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Old Mar 7, 2004, 1:14 AM   #21
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Here's something I don't understand. Hopefully someone here can help me out.

This website claims that at close distance a flash duration is in the order of 1/20,000 seconds: http://webs.lanset.com/rcochran/flash/hss.html If you go read the specifications for the 420EX or 550EX or the Sigma DG super, they all say that Flash duration is around 1/800 second (give or take). A far cry from 1/20,000. What is going on here? Note I'm not comparing high-speed sync flash, just plain normal sync.

Thanks,
Barthold
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Old Mar 7, 2004, 6:28 AM   #22
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Bathold

It's most likely their max ouput rating on full manual... A Flash output (ie intensity) is regulated by its duration. It's like filling up a cup of water by turning on and off the faucet: The flash always put out the same amount of light (same as the water pressure), but when the TTL circuit inside the camera detects there's enough light on a subject (ie the cup is full) it cut the light off earlier (turn-off the tap).

This is the same as when you reduced the power setting on the flash when its on manual, for example at 1/4 power -> its duration is now reduced to 1/3200 (1/800 x 1/4), and at 1/32 power its duration is changed to 1/25,600... and so on. The difference is when the camera is on TTL, this fast ON/OFF cycle is performed for you all automatically, especially at close distances!

... All it's saying is 1/800s is the max limit, for example a pint of water only (unlike a real faucet where you have an unlimited amount). :lol: :lol: :lol:
http://www.chem.helsinki.fi/~toomas/...e/regular.html
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Old Mar 7, 2004, 9:19 AM   #23
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Actually Bart

What you want here is slower flash, that's what you're paying for, ie more output power... (more water from the faucet ops
http://www.qtm.com/home/faq_qfl.html#qf17
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Old Mar 7, 2004, 9:17 PM   #24
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Hiyas NHL,

Thanks for the links, those are useful! Thus the 1/800 sec you see for the flash specifications is the time it takes for the flash to output all its got in it. I would assume that that would correlate to the max guide number.

Thanks!
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Old Mar 13, 2004, 12:32 AM   #25
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Well, my Sigma EF-500 DG Super arrived, and it is a big disappointment. It is back in the box to be exchanged for a 550EX. The reason I bought it was to have a master-slave setup with my Canon 420EX. These two do not play well together. Here are the issues I've found:

1) The Sigma has its own flash-exposure compensation. Even when it is set to zero, my 10D shows the flash-exposure compensation icon in the viewfinder. At best this is harmless. Maybe there actually is some flash exposure compensation going on I don't know about (and yes, I've checked the 10D, its flash exposure compensation is also set to zero).

2) The Sigma can zoom with the focal length of the lens. By default this zoom is disabled in wireless-flash mode. Very annoying, you need to press the zoom button 5 times to cycle through all options to get to auto. Apparently the flash remembers the last settings it was set for when you turn it off, and then back on. This seems to be true for most settings but not for the zoom.

3) The Manual sucks. It is all of 11 pages long to describe this complicated flash. There are some sentences in French in it as well. The 420EX manual is about 50 pages, which translates to about 25 Sigma-sized manual pages. But the 420 EX is a fully automatic flash, there's not much to explain :-)

4) The most important part. The Sigma and the 420 (acting as a slave) could not agree on the flash output, typically resulting in overexposed (and I mean completely white) images. Sometimes it seems to work OK, but most of the time it didn't. For example, I could get a correct picture of something 4 feet away. I then focus on someting 10 feet away and both flashes fire at full output making a nice white completely over-exposed image. I've tried all 4 channels and all 3 groups on the 420 EX. The Sigma BTW does not have a group selector when in master mode. Not sure if that matters though (it does in slave mode).

5) [edit]. The manual for the Sigma tells you how to disable the flash from firing in a master-slave setup, but that didn't work. Even when I had it disabled the Sigma would still fire.

As a final note, the Sigma feels it is built cheaper than the 420EX. Especially the hinge to rotate the flash-head just feels it won't take too many adjustments before it'll give out, compared to the 420EX.

Anyways, I hope the 550EX is better!

Barthold
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Old Mar 13, 2004, 8:26 AM   #26
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Quote:
Originally Posted by barthold
Anyways, I hope the 550EX is better!
It should be, it costs twice as much! :lol: :lol: :lol:

Quote:
Originally Posted by barthold
The manual for the Sigma tells you how to disable the flash from firing in a master-slave setup, but that didn't work. Even when I had it disabled the Sigma would still fire.
... did you see the "no-flash" icon on the panel when you select the arrow? This is how you turn this device into a "controller" only.

Quote:
Originally Posted by barthold
The Sigma BTW does not have a group selector when in master mode. Not sure if that matters though (it does in slave mode).
This is the same as the 550EX... Groups only apply to slaves (ie when the units are not mounted on the camera) and controlled through the "no-flash" option as above or with an ST-E2. The master on the camera is unique hence no group settings!

Quote:
Originally Posted by barthold
The Manual sucks. It is all of 11 pages long to describe this complicated flash. There are some sentences in French in it as well. The 420EX manual is about 50 pages, which translates to about 25 Sigma-sized manual pages. But the 420 EX is a fully automatic flash, there's not much to explain
... Can't help you here!

Quote:
Originally Posted by barthold
The Sigma can zoom with the focal length of the lens. By default this zoom is disabled in wireless-flash mode. Very annoying, you need to press the zoom button 5 times to cycle through all options to get to auto. Apparently the flash remembers the last settings it was set for when you turn it off, and then back on. This seems to be true for most settings but not for the zoom.
Ditto - This is the same as on the 550EX... In wireless mode the zoom head is disabled on my 550EX. In this mode who knows where all the flash heads are located to act as fill-in. Hence the zoom head is disabled on the 500DG just as it is on the 550EX (ie fixed at the 24mm position)!!!

I'm sorry to hear that you don't like this flash, but the fact of the matter is the 500DG Super's work fine in my (as well as others) setup(s) at a considerable saving (ie I have two Sigmas and one 550EX). Even it's older generation, the EF-500 Super, is compatible with the Canon E-TTL in both Master and Slave configuration: http://eosdoc.com/manuals.asp?q=ETTLDx

Could it be operator error may be? Normcar can you help our friend here since you've slaved your 420EX to the Sigma's 500DG Super... 8)
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Old Mar 13, 2004, 12:49 PM   #27
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Hi NHL,

Quote:
Originally Posted by NHL
... did you see the "no-flash" icon on the panel when you select the arrow? This is how you turn this device into a "controller" only.
Yes, the thunderbold icon thingy with the circle around it and the diagonal through it. Even with that showing on the display I can get way overexposed images. This is with the camera in P mode, and (as you suggested below) the zoom of the Sigma head disabled in master-slave mode.

Quote:
Originally Posted by NHL
This is the same as the 550EX... Groups only apply to slaves (ie when the units are not mounted on the camera) and controlled through the "no-flash" option as above or with an ST-E2. The master on the camera is unique hence no group settings!
Interesting, how then do you use the 550EX or Sigma as a slave? Is there simply one group when you do that?

Quote:
Originally Posted by NHL
Ditto - This is the same as on the 550EX... In wireless mode the zoom head is disabled on my 550EX. In this mode who knows where all the flash heads are located to act as fill-in. Hence the zoom head is disabled on the 500DG just as it is on the 550EX (ie fixed at the 24mm position)!!!
Ok, that makes sense. Didn't realize that!

Quote:
Originally Posted by NHL
I'm sorry to hear that you don't like this flash, but the fact of the matter is the 500DG Super's work fine in my (as well as others) setup(s) at a considerable saving (ie I have two Sigmas and one 550EX). Even it's older generation, the EF-500 Super, is compatible with the Canon E-TTL in both Master and Slave configuration: http://eosdoc.com/manuals.asp?q=ETTLDx Could it be operator error may be?
Your setup is different than mine, I presume you use the 550EX as master? I was trying to use the Sigma as a master. But sure, it could be operator error. I'm still learning! However, I've seen several things that didn't work as advertised (cannot turn off the master, always showing exposure compensation icon, I never see the distance scale on the Sigma change) that I really doubt all of this is operator error. Most importantly, of the more than hundred shots I've fired in wireless master-slave mode, most of them are over exposed. Not only that, it is not consistent either. I can take a shot of something that is more or less reasonable (bit over-exposed) take a shot of something else, then re-take the first shot and now it is completely utterly over-exposed. I can hear the 420EX strain to re-charge, since it just fired at full blast. If this is operator error I would love to hear it, since I'm obviously missing something important then :-)

I'm guessing that either this unit is defective, or it doesn't play well with the 10D and 420EX combination. Frankly I've spent many hours on this now, and it is not worth my scarce free time. I rather be taking real pictures than trouble shooting! I'm just going to stick with Canon and at least that'll eliminate one possible source of problems.

But NHL, as always, thanks a ton for your input and your willingness to share your knowledge with us. It certainly helped me a lot in my hobby, and I'm sure others as well. You're great!

Barthold
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Old Mar 13, 2004, 10:23 PM   #28
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Barthold

:idea: I think I got it!

How did you point your 420EX? The slave flash(es) has(ve) to face the camera, the front body of the slave's sensor has to face the master unit, ie use the bounce head of the 420EX to face it backward or sideway or whatever to illuminate your subject, but its front has to face the camera/master unit. You have to see the flashing LED on the front of the flash indicating that the slave(s) is(are) ready to fire. If you don't see this, the slave(s) won't see the IR wireless control signal from the master unit either (max. placement angle is 80 degree, 40 degree on either side of the camera...)! I think what happened is your 420EX was triggered by the 1st signal but is blind (by its own flash) to the 2nd signal sent by the 500DG Super to turn it off. This signal is not received by your 420EX since its IR receiving sensor is facing the wrong direction hence your over-exposure... ops:

I've just tried my setup with the 500DG as Master and the 550EX/500DG as slaves and they work together just fine... If I re-orient the front of any slaves away from the camera I had total overexposure!

ie This is 100% OPERATOR ERROR. IMO even if you buy a 550EX and repeat this same setup that you did, it will work unreliably too... :lol: :lol: :lol:


Quote:
Originally Posted by barthold
Quote:
Originally Posted by NHL
This is the same as the 550EX... Groups only apply to slaves (ie when the units are not mounted on the camera) and controlled through the "no-flash" option as above or with an ST-E2. The master on the camera is unique hence no group settings!
Interesting, how then do you use the 550EX or Sigma as a slave? Is there simply one group when you do that?
You use only one group when all the slaves have the same intensity. If you want to use ratio then you need several groups: group A can be set to 1:2 and group B can be set to 1:4 for example. Group C beside having the ability to have a different ratio is unique in that it's the only group that allows flash exposure compensation! 8)

BTW the distance scale on my 550EX does not change either in the wireless mode! :P
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Old Mar 14, 2004, 12:18 AM   #29
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Hi NHL,

Interesting, I did make sure I could see the IR transmitter on the 420EX myself when taking the pictures. But to be completely utterly sure I'll re-test one more time :-) Will let you know!

As for different groups, how can I set the Sigma to group 'C' (to have FEC) if the Sigma has no group selection? The 420 EX has a button to set its group ID, and a button to set the channel ID. The Sigma can only set a channel ID. Thus sounds to me like with the Sigma's you cannot have three separate groups?

Thanks!
Barthold
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Old Mar 14, 2004, 12:56 AM   #30
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Quote:
Originally Posted by barthold
As for different groups, how can I set the Sigma to group 'C' (to have FEC) if the Sigma has no group selection? The 420 EX has a button to set its group ID, and a button to set the channel ID. The Sigma can only set a channel ID. Thus sounds to me like with the Sigma's you cannot have three separate groups?
You do not set the group on the master, this is the same as on the 550EX!

The master only needs the channel ID since everyone in the group will have the same channel ID as the master. This is so to allow up to 4 photographers to shoot simultaneously together without bothering one another... (each with their own master/ID)

Now within each channel ID (ie all master and slaves have to be set to the same channel ID) you can have three groups, A, B, and C: One master with no group assigned, and as many slaves as you want within each group. This why you can only select group when the flash is set as slave on the 500DG Super (ie it's behaving just like another 550EX)! :P

The Master is the controller, it is not part of any group... Still confused? :?
In your case if you set your 420EX to group C you will have FEC... (with the 500DG and the 420EX on the same channel ID)

... You can assign your 500DG Super to a group C slave if you buy another 500DG Super as a master! :lol: :lol: :lol:
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