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LED lights and banding


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1/2500 sec f/1,7 ISO 1600.

 

LED lamps (Philips HUE), shutter speeds over 2000 seconds always banding, tungsten and others no problem, my M8,2 no banding whatsoever.

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Edited by BJN
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Yeah, the Philips HUE lights use pulse width modulation (PWM) to control light intensity.  In other words, the flicker off and on very quickly in order to vary the amount of light they produce.  Your eye (and even a camera) integrates the flickers into a solid source.  But, as you bring the shutter speed up, there will be frequencies at which you can see the flickering.  As far as I know there is no solution to this problem aside from avoiding the shutter speeds where you can see the banding.  There are some dimmable LED's that don't have this problem because they use modify the voltage to change the amount of light produced rather than holding the voltage constant and varying the amount of time the light is on vs. off.  The problem with these LED's--and the reason they aren't more common--is that it is very hard to get a consistent color out of them when the voltage is varying.  Most dimmable LED's these days use PWM, and that means there will be shutter speeds where you can see the flicker.

 

- Jared

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Hmm.  One thing I didn't mention... The 'Q' generally uses a mechanical leaf shutter.  Since a leaf shutter exposes the entire image plane for the duration of the exposure, you won't be able to see this flickering.  The reason it shows up at 1/2,500s is that Leica uses an electronic shutter on the 'Q' at shutter speeds above 1/2,000s.  In general, leaf shutters are immune from this type of issue, while focal plane shutters and electronic shutters are not since they both expose different parts of the frame at different times.  Stick to exposures of 1/2,000s or less with the 'Q' and the leaf shutter should make the problem go away entirely.

 

- Jared

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milsart

I didn't need to expose at those settings I was just showing the result of using a shutter speed over 1/2000 with the HUE lamps.

 

The Q will expose correctly at various other settings under the same lights without banding.

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