mcolella
15th of October 2003 (Wed), 04:22
I was looking for a way to have internal flash working with highest synchro speed (1/250) with the smallest lens aperture (F8) to get maximum DOF with minimum daylight interference in macro shots (http://photography-on-the.net/forum/showthread.php?t=18588) .
I did read about of a way to do it on G1/G2 called "f8 trick" but I also read that it does not work on G3/G5.
This is not true!
You can get the same result on G3/G5 of course with some differences. Here is a little of theory about the "trick" that is, according to me, a normal behaviour.
In Tv mode you set the shutter speed leaving the camera choosing the right aperture. To keep exposure correct, the camera will increase aperture (decreasing F value) as you will increase shutter speed; this is in normal light (no flash). What happens using instead flash? As you enable flash (we are still talking about Tv mode) camera will set maximum aperture (F2 on max wide angle or F3 on max tele) for shutter speeds up to 1/250 (which is max synchro speed for G3/G5) leaving to E-TTL circuit to fire flash in a controlled way to get right exposure. If you select a shutter speed faster than max synchro (above 1/250) camera understand you would like to reduce exposure but, since it can’t fire internal flash at speeds higher than 1/250, it will try to reduce aperture to compensate your needs. It means if you selected 1/500 instead of 1/250 then camera will choose F2.8 instead of F2 (W) or F4.5 instead of F3 (T) just one stop down (as you did selecting 1/500 instead 1/250). This will happen to full shutter speed range leading to have F8 at 1/1600 or 1/2000 on both W and T (should be noted that this process is linear up to 1/1250; 1/1600 and 1/2000 are affected by speed/aperture limitation shown at page 78 of G3 manual).
What does it means?
This is great for macro shots! You can shot at F8 (max DOF) using fastest synchro shutter speed of 1/250 instead of 1/60 (to avoid camera/subject shake due to daylight) still using full E-TTL flash exposition.
Is this helpful?
I did read about of a way to do it on G1/G2 called "f8 trick" but I also read that it does not work on G3/G5.
This is not true!
You can get the same result on G3/G5 of course with some differences. Here is a little of theory about the "trick" that is, according to me, a normal behaviour.
In Tv mode you set the shutter speed leaving the camera choosing the right aperture. To keep exposure correct, the camera will increase aperture (decreasing F value) as you will increase shutter speed; this is in normal light (no flash). What happens using instead flash? As you enable flash (we are still talking about Tv mode) camera will set maximum aperture (F2 on max wide angle or F3 on max tele) for shutter speeds up to 1/250 (which is max synchro speed for G3/G5) leaving to E-TTL circuit to fire flash in a controlled way to get right exposure. If you select a shutter speed faster than max synchro (above 1/250) camera understand you would like to reduce exposure but, since it can’t fire internal flash at speeds higher than 1/250, it will try to reduce aperture to compensate your needs. It means if you selected 1/500 instead of 1/250 then camera will choose F2.8 instead of F2 (W) or F4.5 instead of F3 (T) just one stop down (as you did selecting 1/500 instead 1/250). This will happen to full shutter speed range leading to have F8 at 1/1600 or 1/2000 on both W and T (should be noted that this process is linear up to 1/1250; 1/1600 and 1/2000 are affected by speed/aperture limitation shown at page 78 of G3 manual).
What does it means?
This is great for macro shots! You can shot at F8 (max DOF) using fastest synchro shutter speed of 1/250 instead of 1/60 (to avoid camera/subject shake due to daylight) still using full E-TTL flash exposition.
Is this helpful?