Preliminary Flash Inquiry

for Digital Rebel looking at the following flash units:

Sigma EF500 DG Super
Canon 420EX
Canon 550EX

so i get it the model numbers ( 500, 420, 550 ) refer to its output power but exactly what is the definition of this Guide No. thing ? how much more power does 55 have than 50 ?

also from Sigma's page for EF500 DG Super it seems that it doesnt support red eye reduction for EOS !? and from another page it appears Sigma has a host of other issues ...

can somebody outline in general terms what tradeoffs we are looking at with these 3 flash units ? ( i dont really want to consider 580EX because Rebel supposedly does not have E-TTL2 anyway )



?

http://www.chem.helsin​ki.fi …s/photo/flash-faq.html#gn" target="_blank">GN numbers explained

MT wrote:
http://www.chem.helsin​ki.fi …s/photo/flash-faq.html#gn" target="_blank">GN numbers explained

thanx for the link, looks promising, i am falling asleep right now but i will get to studying it when i am in condition to do so.

The Guide Number is the Maximum Distance a flash can travel at ISO 100 at f/1.0 It is a very useful number because the Maximum Distance your flash can travel at a particular f stop is expressed as the Guide Number / F stop at ISO 100
Distance = GN / f stop

For ISO 200 multiply by 1.4
For ISO 400 multiply by 2

This is useful for comparing flashes and using manual flash. Keep in mind though, that manufacturers may exaggerate their GN's.
Scott

One big thing to note between the 420 and 550 is that the 550 can be fully manual. The 420 is completely controlled by the camera, which means that you only have FEC to limit/increase flash output. The DRebel doesn't have FEC unless you use the hacked firmware, and even then you only get +/- 2 stops of control. This might not be so important depending on what you shoot. If you mostly do family gatherings and general/average use of the flash then it might be insignificant. But if you use the flash at the extremes then it will definitely make a difference.

Fill flash in extreme situations can also be an issue with a 420 because of this. If you need/want to add just a tiny amount of fill flash then the 420 is just about useless IMHO.

Extremes... I do almost all wildlife shooting. For macro photography (butterflies mainly) I found that I get too close for ETTL to be effective, and every shot was basically blown out because ETTL couldn't possibly stop the flash output in time. With the 420 it was all hit or miss because ETTL couldn't do it's job. Yes, I could set up the camera for f/22 but then I lost all the nice background blur and had to settle for longer shutter speeds. I ditched the 420 and got a 550 which I could then set to 1/32nd power or 1/16th or whatever. It's now a manual process but I can make it work with the 550.

My reasoning for getting the 550 works for me - it may mean nothing to you. The 550 is a lot more expensive than the 420, so think hard.

so uhm, no word on sigma ?

No, the model numbers are just model numbers. You need to look at the guide numbers in the specs of each unit. You can find them at www.canonusa.com and www.sigmaphoto.com And the 580EX is slightly more powerful than the 550EX plus it boasts a recycle time half that of the 550EX. I probably would have gotten the 580EX if I hadn't just bought the 550EX before the 580EX was announced.

Hellashot wrote:
No, the model numbers are just model numbers. You need to look at the guide numbers in the specs of each unit. You can find them at www.canonusa.com and www.sigmaphoto.com And the 580EX is slightly more powerful than the 550EX plus it boasts a recycle time half that of the 550EX. I probably would have gotten the 580EX if I hadn't just bought the 550EX before the 580EX was announced.

The model number is not the guide number but the model number is based on the maximum guide number (in meters) of the flash for all the Canon flashes (at leat the EX series flashes). For example, the 580EX has a GN of 58, the 550EX, GN of 55, etc. The same goes for the Sigma 500 DG flashes, too.

Hellashot wrote:
No, the model numbers are just model numbers. You need to look at the guide numbers in the specs of each unit. You can find them at www.canonusa.com and www.sigmaphoto.com And the 580EX is slightly more powerful than the 550EX plus it boasts a recycle time half that of the 550EX. I probably would have gotten the 580EX if I hadn't just bought the 550EX before the 580EX was announced.

Not actually true.
For Canon EX Series Flashes, the first two numbers of the flash are is the Guide Number.
550EX = 55M
420EX = 42M
580EX = 58M
Scott

I'll add the further clarification that the Canon guide numbers are the MAXIMUM guide numbers, and the refer to a single optimal flash zoom length. In the 550EX book, the guide numbers range from 15 to 55, expressed in meters, of course.

---Bob Gross---

Ahem, looks like I beat you guys to the punch.

So somebody tell me. Sigma 500DG Super or 420EX...

Sigma 500DG Super is more versatile, like the 550EX. I recommended it to my brother and I wouldn't have any reservations about adding it to my own 550EX and 420EX collection.

so the alleged bugs on sigma arent too terrible ?

also what is the difference between "USA" and "Imported" versions of canon flashes that they have at phphotovideo ? i live in USA by the way.

Warranty issues I believe. The "Imported" doesn't have the USA Warranty...