BTW keith, you can set the 600RT or 580EX to an external metering built in the flash unit non TTL (thyristor). Go to your flash custom function and switch it external metering.
The Canon 600rt specs don't list a metering capability, and metering in the flash unit is not mentioned in the 600rt users manual Index
Could you provide a link or some direction to the information on in-the-flash-unit metering? I would like to learn more about this feature in Canon speedlites.
The 2nd (darker) image is a bit unusual since Charlie's EXIF viewer says you used center-weighted metering (Don't do that when using flash. You're fighting the E-TTL II system and not letting it do it's job.)
The reflected metering system on a camera wants to assume a "middle gray" (used to be 18% but now it's almost always 12% gray). When you point it at a dark point, it wants to assume it should be capable of being "middle" gray and probably just needs more light. So it'll fire more light to attempt to compensate. This has the undesirable consequence over over-exposing the things that really were middle gray and blowing out things that were high tones.
I grabbed my 5D II body (I usually shoot a 5D III these days, but I still have and occasionally use the 5D II), one of my 600EX-RTs, set the camera to ISO800, f/5.6 and 1/60th (to mimic your settings) and did some test shots playing with the metering modes against both white backgrounds and black backgrounds.
As expected, if I switched to spot mode and allowed the center point to be on a black background, all the non-black things in the foreground were over-exposed. In evaluative mode it was correctly exposed.
The 5D II will use "E-TTL II" mode (more advanced that E-TTL) with that flash. E-TTL II will read focus distance information from the lens (assuming your lens supports it, but most lenses do.) HOWEVER... distance info can ONLY be used if the flash is (a) on the camera and (b) not being bounced (pointed straight at the subject.) Generally you want to bounce or feather the flash whenever possible -- or even get it off the camera or use it in conjunction with external lights (e.g. a side-light). The problem with this is that while the camera may "know" how far the focus distance is from lens to subject, it does NOT know how far away your external lights are, nor does it know how high up your ceiling is when bouncing. That means it can't use distance info (and it knows how to detect this and wont even try) when any of those situations are true. As soon as you tilt the flash head to any position other than straight-ahead, the distance measuring data is no longer used. NOW it's going by how much of a difference it reads at with two different metering measurements. It pre-meters the scene (using no flash). Fires the pre-flash while simultaneously metering the scene again. It compares the difference between the non-flash and pre-flash metering instances to see how much of a difference the pre-flash made. It then uses that info to decide how much power to use when the shutter is open. Since you used spot metering, it was not allowed to take into account anything about your subjects (and they're basically the only thing you cared about getting exposed correctly.) That's what I meant when I said you're not letting the E-TTL II system do it's job.
What really surprises me about that 2nd image is that I would have predicted that with your settings that not only would you not get a correct exposure, you should have had an over-exposed shot (and I'm really surprised you didn't. I cannot re-create your result with my camera and flash and I'm using the same camera, flash, and settings that Charlie says you are using.) This makes me wonder if you haven't dialed in some flash exposure compensation and didn't realize it (the EXIF data doesn't include that info, but then it also doesn't include the lens info either and usually it does. Your image only contains partial EXIF data. The camera would have included that data when it saved the image.)
Check your Flash Exposure Compensation... on the 5D II, the third button (from the left) on the top (in front of the top LCD) is the ISO/flash± button. Press that, then the rear dial can increase or decrease flash exposure compensation. You typically want this at "0" for normal flash power when indoors and using a single light. I decrease this usually to about -1 when shooting outdoor in daytime and using the flash as fill.
In summary...
1. get out of spot-metering mode and go back to evaluative.
2. check your flash exposure compensation and make sure you didn't inadvertently change that.
I use spot-metering in concert venues, but I'm specifically targeting that center point on my subjects face to meter their skin when I use that mode. If you use spot metering, make sure you are taking the meter reading off of something reasonably close to a middle-gray value. It doesn't have to be perfect (you've got lost of adjustment latitude in post production as long as it was reasonably close. Especially avoid black or white.)
421
317
290
272
269
232
197
181
168
162
145
140
135
126
103
