How to solve Theatre Led light problem...

[Stef DK]

Hi there!
As you can see in the picture, this is my problem with theatre LED par lights.
Picture shot with A7iii - 1/125 - f4 - FE 24-105mm - AWB
Any suggestions?

Thanks!
Stef
Picture

 

[Alan Clark]

Welcome to the forum!

Unfortunately the link to the picture does not work.

 

[AlphaWorld]

Try uploading the image directly to here instead of pointing to Tumblr.

 

[AlphaWorld]

At a guess. without seeing the image, you are seeing dark bars on the image?

That would probably be because the lights are using PWM dimming.

With an A9 III the problem basically doesn't exist. The whole image is captured as once, so the lighting is uniform. You might see an image in a burst that is darker, but the whole image will be uniformly darker.

With a few models you can fine-tune the exposure to address the problem (the A1 can do this, I think the other A9 models can, too).

With an A7III, I'm not sure how you fix this. I think you start by using full mechanical shutter, though that may not be enough.

 

[Stef DK]

Thanks for your comments.
This should be the (unedited) JPEG.
It should be a BW-projection combined with blue LED spots.

 

[Stef DK]

Welcome to the forum!

Unfortunately the link to the picture does not work.

Sorry!

 

[Stef DK]

At a guess. without seeing the image, you are seeing dark bars on the image?

That would probably be because the lights are using PWM dimming.

With an A9 III the problem basically doesn't exist. The whole image is captured as once, so the lighting is uniform. You might see an image in a burst that is darker, but the whole image will be uniformly darker.

With a few models you can fine-tune the exposure to address the problem (the A1 can do this, I think the other A9 models can, too).

With an A7III, I'm not sure how you fix this. I think you start by using full mechanical shutter, though that may not be enough.

Thanks for the tip!
During a theatre performance I usually put the shutter in silent mode for obviopus reasons...
I will certainly try your suggestion using the mechanical shutter.

 

[Stef DK]

I think it's called 'banding'... I found some more info in this video (https://www.youtube.com/watch?v=Ap75j-wjCoE&ab_channel=MikeSmith)
Thanks for your help!

 

[AlphaWorld]

I think it's called 'banding'... I found some more info in this video (https://www.youtube.com/watch?v=Ap75j-wjCoE&ab_channel=MikeSmith)
Thanks for your help!

Yes - that's it.

It's far more visible with electronic shutter because the scan time for the entire sensor is generally much slower (the famous example is the 1/10 second time of the A7RIV and V). The A7III should be faster than that, but it's still going to be much slower than the mechanical shutter (the mechanical shutter sweeps over the sensor, then the camera reads the data from the sensor while the second curtain is shut, so it "hides" the slowness of the sensor read).

The A1 scan time is about 1/250, so it's much less affected (fewer bands, if any).

The A9 III has a scan time of approximately zero (faster than 1/80000, at least!), so it's immune.