X-Rite 334 Sensitometer: Inspection and Analysis

dkonigs · Jan 7, 2021

Here's the inside of my X-Rite 396:
(I didn't disassemble it any further than removing the bottom so far, but the exterior looks similar to the 334. Except, you don't need to unscrew it to get to the battery compartment.)

From what I can tell, this thing was probably done entirely in discrete logic and analog components. No evidence yet of a microcontroller, but then again I haven't yet looked at the other side of the board. I suspect they used a more modern design to get the high voltage for the light panel, which is why this version doesn't have a big toroidal transformer like the older 334.

ic-racer · Jan 7, 2021

These were very expensive when new. Easy to test if it will do everything you want.

A single film type at different development times, test them for percent change in contrast index with 1)GREEN,2) BLUE and 3) your enlarger lamp.
Two films of different ISO, test them for percent change in exposure index with 1)GREEN,2) BLUE and 3) your enlarger lamp.

When I did the test all 4 sensitometer light sources I used gave very similar results.

ic-racer · Jan 7, 2021

ic-racer · Jan 7, 2021

If you do want to go down the rabbit hole of sensitometers, there are three different inexpensive WHITE LIGHT sensitometers on ebay right now. They all appear to have incandescent lamps with stepper motor shutter, similar to the Wejex. I'd think they would be easy to repair if they did not work. I'd expect almost no electronics inside.

ProfessorC1983 · Jan 10, 2021

dkonigs said:
Here's the inside of my X-Rite 396:

If you don't mind my asking -- what is the approximate width of the usable exposure area on the 396? Is it wide enough to expose the full width of 120 film? I recently bought a 334, but it's not quite wide enough for my need, which is to expose a 6x6cm step wedge (Stouffer TP120-31) onto 120. Trying to decide if I should purchase a second 334 and arrange the two lamps side-by-side in a custom enclosure, or if perhaps one of the other units available for cheap on the auction site would suffice.

Bill Burk · Jan 11, 2021

Thanks ic-racer these tear downs are amazing!

Yes I treat fresh TMAX-400 as my calibration standard. Where the curve crosses 0.1 above base+fog when developed to the ASA parameters is by my definition -2.7 log meter candle seconds. Life is so easy when you work this way because it’s not hard to hit the ASA parameters within +/- 0.05 on the top right side of the triangle.

dkonigs · Jan 11, 2021

ProfessorC1983 said:
If you don't mind my asking -- what is the approximate width of the usable exposure area on the 396? Is it wide enough to expose the full width of 120 film? I recently bought a 334, but it's not quite wide enough for my need, which is to expose a 6x6cm step wedge (Stouffer TP120-31) onto 120. Trying to decide if I should purchase a second 334 and arrange the two lamps side-by-side in a custom enclosure, or if perhaps one of the other units available for cheap on the auction site would suffice.

The window where the step wedge is located is approximately 3cm wide, but the actual patches on the wedge are a bit less than half of that. So while you could use it with 120 film (exposing a piece of it), you can't use it with a wedge that wide.

ic-racer · Jan 11, 2021

ProfessorC1983 said:
If you don't mind my asking -- what is the approximate width of the usable exposure area on the 396? Is it wide enough to expose the full width of 120 film? I recently bought a 334, but it's not quite wide enough for my need, which is to expose a 6x6cm step wedge (Stouffer TP120-31) onto 120. Trying to decide if I should purchase a second 334 and arrange the two lamps side-by-side in a custom enclosure, or if perhaps one of the other units available for cheap on the auction site would suffice.

Is there a reason you need the patches that big?

So, no one has asked but the 3 on ebay are simple mechanical units and can be modified much more easily than the electronic x-rite sensitometers. Let me know, I'll point them out but you can probably figure it out yourself because LED uses batteries and stepper motor requires AC cord. Also, these units have a bigger box for the diffusion system to even the light from the incandescent lamp.

One of you should pick this one up. Bill?, Professor?, dkonigs? If I bought it I'd have 5 which would be crazy.

ProfessorC1983 · Jan 11, 2021

ic-racer said:
Is there a reason you need the patches that big?

My step wedge itself is square 6x6cm with third-stop steps and I have the exact calibrations for it from Stouffer, so would rather use that than the built-in patches. It was easy enough to pull the wedge sticker off the diffuser on my 334, so I can expose about half of this wedge at a time, but would still be interested in an easy way to do it all in one frame. Hard to tell exactly how wide the lit elements are on those other 'Bay finds. I'll think about it but may just end up building something.

ProfessorC1983 · Jan 11, 2021

Greg Davis said:
You convinced me. I got that one.

Beat me to it! I expect to see a teardown video on your channel within the week.

ic-racer · Jan 11, 2021

Greg Davis said:
You convinced me. I got that one. We'll see what kind of bulb it has once I get it delivered. It says it's for blue sensitive X-ray film, but who knows.

Thank you, thank you, thank you! I have way too much stuff. I am very curious. You see the red and black leads in the bottom? The OLD Wejex has the same. They are for measuring the voltage to the lamp. That is how you can roughly hold calibration the same (but, of course says nothing of actual lamp brightness.) I suspect the leads on the bottom of the blue on are the same function, but we will see.

There are two more interesting sensitometers on ebay with promise in terms of experimentation that may be White Light and not LED:

:

ic-racer · Jan 11, 2021

ic-racer · Jan 11, 2021

ProfessorC1983 said:
My step wedge itself is square 6x6cm with third-stop steps and I have the exact calibrations for it from Stouffer, so would rather use that than the built-in patches. It was easy enough to pull the wedge sticker off the diffuser on my 334, so I can expose about half of this wedge at a time, but would still be interested in an easy way to do it all in one frame. Hard to tell exactly how wide the lit elements are on those other 'Bay finds. I'll think about it but may just end up building something.

View attachment 263521

I think it gets exponentially more difficult to make a larger exposure stage, due to the demands of absolute evenness across the field.

ic-racer · Jan 11, 2021

Dupont Cronex ELS looks interesting. It is also AC powered and does NOT have a Green/Blue switch. The one currently on ebay does not show the stage, but this is what is looks like (from another sold ad):

Bill Burk · Jan 12, 2021

Does that DuPont expose both sides of the film?

ic-racer · Jan 12, 2021

Bill Burk said:
Does that DuPont expose both sides of the film?

It looks like it.
Some xray film is sensitized on both sides and there could be a screen on each side. Not everyone knows this but the x-rays hit a 'screen' that glows. The glow is what exposes the film along with the x-ray. This intensifies the image so the patient can receive a lower x-ray dose, The the screens were made to glow in either green or blue florescence. That is why the x-ray sensitometers have the green/blue function.

acoma · Jan 16, 2021

ic-racer said:
The sensor shortens the time and I tested this, but I did not test if it can lengthen the time. This is certainly worth a try.

Placing an ND filter under the 334's sensor does indeed lengthen the exposure time. I inserted a 0.90 and the highest setting now times out at 6 seconds. That would of course introduce reciprocity issues for many films though. I'll do some testing with it at different settings and try a lower density filter if this is unworkable.

ic-racer · Jan 16, 2021

Good work!!

ic-racer · Jan 23, 2021

Fantastic that you bought that and opened it up; you are a crazy as I am.

Here are some guesses as to how the circuit operates based on the pictures. LP-16-350 is a "Signal" brand power transformer that gives 16V from the mains. The orange capacitor is likely a filter capacitor and the large flat 'transistor' looking device may be a voltage regulator with a heat sink. The round black device by the switch may be the rectifier. It is pretty small but the voltage is pretty small also.

Just another guess here, I don't see a digital timing circuit (like 555 chip) so maybe timing could be related to the storage of charge in the two larger blue capacitors. The old Omega timers (pre Chromegatrol) used something similar. Also looks like two wires from the on-off switch go to the PC board that contains those large capacitors. This would support that they are used in the timing circuit.

ic-racer · Jan 23, 2021

If you were interested in altering the exposure electronically, this circuit could probably be figured out by the pictures and a volt meter as it appears pretty simple (compared to the picture in the original post). For example I see some "DALE" resistors, these frequently were Mil. Spec. and could be part of the timing circuit. Therefore, changing the resistance there could re-set the timer.

ic-racer · Jan 23, 2021

Using a meter to check might be the worst way, due to the myriad of errors that can be encountered. Since you have another sensitometer, using the same film on both of them might be the best approach.

There are a few papers and patents out there on calibrating sensitometers without using a lux meter.

Scott M · Jan 25, 2021

Thanks for sharing your wealth of knowledge everybody! Between Greg's youtube channel, and picking up a copy of Way Beyond Monochrome I've been inspired to pick up a densitometer. There's a Kodak Model 1 branded X-Rite 810, and an ESECO Speedmaster SL-2 sensitometer coming my way from eBay. I'm excited to mess around with making some H&D curves, and have a way to check and compare densities of different film/developer combinations, etc. Thanks for the oddly specific instrument GAS everybody!

Couple questions for you all. A sensitometer is gonna give me a consistent exposure when I'm making step wedges, which will make messing around with all this a little less fussy than using my enlarger to expose a step wedge. But when ic-racer is talking about white light/full spectrum sensitometers, does that allow you to do something more than a sensitometers designed for x-ray film like my SL-2? Obviously it gives you the full spectrum, but does that make a difference in use, in practical terms?

On that point I plan on just sticking with either the blue or green setting on my SL-2, so I'm not comparing apples and oranges. Since I'll be comparing the same step wedge across film stocks, and developers does it matter if I'm using blue or green light when making step wedges? I'm probably missing something, but what is the different with a full spectrum sensitometer or my enlarger for that matter, besides being able to more closely replicate real shooting conditions and/pr daylight? Also, folks mentioned making multiple exposures. Are these X-Ray sensitometers just not bright enough to properly expose a step wedge onto conventional black and white photo film?

Thanks again for sharing, and for the GAS!

ic-racer · Jan 25, 2021

Comparing speed and contrast between films or between processes, the sensitometer light did not make a significant difference in my darkroom.
https://www.photrio.com/forum/threa...ction-and-analysis.180579/page-2#post-2365797

Scott M · Jan 27, 2021

Great!

m00dawg · May 9, 2021

Ok so I got one of these puppies (the 334). Opted to follow ic-racer's instructions on how to get the top off, largely so I could get to the step wedge to setup a baseline with it. Trouble is, it seems to be laminated to the diffuser and my 301 densitometer seems to be getting a bit confused with it and I think the diffuser is part of the problem? It's having trouble with the first few steps or rather they're both reading the same values (sometimes step 2 actually reads more dense but the values tend to move around a bit). As I go down it gets better though.

I plan on using this not so much to do film exposure testing but moreso to have a nice consistent source to help monitor my XT-3 replenishment. The idea being anytime I develop some 35mm from my bulk roll, toss a test strip in with it so I can compare the curves over time to make sure the results are reasonably close. Basically sort of like making my own process test strips. So I just need repeatable results to itself more or less. I plan on continuing to use my enlarger and expose a Stouffer wedge when doing development tests (and at some point will do in-camera testing as well).

I guess that means if I can't read the last few steps reliably that's probably still ok?

X-Rite 334 Sensitometer: Inspection and Analysis

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