Site Sponsors
Results 1 to 11 of 11

Thread: Precision of Flash

  1. #1
    Member
    Join Date
    Mar 2010
    Location
    Switzerland
    Posts
    206
    Post Thanks / Like

    Precision of Flash

    How exact did you photographers find the output from your flash (mono and generator)? Normally you can make 1/10f steps. But already when you test it from one full stop to the other, what is your experience? Anyone made a test?
    When I go from 4 to 5 (one fill stop) and I measure it with a Sekonic 558, then its only 1/2 stop. Sometimes at higher level its much more precise. Also, the 7stops fits exactly, but with finer steps and lower levels...
    Or see I something wrong?
    Thanks, rem






    (I tested it with the new Hensel Porty 1200L and the new Hensel Expert D"

  2. #2
    Super Duper
    Senior Member
    Godfrey's Avatar
    Join Date
    Jan 2009
    Location
    Near San Jose, California
    Posts
    7,926
    Post Thanks / Like

    Re: Precision of Flash

    Quote Originally Posted by rem View Post
    How exact did you photographers find the output from your flash (mono and generator)? Normally you can make 1/10f steps. But already when you test it from one full stop to the other, what is your experience? Anyone made a test?
    When I go from 4 to 5 (one fill stop) and I measure it with a Sekonic 558, then its only 1/2 stop. Sometimes at higher level its much more precise. Also, the 7stops fits exactly, but with finer steps and lower levels...
    Or see I something wrong?
    Through testing with a flash meter and experience. I ignore what the manufacturers' output ratings are.

  3. #3
    Member
    Join Date
    Mar 2010
    Location
    Switzerland
    Posts
    206
    Post Thanks / Like

    Re: Precision of Flash

    Yes Godfrey. But on the other side it would be practical if you now that when you reduce one Stop on the flash it is also one stop in the light and not only 1/2 f stop...
    Anybody measured with his flashes? Thanks!

  4. #4
    Super Duper
    Senior Member
    Godfrey's Avatar
    Join Date
    Jan 2009
    Location
    Near San Jose, California
    Posts
    7,926
    Post Thanks / Like

    Re: Precision of Flash

    Quote Originally Posted by rem View Post
    Yes Godfrey. But on the other side it would be practical if you now that when you reduce one Stop on the flash it is also one stop in the light and not only 1/2 f stop...
    That's the point of making my own measurements. Once I've measured the response curve of the flash unit, I know what the settings will produce.

  5. #5
    langone_peter
    Guest

    Re: Precision of Flash

    I found this flash disappointing. I am not a professional photographer but I am experienced and have owned Cannon SLR's and done some medium format photography. To the positive it does tilt, swivel and the flash head does have a 4 position zoom shroud. It has an auto sensor that is designed to adjust the power of the flash. It comes with a PC cord which the instructions indicate, "is NOT required for normal use,"

    Regards,
    Peter Langone

  6. #6
    Super Duper
    Senior Member

    Join Date
    Nov 2007
    Location
    Royal Oak, MI and Palm Harbor, FL
    Posts
    8,498
    Post Thanks / Like
    Images
    44

    Re: Precision of Flash

    Quote Originally Posted by rem View Post
    How exact did you photographers find the output from your flash (mono and generator)? Normally you can make 1/10f steps. But already when you test it from one full stop to the other, what is your experience? Anyone made a test?
    When I go from 4 to 5 (one fill stop) and I measure it with a Sekonic 558, then its only 1/2 stop. Sometimes at higher level its much more precise. Also, the 7stops fits exactly, but with finer steps and lower levels...
    Or see I something wrong?
    Thanks, rem

    (I tested it with the new Hensel Porty 1200L and the new Hensel Expert D"
    How are you performing this test?

    Distance from strobe head to subject will affect meter readings ... pretty drastically actually.

    Did you test everything as a constant (same modifiers, same distance to subject, and same position/direction of the meter)?

    Just for kicks, I just ran a test like this using my Profoto D2400 generator and one head with a beauty dish modifier. Constant placement/direction of the Sekonic Flash Master L-358 light meter with built-in Pocket Wizard trigger, and I did multiple separate pops to be sure at each setting.

    The meter was set 27 inches away from the front of the beauty dish, and was directly facing it.

    Lowest setting is 19w/s @ f/9 every time ... 38w/s @ f/11 ... 75w/s @ f/16 ... 150w/s @ f/22 ... 300 w/s @ f/32 ... as so on. These are full click steps on the D2400 digital control dial.

    At 19 w/s, when I moved the meter 6 inches further away ... 6 inches! ... the f stop dropped from f/9 to f/8, and at a 9 inches away it dropped to f/7.1 and 2' more inches away it dropped to f/6.3 ... I was able to repeat this multiple times.

    Moral of the story is that tests must be extremely consistent in distance to meter ... especially when the inverse-square law is applied as the distance from the light grows further (where a subject at twice the distance receives only 1/4 the energy).

    -Marc

  7. #7
    Senior Member johnnygoesdigital's Avatar
    Join Date
    Mar 2010
    Posts
    1,579
    Post Thanks / Like

    Re: Precision of Flash

    +1 for the inverse square law. Also, when measuring a multiple light set-up, make sure the white diffuser is pointing directly at the light to be measured, recessed into the meter itself, so as to NOT be influenced by the others. As Godfrey mentioned, knowing the response curve regardless of what the manual says, usually produce good consistent results.

  8. #8
    Super Duper
    Senior Member

    Join Date
    Nov 2007
    Location
    Royal Oak, MI and Palm Harbor, FL
    Posts
    8,498
    Post Thanks / Like
    Images
    44

    Re: Precision of Flash

    Quote Originally Posted by johnnygoesdigital View Post
    +1 for the inverse square law. Also, when measuring a multiple light set-up, make sure the white diffuser is pointing directly at the light to be measured, recessed into the meter itself, so as to NOT be influenced by the others. As Godfrey mentioned, knowing the response curve regardless of what the manual says, usually produce good consistent results.
    Or turn off the other flashes and measure each one separately.

    -Marc

  9. #9
    Senior Member johnnygoesdigital's Avatar
    Join Date
    Mar 2010
    Posts
    1,579
    Post Thanks / Like

    Re: Precision of Flash

    Quote Originally Posted by fotografz View Post
    Or turn off the other flashes and measure each one separately.

    -Marc
    Right, that probably makes more sense.

  10. #10
    Member
    Join Date
    Mar 2010
    Location
    Switzerland
    Posts
    206
    Post Thanks / Like

    Re: Precision of Flash

    Marc, shure, I fixed everything, so the Distance, the Sekonic, the Reflector etc. I made also everything in the atelier with black and grey walls, to avoid any uncontrolled lights. From minimum to maximum is perfect 7 stops, but not so between. Will see, how the new one is working....

  11. #11
    Member
    Join Date
    Mar 2010
    Location
    Switzerland
    Posts
    206
    Post Thanks / Like

    Re: Precision of Flash

    To update, yesterday I received the new Porty 1200L. No bigger difference then 2/10 stops and very linear. ;-)
    rem

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •