Calibrate a Barbieri densitometer

[Michael Geller]

I have read other recent posts on densitometry but have not been able to apply to my situation.

This is my situation. I just purchased a Barbieri Densy 250, version 3.15e, manufactured in 1999. It came with the Operating Manual (April 1997 Edition) and the Transmission Calibration Tablet. Even so, I have been unable to figure out how to use the Transmission Calibration Tablet with the unit.

My questions are:
1) How do I use the Transmission Calibration Tablet?
2) Where can I get reference/control strips for C-41 and E6 that appear necessary to set a standard against which a sample can be judged?

The primary use for the unit is to measure Dmax for Ilford B&W negatives that I develop.

Any guidance would be greatly appreciated.

//Michael

[Len Middleton]

Michael,

Like most instruments, you will need to calibrate it for the zero value and the gain or range.

Check yor instruction to be sure, but typically for zero, zero the reading with nothing in the optical path between the lamp and the sensor.

I would be a little concerned regarding the actual value of your calibrated transmission tablet, as it may or may have not faded over the years, but otherwise might be a reasonable starting point. Anyways, after zeroing the unit then adjust the reading to match the value of the calibrated transmission tablet in the optical path between the lamp and sensor. Done.

Again read your manul to ensure what I suggested is corrrect, but really it should be that simple.

Hope that helps,

Len

[Michael Geller]

Len,

Wow! This is really helpful. Your explanation made all the difference. I was able to use the Transmission Calibration Tablet to set up the densitometer.

Next step:
Any ideas how I might get a copy of a C-41 and E6 control/reference strips? From what I read, these are needed to measure Dmax.

Regards,
//Michael

[Len Middleton]

Michael,

Not certain I fully understand your follow on request.

The densitometer will give you the density of your negative or transparency, including Dmax of the negative.

Are you looking for a reference on the Dmax for a particular film? I would expect that will come from the film manufacturers themselves as the film density and film curves may be different between different emulsions. In this situation, the actual calibration of your tablet becomes more important, as if it is off it could affect your copmparisons.

Hope you find that useful,

Len

[ic-racer]

Len,

Wow! This is really helpful. Your explanation made all the difference. I was able to use the Transmission Calibration Tablet to set up the densitometer.

Next step:
Any ideas how I might get a copy of a C-41 and E6 control/reference strips? From what I read, these are needed to measure Dmax.

Regards,
//Michael

Pre-exposed E6 control strips can be had at Adorama: http://www.adorama.com/KKE6CS.html?u...m_source=gbase

If you do a lot of this stuff you can make your own control strips with a sensitometer (that is what I do).

[Michael Geller]

Great questions!

This is the progress I have made so far. Not sue if any of this answers your questions but it’s worth a try.

After the device boots up, a screen pops up that reads “R,G,B tm ready” (the tm stands for transmission). It will read a negative placed underneath the measuring blade. There is no density option. Unless, it may be reading the denisty under R G & B. For example, I photographed a grey card on Ilford xp5+ and the first negative the reading is R 0.88, G 0.96 and B 0.73. On another photograph of a grey card at a different film speed, the reading is R 0.69, G 0.80 and B 0.53
After the reading pops up, nothing else happens.

Then, if I cycle though the menu options, I find this sequence:
“Read Control Strip C41,” followed by “Show Control Values,” then comes “Read Reference Strip” and what follows is “Edit Reference Values.”

If I select “Read Control Strip C41” the first reading is Yellow, which I suspect is the first of a sequence.

Please let me know your thoughts.

Regards
//Michael