Beamer - banding nightmare

[TimHughes]

Just back from a job with the worst event lighting I’ve experienced and wondering if anyone knows the cause.

The event was a typical business event with a presentation via a beamer on a screen. While the slides looked bright white, any shutter speed much faster than 1/50th caused terrible yellow and purple bands. The brightness of the “white” light from the beamer also reflected around the room causing the banding to appear everywhere.

Anti-flicker didn’t solve the problem. Mechanical shutter was slightly better than electronic shutter but not much.

The only way I could address this was to slow the shutter right down and take many bursts hoping to get enough usable frames free of motion blur. I was lucky and this did mostly work. Still some color correction to do in post. What a stress.

What causes this yellow and purple banding does anyone know?

 

[Pound Coin]

What is a beamer?

if a projector, then yes, I have had this, although not as bad as you describe. Electronic shutter useless, mechanical only useable below 200.

 

[TimHughes]

What is a beamer?

if a projector, then yes, I have had this, although not as bad as you describe. Electronic shutter useless, mechanical only useable below 200.

Thanks, yes Beamer = projector.

They are often a problem but to have to go down to 1/50th was a new experience.

 

[Sangoma]

I expect it was a DLP projector, LCD is less prone to those effects.

 

[Garry Edwards]

I'm guessing that the projector was pulsing at 50 or 60 cycles per second, the only solution that I've found is to shoot at around 1/30th second. And the light would also have a discontinuous colour spectrum, adding to the challenge.

 

[TimHughes]

I'm guessing that the projector was pulsing at 50 or 60 cycles per second, the only solution that I've found is to shoot at around 1/30th second. And the light would also have a discontinuous colour spectrum, adding to the challenge.

I expect it was a DLP projector, LCD is less prone to those effects.

@Sangoma Thanks, seems I have been lucky not to encounter DLP projectors up to now. Something to add to the pre event checklist!
@Garry Edwards I think you’re right. I tried below 1/50th but really struggled to get anything useable due to motion blur of the speakers and participants. The image stabilization did work very well, even up to 200mm. At 1/50th I was sometimes getting lucky.

 

[Phil V]

I know no one never wants to hear this but a hit of flash will help w the subject movement. Even when it’s close to 1:1 with the ambient it shouldn’t produce too much ghosting at 1/30 for a static human.

 

[TimHughes]

I know no one never wants to hear this but a hit of flash will help w the subject movement. Even when it’s close to 1:1 with the ambient it shouldn’t produce too much ghosting at 1/30 for a static human.

Thanks Phil I did try this before the event started and had the gels to match the color temperature. Introducing enough flash to overcome the banding changed the look of the room, and combined with the disturbance to the audience meaning less frames and chances to catch good moments, I decided against. Maybe that was the wrong decision. I checked with a colleague who has shot there too and she confirmed she had the same problem with banding from the projector and used flash, but that she still had a lot of color correction to do all the same.