IMFotograph
Hello
I’ve bought the large Adox filters.
Now I have a few questions about the extension factor for each gradient.
I measured the individual filters using the densi and arrived at the following result:
From filter 2: 0.15
3: 0.24
4: 0.56
My reasoning: the instructions for the Meopta Vario head state: 30 steps on the density dial correspond to one stop.
This means: when changing from gradient 2 to 3 (assuming 10 seconds at gradient 2), half a stop is added, i.e. 5 seconds, making it 15 seconds.
At gradient 4, 18 seconds.
At gradient 5, approx. 39 seconds.
Could my reasoning be correct?
uworischki
If you assume 10 seconds for gradient 2 and an increase of 0.24 seconds when switching to gradient 3 – I hope I’m interpreting you correctly; the factor would be 1.24, after all... then you have about 12.5 s; at gradient 4 and a factor of 1.56, that’s 15.6 s. I wouldn’t adjust it via the aperture, but via the exposure time. It’s simpler and more accurate.
MirkoBoeddecker
On top of that, the density does not correspond to the enlargement factor, as the sensitivity of the papers varies.
The filters are not grey but coloured, and specifically block one or the other ‘emulsion’ or individual ‘emulsion beads’ in single-layer mixed emulsions.
In multigrade papers, two types of emulsion with different sensitivities are mixed.
The soft (green-sensitive) and the hard (blue-sensitive). Depending on the filter used, only one or the other, or both in varying proportions, or (with Gradient 2) both equally, are activated.
These ‘emulsions’ or individual ‘beads’ (in single-layer mixed emulsions) are, as a rule, also of varying sensitivity.
This makes it almost impossible to deduce the extension factor from the density of the filter, and even then, only for a single type of paper after extensive testing.
Not to mention that those who use harder filters generally miss out on deep blacks (to put it simply). With a higher gradient, I can let in relatively more light without my highlights turning grey. This gives me more black, which is usually desirable.
For that reason alone, I wouldn’t work with factors (even if I’d tested them thoroughly) but would simply follow the old rule: new filter, new test strip!
All that maths is of little help in the darkroom if you’re working intuitively by eye and judgement (i.e. looking at the finished print and saying to yourself: good, too light or too dark).
You’ll get the fastest results with experience and intuition, not with a densitometer and a calculator, although using them at the start often helps you understand the relationships involved.
Best regards,
Mirko
