Hi Speed Synch - FM Forums

Moderated by: guardian

Visit the FM Store · Image Upload · Buy & Sell
FM Forum Rules
Canon SLRs, primes, and zooms lenses reviews

FM Forums | Canon-mount SLRs | Join Image Upload
end

hassy501
Offline
[ X ]

p.1 #1 · Hi Speed Synch

Im confused on the hi speed sync method of fill flash......will i be able to shoot at all shutter speeds using hi sync ? Ive experimented and it seems to work that way....akin to the OLD SCHOOL method of the leaf shutters of Hasselblads ?

Mar 29, 2008 at 11:34 PM

jcolwell
Offline
Image Upload: On

p.1 #2 · Hi Speed Synch

Yes, sort of. In order to provide consistent lighting at high shutter speeds, when the top and bottom shutter curtains progress together over the sensor with small separation between them (not one, then the other as at low synch speeds), the flash strobes, or pulsates at high frequency, 50k Hz, I believe. This reduces the effective distance that the flash can cover, but generally gives good results. With a leaf shutter, there is only one flash of light, as the shutter is entirely open at one time. Many leaf shutters go up to 1/500 sec speed, but the bigger shutters for large format (e.g. Copal 3) have lower max speeds, as that's all they can physically do at one time.

Edited on Mar 29, 2008 at 11:42 PM

Mar 29, 2008 at 11:41 PM

hassy501
Offline
[ X ]

p.1 #3 · Hi Speed Synch

Thats great..........will work fine with my beach shoots.......

Mar 30, 2008 at 12:21 AM

Alan321
Offline
Image Upload: On

p.1 #4 · Hi Speed Synch

Be aware that high speed synch mode reverts to normal (more power, single pulse) mode when the shutter speed is at or slower than the synch speed. At very fast shutter speeds you get relatively little effective output power and if you also use a diffuser to soften the flash then you might easily run out of light unless you are close to your subject.

- Alan

Mar 30, 2008 at 07:12 PM

Alek Komarnits
Offline
Image Upload: Off

p.1 #5 · Hi Speed Synch

Ditto what Alan said ... and this is, of course, more of an issue when shooting in bright daylight.

Mar 30, 2008 at 07:44 PM

Steve Blagg
Offline
Image Upload: Off

p.1 #6 · Hi Speed Synch

Also watch your shooting rate Hassy, your flash may get too hot and shut down to cool off!

Mar 30, 2008 at 09:31 PM

hassy501
Offline
[ X ]

p.1 #7 · Hi Speed Synch

Thanks guys.......i really need that feature for shooting at the beach to keep those skies deep blue...........and i'll keep it close to my subjects.........

Mar 30, 2008 at 09:34 PM

Pixel Perfect
Offline
Image Upload: On

p.1 #8 · Hi Speed Synch

For every stop faster than the X-sync speed you see the shutter speed, you lose 1 stop of flash power. So if in bright sun you are using 1/4000 say, that's 4 stops so you'll get 1/16 full power.

Mar 30, 2008 at 09:38 PM

Photon
Online
Buy and Sell: On

p.1 #9 · Hi Speed Synch

Pixel Perfect wrote:
For every stop faster than the X-sync speed you see the shutter speed, you lose 1 stop of flash power. So if in bright sun you are using 1/4000 say, that's 4 stops so you'll get 1/16 full power.
Yes, though there's also a slight loss of total flash output because the efficiency of the pulsed light is not perfect. In general, the optimum setting for maximum impact of the flash relative to the daylight will be achieved at the camera's x-sync speed. That's where you have the best hope of "overpowering the sun".
However, HS sync does allow you to use wider f/stops to control DOF, and there can be some action shots where the high shutter speed is useful to control blur, while the HS flash fills shadows.

The neat thing about leaf shutters is that even while they are opening or closing, the entire field of view and area of the sensor is being exposed. It's a lot like stopping down the aperture, but all the way to f/infinity, i.e., closed.

Edited on Mar 30, 2008 at 11:37 PM

Mar 30, 2008 at 11:34 PM

Pixel Perfect
Offline
Image Upload: On

p.1 #10 · Hi Speed Synch

Photon wrote:
Pixel Perfect wrote:
For every stop faster than the X-sync speed you see the shutter speed, you lose 1 stop of flash power. So if in bright sun you are using 1/4000 say, that's 4 stops so you'll get 1/16 full power.
Yes, though there's also a slight loss of total flash output because the efficiency of the pulsed light is not perfect. In general, the optimum setting for maximum impact of the flash relative to the daylight will be achieved at the camera's x-sync speed. That's where you have the best hope of "overpowering the sun".
However, HS sync does allow you to use wider f/stops to control DOF, and there can be some action shots where the high shutter speed is useful to control blur, while the HS flash fills shadows.

That's why the old 1D with it's 1/500 sync speed was so good. Quite often you only want fill and naturally dial in about -1 -1.7EV FEC to achieve a nice balance, so if you had a sync of 1/250 and ran the shutter speed at 1/500 - 1/800 you'd be getting a similar result to dialing in the negative FEC and using 1/250, but you can use larger apertures like you say.

Mar 30, 2008 at 11:41 PM

Photon
Online
Buy and Sell: On

p.1 #11 · Hi Speed Synch

Pixel Perfect wrote:

That's why the old 1D with it's 1/500 sync speed was so good...

I moved from a Pentax 645 with 1/60 sync to the 1D, and thought "wow, 3 stops more flash fill in sunlit portraits". It does make a big difference, but thanks to the inverse square law, the effect on range of subject distance from flash is less than blind intuition might suggest. Still, a stop is a stop. A medium format focal plane shutter was ridiculous for sun + flash, whereas a 1DMk3 is quite workable with a 580.

Hey, we've crept all the way back to 1/300 on our way from the 1/250 of the Mk2 to the 1/500 of the Mk1. I never saw a good explanation for why we lost the ultra fast speed of the Mk1 shutter. Durability?

Mar 31, 2008 at 03:44 AM

Pixel Perfect
Offline
Image Upload: On

p.1 #12 · Hi Speed Synch

Photon wrote:

Hey, we've crept all the way back to 1/300 on our way from the 1/250 of the Mk2 to the 1/500 of the Mk1. I never saw a good explanation for why we lost the ultra fast speed of the Mk1 shutter. Durability?

No, the 1D had a CCD and had no mechanical shutter, the CCD itself could be switched on or off as fast as you like. Apparently though there were issues with the flash beyond 1/750 as the flash can't fire fast enough to get you all it's output. A CMOS cannot turn off fast enough so needs a mechanical shutter.

Others will know a lot more about this.

Edited on Mar 31, 2008 at 08:29 AM

Mar 31, 2008 at 08:28 AM


FM Forums \| Canon-mount SLRs \| Join Image Upload end