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Modern densitometer choices

 

Something happened to all the old images here and LF forum. As you can see I have updated the images at the end of the thread. It will take years to do that for every thread here and at LF forum (though I am slowly rebuilding them as I go).

The EG&G xenon flash units came in only 2 or 3 models with slightly different capacitors giving a slightly different range of very fast exposures. They all look about the same.

The Wejex is an incandescent device made by TOBIAS, who are still in existence and it is still listed on their website.

The Speedmaster is no longer made but similar to just about any other LED unit that you can pick up for less then $100, now that radiology has almost completely gone digital.

Testing was simple. Each device was used to expose 3 films. T-max processed at two different times and FP4 processed for its recommended time.

The transmission step wedge densities recorded on the films were measured and the values used to calculate EXPOSURE INDEX and CONTRAST INDEX per ASA and ISO methods. The results were shown as a graph.

 
Let me see if I have a picture of it.
 
I was going to post this earlier. This diagram shows some of the components of the Tobias DENSITOMETER light path.
 
Shoot, I thought it told you all you needed. I’d be tempted to buy the as-is EG&G on eBay and assuming the flashbulb is broken, replace it and see if it could be made to fire.
 
Bill Burk said:
Shoot, I thought it told you all you needed. I’d be tempted to buy the as-is EG&G on eBay and assuming the flashbulb is broken, replace it and see if it could be made to fire.
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That's not a bad idea, I just have to wait for something decent to pop up. The ones currently listed are "parts only, as-is" and kinda look like old dusty grimy junk. Makes me wonder how hard they would be to test/fix if not working, and whether replacement parts (for the more critical, less generic bits) are still available.
 
The hundred dollar one is probably broken but they say the flash fired on the four-hundred dollar one. If that's in your budget it probably works just fine. They built that stuff to last.
 
Bill's idea is good. Also, no issue with b&w film and green or blue LED units. But one could just take out the green or blue LED and replace with white if one is afraid of green or blue color. If making one's own Xenon unit, the farther the light from the target, the more even the light, but if enclosing it, you need to worry about side reflections, so a pretty big black box is needed if going that route. The other way is to have a reflective box like the EG&G.

The most modern unit I have seen is the one that Greg Davis has. It is electronic with white LED.

 
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A broken 303 X-rite can also used for its light stage. A simple LED circuit can be used in place of the original if it is broken. The original electronics are more complicated, because for medical use, there is a sensor to monitor the light output during exposure. That extra circuity is probably not needed for B&W control strip exposure in the home darkroom.
 
I could not resist, so I bought one of the $20 BLUE/GREEN X-rite 334 senstometers as a project to replace the LED with WHITE. It is not needed to do that, but it seems everyone is afraid of the 30 or so BLUE/GREEN sensitometers for less than $100 on ebay.
 
I got the 334 and it is NOT LED. I uses a flat electroluminescent lamp. Maybe the perfect sensitometer light source.
 
ic-racer said:
I got the 334 and it is NOT LED. I uses a flat electroluminescent lamp. Maybe the perfect sensitometer light source.
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I saw your post on this. Grabbing one of those is tempting. I just wonder how hard it is to make it have a more typical "daylight" spectrum (or whatever film is usually characterized with), rather than blue/green.
 
I'd just use the 334 as is. Use the Green channel.
 
After evaluating the 334, I'm not as motivated to try and put a "White" LED in one of the LED sensitiomers, as the "White" LED is just a blue one with added phosphorescence.

 
Is there enough power to drive an incandescent tube? Then you could add an 80B filter.
 
ic-racer said:
I'd just use the 334 as is. Use the Green channel.
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Gotcha. I might as well go do that then. Interesting how the instructions for these things always say they're for "X-Ray" or "Cine" film, yet I have absolutely no idea what makes Cine film (from a spectrum/sensitivity perspective) different from any other ordinary camera film.
 
The Cine people may care a lot more about batch to batch consistency than those who use still film.
 
I bought an Xrite 810 years ago. I did think about what would happen if the bulb burned out and I researched on replacement bulbs. They cost $600. Yikes! A year ago, I found the same one on Ebay for $100. I messaged the seller to see if it turns on and it did so I got it. When I got it, I found out that the bulb for the reflected of reading was burned out. Since I'm a tinkerer, I bought some 3mm, warm white LEDs. I desoldered the old bulb and soldered this LED.
https://www.ebay.com/itm/3mm-5mm-8m...rentrq:cf03520f1760ac3ed7992ca8ffcc0b8c|iid:1

After calibration with the reflective calibration tablet from my first densitometer, I got it to work for black and white reflected readings. I checked the readings between the two and they're identical. I have a feeling that the same LED will work for transmitted readings after calibration. I have not use the densitometer for color work. So back to future proofing. I think if the circuitry holds on both densitometers and the bulbs burnout, I could replace them with LED bulbs. I should be good for a while.
 
Bill Burk said:
Is there enough power to drive an incandescent tube? Then you could add an 80B filter.
Click to expand...
There is no diffusion box or anything to adapt a different lamp. It relies on the flat panel, which is quite ingenious. Personally I think this film stage provides the most even illumination of all my sensitometers, including the EG&G.

 
michael_r said:
I don’t know much about these, so perhaps you can explain - I’ve never understood why they were not more widely used where uniformity is a requirement, like in enlargers, or backlights. Why did LEDs instead become the go-to?
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I suspect the electroluminescent panel simply doesn't have the sheer output necessary for an enlarger head. I think De Vere used something similar to make a top glass in a carrier work like an LCD for a flash/ USM effect.
 
It may be hard to compare the light output of one of these without actually buying one and putting it on one's enlarger and comparing actual times with a LED panel.
 
michael_r said:
Also EL panels seem to have similar limitations to LEDs when it comes to the kinds of light they can put out. For example, as far as I can tell, you can't make one of these emit any sort of continuous spectrum white light.
Click to expand...

If you could get three with useful RGB peaks, then 'white' light wouldn't matter as much - or something in the 500nm range would probably be a fair replacement for the Aristo V54 range of cold cathodes. They may also be more susceptible to fading over time than other light sources.
 
There are perhaps millions of combinations of various phosphors that can produce luminescence. Some combinations do have pretty wide spectrums compared to LEDs.



 
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Forgot to mention that it is actually a phosphor component that turns a BLUE LED into WHITE.

 
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