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Beyond the 1/50th M flash sync barrier

Frustrated by the M rangefinder's wimpy 1/50th maximum flash sync speed? In April 2000 "Jay" did the following experiments:

We all know the Leica syncs at 1/50th. That's the fastest speed at which the second curtain doesn't begin its travel until the first curtain has completely crossed the film gate. At 1/60, the flash "catches" the second curtain about 1mm into the frame. At 1/125, approximately 1/2 of the frame is blocked from the flash by the 2nd curtain, and at 1/250 only 1/4 of the frame gets flash exposure.
In practical use, 1/60 is fully usable for flash sync even when flash is the main light source, but that's not much to celebrate. 1/250 is useless even for fill-in. The interesting speed is 1/125. It is fully possible to use this speed for daylight synch as long as you position the subject you want "filled" in the half of the frame that gets hit by the flash […]
The most useful application is for a portrait of a person whose face is in shadow, with the camera held vertically. You need to hold the camera with the shutter button at the TOP LEFT, released with the right index finger reaching over the top of the camera. As long as your subject's face is in the top half of the finder, you can shoot fill-flash at 1/125 with good results.

Then in Jan 2001, Dan Cardish noted the following trick when using the M with studio strobes:

[…] I occasionally use my M6 with studio flash, and it handles well. I nice undocumented feature of the M6 (pre TTL at least) is that with the shutter uncocked, pressing the shutter button flashes the flash, a good way to check sync cords without wasting film.

M6TTL & M7 - X is the limit

This all sounds great, but there's major caveat: in June 2001 John Collier reminded us that the 1/125th trick does not work with either the M7 or M6TTL, as the camera electronics will only trigger a flash when set to the "X" s/speed setting (or slower). Turn the dial above "X" (1/60th, 1/125th etc.) and you lose the ability to trigger a flash. Thankfully the new Leica MP has dropped this "feature", letting you trigger flashes at higher s/speeds again.

High Speed Sync

Good news for high speed flash sync M fans - the M7 released in March 2002 finally does support HSS photography at shutter speeds all the way up to 1/1000th if you use the new Metz 54 MZ3.

How does HSS work? In Feb 2002 Eric M noted the following:

[…] The flash strobes from the time the first curtain starts moving 'til the time the 2nd curtain stops. Instead of having a flash exposure of 1/20,000 (or whatever) in the middle of when both curtains are completely open at the 1/50th, speed, you'll have multiple bursts spread out over 1/250, 1/500, or 1/1000th of a second.
[…] Just as the light from one flash is decaying, it fires again. An almost steady stream of light. Rather than sync the firing of the flash to the precise instant the entire frame is open, it fires the flash all the time. It's not like the flash fires "double" and has an over exposure. It's constantly firing to make a steady light source. That's why it can't do auto or TTL. The flash can't cut itself short...or the exposure wouldn't be even across the image. It also cuts down on the effective guide number of the flash. Takes more energy to continue to cycle the flash like that. Less overall light.
[… M7 HSS only works on manual.] No TTL. No auto shutoff. Get out either your flash meter or your guide number chart. Oh...and really increases battery consumption by the flash, too.
For a general discussion on HSS technology in a Nikon context, see:
1. <>
2. <>

Also, see the following URLs for online Leica forum discussions concerning HSS with the M7:

  1. < #003NT4>
  2. < #008JEC>

HSS with the M6TTL?

So now you are probably wondering, can you use this Metz 54 MZ3 to do HSS with your earlier model M6TTL?…

No. The M6TTL will only trigger a flash - any flash - when the shutter speed is at 1/50th. What about HSS with older Ms? Again no, this time because the older M's do not output the steady electronic pulse through the flash shoe while the shutter is open, which is essential to keep the Metz 54 MZ3 on track during HSS mode.

And in case you were wondering, only three of the flash contacts on the M6TTL are currently being used. The front (small) contact has been set aside for yet-to-be-specified future use.

Will a Nikon SB28 work with the M7's HSS?

No. As noted in June 2002 by "Jay":

Absolutely not. No Nikon or Canon or other speedlight dedicated to any brand other than Leica R8 or M6TTL (which means the SF20 or a Metz with 3501/3502 module) will interface with the TTL electronics in Leica cameras. The SB28 will not even give you straight TTL, only the use of the external non-TTL sensor or full manual. And I remember reading that some people tried using Nikon SB's that way on M6TTL's and the camera's batteries drained right down.

Frying your M's TTL circuitry

Think carefully before trying to use an old flash with your current M6TTL, M7 or MP! The output voltage of these thyristor monsters may fry your electronics.

Net myth? No - see for a discussion of this issue with respect to Canon EOS cameras. Furthermore, see the following link for a detailed table of "Strobe Trigger Voltages" created by different camera flashes:


Finally, see the discussion at < #003wLQ> and the Aug 2003 follow-up at < #005hBr> for a table of common flash units vs. whether or not they are safe on a Leica M.

FWIW I don't think the occasional use is harmful. I own an old Metz 30BCT4, which according to the botzilla list triggers between 70V and 170V. Measuring it with my trusty voltmeter, mine actually reports 160V. Yikes right? Well not really, I've often used it with my M6TTL without problems. As in all things online, YMMV.

Safe voltage adapter

Rather than buy a new "digital safe" flash, you can buy an accessor voltage adapter. The most commonly avaialbe is the "Wein Safe-Sync Hot Shoe to Hot Shoe" (HSHS 990-560), which can be bought for $US 50 from B&H Photovideo — product ID # WESSHSH.

A note about possible broken links

This FAQ has over 900 external links. Over time it is inevitable some of them will break. If you are bothered by this, see this detailed topic elsewhere in the FAQ.

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