Paul C. Buff, Inc. Technical Forum

I've read a lot of threads about this and understand that there are a lot of variables but I thought I'd ask for a simple answer.

Is there a way to tell what flash will be best for using the Pocket Wizard TT5 system when strobing past 1/250? Everything I read points to shooting at full power but Im not sure if I should be looking at 1T or 5T times for maximum effectiveness?

Basically I'd like to be shooting at f2.8, ISO 200, 1/3200 to stop action in bright sunlight and I want the most powerful flash I can get to help achieve proper lighting during that exposure. I'd assume the AB1600 would be the best because it's full power flash would be the slowest but are the X1600 or X3200 going to give me any advantages?

Sorry, just trying to keep it simple so I'm not buying and testing 4 different flash systems.

Hyper sync is a hack for turning a monolight into a short duration constant light.
That means that the monolight with the flattest tail from peak power to T.1 is the best.

That generally means the lowest powered option.

I have a test I did with hyper sync on my tutorial website www.digifotographi.com

dmward, your link doesn't work or your site is down.

I understand that you want a flat and constant tail end of the flash, but you would also want a high intensity burnout too right?

All AB models (and essentially all other non-IGBT lights, have exactly the same characteristic waveform shape from the start to the end of the flash (classic RC discharge curve). Additionally, ABs have identical color, tint and flash duration as RX600/300.

The whole Hyper Sync thing is misunderstood by almost all users. People think that using a slow flash duration light will provide more light than a faster duration light of the same WS rating. When one understands how Hyper Sync actually works, this fallacy can be understood. Take two 600WS flashes, one with a 1/100 t.1 duration and one with a 1/400 t.1 duration. They both have the same discharge curve, but one produces 1/4 the light intensity for four times the time.

Now, look at how Hyper sync works: On a Canon or Nikon DSLR with focal plane shutter it takes the shutter typically 1/250 second or longer from the time the first curtain open to when the second curtain closes. This is why convention sync speed is limited to the 1/250 second sync speed. With continuous light, even at, say a 1/4000 second exposure time, it still takes this 1/250 second for the curtains to slide across the frame, but it travels as a moving slit 1/4000 second wide, so the continuous light must be present for at least 1/250 second to expose the entire frame.

With true HSS, the flash is pulsed rapidly so it appears as continuous light for 1/250 second. But any particular portion of the image sensor is seeing this light for only 1/4000 second. Therefore the actual exposure is only utilizing 1/16 of the total light emitted. So a 64WS speed light effectively becomes a 4WS light and exposure is reduced by 4 f stops in going from 1/250 to 1/4000 second exposure time. Exactly the same thing happens to the ambient sunlight. So the ratio of ambient to flash remains the same and the flash cannot overpower the sun any better at 1/4000 than at 1/250. The difference is action is stopped better at 1/4000, but the lens must be opened by four f-stops . . . so an f8 exposure becomes f2.0. (or you can increase ISO from 200 to 3200 and maintain the f8.

With Hyper Sync, it gets worse. The flash has to be present for the same 1/250 second it takes the shutter to cross the frame, so a t.1 flash duration longer than about 1/200 is needed in order to illuminate all portions of the frame, regardless of exposure time. But the light from a flash is not constant during this time. At the peak of the flash, it is 3.2f bright than it is at the t.1 "end".

The timing of when the shutter is activated is "tweaked" by the Hyper Sync device such the the flash is fired slightly before the shutter so that the peak intensity of flash occurs slightly before the first curtain begins to expose the sensor, and as the moving slit is exposed, the flash intensity is decreasing exponentially over time. So the higher exposure time attempted, the greater the exposure difference from one side of the image to the other, resulting in up to a 3f or so difference in exposure across the image. So you may only be able to increase the exposure time marginally over the inherent flash sync speed of around 1/250.

Indeed, by using a longer flash duration flash, you can improve the edge to edge exposure variation at a faster exposure time, but you are still using only a tiny slice of the total flash power. The longer the flash duration, the smaller slice of the total WS you are using. This is further complicated by the fact the actually intensity of the slice being used is proportionally decreased by the physics of a slower flash source - less light/longer duration.

You can quickly reach the point where a 1000WS slow duration studio flash will produce inferior actual-use results (no real exposure increase but edge to edge evenness than just using a dedicated true HSS speed light (but using 15 times the bulk flash power to achieve it.)

For me, the whole Hyper Sync process is a relative technology dead end, IMHO a toy for people to play with (constantly tweaking and hoping to beat the physics). Some have differing opinions and still want it and may be able to tweak the timing and get a little better result than I've described. That's why the MC2 product is an LPA product rather than a Paul C Buff product. It's very useful for achieving non-Hyper Sync features of PW with Einstein, but if you really want to out perform a dedicated speed light with true HSS, you're really going to need something like a 2400WS slow Speedotron pack and spend 2400WS of light to get 10-20WS of usable light.

If i were me, I would settle for a CCD camera (D40-D70 or G11, G12, etc) and an Einstein and settle for the somewhat lowered image quality, but with real conventional sync up to 1/4000 and higher with ample flash power to overpower the sun, fast recycle time, no waste of power and none the disadvantages of Hyper Sync that, again, IMHO, degrade the image quality as much or more then a CCD camera.

(Note - you will have to use a direct sync cord rather than a radio trigger to get much 1/2000 second due the time delay introduced by any radio tripper.)

Other opinions or debate are certainly welcome here. This is a rather complex to answer in a forum and requires many pages to present in a form all can understand.

Thanks, Paul. That's probably the best summary I've seen :)

Thanks so much for the detailed explanation.

This sounds like pretty bad news for the image I want to make then. It requires shooting in water with fast action sports. So that means no sync cord, and no prosumer camera that doesn't allow for wireless syncing (in a water proof housing no less).

I'm definitely not looking to adopt a system that I use all the time...I know that HSS is more of a pain than it's worth 99% of the time and it's super inefficient. But it doesn't change the fact that it might be the only option for creating the image I want to create in this particular situation.

I'm not worried too much about slight light fall off across the frame because I'm going to be lighting a single athlete with mostly ambient sky/water as the background which not be affected by the flash. Also I'm sure by the time I photoshop and stylize the image the fallout will not be noticeable at all.

Here is a test shot I did with the ABR800 at ISO 400, 2.8, 1/3200 which got me pretty close to the ballpark exposure. It also produced a sharp image when panning the camera which the comparable exposure at Xsync did not (1/250, ISO 200, f16 I believe).



The only problem with this image is that the light was about 5 feet to the right of the lamp and I need it probably 10 feet away for safety reasons. Maybe I could shoot later in the day and drop down to 1/1600 or 1/800 as I'm not sure at what speed will the motion blur start showing up again.

Anyways, thanks for the thorough explanation. It sounds like you don't want to make a recommendation for an AB flash that will perform the best in this situation even if it's not super efficient? I'd buy a D40 for this project if it would work in my water housing but I don't think it will....might have to ebay one and try though :)

Will your camera be IN the water, or UNDER the water? If under the water, your radio remotes will not reach very far (less than a foot, probably), as water is an attenuater for RF signals.

With that said. Depending on the composition of the shot, you may be able to use the "black bar" to your advantage. (In bright ambient light, it is far less apparent than in the studio, due to the ambient contributing to the exposure). Simply place the subject where the black bar would not be (if possible). This can also be manipulated with PW and HyperSync.

In my toying around with it, the 1600 did better than the B400. These were very informal tests, so dont take it as gospel.

That's an interesting idea I did not think about. I'm thinking my subject might be lower in the frame with dramatic sky above which might require shooting upside down which is still possible.

The camera will not be underwater but will be above and around water with splashing and waves hitting the camera for the most dramatic effect. I'm mainly a wedding photographer and know how difficult it can be having PWs perform 100% even near a beach so I have my work cut out.

I might just go ahead and get a AB1600 with the vagabond pack just to have a throw around powerful strobe for random projects. If I can get this to work with either method then I think it will cause a good little buzz on the net since people love technically challenging photoshoots....even if they drive me crazy planning for them :)

A picture says a thousand words - so I'll provide the pertinent EXIF data along with the image - and inquire upon the following...

1. How is this technology a dead end?
2. Where is the image quality degraded?
3. What manner could this have been accomplished in the same or better manner?

Info about the image: Taken @ 5:30 CST on 6.12.11 in central Iowa. Somewhat cloudy day, at the moment it was full sun behind the subject (camera facing directly West). The sky was metering at 1/8000.

Lighting: 1 Einstein with a Vagabond mini. Bounced into a small Westcott soft silver umbrella camera left - feathered across toward camera right.

Triggers: PocketWizard FlexTT5 w/ AC3 and MC2. Einstein set to zone A on a control TL channel. AC3 Zone A on manual and at full power (+3).

Pertinent EXIF: Canon 40D, f2.8, ISO 100, 1/4000

Editing Info: A b/w conversion in Lightroom, that's it

There are times and situations where it will work better than others, with this example being the closest to ideal, and some users may have better skill at tweaking it, and some flashes and perhaps some cameras will do better than others. Shallow Depth of Field with bright ambient light is possible with HyperSync (in some cases). It is also possible with ND filters, in which good copies will have a negligble effect on I.Q..

Additionally, many (most) users we speak to are seeking a solution for stopping action. Unlike a typical shallow DoF portrait, this usually requires the lights to be a good distance away, thereby reducing the amount of flash on target, often to unusable levels. Also, the more flash vs. ambient that is present can yeild a noticable gradation.

Nobody said it is unusable in any capacity, but it is not the magic elixir everyone expects it to be.