24-105L, 50D and 580EX II

[Kryptix]

When using ETTL with the 580EX II on top of my 50D, it changes the flash zoom to whatever the lens is zoomed to (24-105mm), but as the 50D is a 1.6 crop it's actually gunna be wrong, isn't it?

 

[Garry79]

Short answer is no it won't be wrong.

I'm sure someone will be along soon with a longer and more detailed answer.

 

[chris321]

There's another little logo on the screen at the back, it looks like a rectangle with some lines in it...... that means it's recognised the size of the sensor, and will adjust accordingly (or so it says in the manual I believe!)

Chris

 

[Kryptix]

Oh ****, I'm stupid. I just realised... Ignore this post.

 

[andrewc]

My 430Ex IIRC detects a crop sensor camera and adjusts itself so that its not wasting energy lighting parts of the scene that isn't covered by the sensor. I'm sure the 580EX2 would do this as well.

 

[Kryptix]

There's another little logo on the screen at the back, it looks like a rectangle with some lines in it...... that means it's recognised the size of the sensor, and will adjust accordingly (or so it says in the manual I believe!)

Chris

Surely it's actually the same focal length, just a narrower field of view so the actual distance never changes...?

 

[chris321]

Yep, so I think it's only supposed to illuminate what's actually seen by the sensor.

One major new feature for digital shooters is that the flash now knows the sensor size of the EOS 20D (and EOS 1D Mk II with firmware update), and zooms the flash head to give full coverage over only the area seen by the sensor. The 550EX did not do this, and so, for example, "wasted" energy illuminating the 24x36mm frame outside that covered by the 22x15mm sensor