Transmission Densitometer

[pkr1979]

Hi all,

Im in need for a transmission densitometer. I see they sell for pretty different prices at ebay... but I have no idea what to look for.

Any advise anyone?

Cheers
Peter

 

[Bill Burk]

There is a Marshall Studios densitometer on eBay right now. It’s in trashed condition. But because it is a “primary type photometer”, uses the law of inverse squares and a single traveling light bulb. It will work, nothing can fade. It’s missing an eyepiece, easily replaced.

There are two Ilford densitometers on eBay now, one is a very good price. They are not “primary type” but based on a gray dyed wheel. It might have faded. It uses two bulbs which need to be matched. Still, no electronics to go bad. It’s missing a transformer but that could be any old electronics brick you have lying around

 

[nmp]

Would you not need a UV densitometer for alternative processes?

In any case, there is a member here who is doing a project to build a budget-friendly one:

Printalyzer Densitometer - A compact budget-friendly densitometer project

One thing you might consider pursuing in the future is a UV version for people working with alt processes. I understand that both the source and detector are more challenging that for visible light, but it might be an easier problem to solve than a full-color version, and it might actually...

www.photrio.com

:Niranjan.

 

[Bill Burk]

As @nmp said…

@dkonigs is making a new densitometer which is going to be exactly what you need.

I don’t know about UV densitometer availability but there are UV meters from Blak Ray thst can help you verify the bulbs are good and your glass or negatives don’t block UV

 

[pkr1979]

Thanks guys... Im not so sure I know what I need... preferably a machine I could ask what the CI, gamma and curve of any given negative is, and then this machine would tell me the answer... and yep - for UV sources as well @dkonigs are you about to make such a machine?

@Bill Burk will the densitometers you mention help me figure out CI, gamma and/or curve?

 

[bernard_L]

preferably a machine I could ask what the CI, gamma and curve of any given negative is

No machine (at least no affordable machine) will do that. A densitometer gives you the density at a given spot of your negative. Once you have a series of measurements you can derive CI, gamma, etc. You need to have at least a basic understanding of these notions to make any use of a densitometer. If not, you are better off (time- and money-wise) starting from published values and doing systematic tests of exposure and development time until you obtain satisfactory prints. Will take time.
Systematic is the key word, with or without a densitometer.
Edward Weston did not have a densitometer. Nor Alfred Stieglitz. Nor Vivian Maier. etc, etc.

 

[gone]

Test strips. You can make them as sensitive (or not) as you please. That, and keep concise notes on exposure, fltr, etc. I do it in the print margins, right in the front so I can easily see it. This will save you lots of time later if you make more prints of that neg. W/ a microwave, it's a fast process to dry the test strips, or even a test print.

 

[Bill Burk]

@bernard_L says the same thing...

@pkr1979 yes a densitometer will do that but there is work involved.

The densitometer reads a single density value. You will make a few hundred readings.

You need another tool, a sensitometer. I assume you have a contact frame where you plan to expose your tissues. You probably planned on using the same contact frame to expose your separation negatives. But for film exposure it will be under a different light source, like an enlarger. An enlarger can be used with a contact frame and a Stouffer scale to make a sensitometer. So the Stouffer scale is something you will need to buy if you don't already have one.

Using the "sensitometer", you expose a grayscale on the film and develop it. The result will be 21 density values that you need to read with the densitometer.

One sheet of film exposed, developed and read, will give you one curve.

That curve will have a certain gamma (or Contrast Index = CI) measure of how steep the curve is. You developed it for a certain time. Maybe you developed the film 10 minutes and got a CI 0.48

That's one point (10, 0.48) of Time-CI.

Several of these tests at different development times (for example 4, 7 10, 13, 17 minutes) will give you several points on a graph you can connect to create a Time-CI curve.

For color you do all this work three times, once each for film exposed to light through the filters Wratten No. 25 Red, No. 58 Green and No. 47 Blue.

The graphs will also reveal the film "speed" including the filters, which will help you determine exposure later.

This testing will probably take a week or two of evenings work to accomplish. It's about 15 sheets of film, (really fewer sheets because you can cut the 8x10 down).

Now, having Time-CI for the different filters, you can use a little math to figure from the readings of your transparency, what CI will be required to reach the target (e.g., 1.5 to 1.7 density in the highlights) and figure out the exposure to reach the target (e.g., .3 to .6 in the shadows). Different filters give different results. The truism used to be that blue negative would need more time to reach the same contrast but @DREW WILEY mentioned things have changed (so expect the developing minutes to be longer for the green or blue filter negative - I don't know which but this testing will tell you).

 

[Bill Burk]

Meanwhile, absolutely check with @dkonigs to get a new densitometer. All the eBay ones may work - or might not.

I just bought a Blak Ray UV meter for about $50 all-in and the seller has one for the same price that looks just as good. I haven't seen these meters for a such a fair price in a long time, highly recommend you get it so you can verify your UV light source is good. (The bumps on the sensor allow you to slide it along a fluorescent tube to scan for dark spots).

 

[pkr1979]

Thanks for this - I'll get a stouffer scale. And maybe a black ray UV meter too

 

[ic-racer]

If you have experience fixing light meters, a transmission densitometer is essentially a light meter. Since they are frequently bigger than a hand-held light meter, they can be easier to maintain, calibrate or repair.

Otherwise, the prospect of a NEW one right now (dkonigs) is a unique opportunity you might not want to miss.

Personally, I have two of these made in USA Tobias models. They are nice because not only is Tobias still in business making and selling densitometers, they are able to supply some parts, and the schematic, service and owner's manual available. Note the construction with many discrete components that makes service and repair feasible.

 

[RalphLambrecht]

Hi all,

Im in need for a transmission densitometer. I see they sell for pretty different prices at ebay... but I have no idea what to look for.

Any advise anyone?

Cheers
Peter

I'm a big fan of Heiland densitometers;well worth the price!

 

[pkr1979]

There are 2 x-rite densitometers for sale where I live. One is just called 341, and the other 810. Where the later appear to be quite usefull...

Is there any reason not to get one of these? I mean since I'll be using it in relation to UV-light...

 

[AgX]

Basically a enlarging exposure meter can be used as densitometer. Already in the 80's there were such meters that yielded a direct read-out in logD.
The basic differenc with classic densitometers is that they got no own light source, but need an external one.

 

[nmp]

There are 2 x-rite densitometers for sale where I live. One is just called 341, and the other 810. Where the later appear to be quite usefull...

Is there any reason not to get one of these? I mean since I'll be using it in relation to UV-light...

Which one is the UV. As far as I know the 810 is not UV - it is dual transmission and reflective densitometer. Not familiar with the other one.

:Niranjan.

 

[dkonigs]

Speaking of densitometers for UV... One thing I'm still completely unaware of, is any sort of actual standard for what a UV densitometer is supposed to measure. And it really doesn't help that most densitometer manufacturers tend to be somewhat cagey about mentioning such things like spectral standards in their product specs.

For the majority of "ordinary" densitometers, there's the ISO 5 family of standards (formerly known as ANSI PH 2.19, I think). These go into great detail on exactly what is supposed to be measured, for things like "Status A", "Status M", "Visual", and several others. I can't recall seeing anything about UV explicitly mentioned in there.

I personally have two X-Rite 810s and a Heiland TRD-2, in addition to the one I'm in the process of developing. My personal opinion is that the X-Rite is a superior instrument (at least by design), but the Heiland is more compact and easier/quicker to use.

The X-Rite also suffers from age-related issues, so there's no guarantee that one you find on eBay is going to be performing at 100%.