Re: Step Wedge

From: Sandy King ^lt;>
Date: 11/11/04-05:40:49 PM Z
Message-id: <a06020437bdb9a52e8ed5@[]>


Actually, the level of precision specified is not that difficult to
obtain. It does require an exposure system based on light
integration, Metrolux II (control to 0.1 second with accuracy of
1/100 of a second) or a graphic arts integrator such as Olix, NuArc,
etc. And very accurate temperature control is possible with tube
development in water bath.

How much this may cost depends. In my own case I had the Metrolux II
and was using tube development before I began doing BTZS testing so
it did not cost me anything additional. Today there are many
integrators on the used market at almost give-away prices because of
the death of the graphic arts pre-press industry. Same is true of

If I had to replace my current equipment with equivalent quality I am
confident I could do so on the used market on ebay for less than $200.


>Your correct,...but.......
> Actually if thats the degree of accuracy you require, no
>home darkroom test is going to cut it. One requires a sensitometer.
>Controlled exposure duration and a host of temperature, agitation
>and process monitoring thats quite frankly beyond most of the
>applied users in this group. No slur intended.
> I tried while I worked for Omega to set up a very controlled
>test procedure that allow me repeatable results, I was constantly
>trying to Up grade what I was grudgingly given,....and was vastly frustrated
>by lack of time, and resources for doing the job right.
>On Nov 11, 2004, at 3:36 PM, 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.
Received on Thu Nov 11 20:53:38 2004

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