External Flash Metering with Canon 580EX II

GadgetRick

Recently, there was a thread about which Canon flash for someone to buy. Someone mentioned the external flash metering capability on the 580EX II. So, being the curious sort of photog I am, I decided to give it a try using this page which was posted as a guide.

Now, what I don't understand is exactly why I need these two extra modes (Manual and Auto) as it seems the External Metering: Manual is the same as if I'd put the flash in manual and set it up manually. And External Metering: Auto seems like E-TTL to me. I'm confused on what the differences are and why I'd use these modes over doing it the traditional way (i.e. manual on flash or E-TTL).

Thanks.

angevin1

GadgetRick wrote:

Recently, there was a thread about which Canon flash for someone to buy. Someone mentioned the external flash metering capability on the 580EX II. So, being the curious sort of photog I am, I decided to give it a try using this page which was posted as a guide.

Now, what I don't understand is exactly why I need these two extra modes (Manual and Auto) as it seems the External Metering: Manual is the same as if I'd put the flash in manual and set it up manually. And External Metering: Auto seems like E-TTL to me. I'm confused on what the differences are and why I'd use these modes over doing it the traditional way (i.e. manual on flash or E-TTL).

Thanks.

have a look in this thread: http://www.dgrin.com/showthread.php?t=165205

GadgetRick

Thanks! Not sure why I missed that thread but it's excellent!

ziggy53

The manual mode of the flash and the "Auto" mode are important for using the flash away from the camera and without camera automation.

If you have the flash attached to the camera, and if the camera is in manual mode, the flash can still be in a fully automated mode (E-TTL II is the default mode). In other words, the manual mode of the camera does not necessarily affect the operation of the flash.

Manual mode of the flash gives you full manual output control so that the flash is not "tricked" by any ambient circumstances like a highly reflective background or a subject that is very light or very dark. In full manual mode on the flash you can determine flash output by the distance to subject and the effective guide number, which is the most accurate method possible (once you calibrate the flash to your system to determine the effective guide number.)

"Auto" mode means that the flash uses a simple on-board flash sensor to determine flash output. It's not (potentially) as accurate as either using camera exposure automation or even manual flash settings, but it's completely autonomous and may be used to provide automatic flash control for "average" scene values. (You can also increase or decrease the sensitivity of the "Auto" sensor by adjusting the ISWO setting, accommodating known variations in scene density.)

GadgetRick

I understand all that, however, just trying to understand the external auto/manual as it seems like it's exactly like the, "normal," auto/manual on the 580EX II. You can set the external auto/manual via the menus on the body and you set the, "normal," auto/manual directly on the flash.

Just rather confusing what the difference is--if any.

ziggy53

GadgetRick wrote:

I understand all that, however, just trying to understand the external auto/manual as it seems like it's exactly like the, "normal," auto/manual on the 580EX II. You can set the external auto/manual via the menus on the body and you set the, "normal," auto/manual directly on the flash.

Just rather confusing what the difference is--if any.

If you have a "very" recent Canon body, it's true that you can use the camera to program those flash features on the camera from a menu. It's just an optional programming interface.

If you have the flash off of the camera and disconnected from the camera, then you "must" use the flash based interface, of course.

Taken to the extreme the Canon Speedlite 270EX has no display at all and no real controls on the flash for advanced functions and programming the flash is accomplished only through the host camera.

GadgetRick

Ah, I get it now. That's more for the older bodies which didn't give you the option to set it in the body. Now it makes sense!

I knew I could count on you Zigmeister General!

pathfinder

Ziggy, as I readtht link - the External auto mode, is that of the older style thryistor based auto flash like the Vivitar 285hv.

But Canon provides two distinct flash AUTO ( non ETTL ) modes - one fully manual which means you have to coordinate the appropriate aperture just like with the Vivitar between camera and flash, AND an automatic mode, which means the flash will sense the aperture set by the camera via the preflash info.

Is this correct?

ziggy53

pathfinder wrote:

Ziggy, as I readtht link - the External auto mode, is that of the older style thryistor based auto flash like the Vivitar 285hv.

But Canon provides two distinct flash AUTO ( non ETTL ) modes - one fully manual which means you have to coordinate the appropriate aperture just like with the Vivitar between camera and flash, AND an automatic mode, which means the flash will sense the aperture set by the camera via the preflash info.

Is this correct?

I'm not sure that I understand the question, but I'll proceed as if I do understand. This may be more than you were asking, but hopefully it will answer other questions too.

On the Canon 580EX II, there is a Custom Function "05" with 4 settings numbered 0-3.

Setting number "0" is the default setting for both normal attached and detached (wireless) modes of operation on a modern Canon digital SLR.

Setting number "1" is for Canon film cameras only (Type "B" cameras I believe).

Settings numbered "2" and "3" are what I think you refer to and question.

If I understand correctly (no guarantees), setting number "2", the "External Metering: Auto" is a new mode and only works with specific Canon cameras. (The Canon 1D MKIII is mentioned as a compatible camera.) In this mode the flash's meter senses the scene and sends exposure information back to the camera, rather the inverse of normal wireless E-TTL/E-TTL II operation. Since this mode only works with "some" Canon cameras and since you are limited to a single flash as well, I suspect that the number of useful situations is rather limited.

Setting number "3", the "External Metering: Manual" is the auto-thyrister mode (I believe) and it is very similar to an older "Auto" mode flash unit, clamping the flash output when the desired and selected output level has been achieved, according to the flash's built-in sensor (and autonomous from the camera).