what kills flash more. Closed aperture or HSS

Hi,

for the cases you are out and you are trying to kill the ambient light. There are two options, since you are already at base iso.

Shutter speed or aperture.

What would give flash less work to do so? A faster shutter speed where the flash will need to pulse light or fire at sync speed illuminating against a very closed aperture?

Regards

Alex

Rule of thumb is: both equally. So a 1 stop faster shutter speed with HSS and a 1 stop larger aperature yield the same exposure.

HSS is no free lunch, basically it enables you to shoot with flash at larger aperatures, but using the same flash power. Or, you can keep the narrow aperture, speed up the shutter, and help overpower the sun (but this requires a 1 stop power increase for every stop shutter speed).

HS might be a little more efficient - in theory - but I've heard people report similar results there.

One thing to consider using HS or HSS with mono lights is that the colour temperature may be more inconsistent than 'normal' flashes. At least with Broncolor's Siros' using HSS has the unit responsible for the short flash taking preference over ETCT unit that safeguards a consistent flash color temperature. As far as I know the same is with the Profoto B1 and B2 units.

I do not know whether this phenomena also applies to speed lights.

I've heard Profoto's HSS is the most linear out there, but have little to no experience or evidence to back that up. If that's really the case, that creates an odd situation: if the shot is lit properly at 1/3 stop beyond sync (i.e. the slowest shutter speed that's actually HSS), the only gain in changing shutter speed is how short of a time you're capturing.

That said, I'd be surprised if HSS was linear, and I'd be surprised if HSS had any chance of being "as bright" as traditional "pop" flash. HSS has to start flashing before the shutter curtains start moving, and continue flashing until (just) after the curtains stop moving, all the while "wasting" light on those curtains as they move the slit from top to bottom (or whatever direction they go). At one stop beyond sync, they're wasting 50% of their light on the curtains plus another tiny percentage before/after. At two stops beyond, they can fire at a brighter intensity with the knowledge that they only have to sustain it for half the time, but they're wasting 75% on the curtains, etc.

Overheating is the killer. The heating occurs during recharge. The electronics can overheat but it is usually the batteries that get hottest.

Fire too many shots at full power and a hot-shoe flash will overheat. The good ones then shut down until they cool or they slow down the recharge dramatically to allow the flash to cool.

If you fire a lot of full power shots you can also overheat the flash head where the flash tube is located, resulting in darkening (burning) of the reflector and/or window or even a meltdown of the plastic case.

HSS pulses the flash thousands of times a second to give you a pseudo continuous light. It is roughly the equivalent of a full power flash so the heating is similar.

According to Canon their flash units lose 2 stop with HSS. With most hot-shoe flash units you lose 2-3 stops of power vs a regular flash, not just 1 stop.

Be extra careful if you gel the flash. Make sure that there is a good space for air to circulate between the gel and the flash head or you may wind up melting the gel onto the flash window.

Dervast said:

Hi,

for the cases you are out and you are trying to kill the ambient light. There are two options, since you are already at base iso.

Shutter speed or aperture.

What would give flash less work to do so? A faster shutter speed where the flash will need to pulse light or fire at sync speed illuminating against a very closed aperture?

Regards

Alex

Click to expand...

somewhat OT, but if using manual flash, does ISO matter? (not taking into consideration noise, dynamic range, etc) Changing ISO affects both ambient and flash exposure so the fact that one might be at "base ISO" doesn't matter. If at ISO 200 changing to ISO 100 doesn't change the relative contribution of flash and ambient.... Or am I missing something? Thanks.

Add additional flashes.

Seriously, once you hit sync speed, you're fighting a losing battle.

NicholasD said:

somewhat OT, but if using manual flash, does ISO matter? (not taking into consideration noise, dynamic range, etc) Changing ISO affects both ambient and flash exposure so the fact that one might be at "base ISO" doesn't matter. If at ISO 200 changing to ISO 100 doesn't change the relative contribution of flash and ambient.... Or am I missing something? Thanks.

Click to expand...

Long lesson shortened, if you're competing with sunlight, you're going to set the shutter to sync speed. Now one variable of the three that make up the exposure triangle is "locked". You're going to set the ISO to 100, or whatever base is for your camera. Now two variables are locked. Last option you have is aperture, so you're going to stop down enough to get the ambient exposure you want. Now you're at the optimum ambient exposure for your scene, given the constraints of the sync speed and the typical desire to have thin-ish DoF.

Raising ISO dictates that you stop down an equivalent amount, if you want the same ambient exposure. The higher ISO makes the flash more efficient, but the darker aperture negates that gain exactly. The end result is that you have an equivalent exposure with less DoF and potentially more noise. As someone else said, the answer is to add flashes.

ND filters "throw away" ambient and flash equally, so if you've already locked in the right exposure, every stop of ND likely translates into a stop of aperture you can open up.

I use shutter speed to control ambient and aperture to control flash.

Meter for what ambient gives you and go from there. When you add flash and meter, aperture controls flash if you want to darken ambient, increase shutter speed. That works up to sync speed. Up to 1/8000 depends on your gear.

With Strobes I can easily shoot up to 1/8000 f1.4 or 2.8 or whatever my needs are. Strobes are nice in that you dont loose power so to speak. It just fires at the level you tell it to. How much reaches the camera sensor depends on the strobe and camera. I will use 600, 1,000 and 1,100 ws strobes outdoors quite effortlessly.

Suntan said:

Add additional flashes.

Seriously, once you hit sync speed, you're fighting a losing battle.

Click to expand...

I can still stay at sync speed and start making aperture smaller to kill ambient. There are times that I do not care about DOF. IT looks like with the feedback I got that both HSS or smalelr apertures waste the same amount of light

Aperture doesn't just kill ambient light. It kills all light. Once you hit sync speed, and your flash still isn't "bright" enough to balance the scene, you can either move it closer, or use more of them.

A new tool in this arsenal is the MagMod Fresnel Lens that, assuming you are not trying to cover a wide area. It almost quadruples your flash output , useful outdoor with and without HSS. While it is still technically a hard light, it is the best and most even quality hard light you can have and has less front to back fall off because it is further away.