OK, I did test whether or not an ST-E2 can affect a light meter. My conclusion is, yes, it does.
I measure the GN of an ST-E2 at approximately 3.2 (feet) at ISO 100, over a range of 0 to 9 feet. The light meter does not respond to ST-E2 IR signals beyond about 9 feet. My light meter is a Minolta Flash Meter V. My ST-E2 is mounted on a D30. My measurements were performed during actual shutter releases (versus simply pressing the ST-E2 'test' button). The light meter is not sensitive to the IR autofocus signals from the ST-E2, only the communication IR signals that the ST-E2 emits right at shutter release time. I mounted my light meter and camera on tripods, and used a tape measure to set exactly the same height for the ST-E2 and the light meter (42"). I used the measure to record various distances between the ST-E2 and the light meter. I set the light meter to 'Flash' mode to eliminate ambient light interference. I used the flat measuring attachment, versus the dome, for GN measurement. I maximized the sensitivity of the flash meter by setting it to ISO 1600. Measuring from 9' away, actual measurement was f/1.0 + 0.9 at 1600 ISO. This converts to f/0.25 + 0.9 at ISO 100 = f/0.39. Multiplied by 9', this yields a GN of 3.5 (feet). Measuring from 6.6' away, actual measurement was f/1.4 + 0.4 at 1600 ISO. This converts to f/0.35 + 0.4 at ISO 100 = f/0.46. Multiplied by 6.6', this yields a GN of 3.0 (feet). I then averaged the two readings to equal 3.2 GN (feet) at 100 ISO. In summary, I conclude that an ST-E2 is equivalent to about a 3 GN (feet, 100 ISO) flash unit, up to about 9', with respect to influence on a light meter. Now I know why an optical slave plugged into a flash unit will get prematurely tripped when in the vicinity of an ST-E2. Best regards, Bill Neukranz -----Original Message----- From: Neukranz, Bill Sent: Thursday, January 10, 2002 10:48 AM Subject: RE: EOS RE: Flash meters with ETTL I hadn't ever thought about the Minolta flash meter being fooled by the ST-E2 (mounted on-camera) infrared signals. But since an optical slave (plugged into my non-550EX flash unit) can be fooled by line-of-sight ST-E2 IR signals, then I conclude it's possible the flash meter might be affected too. That's a good thought, and I'll test it. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
