UPDATE, JUNE 2024: Strobist was archived in 2021. Here is what I am up to now. -DH


Hacking Your Camera's Sync Speed, Pt 1

This weekend's shooting reminds me of the love/hate relationship I have with my job as a newspaper shooter.

Hate: Working a 12-hour day, much of it in draining heat, only to have a couple of small photos run in the backwaters of the sports section.

Love: Getting to watch two phenomenal pitching performances at the state softball championships. The first game was merely a no hitter, thrown by a sophomore against a team good enough to make it to the 4A Maryland state championship.

The second was a perfect game thrown in the 2A championship, in which another 15-year-old sophomore struck out 19 of 21 batters faced. They gave up trying to hit her half way through the game only to find out that they could not bunt her, either.

It was just an insane performance. And she stood out there on the mound with a huge grin on her face the whole time, knowing that she owned them.

But the three games (and the continuing effects of my #$!@*!! allergies) pretty much made me useless for Sunday. And even on Monday, I am writing through the murky haze of Benadryl. So if I fall asleep in the middle of a sentence, you'll know why.

Today we are talking about sync speed, and how to raise it. But before we explain it, why would we even want to do it?

As we learned in the balancing light posts of Lighting 101, the ambient light exposure is affected by both shutter speed and aperture. The flash exposure cares only about the aperture, as long as you are operating at a shutter speed at which the camera and flash can sync together.

So, for every stop you can raise your shutter speed and still sync, you can open up the aperture one stop. This means that your flash can get the same lighting effect using half the power. Which makes it potentially far more powerful.

In normal operation, the sync speed is the fastest speed at which the entire chip can be reached by the light of the flash at once. At faster speeds, a mechanical shutter basically forms a small slit that travels across the CCD, with only a small portion visible at once. So a single burst of a flash cannot light the whole frame.

There are three ways to increase your effective synch speed: Focal plane flash, partial frame sync and exploiting an electronic shutter.

The first method is very specific to camera/flash combinations, so I am not going to give it much space here. Suffice to say that if you have a high-end digital camera and flash, you should check in your manual to see if it offers anything that says "FP Flash" or "Focal Plane Flash," or "High-Speed Flash," etc.

Basically, it fire a series of pulses (when you are over your normal sync speed) that have the effect of lighting the whole frame as the shutter slit travels across.

If you have this option, definitely enable it. Simple as that. Both my D2Hs and the D2Xs do this with my SB-800's, and it works pretty much seamlessly. (On my cameras, the FP flash enable function is at E-1 in the menu bank on the cameras.)

If you have different camera/flash combos that work in the FP flash mode for you, please post the combo (and, just as important, how to enable FP flash) in the comments. I will bring the info up top in a later post. We can compile a database pretty quickly.

One caveat with high-speed flash is that the flash loses effective power with each increasing shutter speed. This is because of the pulsing nature of FP flash. So you have to work at relatively close range. But you can still darken the sky, and/or shoot with a wide-open aperture to blow out the background. You can also reclaim power by grouping multiple flashes in the FP mode, using the Nikon's CLS or Canon's ETTL controlling systems. If you want to know how to do that for you system, hit the instruction manual.

But today, we are talking about a method that far more of you will have access to: Exploiting electronic shutters for ultra-high-speed sync.

Electronic shutters also have auxilliary mechanical shutters that actually open and close up to, say, 1/125th of a second. This helps to protect the CCD from dust and damage. Beyond that speed, the computer just grabs a progressively smaller slice of time from the CCD and "fakes" higher shutter speeds electronically. Which, as it happens, is totally golden for us.

Why electronic shutters? You can manufacture this type of shutter far more cheaply and it will last for a long(er) time. You are essentially avoiding having to engineer for the stresses of high-speed mechanical shutter operation. Thus, if you have a lower-end digicam, you likely have an electronic shutter. A good clue is if 1/500th of a sec sounds clunky, like you are still shooting at a 60th.

Why is this so cool? If you think about what we said above, you physical shutter is open all at once for all of your shutter speeds. I.e., no slit for the flash to deal with.

So, you can get high-speed flash with any flash. And you are not wasting flash energy on a series of pulses, either. To my mind, this is far more effective than FP flash.

As I mentioned above I use two flagship, company-supplied Nikons: The D2Hs and the D2Xs. But I plunked down my own cash for a body that has quietly become a little darling of the pros: The Nikon D70s.

It is small, light, not particularly heavy-duty and sports a 6.1MP chip. That sounds small by today's standards (the camera is about a year old) but it gives more than 3,000 pixel on the long dimension. Which is plenty for my needs.

You can still find them refurbished by Nikon USA for about $500 USD. I love mine, and it does things my "better" cameras cannot do.

I'm sure that there are other cameras, from various brands, that use electronic shutters. I would love to hear about your combos in the comments, so I can bring them up to the main post on an update later.

Back to the D70s, here is how to fake out the sync. It couldn't be simpler: All you have to do is make the camera think there is not a flash connected. Then it will not arbitrarily limit your shutter to it's nominal sync speed of 1/500th of a second, which is a pretty good sync speed to start with.

As long as there is not a TTL-capable flash connected to the camera - either on the hot shoe or with a TTL cord - you are good to go. So, if you are using a Pocket Wizard or a sync cord, your flash will sync above 1/500th.

This is one case where a PC cord trumps trumps the PW, as the electronics inside a PW will slow down the upper limit on this trick. But even with the Pocket Wizards, I can sync well above 1/1000th of a sec. I do not know if this will work with a Gadget Infinity remote. (It probably won't.) But I know it will work with a PC cord (and a required hot shoe adaptor in the case of a D70s.)

Case in point is this quickie portrait of a high school tennis doubles team. (I had five minutes to do this and two head shots between warm-ups and practice.)

The ambient exposure of the hazy/sunny day was ~1/1250 at f/5.6 at ASA 200. So I underexposed the ambient a stop by shooting at 1/1250th at f/8. The sun, as you can see, is coming across the back of their shoulders. Look at the shadow near the racquets on the ground to confirm.

Now, the high shutter speed gives me a lower aperture and the ability to dominate sunlight with a small flash. In this case, it was a single Nikon SB-26, on a stand (sync'ed by a PW) in manual mode and set to 1/4 power. I put the beam at 85mm to get a little more lighting efficiency, given it was about 10 feet away.

Why 1/4 power? Because recycle time will be negligible. No waiting to fire. But, it is important to note that I could have shot at 1/1 power and dropped the aperture to f/16. Thus, I would have been able to overpower daylight by three stops. Now, that is power.

Here's your limiting factor: The actual duration of the flash pulse itself.

A manual, full-power flash takes about 1/1000th of a second to discharge. A half-power flash discharges in about 1/2000th of a sec, a quarter-power flash in 1/4000th, etc.

So you are not going to get all of a full-power flash in a 1/8000th of a sec, no matter how your shutter slices it. Basically, you can sync a full-power shot at 1/1000, a half-power shot at 1/2000th, a quarter-power shot at 1/4000, etc. This assumes a PC cord with no time loss due to the electronic circuitry in remotes. But I can consistently do a half power flash at 1/1250 with my Pocket Wizards. Beyond that it gets dicey. But I can always switch to a PC cord to further stretch it.

Next, we will talk about how to work beyond the limits of your mechanical shutter. Long story short: Not camera/flash model dependent, but less stretching to be had.

And again, please list your various electronic shutter cameras (and their fast-sync capabilities) in the comments, and I will bring them up to a round-up post when time permits. If you are not sure, just test against a wall indoors to see what your off-camera outfit is really capable of.

You might be surprised.

Related post: Balancing Light, Pt 1
(Part two continues, linked from Part 1)


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