In a message dated 7/2/05 10:48:01 AM, power_windows4789@yahoo.com writes:
Brian, properly hypered tech pan should have between
> a
> .7 and 1 ND base fog. Otherwise its damn clear. So
> what does that look like? Get an ND filter set from
> a
> photo store and go see...
Brian:
I disagree somewhat.
The usually accepted target base fog density for hypered Tech Pan film is 0.6.
This means that the density of an unexposed but developed area of the film reads 0.6 on a transmission densitometer. To the eye it appears more than slightly grey.
What is the 'correct' base fog level?
That depends on your optical system and the object you are imaging.
If you're going after really faint fuzzies with an F10 SCT you'll want 0.6 abd process 10 minutes in D-19 @ 68 degrees F. If you are after brighter objects with faster systems you might want 0.4 or 0.5 and process for only 5 or 6 minutes. This is the case with my Schmidt Camera which is f1.5. If you use HC110 dilution B (for less contrast) you'll have to run some tests for yourself.
You can take the test film to a photolab and they will usually gladly read he density for you.
Even the camera shop or 'moto photos' will do it as well.
The above suggestion about getting a set of Neutral Density filters and use these as a comparison is another solution. Kodak makes a whole line of Gel ND filters in 1/3 f-stop increments; 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, etc. They come in 2x2 and 3x3 inch sizes. You can somtimes find them at flea-market type camera shows for a few bucks each.
Kent Kirkley
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