Do rotary processors affect how the film looks in the end? (tonality, film speed / shadow detail, etc.)

dcy · 2025-09-08T15:56:19-0400

To be clear, I am *not* in the market for a rotary processor. The reason I am posting is that I just randomly saw this comment on Reddit saying that, with many films, rotary processors lead to increased contrast and less shadow detail (i.e. loss of speed), and just worse tonality.

From my naive point of view, it sounds odd that an expensive devise that is primarily purchased by the people most dedicated to the craft would consistently make the final negatives come out worse. People who spend $500 on a Jobo rotary processor are not people who look at worse tonality and loss of shadow detail and say "meh, good enough".

If you've used a rotary processor, or know something about them, perhaps you can clear this up for me?

koraks · 2025-09-08T16:25:19-0400

dcy said:
saying that, with many films, rotary processors lead to increased contrast and less shadow detail (i.e. loss of speed), and just worse tonality.

If you develop the same film to the same gamma in rotary vs. manual inversion, the images will come out exactly the same. Since agitation is constant in a rotary processing setup, you'll get the same gamma at a slightly shorter development time than when doing manual, intermittent inversions. This accounts for some of the difference; if you develop two rolls for the same time and one is done in rotary/constant agitation and the other with manual/intermittent inversions, the former will come out with a higher gamma. Grain may be ever so slightly more pronounced, but you'd be hard pressed to be able to really spot that difference. The rest, i.e. 'worse tonality' is just bollocks really.

Agitation can of course affect the evenness of development. Inadvertent agitation patterns can cause unevenness. This can either occur with rotary or manual inversions, but IME it's generally a little easier to avoid unevenness when doing manual agitations, since you have full control over what happens.

xkaes · 2025-09-08T16:25:28-0400

Every processing method -- whether for film or paper -- will produced different results. And every processing method has to be used AND adjusted to produce the results that satisfy YOU. You should always run tests (whether simple or complex) to achieve your goals. If your first tests show too much contrast or too little, there are ways to adjust it. If your first tests show too much speed or too little, there are ways to adjust it.

Anyone who tries a new approach can get "unsatisfactory" results -- and trash it on-line -- but that does not mean that the approach won't work wonders for someone else. That's one of the reasons why no two photographers do everything the same way in the darkroom -- even if they use the same gear!

MattKing · 2025-09-08T16:41:36-0400

Continuous agitation is different than intermittent agitation. So there are differences between what roller transport processing/rotary processing does and intermittent inversion agitation does.
Some film and developer combinations respond significantly differently. A large number of such combinations will respond essentially the same if you adjust the development time or temperature in order to match contrast levels. A few such combinations will respond the same without changing the time or temperature.
Most long standing film and developer combinations were designed for continuous agitation (roller transport) or nitrogen burst agitation (dip and dunk transport) in a commercial setting.
Intermittent inversion agitation was intended as a workable compromise that the small volume user could use.
I use a combination: 30 seconds continuous rotary agitation plus the balance of time inversion agitation for 5 seconds every 30 seconds (in the developer), followed by continuous rotary agitation for all the steps thereafter.
I have used continuous rotary agitation in the past for the developer as well (either HC-110 or XTOL, mostly replenished) with excellent results. It just doesn't play well with my preference for putting two 120 rolls at the same time on a Paterson type reel - the two films wander too much in the reel during the development stage.
The Reddit thread you linked to is like a bunch of Reddit stuff - full of confirmation bias and/or people who are using non-standard approaches or under-exposing their film.

DREW WILEY · 2025-09-08T17:17:11-0400

There are several potential problems when rotary processing. They can oxidize the developer more. Most of them, like the Jobo, run at too high an RPM to be ideal for certain processes. And then, you've got the issue of relatively slow fill and drain times with certain drum designs. Some b&w developers do better than others in rotary processing.

Loss of shadow detail is due to underexposure of the negative, plain and simple. But overdevelopment will lead to overall excessive contrast and density. And sometimes there can be streaking issues too. The whole point is to understand what your equipment can do best, and what it can't.

I'm not bashing rotary processing. I have some very nice customized rotary machines with superior gear-motor controls and 3-way rocking agitation. And I can do up to 30X40 inch prints with them. And of course, I once used them for black and white film processing, although I now prefer either simple hand inversion drums for roll film, or tray development for sheet film.

Lachlan Young · 2025-09-08T17:33:21-0400

dcy said:
on Reddit saying that, with many films, rotary processors lead to increased contrast and less shadow detail (i.e. loss of speed), and just worse tonality.

It's not a new claim and it's just as nonsensical now as it was decades ago.

The major research labs did a lot of rheology research, including very detailed and extensive work on agitation. The outcome was (and this was also where Richard Henry (one of the very few independent researchers able and willing to work to levels that were baselines in the big research labs) ended up at as well) that if agitation was sufficient to deliver truly even processing across the film area, the differences between good quality intermittent and continuous agitation (when developed to the same aim contrast and all relevant aspects controlled for) are nil. Semi-stand and various other less-than-well-thought-through-but-very-forcefully-shoved-on-the-unwitting procedures generally don't meet the baseline for even processing. A great deal of effort has been expended in manufacturing research in making emulsions that deliver the same sharpness as absolute standstill developing conditions (which is sharper, but hideously uneven) when given enough agitation for even density across the film area.

thinkbrown · 2025-09-08T17:56:30-0400

Man, I don't think I've ever seen a thread with this much consensus on photrio before

pentaxuser · 2025-09-08T18:24:21-0400

dcy said:
From my naive point of view, it sounds odd that an expensive devise that is primarily purchased by the people most dedicated to the craft would consistently make the final negatives come out worse. People who spend $500 on a Jobo rotary processor are not people who look at worse tonality and loss of shadow detail and say "meh, good enough".

If you've used a rotary processor, or know something about them, perhaps you can clear this up for me?

Haven't you cleared this up for yourself with your above argument?

pentaxuser

Vaughn · 2025-09-08T18:34:10-0400

From the link: "One gentle flip per minute is optimal for B&W." I wonder what the author's stand is with stand development. Sounds like someone found the best way for themself and believes in it.

I tray-developed for a couple decades, and still do for 11x14. For the last couple of decades or so, everything smaller than 11x14 goes into Jobo Expert Drums and rotated at 15 rpm...that's how fast my Unicolor motor base can go. I contact print in alt processes with no burning/dodging...so any uneveness in processing would be undesirable. So far so good. But I am always expanding the DR of the film, which probably uses the advantages of the continous agitation (instead of continous agitation fighting attempts to contract the DR).

Palms, Spring, Death Valley, 8x10 pt/pd print.

GregY · 2025-09-08T19:04:55-0400

dcy said:
To be clear, I am *not* in the market for a rotary processor. The reason I am posting is that I just randomly saw this comment on Reddit saying that, with many films, rotary processors lead to increased contrast and less shadow detail (i.e. loss of speed), and just worse tonality.

From my naive point of view, it sounds odd that an expensive devise that is primarily purchased by the people most dedicated to the craft would consistently make the final negatives come out worse. People who spend $500 on a Jobo rotary processor are not people who look at worse tonality and loss of shadow detail and say "meh, good enough".

If you've used a rotary processor, or know something about them, perhaps you can clear this up for me?

D, if you're using a motor driven device, or if you're continually rolling a tank in your sink by hand....your processing times will be different than normal processing with 5-10 sec inversions /min. You can adjust either method to deliver the negative you want.

dcy · 2025-09-08T19:07:13-0400

DREW WILEY said:
Loss of shadow detail is due to underexposure of the negative, plain and simple.

Yeah. That part really confused me. But then again, there are "speed reducing" and "speed enhancing" developers, so...

Before today, I was under the impression that rotary processors just develop faster because it replenishes the developer, so you have to shorten the development time. The idea that they'd do anything other than shorten development + add consistency was a surprise for me.

DREW WILEY · 2025-09-08T19:40:55-0400

Sure, Greg, one could hypothetically roll a drum back and forth in a sink, or even on a sidewalk. But automating it provides a little more consistency, especially if you have 3-way agitation like I do. But as I already indicated, I prefer to use hand inversion drums for roll film, and tray development for sheet film.

Drum development doesn't favor just any developer. It depends. With some, you need to replace the air in the drum with an inert gas like argon, or else use so much solution that it effectively does the same thing.
Over time, Jobo improved their motor somewhat; but I still think they're undersized and run at too high an RPM at even the lowest setting. I do use Jobo hand inversion tanks, but not their rotary system.

Melvin J Bramley · 2025-09-08T20:19:51-0400

I spared no expense on my film roller.
As I often use dilute developer , this is most convenient.

mshchem · 2025-09-08T21:48:30-0400

Melvin J Bramley said:
I spared no expense on my film roller.
As I often use dilute developer , this is most convenient.

Not questioning your setup, looks nice.

Jobo tanks hold the Jobo plastic reels locked in place to insure the reels rotate along with the Tank. No variation .

You definitely want to have a device that reverses tank rotation as well. Like the Unicolor to name one.

I only use the published times and developer dilution(s) . One reason I use XTOL undiluted as many Jobo tanks when used fully loaded don't have enough volume for diluted developer.

RalphLambrecht · 2025-09-08T22:50:41-0400

dcy said:
To be clear, I am *not* in the market for a rotary processor. The reason I am posting is that I just randomly saw this comment on Reddit saying that, with many films, rotary processors lead to increased contrast and less shadow detail (i.e. loss of speed), and just worse tonality.

From my naive point of view, it sounds odd that an expensive devise that is primarily purchased by the people most dedicated to the craft would consistently make the final negatives come out worse. People who spend $500 on a Jobo rotary processor are not people who look at worse tonality and loss of shadow detail and say "meh, good enough".

If you've used a rotary processor, or know something about them, perhaps you can clear this up for me?

in general NO. what they do however give you is a uniformly developed negative and well worth it over manual development.

dcy · 2025-09-09T00:02:45-0400

mshchem said:
You definitely want to have a device that reverses tank rotation as well. Like the Unicolor to name one.

What happens if it doesn't reverse direction?

MattKing · 2025-09-09T00:07:04-0400

dcy said:
What happens if it doesn't reverse direction?

There is a real risk of the agitation being insufficiently random, resulting in uneven development.

mshchem · 2025-09-09T01:05:59-0400

dcy said:
What happens if it doesn't reverse direction?

It's especially noticeable when trying to develop something like sheet film in a tube, you can get streaks referred to as "bromide drag" . But the main point is certain tanks are designed to not allow the reels to spin inside, like Jobo. Others like Paterson spin freely with the little twirling stick provided.

Like a turbohydromatic transmission, fluid drive etc To get a vehicle rocking when stuck in some godawful Vancouver snow bank, you slowly go back and forth between forward and reverse.

If the reel is not locked to the tank, theoretically the tank can rotate and the reel will stand still.

I'm not suggesting that this happens in real life! Still it's a variable that the German (presumably) engineers at Jobo couldn't tolerate, a good reason why the Jobo system is essentially the same 40+ years on.

Some drum bases have eccentrics that not only spin the drum but rock it back and forth as well. I think Simmon Omega produced this style.

I remember the first time I saw a Jobo CPP2 in person, used, sometime in the late 80's. I damn near burst out laughing. I couldn't imagine spending my hard earned money on such a contraption.

All anyone needs to process any roll film is a ordinary Paterson tank, a water bath, a thermometer and a timekeeping device, and of course access to hot and cold water. Nothing else is required if you can follow the instructions from the manufacturer.. I developed film this way for 30 years color and black and white.

Now I'm using Jobo machines, fun, especially if you have time to kill setting it up and taking it down.

MattKing · 2025-09-09T01:52:55-0400

You can even do rotary processing with steel reel tanks - but if the tank is steel as well, you may be bothered by the infernal racket!

Vaughn · 2025-09-09T02:20:51-0400

dcy said:
What happens if it doesn't reverse direction?

I use a Unicolor motor base with the auto-reverse disabled. I use the larger 3005 and 3006 Expert drums. Their larger diameter only allows for about a full rotation before it auto-reverses.

Instead, every minute or so (about 10 to 15 rotations) I lift and turn the drum 180 degrees and set it back onto the rollers...reversing the rotation. I do it less for fix and washes.

Vetus · 2025-09-09T03:38:39-0400

DREW WILEY said:
Sure, Greg, one could hypothetically roll a drum back and forth in a sink, or even on a sidewalk. But automating it provides a little more consistency, especially if you have 3-way agitation like I do. But as I already indicated, I prefer to use hand inversion drums for roll film, and tray development for sheet film.

Drum development doesn't favor just any developer. It depends. With some, you need to replace the air in the drum with an inert gas like argon, or else use so much solution that it effectively does the same thing.
Over time, Jobo improved their motor somewhat; but I still think they're undersized and run at too high an RPM at even the lowest setting. I do use Jobo hand inversion tanks, but not their rotary system.

Hello Drew, what developers are ideal for rotary, are there any particular developers that are unsuitable? If oxidation is a problem can those developers be used but with less dilution?

mshchem · 2025-09-09T04:00:52-0400

Vaughn said:
I use a Unicolor motor base with the auto-reverse disabled. I use the larger 3005 and 3006 Expert drums. Their larger diameter only allows for about a full rotation before it auto-reverses.

Instead, every minute or so (about 10 to 15 rotations) I lift and turn the drum 180 degrees and set it back onto the rollers...reversing the rotation. I do it less for fix and washes.

Expert drums have a lot going for them, even rolling in a single direction with the chambered 3005 and 3006, probably be just fine, nice to do an occasional rotate the drum routine

pentaxuser · 2025-09-09T09:44:36-0400

dcy said:
What happens if it doesn't reverse direction?

It keeps on travelling in the same direction and I guarantee that is the unequivocal answer which I defy anyone to challenge.

Slightly more seriously, can I ask of the others: What is the actual evidence of uneven development and aren't there non-Jobo versions of mechanical rotation devices that have rollers that only spin in one direction?

pentaxuser

loccdor · 2025-09-09T10:02:15-0400

Out of all the photo communities on the internet, Reddit's AnalogCommunity has some of the highest percentage of false information. They have a sub dedicated to making fun of them, AnalogCircleJerk, which I find entertaining.

Alan9940 · 2025-09-09T10:09:50-0400

RalphLambrecht said:
in general NO. what they do however give you is a uniformly developed negative and well worth it over manual development.

+1

After many years of developing 4x5 and 8x10 film in trays, I invested in a Jobo CPP-2 and Expert Drums in the mid-90's. My stress testing of this outfit proved to me that I really didn't know what evenly developed sheet film looked like. Been happily using this setup for 30 years now without a single equipment failure.

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