Sunday, May 05, 2013

What Really Happens When a Fuji X100s "Syncs" at 1/4000th of a Sec



For leaf-shutter flash geeks only: high-speed Phantom v1610 video of a Fuji X100s shutter not-quite-really syncing at 1/4000th of a sec.

Sorry, I know many of you will be bored to tears by this. But the full technical article photographer Kevin Housen developed around this video (and others, at different shutter speeds) will really peel the onion for you if you want to know about the demonstrable quirkiness of this camera and ultra-high speed sync.

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22 Comments:

Blogger Mac said...

So the max sync speed at f/2 is really 1/500 on the shutter speed dial. Still PDQ - but not the jaw-dropping speed we might have thought.

May 06, 2013 4:27 AM  
Blogger Mac said...

So the max sync speed at f/2 is 1/500 on the shutter speed dial. Still PDQ - just not the jaw-dropping speed we first thought.

May 06, 2013 4:29 AM  
Blogger MacLo said...

"figata" ;)

May 06, 2013 5:17 AM  
Blogger David Donnelly said...

Like. I am an engineer :)

May 06, 2013 8:20 AM  
Blogger Jake said...

Very cool video.

Doesn't the shape of the aperture affect things like the quality of bokeh and the "star" like appearance of bright lights? Seems like wide open at shutter speeds faster than 1/600 you would start to get some odd effects due to the irregular aperture. Have you noticed such things or do you just avoid the combination of wide open aperture and very fast shutter speed?

May 06, 2013 9:22 AM  
Blogger David Beholder said...

So what is real sync speed at what aperture if it's aperture dependable. I can't find the data =(

May 06, 2013 2:08 PM  
Blogger Unknown said...

@ David & Jake

The whole question of sync speed is a little muddy. Technically, you can't sync wide open on the x100s faster than 1/600 on the shutter. But really what that means is your depth of field won't be quite what you think it is. And, yes you will see some change in the bokeh. There was a link in David's post from a few days ago that showed some images taken at different shutter speeds. They noted the bokeh had kind of an elongated shape. But they had to kind of pixel peep to see the difference.

From a strobist's point of view, I don't think its too big of a deal. At 1/4000 with an OCF set to 1/8 power there isn't much loss of light (as David has noted before). And I suspect even 1/4 power would be useable, though I haven't tried it. In any event, way better than your standard DSLR!

May 06, 2013 3:11 PM  
Blogger Neil Benda said...

So is this camera faster than the Nikon D70s?

May 07, 2013 7:21 AM  
Blogger Lee Hammond Photography said...

There is a little more, including the PW/cable comparison vs flash power level, here: http://www.khousen.com/blog/files/f9ec55a80ee0fbde5e9c97c0183beec2-2.html

May 07, 2013 4:04 PM  
Blogger An Atheist said...

I understand (or thought I understood) how shutter speed and aperture work so I am a little confused why f/2 isn't really f/2 because the shutter doesn't open and then close as expected. If aperture is wide open then how does a faster shutter or slower shutter change depth of field? I thought the two were not dependent on the other? I realize the amount of light is affected by their individual settings, but not depth of field.

May 07, 2013 4:25 PM  
Blogger LudaCliff said...

Very interesting post. This past week I have been testing this on my x100s with a Quadra pack, A-head, and SkyPort TX. With the Quadra set all the way down (P2.0/25Ws) and camera at f/2, I noticed the flash power was most optimal at 1/500. Flash power decreased as shutter speed increased (1/640, 1/800, 1/1000, etc.) There was almost a 1 stop difference from 1/500 to 1/1000. I have been searching the web the last few days for more info on this, but this post pretty much answers it for me. Flash power at 1/640 and 1/800 looked like a good trade-off for shutter speed. If not, I would use an ND (built-in or external) and increase flash power.

May 07, 2013 8:41 PM  
Blogger Adophgraphy the art and science of imagery said...

The interesting thing for me is, that Sony didn't have this problem with their Sony DSC-R1 which was capable of syncing flash at its widest aperture (f2.8) at speeds as fast as 1/2000.

May 07, 2013 8:48 PM  
Blogger Bernardo Nielsen said...

Very nice visual explanation!

I'm a bit confused on what would be the best choices for off-camera flash units and triggering methods for the x100/s's high speed sync.

I guess I need to look for units with high outputs and fast t.1 times.

The way to trigger the units also has an influence on the outcome. Would I be right to think optical slaves are faster than radio triggers (light is faster than radio waves)? TTL cords have proven to be faster than PWs... Maybe I should consider buying mostly optical slave flashes for use with the x100?

May 07, 2013 9:45 PM  
Blogger Mark Davidson said...

Well, it really can sync at 1/4000 it just wont do it in a manner that you think it will.

If you work around the limitations you still get sync, just less light.

May 07, 2013 11:32 PM  
Blogger Clark Schierle said...

Interesting. So does this mean that any part of the photo lit by ambient is experiencing a true F/2 while the flash lit subject is being exposed as closer to F/2.8 at 1/4000? If so this could still be really useful for the whole overpowering daylight with and ND filter for smooth bokeh scenario since the background blur would be defined by the F/2 while your subject would be lit at F2.8. May actually help to have a bit more DOF on the subject to make them pop against the blurry background, as long as your flash has enough juice to overcome the one stop loss of light and a t.1 of less than 1/600 at that power.

Still a pretty sick little camera. My X-E1 should be very nervous.

May 08, 2013 10:55 AM  
Blogger Jake said...

So does this mean that any part of the photo lit by ambient is experiencing a true F/2 while the flash lit subject is being exposed as closer to F/2.8 at 1/4000?

I think not. At 1/4000 The sensor doesn't even start exposing until the leaf shutter is nearly closed. The "nearly shut" leaf shutter acts like a second aperture at 2.8 or 4 or 5.6 (depends on how close to shut it is, the faster your shutter the closer to shut your leaf shutter is when you start the exposure), so if your set to f/2.0 at 1/4000 you would actually be shooting something like f/2.8 or f/4.0 or f/5.6 at 1/4000. I do not know what the "effective aperture" would actually be, only that it would be smaller than you asked for.

May 08, 2013 1:43 PM  
Blogger Petar Maksimovic said...

@An Atheist
Well as i understand it, light goes in trough the same hole/tunnel where shutter and aperture are located, so if the shutter disturbs that opening by closing partially in a weird time sense it's gonna effect the aperture to.

May 08, 2013 6:16 PM  
Blogger Unknown said...

@ Adophgraphy

I'm not familiar with the Sony, but I would have said the Fuji syncs pretty well at 1/4000 (well... maybe 1 stop loss of light) before I saw the high speed video. Without it you wouldn't know that the shutter is halfway closed when the flash fires (and the exposure starts).

If the shutter closing time of the Sony is about the same as the Fuji (I don't know if it is or not), then the Sony would behave about the same as the x100s.

Kevin H.

May 08, 2013 10:12 PM  
OpenID seersuckersuit said...

Seems to take a lot of the shine away from the x100s leaf shutter. Correct me if I'm wrong, but effective 1/600 sync speed on a camera with native 200 ISO = 1/300 on a 100 ISO DSLR, so only a quarter-stop of ambient dimming more than you'd get from a standard DSLR.

May 10, 2013 8:44 PM  
Blogger Unknown said...

@ seersuckersuit

Doesn’t work that way. Sync speed is sync speed.

I don’t think it takes much of the shine off the x100s. You can shoot at 1/4000 at 1/8 power on the flash w/o much loss of light. At 1/1000, you should be able to go all the way to ½ power on the flash. That was based on my tests with a Canon 430EXII flash. But I suspect others will be similar, some better. This is way better than you could ever do with most DSLRs – as David has pointed out.

Kevin H

May 11, 2013 8:56 AM  
Blogger Clement said...

Just a suggestion for Fuji if they want to get extremely awesome. Can you make a firmware upgrade that would allow us to trigger the flash slightly ahead? We'd be able to shoot with our radio triggers and we'd also be able to get an extra humff from a flash at full power. There is a bit of lag when the shutter has to close before the shot, those micro-seconds could be used to our advantage.

May 15, 2013 5:16 AM  
Blogger Pj Smith said...

It seems as though a few commenters are confused about the function of the shutter for this camera, which is totally understandable. A conventional DSLR has a focal plane shutter, which due to it's location at the focal plane only affects the exposure time of the sensor (in essence casting a shadow on the sensor).

From my understanding, this camera has a shutter which is closer to the lens and out of the focal plane. That means it acts as a second aperture and doesn't cast a shadow on the sensor. This is important because for shutter speeds above 1/1000s the shutter is at least partially closed before the sensor turns on, and if it cast a shadow you would have a vignetted photo. Instead, all you have is a reduced intensity (as if you'd stopped down) as the sensor waits for the shutter to close the rest of the way.

In summary, at shutter speeds faster than 1/1000s the camera is effectively shooting at a higher f/#, with its consequential larger depth of field.

May 17, 2013 3:13 AM  

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