Weird Flash Sync problem, please help!

AshMashMash

AshMashMash

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Ok, I have the weirdest problem ever with my Canon 450D, and it's taken me 205 photos to even work out what the problem is.

So, I was trying to take a picture of a lit up box, using the onboard flash as the Master flash, and a Jessops 360AFD flash as the Slave flash:

IMGP0003-2.jpg


IMG_4576.jpg


This of course, works. As I didn't want it lit from the front at all, I covered the onboard flash using a gel, as so:

IMGP0002-1.jpg


The Slave flash does fire with this set up. DOES fire, definitely.

HOWEVER, and this is the confusing bit, with this set up, when I put the gel in front of the onboard flash, it set's the flash out of sync. The shutter does open, as I can see a torch I held there:

IMG_4567.jpg


And the flash DOES flash, Master and Slave. However the image I get through is this:

IMG_4577.jpg


Why, WHY, WHHHY does the onboard flash become out of sync when a gel is held in front of it?!

Thanks so much for any help :thinking::thinking:

EDIT:

at 1/10 shutter speed I get better results: some of the flashes sync correctly. However at anything from 1/10-1/200 (which is the sync speed for the flash on the 450D) it doesn't work... well, maybe once in 20 shots or so it will. Sorry, I should have pointed that out... yes I did test the shutter speed
 
Are you sure the Jessops flash is firing? You've covered your onboard flash so hardly any light is coming out of it and you've got the Jessops flash face down so that the optical sensor is blocked by the take-away cartons.

I wouldn't be surprised if the Jessops sensor isn't receiving enough of a trigger flash to fire.

EDIT - one thing's for sure, the onboard flash isn't out of sync - the gel can't change how the onboard flash performs but it will affect how much light reaches the Jessops flashgun.
 
incapete said:
Are you sure the Jessops flash is firing? You've covered your onboard flash so hardly any light is coming out of it and you've got the Jessops flash face down so that the optical sensor is blocked by the take-away cartons.

I wouldn't be surprised if the Jessops sensor isn't receiving enough of a trigger flash to fire.
Click to expand...

Nope, definitely, definitely firing, I am watching it each time, definitely firing. That was obviously my first thought too.
 
incapete said:
Are you sure the Jessops flash is firing? You've covered your onboard flash so hardly any light is coming out of it and you've got the Jessops flash face down so that the optical sensor is blocked by the take-away cartons.

I wouldn't be surprised if the Jessops sensor isn't receiving enough of a trigger flash to fire.

EDIT - one thing's for sure, the onboard flash isn't out of sync - the gel can't change how the onboard flash performs but it will affect how much light reaches the Jessops flashgun.
Click to expand...


:agree:

The 360AFD has an optical slave, not an infrared one, by blocking the light coming out of the onboard you're preventing the 360AFD from sensing the triggering flash.
 
Flash In The Pan said:
:agree:

The 360AFD has an optical slave, not an infrared one, by blocking the light coming out of the onboard you're preventing the 360AFD from sensing the triggering flash.
Click to expand...

Yeh, this was my first thought, and after testing with 205 photos, it's definitely firing the Slave off. I am watching the slave and it blind's me each time!
 
What about the shutter speed then? There's a maximum speed which you can sync up to - what were you shooting at?
If you think you're getting sync problems then the first thing to try is a longer exposure.

Isn't one of the techniques for a drip shot to have a reasonably long exposure but to use the flash to illuminate the drip as it falls/hits - you don't try to fire the shutter at the precise moment, merely trigger the flash so it doesn't need to be triggered by the onboard at all.
 
incapete said:
What about the shutter speed then? There's a maximum speed which you can sync up to - what were you shooting at?
If you think you're getting sync problems then the first thing to try is a longer exposure.
Click to expand...

Well... at 1/10 shutter speed I get better results: some of the flashes sync correctly. However at anything from 1/10-1/200 (which is the sync speed for the flash on the 450D) it doesn't work... well, maybe once in 20 shots or so it will. Sorry, I should have pointed that out... yes I did test the shutter speed :bonk:
 
I'll stick my neck out on this one, although I'm not sure I'm right...

Change the shutter speed to say 1/30th, I think it will then work.
If it does, I'll leave it to someone else to explain what I've based my belief on:)

Edit: I took too long working out the physics, so much so that you answered your own question, although I would have thought that it would work perfectly at 1/30th or slower.
 
Garry Edwards said:
I'll stick my neck out on this one, although I'm not sure I'm right...

Change the shutter speed to say 1/30th, I think it will then work.
If it does, I'll leave it to someone else to explain what I've based my belief on:)
Click to expand...

See above, sorry! :lol: Editted it into the first post now :bonk: Thanks though :)
 
It's down to you covering the onboard flash, it's nothing to do with the flash being out of sync. Remember too that 1/200 or whatever is the maximum speed that your camera will sync at, it's not mandatory to set it to that speed ;)
 
Flash In The Pan said:
It's down to you covering the onboard flash, it's nothing to do with the flash being out of sync
Click to expand...

Well... yeh, I agree... except, honestly, the Slave flash is firing, certainly, no question about it. So perhaps covering the flash slows the sensor on the Slave perhaps? :thinking:
 
So what's changed from what you normally do, Ash, you've done this stuff hundreds of times in the past?
 
DekHog said:
So what's changed from what you normally do, Ash, you've done this stuff hundreds of times in the past?
Click to expand...

Well... the reason I was trying to fire the slave using the onboard flash was because my Infrared slave flash firing thingy I bought seem's to be malfunctioning :| Which I am not pleased about.

Previous to that other set ups have allowed me to use a flash extension cord from jessops to fire the flash... I don't like using the onboard flash due to the slow recharge times.
 
I know that it doesn't help with the sync question but if the OP's still trying to get the drip shot then a nice dark room, a 2 to 3 second exposure and a manually triggered off-board flash is a good setup to try.
 
incapete said:
I know that it doesn't help with the sync question but if the OP's still trying to get the drip shot then a nice dark room, a 2 to 3 second exposure and a manually triggered off-board flash is a good setup to try.
Click to expand...

Oh I'm fine with the drip shots! :lol: Well... I would be if the darn flashes would work! :bang:

Edit:

I'll throw something else into the mix. 99% of the time if I hold a torch facing the lens, the flash fire's correctly:

IMG_4553.jpg


99% of the time if I don't, it doesn't. Again... WTF?! It's highly repeatable: torch = sync, no torch = no sync :|
 
AshMashMash said:
Well... yeh, I agree... except, honestly, the Slave flash is firing, certainly, no question about it. So perhaps covering the flash slows the sensor on the Slave perhaps? :thinking:
Click to expand...

It's a long time since I did any physics but I guess it's possible that by covering the onboard flash you're forcing the optical trigger to fire only after the light has bounced off the ceiling, back to the table and then up through the take-away boxes... by which time the shutter has finished firing.

Although I'd have still thought that an exposure of 1/10 would have been long enough to get it every time!
 
incapete said:
It's a long time since I did any physics but I guess it's possible that by covering the onboard flash you're forcing the optical trigger to fire only after the light has bounced off the ceiling, back to the table and then up through the take-away boxes... by which time the shutter has finished firing.

Although I'd have still thought that an exposure of 1/10 would have been long enough to get it every time!
Click to expand...


Yeh exactly :| I can't imagine I can slow the speed of light down to less than 1/20 seconds?! LOL!

Edit: SO weird! I swear I'm not making this up... I have a row of "black", "torch", "black", "torch" pictures...
 
incapete said:
It's a long time since I did any physics but I guess it's possible that by covering the onboard flash you're forcing the optical trigger to fire only after the light has bounced off the ceiling, back to the table and then up through the take-away boxes... by which time the shutter has finished firing.

Although I'd have still thought that an exposure of 1/10 would have been long enough to get it every time!
Click to expand...

Given that light travels approx 186,000 miles per second, unless the extra distance traversed due to the bouncing around the room equates to over 18,600 miles then it's highly unlikely to be the cause of the problem. ;)

It looks like the camera's set to manual mode, but could the op confirm the ISO, aperture and shutter speed in each of the different situations above?
 
really sticking my neck out on this one as i dont have a canon.

could it be that when its 'dark' there are more preflashes, otherwise the flash is straight forward so it syncs fine.
 
DigitalRelish said:
It looks like the camera's set to manual mode, but could the op confirm the ISO, aperture and shutter speed in each of the different situations above?
Click to expand...

Sorry, I did in one of the posts further down:

1/200, F/16, ISO 100. Flash sync works better at 1/10, though still not 100%, and pretty much not all (perhaps 5% of the time) at anything from 1/10 to 1/200 shutter speeds.

B3R said:
could it be that when its 'dark' there are more preflashes, otherwise the flash is straight forward so it syncs fine.
Click to expand...

It's on manual mode and there's no Preflash.
 
Hmmm, the only thing I can think of is that the slave flash just isn't outputting enough light to register. In image #2, it looks like the light is primarily coming from the back of the shot i.e. from the on-board flash.

Could you repeat #2, but switch off the slave so that we can see the difference it makes?
 
DigitalRelish said:
Hmmm, the only thing I can think of is that the slave flash just isn't outputting enough light to register. In image #2, it looks like the light is primarily coming from the back of the shot i.e. from the on-board flash.

Could you repeat #2, but switch off the slave so that we can see the difference it makes?
Click to expand...

Picture #2 is simply a lucky shot where the flash sync'd. There is certainly enough light from the slave to light it! It randomly goes from bright, like number 2, to pitch black (un-sync'd) like #5.

But yep, as you requested: onboard flash, no slave:

IMG_4579.jpg
 
I'm not thinking about the flash taking too long to reach the sensor, it would have to be a very long way away for that to make any difference. I'm thinking in terms of an electrical delay in the slave circuit caused by such a low amount of light reaching it. I've never experienced it with a hotshoe flash but have experienced it a couple of times with studio flash
 
Garry Edwards said:
I'm not thinking about the flash taking too long to reach the sensor, it would have to be a very long way away for that to make any difference. I'm thinking in terms of an electrical delay in the slave circuit caused by such a low amount of light reaching it. I've never experienced it with a hotshoe flash but have experienced it a couple of times with studio flash
Click to expand...

Ah ok! Well this would make sense: less light, longer delay from slave sensor... annoying, but make's sense :thinking: Thank you!
 
Check it out: the slave fired EACH time here, but it sync'd on only some of the shots:

syncnot.png
 
What power is the flash set at? Guess it might be worth upping the power and opening up the aperture to make sure there's enough light getting through?
 
incapete said:
What power is the flash set at? Guess it might be worth upping the power and opening up the aperture to make sure there's enough light getting through?
Click to expand...

Tried all that, though thanks :) Look at the picture above.

Also, I know for absolute certain that the flash on 1/16th power, with F/16 ISO 100 will let enough light in, from all my previous shots.
 
Does the slave have a standby mode at all? What are the time intervals between the first three shots; 4458, 4459, 4460?
 
DigitalRelish said:
Does the slave have a standby mode at all? What are the time intervals between the first three shots; 4458, 4459, 4460?
Click to expand...

It doesn't go into standby on slave mode. All those shots are literally seconds after each other :) I ensured it fired each time, which it did. The dark ones are where i held the gel over the on board flash, but the slave DID fire, as I say.

EDIT: times: 21:19:53, 21:20:08, 21:20:20
 
DigitalRelish said:
Does the slave have a standby mode at all? What are the time intervals between the first three shots; 4458, 4459, 4460?
Click to expand...

AshMashMash said:
It doesn't go into standby on slave mode. All those shots are literally seconds after each other :) I ensured it fired each time, which it did. The dark ones are where i held the gel over the on board flash, but the slave DID fire, as I say.

EDIT: times: 21:19:53, 21:20:08, 21:20:20
Click to expand...

For general reference, that flash does have a standby mode - I think it's 90seconds of inactivity. It's a PITA if you're using basic radio triggers. :thumbsdown:
But in this case Ash has clearly not hit this problem so at least that's one thing we can discount!
 
I don't doubt that the slave fired, but up until recently (last night) I had an annoying sync issue and it was caused by my SB-900 going into standby. The first shot after being woken up always left me with a dark band across the frame as though it wasn't quite syncing properly. After extending the time-out period, my issue was solved. Just wondered whether you had the same issue here.

I think I'm out of ideas!
 
incapete said:
For general reference, that flash does have a standby mode - I think it's 90seconds of inactivity. It's a PITA if you're using basic radio triggers. :thumbsdown:
But in this case Ash has clearly not hit this problem so at least that's one thing we can discount!
Click to expand...

Yeh but it doesn't go into Standby in slave mode :) I've had the Standby problem confusing me before... when using it not in slave mode. But it stays on permanently while in slave mode. Though ta!

DigitalRelish said:
I don't doubt that the slave fired, but up until recently (last night) I had an annoying sync issue and it was caused by my SB-900 going into standby. The first shot after being woken up always left me with a dark band across the frame as though it wasn't quite syncing properly. After extending the time-out period, my issue was solved. Just wondered whether you had the same issue here.

I think I'm out of ideas!
Click to expand...

Ahhh ok ok. Well as you can see, those are 15 and 8 seconds apart... so yeh, weird! Best answer so far was Gary Edwards' one I think, seem's to fit!
 
DigitalRelish said:
I don't doubt that the slave fired, but up until recently (last night) I had an annoying sync issue and it was caused by my SB-900 going into standby. The first shot after being woken up always left me with a dark band across the frame as though it wasn't quite syncing properly. After extending the time-out period, my issue was solved. Just wondered whether you had the same issue here.

I think I'm out of ideas!
Click to expand...

Interesting - I'd not heard of that.

I'm out of ideas too!
 
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