Problem syncing studio flash... canon

[martin eccles]

I am sure this problem has come up before could someone answer this conundrum.....ok ive got studio flash with built in slaves, that of course trigger the flash when it sees a flash from another source ... so far so good, my camera canon 350d can see its own flash BUT it cant see the studio flash when its triggered by the camera's pop up flash.....now the laws of physics surely would dictate that the speed of light would be such that the this would trigger the studio units at the same ish time, maybe there is a delay in the circuitry. Ive used a very slow shutter speed to try to prove this but no joy, the 350's flash sync is 1/200 which i would think would be slow enough to catch the studio flash. I would not be using the camera flash to trigger the studio units in a shoot!! im just trying to solve this problem Help would be much appreciated........I hope this thread will let me know if ive got a reply by email it would help me find this page again ... sorry to sound rather ignorant .

thanks guys
Martin

[Ken MT]

Could it be that you are using other than manual on your camera? If you use P,A or T on the camera, the flash sends a preflash that it uses to calculate that exposure for the ambient light, before it uses the main output for the image. Therefore the studio flash will go off before the shutter is open on the camera. You may be able to set the studio flash so that it ignores the preflash, or alternatively use manual on the camera, setting the shutter to say 1/125 and the aperature to say f8, and either move the strobes, or else change the iso, to get the desired exposure.

[Colin Southern]

Hi Martin,

It'll be the pre-flash as Ken mentioned. Several ways around it - personally I'd just use a wireless transmitter.

[martin eccles]

sorry guys but im stunned !! ...ok perhaps i should have said that i was using manual with no pre flash only a complete numpty would not realise that Doh! .. but of course you dont know me but actually thats quite funny.. I must say im impressed with the speed of your reply... I dont see how a change of aperture is going do the trick and I did say that i used a slow shutter speed to try to prove the point. this camera has two shutters but again i cannot see why this is happening i never had this problem with my bronica etrsi or the nikons this camera is fast heading towards the bin .... if i could afford it.... At the moment i am on a tight budget so a remote is out of the question ....mmmm thinking of selling my Sekonic 508 should need a flash meter these days ....thanks guys

[Colin Southern]

I could be wrong, but I'm pretty sure the 350D still fires a pre-flash in manual mode. Next cheapest solution is a hotshoe adaptor -> PC cable.

I use a Sekonic 758DR in the studio all the time - absolutely essential.

[martin eccles]

Ok Colin I take your point but im sure it doesn't fire a pre flash ..i would see it surely

[Colin Southern]

Ok Colin I take your point but im sure it doesn't fire a pre flash ..i would see it surely

Most folks can't see pre-flashes.

If the strobes are firing - and not appearing in the shot - then it can really only be a timing issue. If the 350D has FEL, use that first - wait for the strobes to cycle - then take a 2nd shot. If it works then the problem is preflash.

By the way (sorry, missed this before) - set your shutterspeed to 1/100th or 1/125th - most strobes won't sync above about 1/160th

[martin eccles]

sorry colin youve lost me there what is FEL

[Colin Southern]

sorry colin youve lost me there what is FEL

Flash Exposure Lock. It fires a preflash - locks it into memory - and then uses that value (without firing another pre-flash) the next time a shot is taken. Not sure if the 350D has it though.

[martin eccles]

just read on a canon site it has fel .need find out how to turn it off and see if that cures it thanks for your help colin

if anyone else knows anything about this please let me know ..thanks guys

[Colin Southern]

just read on a canon site it has fel .need find out how to turn it off and see if that cures it thanks for your help colin

Hi Martin,

Um - not what I meant. FEL is a temp work-around to see if it's the preflash that's upsetting your exposures; since it's not normally used, you can't "turn it off" per se.

[martin eccles]

I did understand what you said, I have just taken a shot of the studio unit with my hand over the pop up and it worked, i took a pic of the flash head firing..... my hand had dulled the pre flash so the slave did not see it but it did see the main flash and triggered the flash head mmm interesting, this has answered my question quite eloquently colin I will get a hot shoe adapter and a sync lead, im hoping the camera will recognise it has a hot shoe and will not fire the pre flash. I was getting worried as i have just turned my spare room 12'x15' into a dedicated studio i think i can just be able to do full length and portraiture, I thought for a while i had wasted my time and was feeling rather despondent but thanks to you I am on my way to solving the problem thanks mate

[Colin Southern]

No worries Martin,

Couple of things to remember though ...

1. Even if the pre-flash could be disabled (assuming optical triggering) then you still don't want hard on-axis light entering the exposure -- with a hotshoe adaptor a microswitch in the hotshoe is triggered and the pop up flash won't pop up - so solves that problem.

2. 12 x 15' is pretty small for full-length portraiture - you'll end up having to use a wide angle lens and that'll give you a degree of distortion, and if you put the subject close to the backdrop, you'll probably get cross contamination between fill & background lights. I'm normally using about 21 feet of my studio for shots like these ...

[martin eccles]

very nice too ..... i wish i had 21 feet to play with, you're lucky to have the space either in your house or an undustrial unit, i consider myself lucky to have no more kids in the house or a misses for that matter haha !! peace ..... so i have to make do I have a nice 24mm 70mm lens that actually worked very well in this space and has a sweet spot at f8. I understand that my lighting will not be as controllable as would be ideal, my "studio" lol is painted out in white and should give a pretty even softbox effect I will work with gobos to give my lighting some character....i will have experiment and get some pics up so you can critique them .... I must go to bed now as it is 02:30 here in the uk

Thanks for all your help

Martin

[martin eccles]

By the way Colin I love the shots of Shanon what a lovely looking girl shes got a wonderful face and youve brought the best out in her ...lovely

[Colin Southern]

Hi Martin,

The "sweet spot" really doesn't enter into it; correct sharpening workflow will have a far bigger effect - but you'll need F8 to F11 for DoF control anyway. Personally, not a bit fan of all white -- causes cross-contamination all over the place. My personal preference would be for all black, but that would make the place like a "morgue of death" to work in -- so in reality I have a black ceiling / gray floor, and draw black curtains around the walls.

My studio is 30 x 24 feet

[Colin Southern]

By the way Colin I love the shots of Shanon what a lovely looking girl shes got a wonderful face and youve brought the best out in her ...lovely

Thanks Martin,

It's pretty standard stuff though to be honest - standard lighting / backdrop / makeup etc. You wouldn't know that she's only 16 though.

[Ken MT]

Another thought. If you set the flash to second curtain flash, and use a long exposure, say 10 sec, then you will see the pre flash when you press the shutter, as well as the main flash as the shutter closes.