Using non-Canon flash units with the Canon 10D

[jerry_junkins]

I have a Canon 10D and will be using it with my studio lighting

(Elinchrom 1500 micro and A3000N heads). I was looking through the

operation manual for the 10D and was reading about using non-Canon

flash units with the 10D. Here is what it says:

 

"The EOS 10D can synchronize with compact, non-Canon flash units at

a shutter speed of 1/200th second or slower. With large studio

flash units, the flash sync speed is 1/60th or slower. Be sure to

test the flash you are using beforehand, to make sure it

synchronizes properly with the camera."

 

Why would the sync speed be different for large flash units? I will

be using Pocketwizard transmitter and receiver with my lighting. My

question is this: how does the camera know what you have attached

to it and how can it change the sync speed for the two different

types of flash? Thanks in advance. Jerry

[skipd]

My guess would be that Canon expects that some studio flash units may have a longer duration of the flash than other, typically smaller, units. You, the photographer, would have to experiment with any non-Canon flash and decide what the fastest shutter speed is that would sync properly with the flash unit.

[twmeyer]

do your testing on an <i>evenly lit</i> white background. This way you can instantly see the underexposure caused by a too-fast sync speed as a gradated darker strip along the long dimension of the frame. This shows up as soon as the sync speed becomes too high, by even half a stop... t

[jim_leonard]

If my thinking is correct, the smaller the aperture, the more pronounced the edge of this darker band will be. Also packs will have different timing characteristics based on the output level and may even have different timings characteristics based on other things (look at the section Dependence of Flash Output on Charge Time on this page: http://eosdoc.com/manuals/notes/discharge/ ). In other words thorough testing with a new system of any kind is a good thing.

[twmeyer]

Jim references other concerns than how the Canon 10D camera will function with studio type strobes. Regarding the issue of aperture magnifying the effect of shutter speed on uniform exposure of the recording CCD; I don't believe there is any connection between the exposure that is reduced by shutter blades moving at a faster setting than that which exposes the entire CCD simultaneously, and the aperture set in the lens. The aperture may affect overall density, or increase the apparent sharpness of any obect in the cameras field of view, but will not amplify the exposure cuttoff effected by the shutter's presence within the image area. <p>Stopping down <i>will</i> amplify the vignetting effect of a too thick filter ring or a hood made for a longer focal length lens than the lens that formed the image.<p>Also, the page referenced seems to be describing flash duration and peak discharges of the Canon flash at various sync speed settings, not the studio type strobe unit at issue in the original post. It also seems to be discussing the repeating, stroboscopic output of the Canon unit that enables high shutter speed flash exposure with that specific flash/camera combination... t

[jim_leonard]

Tom:

 

Regarding my aperture comments, I'm not suggesting that changing the aperture will change whether there will be a flash sync problem, just that it will be made more apparent in the same way that dust on the sensor is much more apparent at very small apertures, ie just as the shadow of the dust is clearer, the shadow of the shutter will be clearer.

 

As to the duration of the flash, all I'm saying really is that you should test everything well. Who's to say a studio flash doesn't have a similar characteristic to the 430EZ that was tested. And no I wasn't refering to the high speed sync setting on the flash, I was refering to the section where the author popped the flash once a second for 8 seconds. As I said above read the section "Dependence of Flash Output on Charge Time" on that page. Basically what the article alludes to is that one second isn't enough to completely recharge the capacitors but they're charged enough to fire the flash at the level requested so the duration of the flash was increased as the voltage in the capacitor dropped to keep the total light output constant. Thus flash duration on a 430EZ is not just variable dependent on the output level but also can vary by a factor of 3 or 4 AT THE SAME OUTPUT LEVEL.

[twmeyer]

I'm with you Jim on one out of two points. The comments about the Canon flash may certainly all be accurate (I don't use Canon, don't really enjoy unravelling technical documents, and couldn't apply that information to my own work, so I'm reluctant to invest the time to verify it. So for this moment, I'm perfectly willing to accept it as accurate...why not?). However, I'm just not sure how that data relates to Jerry's question "<i>Why would the sync speed be different for large flash units?</i>".<p>As for the the other issue, maybe you're right, maybe I'll never know for sure. Maybe we both have better things to worry about, and Jerry can figure it out from here. <p>My S2's top sync is 1/125, but on a black background, with the important subject at least 1/3rd into the frame, I can use 1/180th... probably because the sensor is smaller than the 35mm frame that the sync speed was based on (like the N80) and the second curtain just barely clips the edge of the frame @ 1/180th. It won't work at all on a white background, as the shutter blade's second (trailing) curtain vignettes the image at that elevated speed... t