Midtone Machines Chromabox Automatic Processor

AndrewBurns · Jan 14, 2021

Hey all I've had a request elsewhere to post some information about the product I've been working on here, so if you haven't heard of it before this might be of interest to you.

My name is Andrew Burns, an engineer and photographer living in New Zealand (mostly shooting 4x5 these days). About 1.5 years ago I started a company called Midtone Machines developing a fully automatic film processing machine I call the 'Chromabox-4'.

My website is just a blog at this point but it contains a lot of detail about the process I've followed to get the machine to the point it's at today. http://midtonemachines.com

I've also written an article about the machine on the 35mmc website:
https://www.35mmc.com/25/11/2020/mi...-my-automatic-film-processor-by-andrew-burns/

And I recently participated in a webinar hosted by Silvergrain Classics magazine, the recording of which hasn't been uploaded yet.

The Chromabox-4 is a very similar design to the old Phototherm machines. I didn't start out intending that to be the case (and I've never personally used or pulled apart a Phototherm) but given the requirements I started with it was clear to me pretty quickly that the best design to do what I wanted was very similar to the Phototherm and there didn't seem to be a point in re-inventing the wheel for the sake of it.

The machine as it currently stands can:

Take up to 4 x 35mm, 2 x 120 (or 4 if you double-stack the reels), 6 x 4x5 or 4 x 5x7 rolls/sheets of film at a time
Has channels for up to 6 chemicals not including water
Is fully user-programmable so you can write and modify whatever 'recipe' you want in addition to the pre-loaded programs
Is capable of heating any chemical for any process step to whatever temperature you want between 20 and 45.5 degrees Celsius
Is able to return used chemicals either to the same bottle they came from, to the waste container or to a different bottle for replenishment
Uses standard Patterson-type film spools, so generally whatever fits into a Patterson tank will also fit into this machine

I'm currently in the testing phase of the prototype and have developed some B&W and C41 sheet film without issue. I'll be running a demo day at a local film lab next weekend where I'll be spending all day developing people's film for free to get more testing on the machine and I will also soon be building and sending out beta-test units.

I'm hoping that in the next few months I can start taking pre-orders via Kickstarter, the reason I plan to do this is to generate enough orders to take advantage of economies of scale with my suppliers. I'll be offering a significant discount on the retail price for pre-orders, but if you're not comfortable with that then I'll be selling them normally after the pre-orders are delivered. I'm currently looking at a retail price of ~$2500 USD but this will depend on demand (more demand means I can bring the price down of course).

If you have any questions or comments I'm more than happy to answer them either here or via email!

Lorenzot · Jan 14, 2021

NZ represent!

rick shaw · Jan 14, 2021

How is the programming / recipe creation done? Is that a touch panel, or is there USB upload?

Thanks. looks very good.

MattKing · Jan 14, 2021

I've noted your earlier posts, with interest. And I will continue following this.
By the way, it is Paterson, not Patterson.

mshchem · Jan 14, 2021

Makes great sense to use a core that will except the most abundant reel on the planet, Paterson, also includes the winged version made by AP, and even the Hewes version for Jobo/Paterson. I've been following this project over on the large format site. Amazing progress in a short period. For a fully automatic unit this shows great promise. I would encourage folks to visit the Midtonemachines.com website. I like the valving, everything is laid out to be user serviceable, this is essential! 6 chemistry, all due respect to the excellent Tetenal process, if this is to be used by a retail shop or studio, it needs to be able to handle standard E6.

I am wary of "walk away from" machines, but for a small shop, or a studio this looks very promising.

PS the enterprise in China makes a hybrid reel, part Jobo part AP with the tab divider for double loading 120, I use Jobo machines now, but loading 2 120 onto 1 Paterson reel is pretty easy.

AndrewBurns · Jan 14, 2021

rick shaw said:
How is the programming / recipe creation done? Is that a touch panel, or is there USB upload?

Thanks. looks very good.

Rick, there's a colour LCD screen and a little joystick on the front which is used to control the machine including creating/editing recipes. I decided against a touchscreen because they can be annoying to use in small sizes and especially bad if you're wearing gloves which might have water or photo-chemicals on them!

MattKing said:
I've noted your earlier posts, with interest. And I will continue following this.
By the way, it is Paterson, not Patterson.

Thanks, I'll fix that in the future

mshchem said:
Makes great sense to use a core that will except the most abundant reel on the planet, Paterson, also includes the winged version made by AP, and even the Hewes version for Jobo/Paterson. I've been following this project over on the large format site. Amazing progress in a short period. For a fully automatic unit this shows great promise. I would encourage folks to visit the Midtonemachines.com website. I like the valving, everything is laid out to be user serviceable, this is essential! 6 chemistry, all due respect to the excellent Tetenal process, if this is to be used by a retail shop or studio, it needs to be able to handle standard E6.

I am wary of "walk away from" machines, but for a small shop, or a studio this looks very promising.

PS the enterprise in China makes a hybrid reel, part Jobo part AP with the tab divider for double loading 120, I use Jobo machines now, but loading 2 120 onto 1 Paterson reel is pretty easy.

Cheers, I got a lot of feedback from some small film labs and users who have similar machines before starting and 6 chemical channels was a frequent requirement. Even if you don't plan to run E6 for example you could have three dedicated to C41 and the others dedicated to B&W so you don't need to change bottles all the time. Or you could have the first three set up for C41 and another two used as capture tanks for replenishment or sliver recovery. Replenishment and waste separation are another thing that small labs are very interested in. I get the concerns about leaving machines alone while they're running, I still watch the prototype like a hawk, but as you say for a lab, studio, community darkroom, university etc. it means you can be a lot more productive with your time.

mshchem · Jan 14, 2021

AndrewBurns said:
Rick, there's a colour LCD screen and a little joystick on the front which is used to control the machine including creating/editing recipes. I decided against a touchscreen because they can be annoying to use in small sizes and especially bad if you're wearing gloves which might have water or photo-chemicals on them!

Thanks, I'll fix that in the future

Cheers, I got a lot of feedback from some small film labs and users who have similar machines before starting and 6 chemical channels was a frequent requirement. Even if you don't plan to run E6 for example you could have three dedicated to C41 and the others dedicated to B&W so you don't need to change bottles all the time. Or you could have the first three set up for C41 and another two used as capture tanks for replenishment or sliver recovery. Replenishment and waste separation are another thing that small labs are very interested in. I get the concerns about leaving machines alone while they're running, I still watch the prototype like a hawk, but as you say for a lab, studio, community darkroom, university etc. it means you can be a lot more productive with your time.

I think E6 is going to grow substantially if Fuji and Kodak keep prices reasonable. It's so much easier to scan, the small analog specialist who offers E6 development will sell slide film. The small shop that can set up C41 and E6, it's doable back in the era of Kodak, there were schemes for using some common plumbing for bleach, the fixer is the same. Having a set of programs that allow for push processing C-41, different replenishment etc. The key is no backwards contamination. I think your valving is got the potential for very little chance for cross contamination, as compared to some of the older machines.

AndrewBurns · Jan 14, 2021

mshchem said:
The key is no backwards contamination. I think your valving is got the potential for very little chance for cross contamination, as compared to some of the older machines.

Yes I've been attempting to minimise the potential for back contamination at every point. I've designed the plumbing such that it's possible to pump both water and air through all of the tubing any time a chemical is used, and the machine will automatically flush the lines between each chemical. I also recommend a water wash step between each chemical to prevent forward-contamination too even though that's typically much less of a problem (unless you want some chemical carry-over for some reason). I've done some tests with water coloured with dye and I can't detect any backwards contamination.

AndrewBurns · Jan 21, 2021

Started to assembly the first beta test Chromabox processor. I plan to send a few of these beta machines around the country (and eventually world) to get some real-world use and feedback so I know that the product I eventually do release is the best it can be.

Larry Cloetta · Jan 21, 2021

Continues to look very promising, Andrew. I’ve followed all the updates over at the midtone machines website, and did have one question. Could you possibly detail where this is right now with regards to thermal drift in a variety of scenarios. Black and white, long developing times vs. short developing times, E6, effect of ambient room temperature on the expected amount of thermal drift and possible guidelines for the end user in that regard, whether any of that seems to matter with regard to the end results, etc.
As best you can at this point, even though that sounds like a big ask, it’s one thing I have been curious about.
You do have some nice photos over on your separate site dedicated to those, btw. Best wishes for that venture.

Andrew O'Neill · Jan 21, 2021

Very cool. Enjoy following your progress, Andrew.

AgX · Jan 21, 2021

AndrewBurns said:
The Chromabox-4 is a very similar design to the old Phototherm machines. I didn't start out intending that to be the case (and I've never personally used or pulled apart a Phototherm) but given the requirements I started with it was clear to me pretty quickly that the best design to do what I wanted was very similar to the Phototherm and there didn't seem to be a point in re-inventing the wheel for the sake of it.

At first sight it reminded my of the small, full automatic processors offered by Durst and by Jobo.

The interesting thing is that you go the Paterson way, when so far rotational processing, at least at this forum, is related to Jobo tanks and drums.

AndrewBurns · Jan 21, 2021

Larry Cloetta said:
Continues to look very promising, Andrew. I’ve followed all the updates over at the midtone machines website, and did have one question. Could you possibly detail where this is right now with regards to thermal drift in a variety of scenarios. Black and white, long developing times vs. short developing times, E6, effect of ambient room temperature on the expected amount of thermal drift and possible guidelines for the end user in that regard, whether any of that seems to matter with regard to the end results, etc.
As best you can at this point, even though that sounds like a big ask, it’s one thing I have been curious about.
You do have some nice photos over on your separate site dedicated to those, btw. Best wishes for that venture.

Thanks Larry I've done some level of testing with a thermocouple inserted into the developing tank measuring temperature drift vs. time. As you probably know the chemicals are heated first in a separate tank, there's a pump circulating the chemicals in that tank to ensure even temperature and temperature there is monitored by a factory-calibrated digital temperature sensor.

Once pumped into the developing tank temperature is maintained by a silicone heating pad which the tank sits on, because the chemicals only fill the lower half of the tank the heat pad only covers the area where the chemicals are. The objective of the heater pad isn't really to change the temperature of the chemicals but to stop them from cooling down via heat loss to the environment. The fluid temperature in the tank isn't measured directly as in the Phototherm (the temperature sensor inside the tank is prone to failure I believe) but the pad temperature is measured and controlled.

In the conditions I've tested so far temperature control in the developing tank is adequate, especially for C41 where the developing step is quite short, but I have more testing to do as you say to ensure that the control is accurate enough in various ambient temperatures. Realistically I think it's fair to specify that the machine will have to be operated in a specific ambient temperature range, it's most likely that you'll have it in a room in your house or a lab where the temperature isn't going to be freezing or boiling.

Andrew O'Neill said:
Very cool. Enjoy following your progress, Andrew.

Thanks!

AgX said:
At first sight it reminded my of the small, full automatic processors offered by Durst and by Jobo.

The interesting thing is that you go the Paterson way, when so far rotational processing, at least at this forum, is related to Jobo tanks and drums.

Yeah the JOBO system relies on the entire tank rotating and that means the chemicals have to be filled and drained through the axis of rotation (otherwise the fill/drain port would leak chemistry every revolution) and so to drain the chemicals out through the middle of the tank requires the whole thing to be lifted up vertically. The vertical lift mechanism is pretty complicated and takes up a lot of space from what I've seen. If you want to avoid lifting the tank and fill/drain through the bottom the tank has to be fixed which means spinning the film inside, I could have tried to re-invent the wheel when it came to film spools but there are already so many options on the market for Paterson-type spools it made sense to design the machine to fit those.

ic-racer · Jan 21, 2021

Looks good!

Nodda Duma · Jan 22, 2021

Very cool, Andrew.

Just a note to help avoid a potential gotcha: The silicone tubing used for peristaltic pumps will deform / change hardness (gets slightly softer I think) with use, which changes the flow rate over the lifetime of the tubing. So for example, when making emulsion I characterize the pump rate of my silver nitrate / salt lines and find I need to adjust motor control voltage every time I do a run. The rate of change in pump rate is relatively rapid with new lines and then slows down significantly, so it's not a strictly linear change. The rate of deformation increases with increasing temperature, so the rate of change for pump lines moving higher temp chemicals will change quicker.

As such, the tubing may need to be a maintainable part, unless you have a feedback loop to control and compensate for the variation in flow rate over time. Even then in practical terms such a control loop extends the maintenance lifecycle vs. eliminating it. What I'm not sure about is if the rate of change is deterministic. That is, whether characterizing the pump rate decay of a few samples represents an entire production lot of tubing, but you can test that. If it is, then you don't necessarily need a feedback loop and/or it may change at a slow enough rate that you can say "replace tubing at the pump heads every 50 uses" or something like that. You can, of course, get tubing couplers so that just a short length at the pump head need replaced.

Hope this helps!

- Jason

Louis J. P II · Jan 22, 2021

AgX said:
At first sight it reminded my of the small, full automatic processors offered by Durst and by Jobo.

.

Owning a Photo Threm Super Sidekick 8 & a couple Jobo processors presently or in the past I can say Andrews machine is much closer in look & design to my Photo Therm SS8 than to any Jobo machine I have own or owned. I'm not familiar with Durst processors.

Nice work Andrew!

AndrewBurns · Jan 22, 2021

Jason,

Lots of good info there. The Chromabox doesn't use peristaltic pumps (I couldn't find one at a reasonable price with a high enough flow rate), it uses a gear pump for chemical transfer. The volume of chemistry for a given cycle is set by floating magnetic level sensors in the heating tank, and a turbine flowmeter is used to determine when all of the chemicals have been drained out of the developing tank. I try to avoid as much 'open loop' control as possible because as you say things change over time. For example the gear pump will likely pump less efficiently over time as it wears and so if you were relying on open-loop time-based control it might eventually fail, with the sensors I have however it should just keep operating (and maybe take slightly longer to run a cycle).

I have thought about a future version of the machine including a peristaltic pump for dosing control, so that liquid concentrate developers could be automatically mixed in the machine rather than having to be done manually. Given what you've said about pump variability over time I might look at using an oval gear flowmeter or something to give more accurate control. But that's a ways off yet, need to finish the existing machine first!

Nodda Duma · Jan 22, 2021

Ah yes if you need high flow rate, that’s a better pump choice. More consistent, less “pulsing”

ic-racer · Jan 22, 2021

Louis J. P II said:
Owning a Photo Threm Super Sidekick 8 & a couple Jobo processors presently or in the past I can say Andrews machine is much closer in look & design to my Photo Therm SS8 than to any Jobo machine I have own or owned. I'm not familiar with Durst processors.

Nice work Andrew!

AgX might be referring to the Jobo ATL1000/1500

AgX · Jan 22, 2021

Yes.

And I referred also to the Durst Filmetta
https://i.ytimg.com/vi/-U6naskaS-U/maxresdefault.jpg

(later marketed by Tetenal)

AndrewBurns · Feb 27, 2021

Hey all, been a while but things have been busy in the background.

I just got around to making and uploading a short video showing the user interface for the Chromabox-4, showing some operation, and discussing the advantages of this type of machine compared to others (particularly for high-volume users like labs, darkrooms, schools etc.). Check it out! Apologies for the video quality, filming and editing videos is definitely not a strong-suit of mine.

Mick Fagan · Feb 27, 2021

Andrew, really looking good, but please stick with metric figures. 44 gallons is fine; maybe................

44 US gallons is 166 litres, however, 44 UK gallons is 200 litres, so which is it?

Mick.

AndrewBurns · Feb 27, 2021

Haha sorry, 44 gallon drum was just an example of 'big container' as I thought most people would be familiar with the size of the common 'oil drum'. The actual volume doesn't matter, if you had a process which used salt water you could dip the tube into the ocean and have access to trillions of litres... The point is that because the machine sucks in and discharges chemistry from hoses you can use whatever size container you have, so if you're purchasing or mixing chemistry in bulk you can draw directly from those large containers rather than having to decant them into small bottles which fit inside the machine, or pour them into bottles which are permanently mounted into the machine.

This is also very useful if you want to do replenishment, because you can pump each chemical out to a different container compared to where it came from. So if for example you were doing one-shot C-41 process with Kodak flexicolor chemistry you could discharge all of your used chemistry into different containers, and after you've collected enough you could replenish those chemicals and use them again. Just like how a minilab works except you'd have to add the replenisher yourself.

AndrewBurns · May 7, 2021

Just uploaded a new blog post with some more detail of the progress I've been making. Mainly talking about the two beta test machines I'm building and where in the world I'm sending them to. Also recieved some QWD ECN-2 chemistry which I'll be testing and using to dial-in the pre-programmed recipes the machines will eventually ship with.

http://midtonemachines.com/news/decals-and-beta-machines/

Michael Firstlight · May 7, 2021

Wonderful work and progress..as a PhotoTherm user I'm impressed- looks like a better Phototherm than Phototherm. a few questions

Do you plan a larger 8 reel tank eventually
Is it self-cleaning?
WIll there be a US 120v version
Do you plan to start a FundMe sort of thing

Keep up the great work!

MIke

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