Re: Step wedges

Keith Schreiber (StillPoint@worldnet.att.net)
Fri, 22 May 1998 01:38:08 -0700

Oops. The diagram below did not survive the trip through cyberspace. Sorry.
I hope you all get the idea.

Keith

>>What is the practical difference between the two mentioned above? Could I
>>produce something myself cheaper?
>>
>>Dwight
>
>
>Okay, Dwight. I've been thinking about this all day and I think I've got
it.
>You need a sheet of film with even density of 0.15 cut into 20 strips of
>whatever width you like - let's say 1". Then let's make each step 1/4" wide
>so then we cut the 1" wide strips into pieces of 1/4, 1/2, 3/4, 1, 1 1/4, 1
>1/2, 1 3/4, 2, ..., and 5". There are only 20 because for step 1 (which
>approximates unexposed film base) we'll use a piece of 0.05 density. Here
is
>a diagram:
>
> ---- 21
>
>-------- 20
> ---
-
>-------- 19
> -------
-
>-------- 18
> -----------
-
>-------- 17
> ---------------
-
>-------- 16
> -------------------
-
>-------- 15
> -----------------------
-
>-------- 14
> ---------------------------
-
>-------- 13
> -------------------------------
-
>-------- 12
> -----------------------------------
-
>-------- 11
> ---------------------------------------
-
>-------- 10
> -------------------------------------------
-
>-------- 9
> -----------------------------------------------
-
>-------- 8
> ---------------------------------------------------
-
>-------- 7
> -------------------------------------------------------
-
>-------- 6
> -----------------------------------------------------------
-
>-------- 5
> ---------------------------------------------------------------
-
>-------- 4
> -------------------------------------------------------------------
-
>-------- 3
> -----------------------------------------------------------------------
-
>-------- 2
>---------------------------------------------------------------------------
-
>-------- 1
>
>Not only would this would this provide a step-wedge of 21 increments of
0.15
>density, it would be shaped like a wedge as well with 1 film thickness on
>one end and 21 on the other which would make it about 1/4" thick. This
>probably wouldn't work to well if you print with a diffuse light source.
>:-o
>
>We could use this wedge as a "master" from which to make as many single
>layer step-wedges as we need. Choose a film/developer combination that
>yields as near to a straight line response as possible with minimal base
>density (maybe TMX developed in Tmax RS which has a long straight line with
>no shoulder to speak of and very little toe). Figuring out exposure and
>development times will be the hard part.
>
>If anyone tries this, let us know if it works.
>
>Cyantifically yours,
>Keith
>
>
>
>
>