Interpreting C-41 control strip results

koraks · Apr 27, 2023

Steven Lee said:
A tool in Photoshop or similar image editors that allows you to examine RGB values of an image area.

@pentaxuser
Exactly. As here, e.g. in GIMP:

Applied to the right-side strip in Steven's earlier image of both test strips:

Note RGB values in top left of the dialog.

pentaxuser · Apr 27, 2023

Thanks for the reply I don't use Photoshop so hadn't heard of this tool

pentaxuser

koraks · Apr 27, 2023

It's a default feature in probably every graphics editing program, including Windows Paint.

Ericc · Jun 4, 2023

Just a quick update. I finally got my control strips to align with the reference strip. I'm using a paterson tank developing 120 film.. I had to deviate from the published temps/times but I'm now able to get the test strips into spec.

I had to increase the temperature to 102F (verified with a calibrated temperature sensor). Agitation was one inversion of the tank per second for the entire time minus that last 10 second. I preheat the paterson tank for about 20 minutes with film loaded using a 12V heat tape wrapped around the tank. (Dry tank) this gets the plastic/film/reel up to temperature before chemistry is added.

Chemistry was newly mixed Fuji Developer, Kodak bleach, and Kodak fixer, stabilizer.

Times used where:

Develop (102F) 3:45
Bleach (102F) 6:30
Wash (75F) 3:15
Fixer (102F) 6:30
Wash in sink with running water 3:15
Stabilizer 1:30

koraks · Jun 5, 2023

Wow, I'm surprised it takes this much apparent overdevelopment to get the target densities!

brbo · Jun 5, 2023

Yes, very surprised to see one needs 3:45 to be within specs.

I've never checked my processing with control strips, but I'm thinking I really should...

MattKing · Jun 5, 2023

How is your timer ?

sillo · Jun 5, 2023

Anywhere between 3:15 and 3:45 is what Kodak specifies in z131 for rotary processing

Steven Lee · Jun 5, 2023

MattKing said:
How is your timer ?

Ericc · Jun 5, 2023

MattKing said:
How is your timer ?

I use an app on my iphone that handles the timer. I'd be surprised if it was not reasonably accurate.

Ericc · Jun 5, 2023

sillo said:
Anywhere between 3:15 and 3:45 is what Kodak specifies in z131 for rotary processing

Thanks for quoting that. I'm glad that I'm not totally out of the recommended processing range.

MattKing · Jun 5, 2023

Ericc said:
I use an app on my iphone that handles the timer. I'd be surprised if it was not reasonably accurate.

It probably is accurate. When I posted that, I was trying to figure out how to do so in a way that made it read sslloowwllyy.

jejes · Feb 7, 2025

Please, what are the nominals densities of Kodak Strips. Or should i read the strip that comes with my pack.
I have read Z131 and Z99 but i don't find any standard densities.

Thank You

Ericc · Feb 7, 2025

jejes said:
Please, what are the nominals densities of Kodak Strips. Or should i read the strip that comes with my pack.
I have read Z131 and Z99 but i don't find any standard densities.

Thank You

Most test strip packs should come with a paper insert with the densities listed for the test strip . If you loose that then you can use the reference strip and read the cells with your densitometer. The paper is useful also to verify your densitometer as you should get similar values as provided on the reference paper.

-Eric

jejes · Feb 7, 2025

Ericc said:
Most test strip packs should come with a paper insert with the densities listed for the test strip . If you loose that then you can use the reference strip and read the cells with your densitometer. The paper is useful also to verify your densitometer as you should get similar values as provided on the reference paper.

-Eric

Yes i mean i get a paper with tolerances but not real densities, it's supposed that i have to read the test strip and suppose the densities from test are going to be the densities of my developed test +- tolerance from the paper.
But is there any nominal densities around?

Thank You

Ericc · Feb 7, 2025

These are the values of my Fuji C-41 strip. Columns are not labeled but are R/G/B from left to right. Values on the far right are with corrections applied. This is from my densitometer so depending on your calibration your device may yield a different value.

-Eric

jejes · Feb 23, 2025

I can‘t finde here in Europe a dealer to buy the control film strips Fuji or Kodak. Please suggestions?

koraks · Feb 23, 2025

jejes said:
I can‘t finde here in Europe a dealer to buy the control film strips Fuji or Kodak. Please suggestions?

Contact FUJIFILM and ask them to be brought into contact with the distributor(s) in your country. They should in turn be able to point you to one or more retailers who can sell you the product, provided it's still being made. Which I doubt.

brbo · Feb 23, 2025

jejes said:
I can‘t finde here in Europe a dealer to buy the control film strips Fuji or Kodak. Please suggestions?

What happened to your Kodak dealer? Do they only carry ECN-2 controls strips?

jejes · Feb 26, 2025

brbo said:
What happened to your Kodak dealer? Do they only carry ECN-2 controls strips?

Yes, he can supply me. But Kodak it’s 100ft roll and fuji are 50 cutted strips, I prefer Fuji.

sfaber17 · Mar 6, 2025

Steven Lee said:
Quick update: I have played with temperature some more. By raising it by 1F I was able to land within spec, but the green and blue continue to maintain a solid density gap vs red:

View attachment 336109
And the orange mask in my strips is never as pink-ish as the control strip. The LD numbers describe the difference perfectly. At this point I am giving up, and I am questioning the validity of my approach of using Fuji control strips with Kodak chemicals.

I was doing both Kodak and Fuji control strips back in 2016 with homemade C41 and had the Kodak strips within the limits and the Fuji strips were down .10 in Green LD. I think .10 was almost within or within control limits. One thing I remember was the Kodak strips were not supposed to be frozen, but Fuji strips were supposed to be frozen but once you took out a small package to defrost, you kept them refrigerated but not re-frozen. I had an old post with some results.

Steven Lee · Mar 6, 2025

@sfaber17 Since I posted that, it's been determined that the last batch of Flexicolor manufactured by SinoPromise was defective. After switching to Fuji Hut C41 all my readings have been right on the money.

lamerko · Mar 6, 2025

This may be a bit of a dumb question, but where did you find the reference strips?

jejes · Mar 6, 2025

I have spoken with FUJI Spain there is no stock of fuji strips in Europe, is anyone able to find them in EU?

Thank You

foc · Mar 6, 2025

jejes said:
I have spoken with FUJI Spain there is no stock of fuji strips in Europe, is anyone able to find them in EU?

Thank You

I did a Google search and this turned up, it might help.

https://www.processuk.net/FUJI_CONTROL_STRIPS/cat740598_659672.aspx

Not the EU officially but near enough. You will probably have to pay Vat at point of entry (DDU)

Interpreting C-41 control strip results

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