[Alt-photo] 365 nm. UV-Densitometer .

[Erich Camerling]

Dear members,

In 1981 I developed and built my first visible-light densitometer ( 
calibrated with Kodak Wratten no.96 neutral density filters) that 
functioned very well in combination with silver negatives.

But in 2007 I had to go across printed colour negatives . And that gave 
me a lot of problems / troubles !

So I studied the article from Mike Ware :" An investigation of Platinum 
and Palladium Printing " ( The Journal of Photographic Science. Vol 34. 
1986 .page 13 - 25) and red that the maximum sensitivity in alt-photo 
processes ( like kallitype , argyrotype , VDB and platinotype ) is
~ 315 - 365 nm UV-light .Because I use Philips Cleo Bodycare fluorescent 
lamps ( 315 - 380 nm , peak 350 nm ) in a light box and found data 
about  Epson R 2400 inks = Ultrachrome K3 ( 
www.albertonovo.it/scan/epson_inks.html ) with a maximum A ( optical 
density  ( O.D.) ) for black , blue , cyan and green ink in the range 
between 330 nm and 360 nm. ( O.D. = ~ 3 ) I  started a search for a not 
too expensive densitometer in that range. ( X-rite 361T is measuring at 
380 nm for UV ( O.D. for inks = ~ 1.5 - 2.5 ) warm-up time 5 minutes ) 
and too expensive for me.($ 2850,=) But I couldn't find such a 
densitometer and then I decided to develop my own UV-densitometer.
Waiting for a 340 nm. LED didn't give a serious result , so I bought a 
Nichia UV-LED  : NCSU033B .  365 nm. ~ 325 mW @ 500 mA. Price ( In the 
Netherlands ) ~ EUR 80.=   as a UV light source.
For the sensor I bought an EPD-365-0-2.5 GaP-UV-photodiode  ( max. 
sensitivity  360 - 370 nm ) Price  EUR 75.= .

Then I started developing the electrical circuit. But unfortunately that 
was much more complicated then building a visible-light densitometer.!!
After a lot of attempts who all became a failure I became a little bit 
desperate.But a good friend of mine  would help me.And he did it on an 
incredible intelligent way.

So now I have a perfect working prototype 365 nm. UV-densitometer with a 
professional  quality  (  range D = 0,1 - 3.5 with delta D = ± 0.02 . No 
warm-up time )  for an amateur price: ~EUR 500.= when you-do-it 
-yourself !!!!!

To be continued next week.

PS. Because I had lessons in English more than 40 years ago there is a 
serious possibility that I will make grammatical mistakes.
         Please correct me (on my personal e-mail address ) and I will 
improve/rectify/correct  the text on internet.