Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
11-26-2009, 09:39 PM   #1
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 10,836
Manual power levels with an Auto Flash

Auto flashes are handy when used on their own. They use a thyristor to shut off the flash once the exposure has been deemed sufficient by the flash.

When using multiple flashes in conjunction, however, it is best to set their power levels manually, i.e., not let the flash decide which output level to use.

Many Auto flashes do not allow the setting of the power level but here's a trick to get at least one manual level:

If one blinds the photo diode with which the flash measures the exposure (say with a opaque tape), the flash will always go full power with respect to a particular setting. Depending on the level chosen, this will result in a consistent flash output, corresponding to a manual power setting.

The Vivitar 2500 has four settings:
  • M (manual) = full power
  • blue (auto setting 1) = up to full power
  • red (auto setting 2) = up to ~1/3 power
  • triangle (autowinder mode) = 1/8 power
So with this flash one can achieve three output levels: full, ~1/3 (requires blinding of the photo diode), and 1/8.

I suspect that one of the auto setting of an auto flash will always go up to full power. I wouldn't make sense if the flash weren't trying to give "its best".

P.S.: When using older flashes, always make sure that their trigger voltage is not too high when using them on-camera.

Last edited by Class A; 11-30-2009 at 02:41 AM.
11-26-2009, 09:57 PM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 49,684
I've copied this thread into the articles section as requested. Please add any future improvements here:

Feel free to continue discussion here as needed.

Adam Webmaster (Site Usage Guide | Site Help | My Photography) server and development costs are user-supported. You can help cover these costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:


  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
auto, exposure, flash, flashes, level, levels, lighting, output, photo studio, power, power levels, strobist
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Manual power levels with an Auto Flash Class A Photography Articles 1 11-27-2009 12:29 PM
Auto power shut down on the AF 360FGZ Russell-Evans Pentax Camera and Field Accessories 4 06-26-2009 01:05 AM
For Sale - Sold: Multiple Auto (Digital & Film) and Manual Lenses, flash + more jjdgti Sold Items 18 10-03-2008 09:30 AM
540FGZ & auto power off Groundloop Pentax Camera and Field Accessories 4 05-28-2008 11:29 PM
Optio W10 and Auto-Levels betsypdx Pentax Compact Cameras 0 08-29-2007 11:06 PM

All times are GMT -7. The time now is 12:30 AM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]