Self-making/DIY control strips thoughts

[czygeorge]

Hi all
I've have always used the Kodak's control strips.Because I need it to do quality control of my chemical and process

But unfortunately it is very expensive and hard to get
And it is difficult to ensure stability
(long transportation and because need to take few every use,which makes me have to freezing and thawing the whole strips rolls for months)

And also what i know is those old motion film process factory/lab was making their own control strips and had their own aim value.I think this way is very reasonable and comfortable for quality control

Therefore, I especially want to make the control strips/sensitometory strips by myself

#What I want to do is:
making expose on fresh 5207 which has not been x-rayed(it's very hard to get in my country)
And once develope with the Kodak ECN-2 control strips to ensure that this strip is no problem in process,and confirm this as a reference aim value

#But what hard is:
I think sensitometer is needed since it need very accurate short explosion( i once consider use enlarger and stouffer but because of this reason it can't work)

and I think original strips is made by gray 1/3 stops 21steps,but what sensitometre give is blue light or green light.Which makes me confused if it can give density to orther 2 layers(R and G/B)

Any thought, advice or discussion is very welcomed and needed
Thanks a lot!

 

[Bill Burk]

Electronic flash would be better than a blue/green X-Ray sensitometer.

There are Kodak publications that could help you with process monitoring. For example you could get “Kodak Color Process Monitoring Z-99 N8135” off eBay.

I would even recommend a slide duplicator where you would expose a test frame of a known good color test slide and then you try to print from it. This would be a test shot in addition to step wedge and color patches

For example:

BOWENS ILLUMITRAN SLIDE COPYING STAND W NIKKOR LENS, CAMERA, ADAPTERS,

 

[Romanko]

Therefore, I especially want to make the control strips/sensitometory strips by myself

You will need: (1) a grey card or a sheet of white paper; (2) a reliable 35 mm camera; (3) a light meter; (4) a tripod; and (5) bright sun. Figure out the exposures you need from the nominal values of Kodak control strip and expose your film accordingly. Use the Kodak control strips that you already have to fine-tune your processing and process a piece of film you've just exposed. This is your reference. Measure the densities and you can go from here. A half-frame camera would reduce your film costs. You will be relying on the accuracy of your camera shutter/lens aperture. If that is insufficient, you can get an adjustable neutral density filter, calibrate it and use to control exposures.

 

[koraks]

i once consider use enlarger and stouffer but because of this reason it can't work

Use an ND filter. It's just a lot of work to make a bunch of test strips and getting the film and the step wedge/stouffer tablet to align well every time in the dark requires some ingenuity.

(5) bright sun

I'd never rely on the sun as a benchmark light source. Too much trouble getting repeatable results across different batches and even within a single batch with season, time of day, atmospheric conditions etc.

Other than that, an approach using a camera can work, but use a controlled light source.
It's even possible to use something like a LED panel and a big step tablet (e.g. a full 4x5" sheet). Use a macro lens and allow some margins along the edges so any vignetting around the corners doesn't affect the outcome. Of course stop down to f/22 or so.

 

[czygeorge]

Hi all!
Really thanks for your all suggestion,that's so brilliant!
These are very good way and better than what I was thinking

Now I think I can use these two methods
1.Use a tripot, medium format camera and macro ring, and use some tricky way to insert 35mm film in it, so the image can be long enough to put full stouffer in

And use a good led pannel(Ra98) put stouffer on it.Than shoot it with correct exposure

Also we can shoot gray card in reflection way too(and do low and high density by adjust shutter speed)!
So we can determine the process quality by reading LD MD HD Dmin and Dmax
But sure it needs a spot densitometer,my xrite 892 may not be able to read this

Second is making contact print(5207 and stouffer),And use a flashlight (I think I will try 580ex and use the minimum power 1/125) to expose it

I will try both way and post the result(maybe need months because my 892 need to find calibrate too).Hope we could make it

 

[koraks]

And use a good led pannel(Ra98) put stouffer on it.Than shoot it with correct exposure

Keep in mind that 'correct exposure' would be an exposure that gives you a useful number of steps on the Stouffer. So you want the clear steps to be someplace high up in the curve; i.e. you'll need to overexpose for the illumination level of the LED panel by several stops.

medium format camera and macro ring, and use some tricky way to insert 35mm film in it

Note that in the idea of shooting a step wedge on a light table you could even do this with a 35mm camera; the main issue will be that the test negative will turn out kind of small. A Stouffer 21 step will not work well because if limitations in the spot size of your densitometer. But if you use a wedge with fewer steps, you could get away with it; e.g. Stouffer T5100. It could even be a DIY step wedge; as long as you calibrate the readings initially using your Kodak strips, you should end up pretty close.

And use a flashlight (I think I will try 580ex and use the minimum power 1/125)

Works in principle, but keep in mind that distance between the flash and the film, reflections/bouncing of the flash against walls and objects in the space etc. will all affect exposure. So ideally you make a setup that you can recreate very accurately.

 

[Romanko]

So we can determine the process quality by reading LD MD HD Dmin and Dmax
But sure it needs a spot densitometer,my xrite 892 may not be able to read this

Yes, I suggested using a gray (or white) card and exposing a full 35 mm frame per step for two reasons. First, you will have enough area to accurately take density readings. Most densitometers require something like 4 mm diameter sample. The second reason is vignetting.

I agree with @koraks regarding the controlled light source. I realized that you will need to produce control strips on an ongoing basis. Daylight would only work if you are exposing several control strips within a few minutes.

Instead of using a Stouffer wedge you might want to make your own using frames exposed with your 35 mm camera on black and white film. It will probably take a few attempts before you get the densities you want. You can then use your template for contact printing.

I also suspect that your reference control strip does not need to replicate the density of the Kodak control strip exactly. You might get away with some deviations since you will be using your reference control strip to monitor the process.

So ideally you make a setup that you can recreate very accurately.

Something like a flash on a copy stand, ideally dedicated to this application.

The device that can produce control strips is called film recorder. Maybe you can find someone who has it and can print the control strips for you.

 

[koraks]

Instead of using a Stouffer wedge you might want to make your own using frames exposed with your 35 mm camera on black and white film.

Precisely; I've done similar things with x-ray film and an enlarger. Works OK; like you said, give it a couple of tries. It's really not much different from making a test strip on paper; just shorter exposures.

 

[Romanko]

Precisely; I've done similar things with x-ray film and an enlarger.

You can always contact Stouffer and check if they can make a custom step wedge for you. I bought from them directly and they provided an excellent service. Though, it's more fun to do it yourself.

 

[koraks]

Yes, I considered that. Or https://www.danes-picta.com/

 

[bernard_L]

I would argue against exposure under an enlarger because unless you have a calibrated lux-meter and know how to work through the photometric equations you won't know how many lux-seconds your film has received and won't know whether you have achieved box speed. However, if done properly, may provide a consistency check.

Doing in-camera exposure with a known good, TTL-metering camera allow you to relate to ISO speed, and familiar notions exposure time, f-number. Why TTL metering? because the transmission of the lens is automatically taken into account (F-number versus T-number).

Achieving the equivalent of an industrial grade control strip is a tall order. But what is actually your goal? Checking for consistency is a different goal. Controlled exposure of a gray card at three levels allows you to check for various things: chemistry exhaustion, film fogging, achieved ISO, crossovers...

 

[koraks]

However, if done properly, may provide a consistency check.

I think that's the main purpose. It'll give a check that's relative to a couple of uncontrolled parameters, but as long as those are kept constant, the lack of an absolute speed measure (for instance) won't hurt. Neither will it e.g. be much of a problem if the grey patches don't turn out to be perfectly grey, or even crossed over. As long as they're always the same across development runs, then at least the process is performing consistently. If, moreover, this process is initially benchmarked against an absolute reference (the Kodak strips + density measurements from a calibrated densitometer), I'd wager to say that you're doing an OK job in shoestring setup.

 

[Romanko]

you won't know how many lux-seconds your film has received and won't know whether you have achieved box speed.

The goals here are different from sensitometric tests of the film. We just need to find a way to consistently achieve several known Status M densities on the control strip. Apart from the densities, no other absolute measurements are not required. Once we have repeatable exposures we can do the rest by trial and error.

 

[czygeorge]

Hi all
Really thanks for discussion and inspirational which are really helping

And these 2 days I read many articles written by motion film process factory in my country(80s 90s)

Have to say I get really shocked by their professional work and enthusiastic on quality control

Here's what I learned
The standard control strips(DIY or kodak) should have LAD(grey card) in 11th STEPS.And than I guess is just 1/3 steps above and under to have total 21 steps(Those are old motion film factory did this by their densitometer)

So I think we can just try expose grey card(may need a expensive one) by camera and adjust exposure to HD and LD
And also when shoot a batch we need to put them in room temperature for 24 hours and then put them to -18℃

Unfortunately my x rite 892 sure need calibrate since its reading of reference strips 11th step is not LAD(0.8 1.2 1.6)

Also I think jobo processing is not a very good way to process color negative to make quality that good like only have inaccuracy ±0.01(those motion film lab can did)
But hope we could try best to do it better and make this work