highscore
Hi everyone
After giving it a lot of thought, I’ve finally gone and bought a densitometer on eBay.
And now I’m sitting here in front of it and I’m not quite sure how to use it. (don’t laugh)
It’s probably an older model from Bacher KG
Model: Bacher RT1 Type 3200
Features:
One small and one large sensor
Three buttons: 1. on/off 2. lamp on/off 3. reset measuring unit
The internal lighting is provided by a 15-watt fridge bulb
When I measure the (botched) strip of negatives I made as a test (using the small probe), I get plausible readings.
0.08, 0.74 and 1.2; I’ve zeroed out the base fog.
Now my questions:
Does anyone know this device or have a manual for it?
How do you think I should make a good test strip? I’ve read a lot about it, but......
Does this device display the correct density values straight away, or do I need to do some calculations?
Thanks
Highscore
moma
Hi Highscore
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Your Densi displays logarithmic values. I can’t tell you off the top of my head how to convert these – but you can find that online.
A test strip is nothing more than a graduated grey scale – you used to be able to buy them (maybe you still can :-?)
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If you have constant conditions – such as fresh developer, the same temperature and times – you can, in principle, measure your negative density and work out the exact exposure time needed to ‘produce’ the first shade of grey on the paper.
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In gravure printing, an isodensity chart used to be created. It’s nothing more than graph paper with density (logarithmic values) and time (development) plotted on the coordinate axes, and the resulting positive density (in this case, front-view (!) – photographic paper) (note the distinction between front-view and back-view measurements) is plotted as a curve.
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Once you have done this – provided the negative density (and perhaps also the density range (= highest density minus lowest density)) is known – you can read off your exposure and development times.
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The more accurate you are when plotting the isodensity curve, and the more consistent your environmental conditions are afterwards, the more foolproof your system will be.
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Hope it helps
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:-)
highscore
Hi Moma
At the moment, I'm a bit confused by the calculation formulas.
And besides, it's far too hot in the lab ;-)
moma
High score
You don’t need to do any maths.
I only wrote that so you’d understand what sort of values he’s spitting out there.
Light travels in squares – logarithms are linear. That’s why.
:)
highscore
Hi MoMA
Well, that puts my mind at rest then ;-)
Because my second test strip produced results that left me puzzled
I’d done the exposure too quickly.
My third one’s still waiting. It’s too warm
But anyway
Does anyone recognise my camera?
Regards
Highscore
