Is 420Ex fully compatible with 40D?

Does 420EX can be used in 40D body? Do I need to set FEC whenever I do a flash photgraphy?

Would I get an inconsistence flash output even if I do an FEC setting?

Is it when I mount 580EX-II the flash is smarter than 420EX in calculating correct exposure?

i just used my 420ex on my 40d earlier tonight. Had no problems other then dead batteries in the flash.

420ex is the same as the other E-TTL flashes and should give you the same results and will work fine on all current newer bodies. It should meter the same automatically and such as the 430ex (its replacement). Main difference is in the controls and extra features.

https://photography-on-the.net/forum/showthre​ad.php?t=113838

Thanks FYI. Then I would keep my 420Ex.

I'm planning to get a 580EX-II. Can I use 420Ex as a slave? If yes do I need to buy any wireless controller/adaptor/oth​er accessories?

The 580 when set to master will fire the 420. Indoors it works fine but it is spotty when outside.

Thanks goforphoto.I notice that for the 420Ex is taking indoor potraits, the flash range is quite short.

I used to direct flash (since bounce would shorten its power) and increase ISO (i.e up to 1600 depending on lighting condition) but with no satisfactory result.

The best result obtain tend to be in a range of 6-9feets.

Would the 580Ex II helps me in that situation?

Also with 580Ex II can I lower the ISO up to 100 if it's not that dim i.e mal lighting?

My 420EX works fine with my 40D.
Judging from a couple fo threads a few weeks a go it seem that its more compatible than the 580EX as owners of the 420Ex can select some of external flash settings that seems to be greyed out for 580EX users.
At least, thats how the thread's ended up i believe.

I think the newer 430EX has some kind of white balance information it communicates to/from the body (I assume the 580 has this as well) - I know there was a firmware update for my 20D to enable this, so I assume the 30D/40D already has this capability.

danielyamseng wrote in post #4255063
Thanks goforphoto.I notice that for the 420Ex is taking indoor potraits, the flash range is quite short.

I used to direct flash (since bounce would shorten its power) and increase ISO (i.e up to 1600 depending on lighting condition) but with no satisfactory result.

The best result obtain tend to be in a range of 6-9feets.

I don't have any problems with bounce indoors, as long as the ceiling isn't too high. Is your viewfinder covered, either by your face or the eyepiece cover, the flash will underexpose if it is uncovered when shooting.

danielyamseng wrote in post #4255063
Thanks goforphoto.I notice that for the 420Ex is taking indoor potraits, the flash range is quite short.

I used to direct flash (since bounce would shorten its power) and increase ISO (i.e up to 1600 depending on lighting condition) but with no satisfactory result.

The best result obtain tend to be in a range of 6-9feets.

Would the 580Ex II helps me in that situation?

Also with 580Ex II can I lower the ISO up to 100 if it's not that dim i.e mal lighting?

The 580 is certainly more powerful than the 4xx series. I myself have a 580 "main" flash and a couple of 430s that I occasionally use as slaves -- I set up a big reflector or two and bounce all flshes. Nice muted lighting for casual (non-studio) portraits.