Paul C. Buff, Inc. Technical Forum

Reflectors won't work most of the time as we have wind here a lot. For the size reflector I need, I would need at least one or two assistants holding it. The flash setup I use right now is small and easy to set up on a normal light stand. It also allows me to adjust the power from the camera which is a big advantage.

Oh well I guess for now I will stick to my SB-800 flashes. Not ideal, but it works.

That's unfortunately the problem w/ reflectors....you'd probably need one of those big 74" oval ones. Too bad you can't enlist an "escort" to help :)

What about this...

A) Use a AB400 (or WL set at 1/4 output & full power) which will give you flash duration of 1/2000
B) Use film ND filters to tone down the flash output to what you need
C) Use 1/200, 1/250, or what ever max standard sync speed is on your camera
D) Set the camera for rear-sync flash timing

I would think the 1/200 or 1/250 would eliminate background blur enough and the 1/2000 flash duration would freeze the dancer as you wish. Rear sync would keep any ambient from causing blur after the flash.

*** You could also use a Einstien set at low power for 1/6000 second an combine that with your camera's max standard sync speed and rear curtain sync for a better result.

On a moving subject, you would still have ghosting/blur. Lets take and extreme example in that without flash, you have a silhouetted figure on a light(er) background. If it does not move, then the dark shape will be deliniated from the back ground by a sharp line, as everything that is masked, is done so for the entirety of the exposure.

With the flash still off, and the subject starts to move, the general shape of the subject will remain equally as black, as something will be masking the background throughout the exposure. The edges of the shape will be more or less translucent/ fuzzy/lighter, as the subject is only covering the background for part of the exposure, allowing light from the background to show for the other part. This would be the "blur", and exists without flash.

Once we introduce flash, the ambient exposure will remain constant, dark in the middle, lighter on the fringes. When the flash fires, it then adds exposure to the foreground subject at the point the subject is at that time. Any movement before or after the flash fires will not be lit by the flash, but will still mask part of the light coming from the background.

What you get is a crisp image created by the flash with a darker halo around the flash lit moving subject on the side moving that the subject was moving from (or to). This halo is the silhouetted subject masking the ambient lit background, but moved before (or after) the flash fired.

By moving the direction of the ambient light, you will shift the luminosity of the blurred area. If the subject is front lit, then the blurred area will take on the color(s) of the subject, and will render what is commonly thought of as blur. Depending on settings of the camera, flash, and intesity of ambient, the halo of blur will remain constant at a constant shutter speed, but the luminosity can vary. Only if there is no ambient impacting the image for the subject to mask or move during would flash freeze the motion entirely.

First curtain or second curtain changes will only dictate which direction the blur or halo appears. Even still, ambient light still enters before first curtain flash sync (the time the sensor is exposed while the first curtain is opening) as well as after 2nd curtain sync (the time after the flash fires as the second curtain finishes its travel). This can lead to halos/blurring on both sides simultaneously to a certain degree.

Additionally, on Canon cameras, 2nd curtain sync is not available, unless you have a dedicated speedlite as the device being triggered (i.e. not a CberSync, PW PlusII, Cactus 5, PC sync cord, etc.).

The only way to freeze ambient is by shutter speed. Syncing flash at higher shutter speed presents a new set of drawbacks, discussed in the sticky threads on this forum.

TS,

Wow, thank you for the very detailed and understandable explanation! While reading your reply, I could not help but wonder what the (typical) threshold is for switching from a studio strobe (even a fast one like Einstein 640) with 1/200th or 1/250th camera shutter, to a speed light based scenario since I assume only OEM speed lights support not only ttl, but also high speed sync.

*** Any thoughts about this threshold from a practical standpoint?

As megapixels increase in cameras like the Nikon D800, I would think this problem would become more noticable when viewing images at 100% in post. But then I have to belive that medium format shooters have been shooting model 'jump shots' for some time and I doubt that MF cameras support any kind of high speed sync.

I can see how needing to pan with a moving subject like a motocross racer or a baseball player would easily need a high speed sync solution to freeze background and subject, but if the camea is realatively steady in relation to the background at 1/250 shutter, then what would be a common threshold when you would switch to high speed sync.

I ask for your thoughs on this as I am just getting started with studio flash (I have AB and one WL so far) and was previously assuming that adding one or two Einstein units would take care of my high speed flash duration needs with about any moving subject but apparently that may not always be the case.

With the release of the PW system supporting TTL and high speed sync with camera OEM speed lights, it would be nice if a product Einstein 640 or some new product could find a way to support high speed sync even without TTL (I prefer to set flash settings manualy anyway)

QUESTION UPDATE: Just before hitting the 'submit' button on this question I decided to read the PW web site with its flex tt gear. They seem to have something similiar to high speed sync called "HyperSync". Is this supported by PB on your strobes? Does it work with AB, WL, and Einstein units? Does it only work on Einstein units? Is this FlexTTx product a good solution/alternative to purchasing OEM speedlights for hypersync support?

Leroy

generally speaking, flash needs to be about 3 stops over ambient for the ambient to not be a significant contributor to exposre (and as a result, blur). Fortunately, shutter speeds can be used to dim ambient without altering flash exposure (at least to a point). How you get there or if you want to get there is the real question. Do you want to have your ambient completely dark? It does not sound like it, so how to get there is not really relevant. However, should you want to get there, set ambient exposure for -3f using ISO and shutter speed first, then stop down the aperture as needed and add as much flash as necessary by using the proper powered light, position, and modifier.



Yes, if you look at it 100%, it very well may be worse. However, if the end use is the same, then the end result would be the same. That is to say if you made a 20x30 print using a 12MP camera and an identical 20x30 with a 36MP camera, the problem would be more or less equal in both 20x30's. In Ps, 100% would make the image bigger. Essentially, the screen has a fixed resolution of +/- 70 to 100 pixels per inch. Lets say 100ppi for ease of math. A Nikon D800 would be 6100x4900 pixels, or a 61x49" print at 100%scren resolution. Compare that to a D700 sensor which is 4200x2800 or a 42x28" print at 100% screen resolution. Everything will appear bigger at 100% at screen resolution. But in 2 same size prints, you will be contracting (or expanding) everything to be equal.

Some MF cameras use a leaf shutter, shich can sync at higher than normal speeds. Also, alot of them still use CCD sensors. My understanding is CCD sensors can be used as an electronic shutter, which basically has all pixels start capturing light and stop capturing light simultaneously. CMOS sensors, again to my knowlege, has to read out the sensor line by line, and cannot have all pixels respond simultaneously. I know the old Nikon D70, D50, D40 cameras can do this with thier CCD sensors, and get sync speed of 1/2500 or higher (depending on sync method). I am not sure if MF cameras can do this as well. Most recent DSLR's use CMOS sensors, and cannot currently do this (though there are some P&S cameras that can still use a very fast shutter speed, but I am not sure how they implement it).


This threshold would be determined by your lighting conditions, camera and camera settings, and speed of movement.


Any type of sync above X-sync would need some form of TTL communications. TTL protocol now not only communicates "how much light do I need", but all sorts of camera and exposure readings and calculates timing, all of which is packaged in proprietary communications. With the way true HSS/FP works in a speedlite, you would need the IGBT's Einstein has, but implemented differently.



You will need to contact Pocket Wizard for any specific questions. Each combination of shutter speed, camera, flash, and power setting will yeild a different result.