----- Original Message -----
From: "Dennis Johanson" <dennis.johanson@telia.com>
>> When looking into Ilford's fact sheets for Multigrade paper I find that they state the ANSI Paper Speed to be 500 for unfiltered paper, but when using their Multigrade Filters 00 - 3-3 1/2 the speed is stated to be 200, and for filters 3 1/2/-4 - 4 1/2-5 the speed is 100. Does this mean that I shall calculate with ISO 6,67 * 200:500 = ISO 2,67 respectively of ISO 6,67 * 100:500 = ISO 1,33,
>> since I have learnt that this Multigrade Paper without filter has ISO 6,67?
That would be a good starting point, just remember the ISO of paper is determined using a very specific type of light source. The paper's ISO speed in conjuntion with the use of filters may re-act different when the light source has "daylight" qualities. Variation may not be considerable, but since you use a precision of 2 decimals in the peper's ISO (6.67) I thought to mention it.
Another starting point would be to take a meter reading through the filter you are using.
Since you seem very accurate in your pinholing, this is what I recommend: make sure the pinhole is round, very clean and that you know the exact diameter (otherwise the ISO for one camera may not be 100% applicable to another one using a different pinhole). Find the f/stop of your camera and make an image assuming ISO-1.5 another with ISO-3 and ISO-6 and finally ISO-12, evaluate the results and decide how that paper behaves for you. Once you know the unfiltered speed you can do a similar exercise using filters, braketting +2 to -2 stops from the unfiltered meter reading using the ISO you found before.
BTW, the same paper for behaves as ISO-6 (unfiltered)
Guillermo
Received on Tue Jul 10 08:38:51 2001
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