LED Lights/ flash units - anyone tried one?

[Scrambler]

I had a brainwave the other day and have ordered some LED lights for video and animation. That of course will be digital capture.

But I saw some (and ordered one) with flash capabilities. I have ordered a Yongnuo YN-140 (I'm a cheapskate, I admit it) but there are others including Manfrotto hybrids and a Z-flash (though the Z-flash only "flashes" while already lit).

The Manfrotto is rated as 1/1000 of a second, the Z-flash at 1/250. I couldn't get a number for the Yongnuo.

I have seen people questioning guide numbers etc - I don't know but the good thing is flash is two stops brighter than the normal level - so meter and close down two stops.

If these flash long enough, can you sync at higher speeds with a focal plane shutter? Like a flash bulb?

If the sync timing is right, it might be that you can sync at lower speeds and at high speeds but not in the middle.

 

[Scrambler]

My Yonguo YN-140 arrived and I've done some testing.
The paperwork says flash sync is 1/250. Not quite sure what they mean by this.

Testing on my wife's Canon EOS700D (Rebel T5i) showed some interesting features. Firstly, the camera will trigger the flash at every shutter speed, but the flash shows shutter capping faster than 1/250.

If the trigger signal matches the first curtain release, it's about a 4 millisecond delay to any usable flash. If it's first curtain closing I guess it's a little faster to get something out. Or there may be a delay? Couldn't find the answer online.

The flash duration seems to be about 100ms.

EDIT: maths was wrong by a factor of 2 - overestimating GN unfortunately! See below for correct numbers.

The effect of the flash increases from 1/250 up to 1/8s but not beyond that - and the flash has visibly turned off even before the 1/8 shutter closes.

Adjusting aperture and duration, the flash reaches full intensity after 1/60s. (apx 15-20ms delay).

Camerapedia lists time to peak of M flash bulbs as 18-20ms, and duration of 8-10ms. An FP bulb might have a longer duration of up to 35ms.

Putting all that together, the LED flash should sync correctly with the M (flash bulb) setting on cameras that have such a setting, and should allow FP-style synchronisation with a focal plane shutter at any speed (using M-sync).

The guide number will obviously change with your shutter speed given the roughly 100ms at full output. I make it about 10 (metric, = apx 32 imperial) at 1/8s and a measly 3.5 at 1/60 (11.5 imperial). At higher x-sync speeds the GN will drop away even faster, but M-sync guide numbers should remain proportional. M-sync GN may be a little higher as the light will be at full output by the time the first curtain opens.

The summary is: this LED flash (Yongnuo YN-140) is a good substitute for flashbulbs for time to peak and for duration, but output is low.

On a camera with M-sync this would be preferred to X-sync, and should allow use of any shutter speed. This may be particularly useful for fill flash.

Now I need to wait for the off-camera cable to arrive and I can test with my IIIc and Geiss Kontakt.

 

[Scrambler]

The summary is: this LED flash (Yongnuo YN-140) is a good substitute for flashbulbs for time to peak and for duration, but output is low.

GN@ 1/60 apx 2 metric/ 6 imperial

GN@ 1/8 apx 5 metric/ 16 imperial

 

[sevo]

My Yonguo YN-140 arrived and I've done some testing.
The paperwork says flash sync is 1/250. Not quite sure what they mean by this.

In general, sync time is a matter of the camera rather than the flash. As it is a (long, constant burn) LED flash that could at least theoretically be used with sync times shorter than the fully open "sync" time of focal plane shutters, it might mean that the burn time is 1/250s, so that shorter times will begin to affect the intensity.

 

[Scrambler]

In general, sync time is a matter of the camera rather than the flash. As it is a (long, constant burn) LED flash that could at least theoretically be used with sync times shorter than the fully open "sync" time of focal plane shutters, it might mean that the burn time is 1/250s, so that shorter times will begin to affect the intensity.

I know I wrote a lot there, sevo, but

1) The burn time is more like 1/10s
2) The LEDs are not at full intensity until the 1/60 shutter speed

So the 1/250 seems meaningless.

 

[sevo]

I know I wrote a lot there, sevo, but

1) The burn time is more like 1/10s
2) The LEDs are not at full intensity until the 1/60 shutter speed

So the 1/250 seems meaningless.

Possible. But it could also be some internal constant. Does it change the colour temperature by lighting different groups (of warm and cold) LEDs, or do all LEDs light up in either setting? In the latter case they overload the LEDs - where the active burn time will be shorter than the afterglow of the overloaded phosphors.

 

[Scrambler]

Two different colour temp LEDs - both groups set to maximum intensity for this test.

I don't have a simple way to test when the lights turn off, other than the effect on exposure (and my eyes!) How much afterglow exists I couldn't say, although I guess some detailed testing of images might give hints.

Based on the histograms of the test photos, the LEDS are at full intensity out to 1/8s.

 

[willie_901]

At this point in time all LED light output (flash or continuous) is too low for many situations. I can't wait to use this technology once the light levels become practical for my work.

 

[cpc]

It is not light level to be concerned with LEDs, rather light quality. It is pretty bad, with non-continuous spectrum and peaks (usually at green or blue). Needs heavy filtration to get it to comparable quality to traditional light sources. And heavy filtration means lower useful power. Which is why manufacturers tend to sacrifice light quality for output.

 

[bobbyrab]

Forgive me my ignorance, but I've seen these small LEDs for continuous video lighting but I didn't know there was such a thing as the flash version. What would be the reasoning behind using LEDs over a conventional flash gun?

 

[Wouter]

The most interesting product on the market seems to me to be the Dedolight Ledzilla. Not cheap though.. Other Dedolight solutions are intesting as well.

 

[Takkun]

Forgive me my ignorance, but I've seen these small LEDs for continuous video lighting but I didn't know there was such a thing as the flash version. What would be the reasoning behind using LEDs over a conventional flash gun?

I suppose it would have the benefit of conserving power and convenience, as well as be less distracting than in steady-burning mode.
But I'm not entirely sure either. LEDs practically negate the first benefit.
But as compared to strobes, you hypothetically can control color balance easier, have the option of steady-burning for video, and have long battery life.

However, having used them only in passing for video work, I have to echo the color quality issue. I got to use a massive array of them (don't even want to know how much they cost) so losing power through gels was not an issue.

 

[Scrambler]

Forgive me my ignorance, but I've seen these small LEDs for continuous video lighting but I didn't know there was such a thing as the flash version.
What would be the reasoning behind using LEDs over a conventional flash gun?

I will use primarily for video so flash definitely secondary.

The reason is prolonged flash duration. As above, shutter speed matters, and sync speed with older cameras may be higher in some circumstances.

Some studio setups use fixed lighting rather than strobes.

Really, it's just one more tool in the kit.