Sandy King (sanking@hubcap.clemson.edu)
Sun, 17 Jan 1999 13:15:43 -0400
Hi Richard,
>
> What kind of step wedge would you suggest?
What you need is a 21 step wedge that reads in .15 log increments (for
example, the first step will read .05 (B+F), the second .20, the third .35,
etc.). These are availabel from Kodak, Stouffer (219.232.7989), or Darkroom
Innovations (602.767.7105). Step wedges come calibrated (very expensive)
or uncalibrated (much less expensive), the only difference being that with
a calibratd one you know the exact reading of a given step, say 1.27 for
step 9. With an uncalibrated wedge the density of step 9 will vary
somewhat, say between 1.25 and 1.35 (and you won't know exactly what it
is). This difference is not important in most photographic applications.
To calibrate your unit, get a step wedge, read one of the steps, then
adjust the rading on the Weston by turning the dial until the log reading
on the display corresponded to that reading. I would use one of the
mid-zone steps, say # 9, that should read about log 1.25. Remember,
starting from clear base the wedge should read something like this.
1. .05
2. .20
3. .35
4. .50
5. .65
6. .80
7. .95
8. 1.10
9. 1.25
Of course,the most accurate thing thing would be to have someone with a
calibrated densitometer read one of the steps for you, then use that one to
calibrate your meter.
>
> I notice there's a button on the front of the arm, and when pressed
>releases
>the top part that contains some kind of mirror which is connected to a
>long cord.
>What is the use of this?
I am not sure about this function. The buttom would seem to merely serve to
release the measuring instrument from the housing, for possible servicing?
>
> I got this machine for about $70 with shiping from Canada. I mainly
>want it to calibrate Panatomic-X film for the zone system (thin based film
>made for the
>military. I've got a 5" by 1000 feet roll of it. I'm cutting it down
>to fit my 34 Graflex reflex camera. The thin base wouldn't work in tanks,
>but I prefer tray development. Anyway, I didn't want to spend a small
>fortune on a digital Macbeth.
I used the Weston Analysizer for quite some time before eventually acquirng
a MacBeth TD504 Analog color densitometer. If caliabrated it will prove
quite accurate in reading the log densities of B&W negatives.
Hope this helps.
Sandy King
>
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