DEAR NICHOLAS, Two things: 1) Don't many timer-controllers have integrators built in and wouldn't they compensate for any ramp up? 2) Due to the intermittency effect, the photographic effect of 10 five-second exposures may not equal the photographic effect of one 50 second exposure, depending on many factors. To completely avoid this, I set the timer with the metronome, ticker, or beeper on, to, e.g. 50 seconds. With a black piece of paper I cover all but one narrow band of the test strip. I then move the black paper every 5 seconds. This way, if I like the look at 20 seconds, it really IS 20 seconds not 4 shots of 5 seconds. So, unless you want to expose your entire print in 4 shots of 5 seconds each, you may be comparing apples and oranges. My method also eliminates the repeating problem of ramp up because this only happens at the beginning which is the greatest exposure band at 50 seconds and, even without an integrator, it will be a nearly insignificant part of that maximum exposure. I think Richard Knoppow will confirm these observations. CHEERS! BOB -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Nicholas O. Lindan Sent: Wednesday, December 19, 2007 8:38 AM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Determining lamp delay / ramp-up There is an application note on the subject of determining an enlarger's lamp turn-on time on the Darkroom Automation web site: http://www.darkroomautomation.com/support/AppNotePH212LampDelay.pdf Although aimed at users of the Darkroom Automation timer, the technique can be used with other timers. Delay is only important when making multiple additive exposures - such as test strip prints where the paper is progressively covered. When making test strip prints the lamp delay time should be subtracted to the determined exposure. The correction is: Corrected time = determined time - (number of the correct strip - 1) * delay time If the lamp delay is 0.16 seconds and strip #5, 17 seconds, is the correct exposure then the corrected time is: 17 seconds - (5 - 1) * 0.16 seconds ~= 16.5 seconds Incandescent lamps have a short delay time, a PH212 has a 0.05 second delay time. Cold light heads can have significant delay times that vary with the temperature of the lamp and the time between exposures so test prints should be made in a very consistent manner in order to be able to compensate a cold light head. Some timers have their own parasitic delay time that adds to the lamp's delay and makes additive exposures quite inaccurate. The technique described also compensates for the timer delay. -- Nicholas O. Lindan Darkroom Automation A Unit of Cleveland Engineering Design, LLC Cleveland, Ohio 44121 ============================================================================ ================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. __________ NOD32 2732 (20071219) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.