SV: Exposure times for paper as film with filter

Dear Guillermo

Thank you very much for a most elaborate answer. I felt quite lost since my exposures didn't come out at all as expected, and after having gone through the whole procedure from the start the only thing I could think of was the filter factor. Your kind answer gives me new inspiration and tomorrow I will put my former cake tin in a black plastic garbage bag, meet the world and create ART (Inshallah).

Yes, I normally try to do things in a correct way, but maybe not to the extent that I measure ISO for pinhole camera paper by two decimals. The reason for this is that I found an excellent site regarding pinhole camera at http://www.oberberg-online.de/%7Ereincke/ where the figure was stated as 6 2/3, and that is what I converted to decimals. Although the site is in German I could highly recommend it even to not German speaking photographers since the tabular statements are very clear, come in logical order and are very easy to use.

I used part of a disposable aluminum pie form for the hole and took a 0,5 mm pin to drill very carefully with. Then I sanded with a very fine paper that came with a spray can for touch ups on my car. I repeated the procedure from the other side of the aluminum and then once more from the original side. Through a magnifying glass my second try seems to be a rather round hole with clean edges and also close to the desired diam of 0,65 mm. I drilled a 3 mm hole in the cake tin, glued the aluminum on the outside of the tin and then made a little hole in a piece of carton larger than the aluminium which I put on top of and glued outside of the aluminum. This way my pinhole is somewhat protected and easy to change.

I shall follow the procedures that you suggest and will most surely get on the right track. Just one little note though. I think that a meter behind a filter in some cases doesn't react the same way as at least a film. Metering without a filter and then adding the filter factor will probably give a more precise result - all right, I am very accurate.

Kind regards

Dennis

----- Original Message -----
From: G.Penate <penate@home.com>
To: <pinhole-discussion@pinhole.com>
Sent: Tuesday, July 10, 2001 2:38 PM
Subject: Re: [pinhole-discussion] Exposure times for paper as film with filter

>
> ----- 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
>
>
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Received on Tue Jul 10 16:44:53 2001