HSS and power consumption

I have a few questions in regards to HSS, mostly about power consumption. I was wondering if you could help clarify a few things for me.

1. How much power does HSS consume on average compared to regular sync speed? For example, Eneloops might give me 250 speedlite pops at 1/125 at full power. What ballpark number can I expect at 1/500? 50, 100, 200 pops?
   
2. Related to my previous question, is there a difference between 1/320 and 1/600 in HSS mode in terms of battery consumption? I'm assuming that the longer pulsation required by 1/320 would waste more power. Is this correct?
   
3. if I set my flash at 1/1 in HSS mode the output capacity is reduced by about 2 stops I believe. Will the proportions be maintained as I set it to 1/2, 1/4, 1/8, 1/16, etc? I mean, will 1/16 be 4 stop less than regular full power or 4 stop less than the -2EV output (so 6 stops in total)? The flash, even in HSS mode is technically capable of outputting regular 1/16 amount of light, but I'm not sure if it does. If it does, then the progression in HSS mode is no longer linear.
   

tonytony wrote in post #16401476
... is there a difference between 1/320 and 1/600 in HSS mode in terms of battery consumption? I'm assuming that the longer pulsation required by 1/320 would waste more power. Is this correct?

Beyond sync speed, the shutter curtains are moving as fast as they can. The exposure time on the sensor is determined by the size of the shutter slit. The speedlite has to rapidly pulse the same length of time whether your shutter speed is 1/320 or 1/600 to fully illuminate the sensor.

tonytony wrote in post #16401476
2. Related to my previous question, is there a difference between 1/320 and 1/600 in HSS mode in terms of battery consumption? I'm assuming that the longer pulsation required by 1/320 would waste more power. Is this correct?

No. The pulse duration is the same in HSS. The higher the sync speed you use on your camera the more power you will consume for the same exposure.

rudy_216 wrote in post #16401534
The higher the sync speed you use on your camera the more power you will consume for the same exposure.

Why do you say that?

The slit between the leading and trailing shutter leaves travels across the film/sensor at the same speed for every shutter speed faster than the "max sync speed". Thus, the Speedlite should be creating pretty much the same pulse train for all the shutter speeds faster than the "max sync speed".

Though it's technically a rapid series of weak flashes, think of HSS as a continuous light source that lasts throughout the duration of shutter curtain movement. The shutter will limit the amount of this light that reaches the sensor, just as it limits any other continuous light source.

The distance scale on the back of the flash tells the story.
At 1/250 f/4 ISO 100, zoomed to 50mm, the 580EX II will indicate a distance of 40 ft.
Click the shutter speed up to 1/320 and open the aperture to f/3.5 (the same ambient exposure) and the distance scale drops to 20 ft. This is the efficiency-robbing reality of HSS.

Now if you continue to speed up the shutter and open the aperture to keep the ambient exposure the same, the distance scale will stay where it's at from that point on.

However, if you speed up the shutter without opening the aperture, you will see the distance continue to drop with faster shutter speeds.

When manually setting the flash power, whether in normal flash or HSS mode, you will lose 1/2 the distance range for every two stops you dial down the power. Hopefully that makes sense.

Curtis, your clear explanation totally clears question 2. Do you have suggestions for 1 and 3?

The question of how much power you lose with HSS is hard to answer precisely, since you can't use normal flash above X-sync speed and you can't use HSS at or below X-sync speed. You can't make a direct comparison. But the distance scale indicates a loss of about two stops, so in theory the flash is using four times as much energy for any given shot, and a set of batteries would be good for only 1/4 as many shots in a given situation.

For question #3, again, the distance scale will tell the tale. 1/16 power on HSS will get you half the distance of 1/16 power using regular flash at X-sync speed with compensating aperture settings.

I have a feeling you're overthinking this, Tony.

Thanks Curtis. I think I got it. Hmm, power packs might be needed then.

Tony,
About number of flashes...you flash's power capacitor is the bucket of power, your batteries are merely the supply to the hose that fills the bucket.

• NO MORE power can be put thru the flashtube than is contained within the bucket. Whether you fire conventional flash at full power, or you fire in HSS mode, the size of the bucket is unchanged....SAME quantity of water from the bucket....same amount of electricity is expended.
  
• NO MORE power can be put INTO the bucket from the batteries in using HSS, and the batteries are still the same old batteries in HSS. Whether you fire conventional flash at full power, or you fire in HSS mode, the size of the supply to the hose is unchanged....SAME total quantity of water into the bucket thru the hose before the supply to the hose is drained...same total number of flashes.
  

• The supply to the hose gets larger, with increased total milliamps contained within the batteries
  
• The hose itself gets larger in diameter, decreasing the filling time of the bucket (shorter recycle)
  

Very good analogy Wilt...

110yd

110yd wrote in post #16402983
Very good analogy Wilt...

110yd

Yup, most excellent.

BTW, howz fishin'?