I already have a Canon 580EX II already which I use primary as a main flash. I'm trying to get into off-camera flash and also multi-flash. I also brought the YN-622c to start with, this way I can already do 1 light off camera. So, even if I buy the YN-568EX II, it will be use mainly as slave. I read that YN-500EX has guide number 53 which the YN-568EX II has 58. The true is, I have no idea exactly what that mean in the real world nor do I trust the claim. So, how big is the different between YN-500EX vs YN-568EX II in the real world? Obviously I pick these two because they support HSS which I may use very often.
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
If picture worth a thousand words, how many megapixel is it?
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
I know it's a little late, but I hope it helps.
(I don't have either of these flashes, but I'm on the same path as you are. I already have a 580EX II and a 430EX II, and thinking about adding another a flash, or two, to my arsenal.)
The difference in price aside, YN-500 is still about 2oz (50g) lighter and compacter than 568EX. It looks to me that it has about the same size and weight of 430EX. It may not seem a lot if you're a professional photographer who has to move a ton of gears around. But if you're like me, every inch of space in your bag, and every ounce of weight off your back, is a miracle.
Besides, if 0.5EV less power is your only concern, you can always compensate that by a couple of tricks and techniques. Having said that, I personally rarely reach the 58GN limit of my 580EX II (i.e. shooting through an umbrella in a bright sunny day while trying to under expose the background).
Well of course, you need to know which one works for you for your particular purpose at that moment but here are a couple of tricks I can think of:
1. Switch flashes. If you already have a 580EX II use it in the most power demanding position. Use the YN-500 for less demanding lights and angles.
2. Get it closer! Getting your light a few inches closer can easily compensate 0.5EV.
4. Compensate it with ISO, F stop, or Shutter speed or a combination of them. I can hardly think of a situation in which I absolutely can't play with any of these three and have to entirely rely on my speedlight.
4. Get help from a fill light. (either a reflector, ambient light, or any kind of available light, even a an iphone led!)
6. Remove\minimize light modifiers.
7. ZOOM it! The GN increases when you zoom your light. If your shooting outside with a 85mm lens, there's barely any advantage in having wide zoom on your flash. I'd go even further and say try 105mm. Because A) you'r subject is not filling the frame. B) At times, you'll end up a with a nice vignette.
8. Add some Exposure in post processing. People do much more drastic changes than 0.5EV compensation and that you won't be ever able to notice.
The bottom line is, the difference in power between YN-568 and YN-500EX is most probably not going to hold you back. Unless you're absolutely sure that you're going to need that extra power, go with the YN-500EX and enjoy the compact size of it, and save up a couple of dollars for your next ventures.
