useing a densitometer to read a pyro neg

[mitch brown]

hi
i want to have the local lab use there color densitometer to read my pyro test neg are ther any issues ? i belive i read somewhere about useing a blue filter. can anyone help.
thanks
mitch

 

[Roger Hicks]

hi
i want to have the local lab use there color densitometer to read my pyro test neg are ther any issues ? i belive i read somewhere about useing a blue filter. can anyone help.
thanks
mitch

Dear Mitch,

This is an example of false precision.

Unless you have a solid grasp of what densitometer readings mean with different coloured light, the reading are worthless.

You also have to be able to relate YOUR densitometer readings to YOUR enlarger/paper/preferences.

Sorry to appear rude, but what do you expect to learn from these readings?

Cheers,

R.

 

[mitch brown]

i am trying to establish FB+F .10 for a film speed test.
thanks
mitch

 

[Roger Hicks]

i am trying to establish FB+F .10 for a film speed test.
thanks
mitch

Dear Mitch,

Ooooooh.... Not all that meaningful. Unless YOU can take repeated density tests, I'd dispute any use at all.

0.10 was chosen for at least two reasons: originally (DIN standard) easy to measure with crude densitometers, then (revised ASA standard c. 1959) suitable for Delta X contrast criterion. You can print 0.03, and 0.05 is more than adequate for most applications.

Without being unduly cynical/dismissive, I'd suggest (if you want reasonably objective criteria) that you shoot a step wedge (I use an old Agfa wedge, but Stouffer is better), dev and print.

More enthusiastically, I'd be in favour of shooting real subjects and printing them. When the majority of subjects print on grade 2 or 3, your exposure and dev time are about right.

Your 'failures' in the testing process will still be printable but an interactive process -- +/- 1/3 stop and +/- 10 per cent dev time with each step -- will zero you in to perfection.

Cheers,

R.

 

[jd callow]

By following Mr Hick's advice you will have denied your self a fetish enjoyed by more than a few people.

 

[lee]

Have them use the blue channel

lee\c

 

[photomc]

Have them use the blue channel

lee\c

would agree with lee, though a bit more information could help.

If you plan to use the information to print say Plt/Pld vs graded or variable contrast paper, you might want to have them use a UV channel if they have one. What size negative, you say film test but what type of image...there are a large number of variables, that will probably match responses to this thread...some find the information of little or no value to those that find it most usefull.

Good luck either way.

 

[Tom Hoskinson]

To evaluate pyro stain density use either the densitometer's blue channel or the UV channel (if it has one).

 

[Robert Hall]

UV, of course, if your light source will be UV. If you are printing silver, you may only have a halogen type source. Measuring UV will not help much at all.

If you print in silver, color readings on the densitometer will render poor information at best.

You may be well served to call Fred Newman at the View Camera Store and chat about such things. He has testing available as well. It may be what you are looking for.

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Best of luck.

 

[Tom Hoskinson]

UV, of course, if your light source will be UV. If you are printing silver, you may only have a halogen type source. Measuring UV will not help much at all.

If you print in silver, color readings on the densitometer will render poor information at best.

You may be well served to call Fred Newman at the View Camera Store and chat about such things. He has testing available as well. It may be what you are looking for.

Dead Link Removed

Best of luck.

I contact print Pyro stained negatives on Azo (Silver Chloride) Paper. Azo is UV sensitive.


If you are contact printing or enlarging pyrogallol or pyrocatechol stained negatives on UV sensitive paper (with a UV light source) then UV channel (or blue channel) densitometry will yield very useful Contrast Index and other D logE information.

Search for Sandy King's many APUG posts on this topic - or PM him.