BTZS.org Message Boards


Film & Paper Testing Film & Paper Testing Discussions

Messages 441 to 450 of 653 (Total: 653)

First | Prev | Next | Last

Subject

Author

Date

Re: How are you going to replace DDX?

Fred Newman

10:29 23 Sep 04

Re: How are you going to replace DDX?

David Rude

9:10 24 Sep 04

Shutter vrs Enlarger Timer

Larry Francis

13:18 16 Sep 04

IS THE FOLLOWING ANALYSIS CORRECT?

As a result of all my recent film testing, I began thinking about mounting a large shutter in place of an enlarger lens on my enlarger. I was thinking the shutter would be more accurate at 0.5 seconds than my Kearsarge timer in combination with the Aristo cold light head. The Kearsarge is probably repeatable, but the lamps in the Aristo may create variance due to ramp up/ramp down of the light cycle; and the lamps put out different amount of light depending on how warm they are. So my first reaction was: leave the lamp on and use a shutter to control the duration of 0.5 seconds.

But I'm now thinking that control (more light vrs less light) will affect the "film speed" of the curve but not the gradient of the curve. Yes, five exposures that were dramatically different may impact your PSP, but a Kearsarge/Aristo combination is not likely to produce that much variance. And in the final analysis the gradient curve from the Plotter program will not be affected by 5 exposures that aren't exacly 0.5 seconds.

So, moderate variances in time/light may impact the curve's film speed, but not impact the curve's gradient. As a result I am not going to go the expense/time to fabricate an accessory to my enlarger to accurately control time/light during film test!