Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,707   Posts: 1,548,544   Online: 1124
      
Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 27
  1. #11

    Join Date
    Jul 2004
    Shooter
    Large Format
    Posts
    193
    Has anybody actually tried it? I did. Not telling what I found. You'll learn a lot in two, or maybe even a single sheet of paper.
    Bruce Barlow
    author, "Finely Focused" and "More Finely Focused"
    www.bwbarlow.wordpress.com

  2. #12
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,574
    Images
    1
    Quote Originally Posted by BBarlow690 View Post
    Has anybody actually tried it? I did. Not telling what I found. You'll learn a lot in two, or maybe even a single sheet of paper.
    Yes, I have.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  3. #13
    Nicholas Lindan's Avatar
    Join Date
    Sep 2006
    Location
    Cleveland, Ohio USA
    Shooter
    Multi Format
    Posts
    2,376
    Images
    4
    2 + 2 does equal 4; heck, 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 20 -- if the timer is accurate and you compensate for any lamp warm-up time. However, if you have a cold light head without a shutter, or the least an integrating/compensating timer, it probably isn't possible.

    The following application note on the Darkroom Automation web site gives a method how to determine lamp warm up time:
    http://www.darkroomautomation.com/su...2LampDelay.pdf
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  4. #14
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,574
    Images
    1
    Quote Originally Posted by Nicholas Lindan View Post
    2 + 2 does equal 4; heck, 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 20 -- if the timer is accurate and you compensate for any lamp warm-up time. However, if you have a cold light head without a shutter, or the least an integrating/compensating timer, it probably isn't possible.

    The following application note on the Darkroom Automation web site gives a method how to determine lamp warm up time:
    http://www.darkroomautomation.com/su...2LampDelay.pdf
    Nicholas

    Are you saying: the intermittency effect does not exist?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #15
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,289
    Images
    148
    No he's saying you can have an "inaccurate timer" that takes it into account

    i.e. has a additional time added to compensate. So 2 secs is 2 + enough milliseconds to compensate for the ramp up/down time, but it would need to be calibrated for different light sources.

    Ian

  6. #16
    Nicholas Lindan's Avatar
    Join Date
    Sep 2006
    Location
    Cleveland, Ohio USA
    Shooter
    Multi Format
    Posts
    2,376
    Images
    4
    Quote Originally Posted by RalphLambrecht View Post
    Are you saying: the intermittency effect does not exist?
    The 'intermittency effect' is an effect of the quantum response of a silver salt crystal to a photon of light. In conventional emulsions a crystal has to be hit at least twice with a photon within a certain period of time. If too much time passes between photon hits then the crystal 'relaxes' and is not activated (exposed) when the second photon hits. This is the principle behind reciprocity failure, where the photon flux is so low that too much time passes between photon hits and therefore extra exposure time is required to statistically assure a double-hit. It is also the principle behind intermittency where an exposure is paused and the pause time is long enough to allow the crystal to relax and become 'unexposed' again. The critical photon inter-arrival period varies between emulsions - as evidenced by the different reciprocity and intermittency factors for different films and papers.

    The lack of interimittency is the reason for the excitement about 'single photon' emulsions - it's not so much that they are twice as sensitive as that there is no reciprocity failure.

    Intermittency has little to no effect in the range of exposure times encountered in printing with printing paper emulsions. See the experimental results in the application note. Or make your own instrumented or shuttered experiments and draw your own conclusions. Or, See Meese, et. al., again....

    Intermittency effect has nothing to do with lamp warm-up and stabilization time.
    Last edited by Nicholas Lindan; 07-25-2010 at 01:52 PM. Click to view previous post history.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  7. #17
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,574
    Images
    1
    Quote Originally Posted by Nicholas Lindan View Post
    ... Intermittency effect has nothing to do with lamp warm-up and stabilization time.
    Nicholas

    I agree with your statement above, but I don't think anybody claimed that. In my experiments, the intermittency effect is strong enough to through a regular test strip off by up to 1/12 stop.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #18
    Nicholas Lindan's Avatar
    Join Date
    Sep 2006
    Location
    Cleveland, Ohio USA
    Shooter
    Multi Format
    Posts
    2,376
    Images
    4
    Quote Originally Posted by RalphLambrecht View Post
    but I don't think anybody claimed that
    I think it was in one of the references you gave, last two paragraphs:

    http://jbhphoto.com/articles/intermit/intermit1.htm


    Quote Originally Posted by RalphLambrecht View Post
    In my experiments, the intermittency effect is strong enough to through a regular test strip off by up to 1/12 stop.
    What was your test protocol?

    In my experiments a 1 second error accumulated from 20 x 1 second exposures - that is 5% or 0.07 stops or 1/14th of a stop. Adding a 50mSec correction to each exposure removed the error. It may have corrected intermittency but as with the correction 30 x 1 = 1 x 30 and 10 x 1 = 1 x 10 the effect seems to be entirely lamp warm-up time, as confirmed by the measurement of the turn-on and turn-off light output measurements shown in the application note. Additionally, the required correction time changes if a ferroresonant stabilizing transformer is added to the system.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  9. #19
    Anscojohn's Avatar
    Join Date
    Dec 2006
    Shooter
    Medium Format
    Posts
    2,727
    Images
    13
    All things being equal (if they ever are!?), it is reciprocity failure.
    John, Mount Vernon, Virginia USA

  10. #20
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,574
    Images
    1
    Quote Originally Posted by Nicholas Lindan View Post
    I think it was in one of the references you gave, last two paragraphs:

    http://jbhphoto.com/articles/intermit/intermit1.htm...
    Nicholas

    Cut me some slack here. I referenced that article for the OP so he could read up on the intermittency effect, but I never claimed that this effect has anything to do with lamp warm-up. They are totally unrelated.

    Quote Originally Posted by Nicholas Lindan View Post
    ... What was your test protocol?

    In my experiments a 1 second error accumulated from 20 x 1 second exposures - that is 5% or 0.07 stops or 1/14th of a stop. Adding a 50mSec correction to each exposure removed the error. It may have corrected intermittency but as with the correction 30 x 1 = 1 x 30 and 10 x 1 = 1 x 10 the effect seems to be entirely lamp warm-up time, as confirmed by the measurement of the turn-on and turn-off light output measurements shown in the application note. Additionally, the required correction time changes if a ferroresonant stabilizing transformer is added to the system.
    Fair enough. You are right. There are several effect at work here: intermittency, lamp ramp-up/down and stabilized-transformer delay.

    I can adjust my timer to compensate for it. My transformer delay was measured at 400 ms, and I'm not fully aware of my lamp ramp-up/down. I will measure it and ask Phillips for the data sheet to compare. Unless that's done, I can't really measure the effect of intermittency.

    I have modified my enlarger to mount a large-format lens and shutter, but LF shutters are not accurate enough (+/- 1/6 stop) to reliably measure intermittency either.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

Page 2 of 3 FirstFirst 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin