Nikon D610 flash sync: limited to 1/200 or 1/250 possible?

Question

I'm using a Nikon D610 and I'm a little bit confused about the whole "auto FP" thing for Nikon. From what I understood, auto FP permits flash sync at high speed with a "power loss" for the flash.
In the D610 manual (p. 234):

1/250 s (Auto FP) : Auto FP high-speed sync is used when a compatible flash unit is attached. If the built-in flash or other flash units are used, shutter speed is set to 1/250 s.

However, this speed is only available with auto FP; it's not available "alone", unlike the 1/200 s.
Does that mean that a "real" flash sync at 1/250 s is possible with the D610, without power loss? I didn't find a clear answer.
My goal is to use this speed with an off camera flash, triggered by a wireless unit.

EDIT: the proposed duplicate is not absolutely clear on the subject: there's not a clear "yes" or "no".

Answer 1

HSS (High Speed Sync) is a radically different flash mode than regular speedlight flash. HSS flash units, in HSS mode, switch to becoming a continuous light, continuous for only the duration of the focal plane shutter travel (i.e, Not an instantaneous speedlight pulse). Continuous light (such as sunlight or incandescent light) has no sync issue, it is always on anytime the shutter opens. So continuous mode allows high speed shutters, called high speed sync, because there is no sync issue. HSS is anything BUT high speed flash, it is the opposite, fully dead slow, continuous like sunlight, which cannot stop any motion, but simply has no sync requirement.

HSS does have the fast shutter speed to help, but speedlight flash is faster than the shutter, and runs circles around HSS, in regard to speed or power. Speedlight flash duration depends on power level, and is tremendously fast at low power levels, perhaps 1/3000 second at 1/4 power, and perhaps 1/30,000 second at 1/32 power level. It is called "speedlight".

The point of HSS would be to allow a fast shutter speed so that maybe f/2.8 would be possible with flash in bright sunlight. But the power range is limited.

Auto FP is just Nikons way to enable HSS. If you set 1/250 Auto FP, then 1/250 is still speedlight mode, but any faster shutter (allowed then) is HSS mode. Saying, if the camera recognizes the flash is present, then the shutter speed will not be allowed to go faster than speedlight sync speed. But in Auto FP, it will, and will become HSS mode then.

Both the flash and the camera have to be compatible about HSS. That leaves out any wireless radio trigger. Except the Nikon Commander can do remote HSS. But the real meaning is that regular speedlight mode and regular 1/200 second is likely far better, and works with the wireless trigger.

Here is more elaboration about HSS: http://www.scantips.com/lights/flashbasics2b.html

Answer 2

With the Cactus V5 "manual only" triggers you'll probably not be able to use the '1/250 s (Auto FP)' setting to sync at 1/250 s. You might even have trouble using 1/200 s with manual flash triggers not detected by the camera.

Since the camera probably won't even detect a flash is in use, the camera will let you use any shutter speed you want. But you'll likely have issues with 'black bars' at the top and/or bottom of your image if you push it past 1/200 second. You may even need to go a bit slower than that, depending on how fast the Cactus triggers relay the 'Fire!' signal to the Metz flash.

With a CLS-compatible Nikon flash on the hot shoe or even if using an SU-800 optical controller or a set of radio triggers that are fully CLS/i-TTL compatible to control a CLS flash capable of Auto FP you should be able to use the 1/250 s sync off camera. Your camera's built in flash and most CLS-compatible flashes mounted on the hot shoe will certainly sync at 1/250 s when the '1/250 s (Auto FP)' option is selected. (Please see pages 146, 234-35, and 294 of the Nikon D610 User Manual)

Here's the best, most concise explanation I've seen about how the 1/250 s (Auto FP) and 1/320 s (Auto FP) settings work when selected under the 'Flash sync Speed' menu item of Nikon bodies capable of Auto FP. But it assumes you are using a flash that the camera can detect and communicate with beyond the 'Fire!' command.

Answer 3

On a modern DSLR such as your Nikon, [approximately] every shutter speed between the minimum and maximum is [usually] available...e.g. 1/17 second, 1/1122 second and so on. However, only some of them can be set by the user -- typically in 1/2 or 1/3 stop increments. The camera is able to select the other shutter speeds in "automatic" modes such as Aperture Priority and Program modes to precisely control exposure.

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Answer 4

TL;DR:
1/250 s speed sync is available with a manual "dumb" flash sync'ed with a cable, but not with a Cactus trigger.
1/200 s (and not above) is available with a Cactus trigger.
For the detailed tests, see below.

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OK, so just for the sake of it, I did a few tests. I took 4 photos, same aperture, same lightning condition, with the flash off-camera, sync'ed with a cable (using only the single plot of the hotshoe, so no TTL or other fancy thing). Only the speed is changing.

Exposed at 1/320 s, f/2, without flash: -> Well, just a plain boring photography of my wall, but with good exposure. You can admire the vignetting of the Nikon 50 mm f/1.4G.

Here, exposed at 1/320, f/2, flash at full power: -> I did the opposite to make the black line more noticeable! So, easy to say here that the speed is beyond the flash sync speed. Not surprising, as the D610 doesn't mention this speed available for flash sync.

Here, exposed at 1/250 s, f/2, flash at full power: -> Yes, this picture is entirely white: meaning, this speed works!

And, no surprise, exposed at 1/200 s, f/2, flash at full power: -> Picture entirely white: this sync also works.

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EDIT: and now the test with the Cactus. The documentation mention a top speed at 1/1000 s, so 1/250 s should be OK, right?

1/320 s @ f/2, flash at full power: -> We can see a larger band than with the straight cable...

1/250 s @ f/2, flash at full power: -> The second curtain is starting to show... So this speed is not possible with the Cactus trigger :(

1/200 s @ f/2, flash at full power: -> This speed is OK.