[pure-silver] Re: Determining lamp delay / ramp-up

Yup, that'll work.
                HOLIDAY CHEERS!
                        BOB

-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of C.Breukel@xxxxxxx
Sent: Wednesday, December 19, 2007 10:30 AM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Determining lamp delay / ramp-up

Bob, 

If one would use a test strip printing device as described in Ralp
Lambrechts "Way beyond Monochrome", one exposes only one part of the
negative (usually the critical highlight with everytime the complete
exposure, move the teststrip in the  holder and expose the same stop
again , this time longer (in my case 1/4 F stop).

Best,

Cor

> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-
> bounce@xxxxxxxxxxxxx] On Behalf Of BOB KISS
> Sent: woensdag 19 december 2007 14:16
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: Determining lamp delay / ramp-up
> 
> 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
> 
>
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