Weird Flash Sync problem, please help!

[incapete]

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!

Hmm, that might help with my radio trigger problem - set them to slave mode and they stay on between shots! Cheers!

 

[AshMashMash]

Interesting - I'd not heard of that.

I'm out of ideas too!

Haha.... right, I'm gonna hit the sack. Thanks for all the input guys, much appreciated! Look's like it's probably as Gary Edwards' said... seem's like there's not much I can do but get my Infrared flash trigger fixed :bonk:

EDIT: I am guessing they won't fire using radio transmitters while in slave mode though? They don't if attached to the camera...

 

[incapete]

Haha.... right, I'm gonna hit the sack. Thanks for all the input guys, much appreciated! Look's like it's probably as Gary Edwards' said... seem's like there's not much I can do but get my Infrared flash trigger fixed :bonk:

EDIT: I am guessing they won't fire using radio transmitters while in slave mode though? They don't if attached to the camera...

I'll certainly be checking it out tomorrow!

 

[Garry Edwards]

seem's like there's not much I can do but get my Infrared flash trigger fixed :bonk:

Or just raise the slave off the 'ground' a bit so that more light reaches it...

 

[HoppyUK]

Seems simple enough to me. The slave gun is firing off the 450D's E-TTL pre-flash and is therefore completely out of sync. You cannot disable the pre-flash on a 450D. It is not a 'master' unit as such.

The flash image in the second pic is the pop-up flash firing, not the slave, which has already been and gone in sync with the pre-flash.

Am I missing something?

Edit: on second thoughts, the second image is the slave firing - sorry. But the intermittent behaviour is because it's a conventional optical slave and is being confused by the pre-flash into erratic behaviour. It's still the same problem though - the pre-flash triggering it out of sync.

Edit 2: the solution is either an optical trigger such as this http://www.warehouseexpress.com/buy-elinchrom-prolinca-i-r-transmitter/p1004773 (I've seen an identical item on ebay for half that price) or a radio trigger/receiver set. Radio triggers tend to introduce a slight delay, fixed by reducing the x-sync speed a bit, which might be a problem with this application but I'm guessing a few millisecs won't make any odds.

 

[david1701]

aren't all canon pop ups ttl only? so the jessops is being fired by the preflash?

 

[HoppyUK]

aren't all canon pop ups ttl only? so the jessops is being fired by the preflash?

I read that somewhere before

 

[AshMashMash]

Or just raise the slave off the 'ground' a bit so that more light reaches it...

It has clear plastic boxes holding it up about 30cm or so off the ground...

Seems simple enough to me. The slave gun is firing off the 450D's E-TTL pre-flash and is therefore completely out of sync. You cannot disable the pre-flash on a 450D. It is not a 'master' unit as such.

The flash image in the second pic is the pop-up flash firing, not the slave, which has already been and gone in sync with the pre-flash.

Am I missing something?

Edit: on second thoughts, the second image is the slave firing - sorry. But the intermittent behaviour is because it's a conventional optical slave and is being confused by the pre-flash into erratic behaviour. It's still the same problem though - the pre-flash triggering it out of sync.

Edit 2: the solution is either an optical trigger such as this http://www.warehouseexpress.com/buy-elinchrom-prolinca-i-r-transmitter/p1004773 (I've seen an identical item on ebay for half that price) or a radio trigger/receiver set. Radio triggers tend to introduce a slight delay, fixed by reducing the x-sync speed a bit, which might be a problem with this application but I'm guessing a few millisecs won't make any odds.

But... it's on manual focus and there isn't a pre-flash :| And it only occurs when I hold the gels right against the flash, not any other time.

And yeh, I have an Infra red flash trigger but it's playing up a bit as of the last couple of days :|

aren't all canon pop ups ttl only? so the jessops is being fired by the preflash?

As above... there isn't a pre-flash? Manual focus, manual mode, and only occurs when the gels are held against it, not normally.

 

[incapete]

But... it's on manual focus and there isn't a pre-flash :| And it only occurs when I hold the gels right against the flash, not any other time.


As above... there isn't a pre-flash? Manual focus, manual mode, and only occurs when the gels are held against it, not normally.

Actually Hoppy's suggestion is probably the best one I've seen so far on this thread and I can only saw that I must have been very tired last night to have not thought of it myself!

The pre-flash is very close to the main flash - so close in fact that you don't notice it but it can trigger an optical slave milliseconds before the shutter fires.

I do a lot of scuba diving and this is a pretty common problem where people take photos using compact digitals - if you use an external flash too (which is the best idea) then you need one which 'knows about' ttl preflash so else you'll never get it to sync. There are also special optical adaptors which can cope with preflash to allow the use of older strobe units.


EDIT- forgot about the weird fact about the gels causing it - I suppose that it's possible that the shots where you didn't use the gels have been lit by the onboard flash only and the slave is being triggered early both with the gels and without. It's only with the gels that the onboard flash is blocked.

The way to test would be to take a shot without the gels and with the slave firing and another with the slave turned off. If the slave IS being triggered early by the preflash then there shouldn't be much difference in the lighting of the two shots.

EDIT AGAIN - you already posted those shots, sorry... there's quite a difference in the lighting after all.

 

[AshMashMash]

Actually Hoppy's suggestion is probably the best one I've seen so far on this thread and I can only saw that I must have been very tired last night to have not thought of it myself!

The pre-flash is very close to the main flash - so close in fact that you don't notice it but it can trigger an optical slave milliseconds before the shutter fires.

I do a lot of scuba diving and this is a pretty common problem where people take photos using compact digitals - if you use an external flash too (which is the best idea) then you need one which 'knows about' ttl preflash so else you'll never get it to sync. There are also special optical adaptors which can cope with preflash to allow the use of older strobe units.


EDIT- forgot about the weird fact about the gels causing it - I suppose that it's possible that the shots where you didn't use the gels have been lit by the onboard flash only and the slave is being triggered early both with the gels and without. It's only with the gels that the onboard flash is blocked.

The way to test would be to take a shot without the gels and with the slave firing and another with the slave turned off. If the slave IS being triggered early by the preflash then there shouldn't be much difference in the lighting of the two shots.

EDIT AGAIN - you already posted those shots, sorry... there's quite a difference in the lighting after all.

Epic post.

Right, ok, I seeeeeeeeeee. I apologise Hoppy... seem's you're right. I thought, with the camera in manual mode and the FEC altered, you wouldn't get a preflash, but seem's you do :| Very annoying.

My other flash (YN460), which has also been playing up, has a setting on it which take's into account the pre-flash, so it seem's. But I have been using my Infrared trigger mainly so never come across this problem before.

So basically: I cannot use my onboard flash as a Master flash, you are correct Hoppy and Pete. And the gel situation must just be a weird thing where it's altering the light amount somehow. Solution: fix my Infrared trigger.

Thank you guys! So much appreciated, learnt something tonight!

 

[Garry Edwards]

Glad that's sorted out, I didn't realise that your flash fired a pre-flash.
A radio trigger would be a better bet than an infra red trigger, much more reliable.

 

[AshMashMash]

Glad that's sorted out, I didn't realise that your flash fired a pre-flash.

Nore did I... Surely that's not needed when in Manual mode? :| I'm not asking it to evaluate and adjust the flash settings, I am telling it to keep them exactly as I tell it. No pre-flash is needed?! Silly thing :bang: Apparently the 7D doesn't fire a preflash in Manual mode but the 450D does :|

A radio trigger would be a better bet than an infra red trigger, much more reliable.

Hmm, perhaps. Any ideas why it would suddenly stop working on me? I can now see a small red/pink flash with my own eyes coming from the infra red trigger. I have obviosuly changed the batteries and ensured the flashes are working correctly.

 

[HoppyUK]

Epic post.

Right, ok, I seeeeeeeeeee. I apologise Hoppy... seem's you're right. I thought, with the camera in manual mode and the FEC altered, you wouldn't get a preflash, but seem's you do :| Very annoying.

My other flash (YN460), which has also been playing up, has a setting on it which take's into account the pre-flash, so it seem's. But I have been using my Infrared trigger mainly so never come across this problem before.

So basically: I cannot use my onboard flash as a Master flash, you are correct Hoppy and Pete. And the gel situation must just be a weird thing where it's altering the light amount somehow. Solution: fix my Infrared trigger.

Thank you guys! So much appreciated, learnt something tonight!

No worries Ash. And the gel thing is a red herring

There's a workaround that I've just remembered. It's not normally any help but for your application it should work a treat - you can 'disable' the pre-flash by firing it with the FEL flash exposure lock button - the * button. It's intended for another purpose but it will do what you want without recourse to separate triggers.

Before your shot, press the FEL button while shielding the pop-up flash - it will fire the pre-flash (and lock the flash output) and if you shield it from the slave that will not fire off it. Then take your pic and the slave will fire in sync with the main flash pulse. Or, you can just fire the pre-flash, let the slave fire off that, wait until it has recycled, then take your pic

Edit: yes, the pre-flash is needed in manual mode. It is only manual on the camera, not the flash, so if you set say f/5.6 manually on the camera the flash will still work in E-TTL to match that. There is no manual flash setting on any Canon camera except the 7D (which is also a master controller) - the only 'manual' flash control is the +/- flash exposure compensation override.

 

[AshMashMash]

No worries Ash. And the gel thing is a red herring

There's a workaround that I've just remembered. It's not normally any help but for your application it should work a treat - you can 'disable' the pre-flash by firing it with the FEL flash exposure lock button - the * button. It's intended for another purpose but it will do what you want without recourse to separate triggers.

Before your shot, press the FEL button while shielding the pop-up flash - it will fire the pre-flash (and lock the flash output) and if you shield it from the slave that will not fire off it. Then take your pic and the slave will fire in sync with the main flash pulse. Or, you can just fire the pre-flash, let the slave fire off that, wait until it has recycled, then take your pic

Ahh ok! Thank you for this. I shall have a go. For this particular application it might not be that much use, as I am taking hundreds of pictures in a sitting (hundreds of flashes) and don't have many spare hands. But either way it's good to know... I shall take a look-see

Thanks again!