High Speedy Synch question....

High Speed Synch question....

Here's one for the experts.

I typically shoot in Av mode with the flash in HSS, for fill when I'm out shooting bird photos. This is because I always want a shutter speed above the x-synch speed of the camera if possible. I realize that in HSS mode, the flash output will be less than normal flash with shutter speeds above 1/250 (MkIIN).

But what occurred to me is if I happpen to shoot in that scenario in lower light, and I'm getting a shutter speed such as 1/100 (in Av mode) will I get less flash with the 580EX still in high speed synch mode than if I had switched it to normal? I have always believed that it doesn't matter, and that the flash output is the same if you are shooting below the x-synch speed of the camera, but I'm not positive about it.

In other words, I keep the flash in HSS because if the situation calls for a shutter speed above 1/250 on the MkIIN, then I won't have the problem of the camera shooting at exactly 1/250 and overexposing the shot. In my mind, it's fail-safe fill flash. But am I correct?

Does anyone here know for sure?

Thanks....

Hi, Tim:

Here's what our "Flash Work" web site says:

http://web.canon.jp/Imaging/flashwork/ettl2/high/index.html

"...the FP high-speed sync flash setting fires repeatedly at roughly 50kHz intervals during the exposure to achieve flash synchronization at all shutter speeds. The camera automatically reverts to normal flash firing when the shutter speed is set slower than the flash X-sync speed."

I would modify this somewhat:

"...the FP high-speed sync flash setting fires repeatedly at roughly 50kHz intervals during the exposure to achieve flash synchronization at all shutter speeds faster than the camera's maximum X-xync speed. The camera automatically reverts to normal flash firing when the shutter speed is set to be equal to or slower than the camera's maximum X-sync speed."

In other words, you can safely leave the Speedlite set to high-speed sync at all times if you like, without worrying about losing range when the shutter speed is equal to or slower than the camera's maximum X-sync speed.

Hope this helps!

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

Thanks, Chuck...

I was hoping you would see my post and respond, since I often read your posts around here.

So I had it right (except for that "Y" typo) that slipped into the title of my original post.

Thanks a lot for responding...

Best regards,

Tim

On a somewhat related note.. why is HSS an option and not just automatically enabled if shooting with Tv faster than max xsync speed? ie. Or why isn't it just always on?

Hi, John:

Canon has never officially commented on that question, so I can only speculate that they intended the use of high-speed sync to be an intentional decision on the part of the user. There's no harm in leaving the function turned on all the time, but it's the photographer's responsibility to realize that maximum flash-to-subject distance range drops off substantially as soon as a high shutter speed is used.

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.