This is copied from a previous post of mine on the subject:
...
Before those that don't like it start complaining, realize that I have 2 580EXs and a 550EX, lightstands, umbrellas, an off-shoe camera cord, a flash bracket (I prefer flash-flippers myself), diffusers and gels for my flashes, and I use bounce all the time when the flashes are actually on the camera.
Nevertheless, the pop-up has advantages, even over all of that.
First, the obvious - it's always with me. Nice for travel, nice when you didn't take a flash and an opportunity comes up, nice for saving weight.
Second. I rarely use flash for illuminating a dark scene. Personally I loathe the flash black-hole look, so I nearly always use flash for fill (altering scene contrast), not for brightening a dark scene (that's what the 5D and 35/1.4L are for). The 580EX has a 7 stop range, the pop-up only has a 5-stop range. But the pop-up is actually around 4 stops weaker than the 580EX. That gives 2 stops of range below 1:128 on the 580EX. There are times when even minimum power on the 580 is too much for gentle fill, especially with a nearby subject, fast aperture and high ISO. There are things that can be done, and I do use the diffuser panel and I do carry ND gels for the 580EX, but they're slow to use, especially if an opportunity comes up unexpectedly.
Finally, the pop-up is closer to the lens axis. Yes, I use a bracket and off-camera flash to get the light farther away and I know the reasons for doing that. However, there are plenty of good reasons to get the flash closer to the axis too. If there weren't, ring-flashes and powerful fashion ring lights (like the Alien Bees AB800) wouldn't be available. I've had to shoot macros through a hole before, and the 580 was totally blocked, but the pop-up did the job. It also leaves a much less obvious shadow (which is the reason for the big studio ring lights like that AB800).
...
Adam mentioned that third one as a benefit for macros. There are other benefits too.
Since I wrote the above, I've found the 580EX can go about 2-stops below the manual setting of 1:128 by using automatic mode. Weird, huh? But I haven't yet experimentally measured the pop-up yet, so that one might still apply, and it sure seems to in certain situations.
Anyway, yes, the pop-up has it's uses even for someone like me that has a lot of external lighting equipment.
For those that use the straw-man of the viewfinder to justify their irrational hatred of the pop-up flash, realize the Elan 7 is full-frame (film) with a viewfinder with very similar specs to that on the 5D, and it has a pop-up flash.
--
Lee Jay
(see profile for equipment)
...
Before those that don't like it start complaining, realize that I have 2 580EXs and a 550EX, lightstands, umbrellas, an off-shoe camera cord, a flash bracket (I prefer flash-flippers myself), diffusers and gels for my flashes, and I use bounce all the time when the flashes are actually on the camera.
Nevertheless, the pop-up has advantages, even over all of that.
First, the obvious - it's always with me. Nice for travel, nice when you didn't take a flash and an opportunity comes up, nice for saving weight.
Second. I rarely use flash for illuminating a dark scene. Personally I loathe the flash black-hole look, so I nearly always use flash for fill (altering scene contrast), not for brightening a dark scene (that's what the 5D and 35/1.4L are for). The 580EX has a 7 stop range, the pop-up only has a 5-stop range. But the pop-up is actually around 4 stops weaker than the 580EX. That gives 2 stops of range below 1:128 on the 580EX. There are times when even minimum power on the 580 is too much for gentle fill, especially with a nearby subject, fast aperture and high ISO. There are things that can be done, and I do use the diffuser panel and I do carry ND gels for the 580EX, but they're slow to use, especially if an opportunity comes up unexpectedly.
Finally, the pop-up is closer to the lens axis. Yes, I use a bracket and off-camera flash to get the light farther away and I know the reasons for doing that. However, there are plenty of good reasons to get the flash closer to the axis too. If there weren't, ring-flashes and powerful fashion ring lights (like the Alien Bees AB800) wouldn't be available. I've had to shoot macros through a hole before, and the 580 was totally blocked, but the pop-up did the job. It also leaves a much less obvious shadow (which is the reason for the big studio ring lights like that AB800).
...
Adam mentioned that third one as a benefit for macros. There are other benefits too.
Since I wrote the above, I've found the 580EX can go about 2-stops below the manual setting of 1:128 by using automatic mode. Weird, huh? But I haven't yet experimentally measured the pop-up yet, so that one might still apply, and it sure seems to in certain situations.
Anyway, yes, the pop-up has it's uses even for someone like me that has a lot of external lighting equipment.
For those that use the straw-man of the viewfinder to justify their irrational hatred of the pop-up flash, realize the Elan 7 is full-frame (film) with a viewfinder with very similar specs to that on the 5D, and it has a pop-up flash.
--
Lee Jay
(see profile for equipment)