Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon EOS dSLR

Reply
 
Thread Tools Search this Thread
Old Mar 14, 2004, 3:10 AM   #31
Senior Member
 
Join Date: May 2003
Posts: 577
Default

NHL, all you said makes sense. Somehow I got it in my mind that the Sigma does not have group settings when used as a slave. Apparently it does. Confusion gone :-)

Barthold
barthold is offline   Reply With Quote
Old Mar 14, 2004, 10:19 AM   #32
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

FYI

From my 550EX manual (with my orange note and yellow highlight):




BTW the 550EX will still pre-flash even when you disable its output when its mounted on a digital camera... this is the actual control signal, but will not contribute to the lighting! The 500DG Super behave the same then and is not faulty!

8) 8) 8)
NHL is offline   Reply With Quote
Old Mar 14, 2004, 8:04 PM   #33
Senior Member
 
Join Date: May 2003
Posts: 577
Default

Hi NHL,

One area where Sigma definitely skipped cost, a decent manual!

I think I figured out why I couldn't disable the Sigma as the master. When you set the Sigma for 'master off', it still fires a pre-flash, but not a main flash. At least that is the best explanation I can come up with. I'm not sure what the use is of firing a pre-flash if the main flash is not going to be fired though. Is the 550 EX the same way?

Careful positioning of the 420EX did improve things. Thus I can believe that I didn't have the 420EX turned far enough, or at too wide an angle in my initial tests. I still see overexposed shots sometimes. The interesting thing is that if I re-take the shot without changing anything the re-take is correctly exposed. But that's ok, it is digital after all.

Barthold
barthold is offline   Reply With Quote
Old Mar 14, 2004, 10:06 PM   #34
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
Originally Posted by barthold
I think I figured out why I couldn't disable the Sigma as the master. When you set the Sigma for 'master off', it still fires a pre-flash, but not a main flash. At least that is the best explanation I can come up with. I'm not sure what the use is of firing a pre-flash if the main flash is not going to be fired though. Is the 550 EX the same way?
Yeap, that's exactly how the 550EX works as well on a digital camera... it fires small control bursts to the slaves, but not its main flash so the master does not contribute to any lighting!


Quote:
Originally Posted by barthold
Careful positioning of the 420EX did improve things. Thus I can believe that I didn't have the 420EX turned far enough, or at too wide an angle in my initial tests. I still see overexposed shots sometimes. The interesting thing is that if I re-take the shot without changing anything the re-take is correctly exposed. But that's ok, it is digital after all.
There's this note on page 52 of the 550EX manual: "The master unit's flash head zoom setting is set automatically to M 24mm. This gives the wireless signal the maximum coverage of 80 degree. You can press the Zoom button to change the zoom setting manually. However, this will narrow the wireless signals coverage"... Are you adjusting the zoom setting on the 500DG (may be pulling out its diffuser help to increase the coverage angle)? ops:


Quote:
Originally Posted by barthold
One area where Sigma definitely skipped cost, a decent manual!
I agree. Most folks like myself who buy theses units are already familiar with the 550EX, and instead of buying the 420EX as slaves, they found a much better option in the 500DG (ie for the cost of one 550EX, one can get two 500DG's which are not only more powerful than the 420EX, but also more fully featured...).

BTW they can also be used as dumb slaves on other camera systems (or studio strobes) with their built-in optical slave which is not present on the Canon's 8)
NHL is offline   Reply With Quote
Old Mar 14, 2004, 10:48 PM   #35
Senior Member
 
Join Date: May 2003
Posts: 577
Default

How does Canon's wireless transmitter (ST-2E or whatever it is called) communicate with the slaves? Since it isn't a flash, it cannot pre-flash to communicate.

I still don't get it though. If you turn of the master flash it still pre-flashes. But wouldn't that pre-flash skew the exposure reading the camera makes during the pre-flash? How does the camera distinguish between a flash as a master and the ST-2E and still get correct exposure?

Thanks!
Barthold
barthold is offline   Reply With Quote
Old Mar 15, 2004, 6:23 AM   #36
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
Originally Posted by barthold
How does Canon's wireless transmitter (ST-2E or whatever it is called) communicate with the slaves? Since it isn't a flash, it cannot pre-flash to communicate.
The ST-E2 works through IR, it may not be visible to the human eyes, but the electronics are still sensitive in this area of the spectrum. Remember your color chart? Visible light is between UV and IR...

Quote:
Originally Posted by barthold
I still don't get it though. If you turn of the master flash it still pre-flashes. But wouldn't that pre-flash skew the exposure reading the camera makes during the pre-flash? How does the camera distinguish between a flash as a master and the ST-2E and still get correct exposure?
You're thinking about the one pre-flash when only a single external head is used on the camera. There's actually several pre-flashes, and wireless transmission(s) one for each group of slaves... Remember this timed sequence of events chart from the French EOS site? The green wireless transmissions can be either visible(flash) or invisible(IR) based, and not just a single burst like your eyes led you to believe. They're actually coded messages in thoses beams similar to rapid burst(s) of Morse code of "On" and "Off":



My bet is if you use the 500DG or the 550EX on a film camera, there won't be any pre-flash since the metering can be done OTF (off-the-film) plane and not through pre-flash metering!


BTW there is nothing new: This wireless flash system was originally pioneered by Minolta almost twenty years ago... On Minolta Xi series, the camera's built-in flash can also serve as your master so anyone can start on the cheap with just a single external flash (page 40 onward...): http://www.minoltausa.com/eprise/mai...etail/5600HS-D

IMO the ST-E2 is overpriced since it does not need a large storage capacitor or a flash tube and it could be priced much less similar to the Minolta's own Wireless Remote Flash Controller (page 51). 8) 8) 8)
NHL is offline   Reply With Quote
Old Mar 15, 2004, 2:03 PM   #37
Senior Member
 
Join Date: May 2003
Posts: 577
Default

Hi NHL,

My point still stands. If the ST-E2 can sucessfully control slaves, then a master flash like the 550EX or Sigma 500 should be able to do the same without firing any pre-flash in the human visible range, right?

Are there any flash systems that communicate using radio frequencies, and therefore don't have the limitations that IR communication has (limited range and angle from the master)?

Barthold
barthold is offline   Reply With Quote
Old Mar 15, 2004, 3:26 PM   #38
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
Originally Posted by barthold
Are there any flash systems that communicate using radio frequencies, and therefore don't have the limitations that IR communication has (limited range and angle from the master)?
Somehow I know this question will come up... :lol: :lol: :lol:
Yes! METZ They have their own RF wireless system which is incompatible with Canon.


Quote:
Originally Posted by barthold
My point still stands. If the ST-E2 can sucessfully control slaves, then a master flash like the 550EX or Sigma 500 should be able to do the same without firing any pre-flash in the human visible range, right?
Correct... if you have a film camera. At least that's how my Minolta 9xi film camera does it, but the Minolta's digital D7i/Hi/A1 still need the pre-flash. My Canon films camera are pre E-TTL era so I can't try, but I guess the newer film EOS won't pre-flash either. My bet is it's all in the camera firmware and whatever was convenient for the programmer to code at the time the camera was developed.

Remember though that even if the main unit won't pre-flash the slaves still do since on the digital cameras it's still a two steps approach by estimating 1st through TTL, with a true main lighting blast the 2nd time around. With film cameras the metering can all be done as one shot at the same time as the mirror is flipped up right on the film plane at the actual moment of the exposure. 8)


FYI you're not alone in questioning this pre-flash business with digital cameras: http://www.friedmanarchives.com/flash.htm
Check out the differences between the film and its digital counter part (the Dimage); "You cannot turn off pre-flash. If you have your flashes and your camera on manual settings (which you would do if you shoot with white backgrounds), the pre-flash is completely unnecessary, and yet it cannot be disabled. The upshot? There is about a 1/4 to 1/2 a second delay between depressing the shutter release and taking the picture. If you like capturing the decisive moment, using wireless flash on this camera makes it even harder by virtue of this unnecessary delay."
NHL is offline   Reply With Quote
Old Mar 21, 2004, 3:33 AM   #39
Senior Member
 
Join Date: May 2003
Posts: 577
Default

Interesting info about the pre-flash. The main thing I have against the master pre-flashing is that it can be distracting. Say you use the camera to trigger some flashes remotely at the other end of a theather. I don't need my master flash to blab out some light too!

Anyways, I received my 550EX. All is well now. With two 420EX flashes as slaves I can do some nice things! Actually it is pretty cool the amount of control you have just from changing settings on the master flash. My biggest complaint about the Sigma is its poor poor manual (well, I'm still not quite convinced the particular copy I have wasn't flawed). The 550EX manual is a complete reference guide with many examples. Very nice. Still it took me a while to figure out that the 550EX is in group A, which is important when you play with the A:B:C ratios. That wasn't exactly clear in the manual.

Barthold
barthold is offline   Reply With Quote
Old Mar 21, 2004, 11:18 AM   #40
Senior Member
 
Join Date: Jun 2002
Posts: 227
Default

Barthold,

does your 550EX when acting as master send out a pre-flash like the Sigma did? It wasn't clear from your post.

I'm hoping to get a flash in the near future and it's coming down to the 550EX or the Sigma 500 DG. This topic has been very informative.
ursa is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 10:44 PM.