either side (like three such bars butted together) this would cover about 80% of the sensitivity range of Status M.

Now, this graph has no real practical value, but it can help one get a sense of how reading at different wavelengths can give different results.

Ps, if it's not clear to people how this is working, try this: looking at the lower plot, labeled "Minimum Density," try to estimate the density value (on the left-hand scale, the y-axis) at the point where my colored bars cross the line. These will be what a Status M densitometer measures. For example, the red bar crosses the line where its density is about 0.2, green at roughly 0.6 and blue at about 0.8. So these would be the Status M densities for Portra film's Dmin, the unexposed "clear" areas. If you now go to the Portra data sheet and find the graph called "characteristic curves" you should find that the lowest points on the curve have about these same values.

 

[Lachlan Young]

no argument from me there, I totally get that. I also get the minimum required chemistry needed per roll, though 1 roll per 250 mL seems very conservative. I’ve not seen a large difference between 150mL per and 200mL per roll, and even 300mL per roll, though I have in the past ran 5 whole rolls in 600mL (And 6 rolls of 120) and when the developer comes out, it looks and smells pretty used. Backing off to 4 rolls per 600mL and that doesn’t really happen. I’d be OK with 3 rolls per 600mL, but much less than that and I might as well close up shop as my throughput wouldn’t be profitable.

I wouldn’t be surprised if 150mL per roll is right on the ragged edge of minimum developer for most emulsions, and potentially not enough if I had 4 rolls of 400/800 speed, or 4 rolls of heavily exposed film. I say this because I have noticed a very marked difference in appearance and smell of the used developer at the end of the run on the times I’ve done 5/6 rolls per batch.

in terms of the starting temperature, you’d be amazed how much heat you lose in a jobo through the simple act of taking the tank off the machine so you can pour in the developer, then pouring in the developer and putting the tank back on the machine. It sounds really high at first blush, but a lot of that heat is totally sucked out just by doing that alone. It’s even worse if you have a jobo with a lift system as none of the channels that you pour the chemistry through are heated, so you lose a huge amount of heat just getting the chemistry through the channels in the lift before it’s even entered the tank. In terms of temperature management, using a jobo is nothing like processing with other systems. The number one problem is making sure you have enough heat going in as you lose a lot of it just getting the chemistry into the tank.

I suspect that the 250ml minimum/ roll (probably more likely 8fl oz) may well have been Kodak's aim point back in the 1970's when C-41 was being formulated as it would give comfortable unity with their recommendation for D-76. I've found that the 2553 tank is fine running 5 rolls of fast film in 650ml single shot - even for optical printing, though the developer effluent is very 'used' as you describe it. It certainly does a better job than a majority of labs seemingly do to Portra 800. I suspect there's probably some very complex nonlinearities going on from agitation etc - and that internal tank shape may even play a role. Not volunteering to do a massive Status M densitometry project to find out though - unless someone has a new/ guaranteed transmissive calibration strip to volunteer for this exercise...

The whole Jobo heating system is based on essentially a fly-through model, which should average out to deliver the correct temperature over the processing time. I recall reading somewhere about Kodak being pretty sceptical about rotary process machines initially (rotary processing machinery seems to have largely been a German innovation) - then launching two rotary paper processors fairly shortly thereafter.

 

[halfaman]

I have processed many times six 120 rolls in a CPE2 and a 1520+1530 tank with 650-700 ml of single shot C-41 chemistry. Results are good to my eyes and I can print and scan with no issues, even when I compare them with rolls processed in a profesional lab. Anyway, it is imposible to use much more chemistry in a Jobo CPE2 with the lift because it overflows through the outlet, I haven't try in my current CPP3 but I don't think I will.

 

[Bormental]

I am surprised we are not discussing 1L processing capacity of Flexicolor fixer and bleach, to be honest. The developer is less controversial, in my opinion. Having to replace fixer & bleach only after 6 rolls of 120 film is annoying. I am even considering replenishing those as well. Any thoughts here? BTW, apparently one cannot edit old posts, so I cannot upload the updated version of the PDF to the original post.