|
|
 | | Author | |
|
| | Date | |
|
|
|
|
Jorge Gasteazoro |
20:46 22 Sep 05 |
|
|
Miles Nelson |
22:25 24 Apr 05 |
|
|
Phil Davis |
8:09 25 Apr 05 |
|
|
Miles Nelson |
13:31 25 Apr 05 |
|
|
Miles Nelson |
19:53 25 Apr 05 |
|
|
Phil Davis |
7:15 26 Apr 05 |
|
|
Miles Nelson |
9:59 30 Apr 05 |
|
|
Phil Davis |
16:58 30 Apr 05 |
|
|
Miles Nelson |
18:38 30 Apr 05 |
|
|
Miles Nelson |
6:56 23 Apr 05 |
  |
I am in the process of calibrating my prsp.I have a ZoneVI 4X5 enlarger head. It is not bright enough to produce EV 4.0 at F/8 with a large enough circle. Besides, I wondered about the nature of flourescent tube light for the film test. I broke out my MINOLTA/BESELER 45A(the one with the flash tubes) which I used mostly for color seperation-Dye transfer work in the past. In short order I produced a set of 3 tmax100 test films dev in ddx 1+6 that when plotted in Winplotter produced a iso speed point of 2.25. If I am correct that means I needed to redo with 1/2 fstop more exposure to move the iso point to 2.4. I then adjusted the 45A's original setting of red50/blue50/green50 to red65/blue65/green65(each unit represents 1/30 of an f stop). The redo set was processed and plotted and the iso speed point was right @2.4 as predicted. The question has to do with reciprosity issues. The 45A is capable of the most precise and repeatable film exposures imaginable. Instead of changing ev values on the base board you simply dial in very exact units of change. However it is exposing the film with a series of computer controlled strobes. The total time the strobing is going on is 6 seconds. My theory is that the individual strobe pulses all added together give well under .5 second because each strobe pulse is extremely short in duration. What should I look for to see if there are reciprosity errors in this set up?
|
|
|
|
|
|
|
|
