Re: Step Wedge

From: Sandy King ^lt;>
Date: 11/11/04-04:27:28 PM Z
Message-id: <a06020435bdb9971d42d0@[]>

For some reason I had it in mind that you wanted to compare of
different film, or perhaps of different developers. For what you have
in mind I think the method you suggest is certainly valid.

On a practical note, remember to take into account the B+F density of
the step wedge. This should be about log 0.05, or about 1/3 of a
stop, so you should probably increase your metered exposure by about
this much.


>I wasn't really planning on doing any hard core film comparisons with the
>test- just basically wanted to see if my shutter and lens and lightmeter
>are giving me close to the density that I am hoping to achieve when I make
>an exposure. Also, I was hoping to plot the curves using a few different
>development times to visualize the effects of plus and minus times.
>Since my negs are destined to be scanned, and corrected, and ultimately
>digitallly printed on film for contact printing, if my results are a 1/10
>stop off here or there, I could probably still sleep!
>On Thu, Nov 11, 2004 at 03:36:39PM -0500, Sandy King wrote:
>> Etienne wrote:
>> >
>> >As an abstract exercise (especially for someone who, like me, occasionally
>> >whips up his or her own negative emulsion for fun), it's interesting to
>> >know what the film does, on its own. But when I load my holders, I'm after
>> >the most direct understanding of what my negatives are going to look like
>> >when they come out of the Jobo, and rolling all of the relevant practical
>> >factors into the material characterization gives me this.
>> >
>> But my point is not that practical testing in the camera is not
>> relevant, but simply that it is invalid as a means of comparing EFS
>> of different films. For that you need a system with a common light
>> source and some control that permits repeatable exposures to an
>> accuracy of about 1/10 of a stop.
>> Sandy
Received on Thu Nov 11 20:50:40 2004

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