Canon 430ex flash in manual with Av

01/08/2008 08:30:24 AM · #1

When I put my camera in Av mode, set the flash to manual mode, switching to lowest output setting (1/64 power)... the camera shutter automatically sets itself to 1/4000. Why would it do that? Why would it be designed that way?

I basically just want to turn off the pre-flash and fire the flash at lowest power ... hoping to be able to rattle off 3 or 4 continuous shots with flash, but I don't want to put the camera in M mode - which would force me to pay attention to the exposure, which I'd like to ignore.

Am I missing something?

01/08/2008 10:03:43 AM · #2

"can you hear me now?"

dwterry

Canon EOS-1D Mark III

01/08/2008 10:04:07 AM · #3

Unless something is wrong ....

In Av mode, your camera doesn't even care that you have a flash. It sets the shutter speed according to the ISO and Aperture that you have set. Therefore, I can only conclude that you had sufficient light coming into the camera that, with the ISO and Aperture you picked, 1/4000 was the proper shutter speed.

In Av mode, the only thing your camera does with a flash, when the flash is in manual mode, is tell the flash to go off. In eTTL mode, the camera does a pre-flash and measures the amount of light and tells the flash how much power to put out on the real flash. But that does *not* change the shutter speed. In Av mode, the camera computes the exposure (shutter speed) based on ambient light (ISO and aperture), completely ignoring the flash. Flash is used for fill only.

01/08/2008 10:05:58 AM · #4

it happens with the lens cap on

:)

Originally posted by dwterry:

Therefore, I can only conclude that you had sufficient light coming into the camera

dwterry

Canon EOS-1D Mark III

01/08/2008 10:07:05 AM · #5

Originally posted by hopper:

it happens with the lens cap on

:)

That's why I led off with the first sentence "Unless something is wrong...". :-)

01/08/2008 10:08:33 AM · #6

also, if I don't click the high speed button, it locks the shutter at 1/200 (max sync). So it's obviously telling the camera to go to the max ... I just don't know why.

with the flash in auto mode ... it works exactly a you describe ... but with a pre-flash

edit to add: custom function 3 is set to 0 (which is auto, not fixed to max shutter speed)

Message edited by author 2008-01-08 10:09:58.

dwterry

Canon EOS-1D Mark III

01/08/2008 10:11:28 AM · #7

What's the shutter speed if you turn the flash off?

Also, is the flash seated all the way on the hot shoe? (any chance the contacts are just slightly off?)

01/08/2008 10:19:10 AM · #8

I just found this:

"If youâ��re in Av mode the shutter speed will be the cameraâ��s X-sync speed and you can manually set the aperture. In M mode you can set the shutter speed to any value from 30 seconds to the cameraâ��s X-sync and the aperture to anything within the lens range."

Taken from here:

//photonotes.org/articles/eos-flash/index3.html

So I guess it's doing what it's designed to do. Complete mystery to me why it would do that.

Next question ... When the flash is firing just for fill (flash in auto mode and camera in Av mode), does the preflash actually fire? I just assumed it does.

01/08/2008 10:51:47 AM · #9

the x-sync is 1/200th though.

i just tried on a 10d - camera in AV - flash in manual at 1/64th - shutter goes automatically to 1/200th. ( 430ex & 550ex both )

do you have high speed sync turned on?

Message edited by author 2008-01-08 10:56:40.

01/08/2008 10:55:33 AM · #10

high speed sync forces the shutter to 1/4000

useless

Originally posted by soup:

the x-sync is 1/200th though.

i just tried on a 10d - camera in AV - flash in manual at 1/64th - shutter goes automatically to 1/200th.

do you have high speed sync turned on?

01/08/2008 10:57:02 AM · #11

by the way, thaks David and Tim for trying to help out ... and anyone else that should happen to chime in

:)

01/08/2008 10:57:09 AM · #12

no - not necessarily.

01/08/2008 10:57:49 AM · #13

true. useless for what i'm trying to do

Originally posted by soup:

no - not necessarily.

01/08/2008 10:59:58 AM · #14

why not set the camera to manual - the shutter to 1/200th and the desired aperture.

set the flash to manual at whatever power you want. if you're trying to balance ambient and flash light - you'll likely need a slower shutter speed anyway...

sounds like a glitch though...

Message edited by author 2008-01-08 11:01:06.

01/08/2008 11:05:21 AM · #15

I want the fastest possible shutter. Here's what I got, and what I want:

200/2.8 with 2x extender, 430ex flash, monopod

shooting birds, animals, whatever i find in january in the northeast :(

Av mode set to f5.6 in order to get the fastest shutter, but because I'm walking around and whatnot, I don't want to have to check for proper exposure ... hence Av mode.

I want fill flash, lowest possible flash output, no pre-flash

Problem: as soon as you put the flash in M mode, Av is rendered useless due to the fact that the camera automatically sets the shutter to either 1/200 or 1/4000

M exposure mode would solve this, but then I wouldn't have auto exposure

Originally posted by soup:

why not set the camera to manual - the shutter to 1/200th and the desired aperture.

set the flash to manual at whatever power you want. if you're trying to balance ambient and flash light - you'll need a slower shutter speed anyway...

sounds like a glitch though...

01/08/2008 11:17:57 AM · #16

the maximum reach of the 430ex at 1/64th power and 105mm zoom is 18feet.

according to the manual.

Message edited by author 2008-01-08 11:18:10.

Telehubbie

Canon EOS-40D

01/08/2008 11:18:07 AM · #17

Maybe try the camera in P mode, and dial in a 5.6 aperture and see what shutter speed it gives you. You might at least be able to see if it's a glitch only in Av mode.

01/08/2008 11:31:32 AM · #18

Most likely true ... but firing the flash even at lowest power will put a catch light in the eyes of an animal from pretty far away. The flash won't be lighting the scene at all.

Originally posted by soup:

the maximum reach of the 430ex at 1/64th power and 105mm zoom is 18feet.

according to the manual.

Message edited by author 2008-01-08 11:32:24.

01/08/2008 11:32:09 AM · #19

It's not a glitch, canon designed it that way ... I just don't know why

Originally posted by Telehubbie:

Maybe try the camera in P mode, and dial in a 5.6 aperture and see what shutter speed it gives you. You might at least be able to see if it's a glitch only in Av mode.

01/08/2008 11:46:00 AM · #20

it doesn't do that with either of mine though - never has...

Originally posted by hopper:

It's not a glitch, canon designed it that way ... I just don't know why

never tried the catchlight thing the way you are talking though.

01/08/2008 11:49:59 AM · #21

Originally posted by soup:

it doesn't do that with either of mine though - never has...

Originally posted by soup:

i just tried on a 10d - camera in AV - flash in manual at 1/64th - shutter goes automatically to 1/200th. ( 430ex & 550ex both )

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

01/08/2008 11:55:22 AM · #22

never 1/4000th...

i can change it from 1/200th to whatever below that.

if i turn on high-speed-sync in AV mode the shutter is set at 1/200th not 1/4000th. ( but i can't adjust the shutter speed above - or below for that matter - because i'm in AV )

why not use TV? as thats more what high speed sync would be aimed at.

you'll still get the auto metering with the aperture changing. maybe not ideal - but you almost always have to compromise one factor or another.

Message edited by author 2008-01-08 11:57:44.

SamDoe1

Canon EOS-350D Rebel XT

01/08/2008 12:11:58 PM · #23

I can set my flash (Sigma EF500 Super) in manual mode and the camera in Av and still have it go lower than 1/200th when needed. The camera meters for the ambient (as if the flash wasn't there) and just triggers it. I have to manually set the flash exposure but it works. The fact that it forces 1/200th or 1/4000th just seems odd to me and it shouldn't behave that way...well really shouldn't cause mine doesn't. Maybe it's a difference among the flashes?

01/08/2008 12:43:30 PM · #24

ok, now I'm stumped ... that doesn't seem to be high-speed-sync mode if it still stops at 1/200?

Originally posted by soup:

if i turn on high-speed-sync in AV mode the shutter is set at 1/200th not 1/4000th.

As far as using Tv mode ... I'd rather gets the fastest shutter speed possible on each shot, not lock it in to one setting