{PLEASE NOTE: This was posted on photo.net a few days ago, but it timed out after receiving 2 responses (much appreciated), and part(b) of my question was not answered.}

EOS 3 body and speedlight 550EX

(a) Is it normal that; when turning on the flash, and in Av, Tv, and M exposure modes, the ambient light meter pattern is always evaluative, regardless of what pattern is actually set?

(b) Is it normal that; when turning on the flash, and in Av or Tv exposure modes, if the ambient light levels fall below around EV 9 (ISO 100), the camera begins to underexpose the ambient exposure? And by around EV 7, ambient exposure is 1 stop underexposed? This was confirmed by switching to M mode and/or turning off the flash. This behavior exists even if there is no difference in light levels between subject and background (like a blank wall).

The E-mail response (within about 1 hour) was that the camera needed to be serviced. I followed up by phone, and the tech said that behavior (a) is normal, but (b) is not.

Now before I send my 3 week old camera to NJ for service, can those of you with this equipment confirm what I was told by tech support? My Elan II does not behave in this manor.

-- kenneth katz (socks@bestweb.net), September 21, 2001

Answers

As far as "a" is concerned, you might want to try manually selecting (on the flash) "TTL" rather than "E-TTL" flash mode.

-- kurt heintzelman (heintzelman.1@osu.edu), September 29, 2001.

AV and TV modes should behave differently. In TV mode, ambient exposure should depend on your available aperture, so at some point (depending on the amount of light, but probably not at a set EV) you should expect underexposure of the ambient light. With AV mode, you should not have underexposure of ambient light, as the camera should automatically go into slow sync mode. Unlike some EOS cameras the EOS 3 has no custom function to defeat this and force X-Sync in AV mode, so it sounds like there is something wrong.

-- Brad Hutcheson (bhutcheson@iname.com), October 01, 2001.

Postscript:

Last week in Stamford CT, a Professional Market Representative for Canon was demonstrating equipment at a local camera store’s “tent sale”, so I took this opportunity to test his EOS 3 and 550EX, and try to duplicate the results I got with my equipment (behavior “b” described above). Sure enough, if the meter was reading f2.8 @ 1/10 @ ISO 400 in Av with the flash off, once the flash was turned on and charged (lighting bolt signal in viewfinder), the shutter speed suddenly jumped to 1/20. And as before, in M mode, the shutter speed stays a 1/10 with the flash on or off. I then repeated this with an EOS 1v and got the same results.

Given this experiment, it seems reasonable to assume that my EOS 3 is operating normally.

-- Kenneth Katz (socks@bestweb.net), November 01, 2001.

Hi Kenneth,

I use a 420EX with my EOS50E/ElanIIE and experience the same behaviour. I think it´s not a problem, but e feature of the speedlites. The camera is waiting for an *READY* message from the speedlite, until then it is behaving like there was no flash attached. That with came to my mind when I saw it, but I will keeping watching this tread, if it appears to be a problem I will be at the doorstep of my suplier the next morning...

Jorrit

-- Jorrit de Jager (jager@isl.is), November 09, 2001.

I just tested my 3 month old eos-3. In case b) I got the same results. I guessed the modes can be ordered like this: 1) P mode 2) Av Tv 3) M

So, only M mode esimates the ambient ligth "correctly". All other modes use some algoritm to balance ambient ligth and flash.

--alex

-- alex f. (afomitchev@hotmail.com), January 04, 2002.