LED Flicker

[Dave Kovacs]

I have seen Chinese LED panels on EBAY that have 600-piece-LED arrays, similar to other brands with American names.

I'd like to know if anyone here has used any of these foreign brand LED panels? Do they have flicker issues?

[John Sprung]

Flicker characteristics could be specific to each make and model, and even vary from unit to unit. If they're not designed for film/video use, it's a crap shoot.

 

 

 

 

 

-- J.S.

[Tim Tyler]

I know a guy who bought two ePhoto 500 LED Ultra Bright things and he said they were a good value. I think he got them from Amazon, not eBay. The ePhoto lights replaced some other cheap LED's he bought then returned which advertised 56k with a high CRI but in fact looked nothing like daylight.

 

FYI: My experience with production equipment has taught me that you get what you pay for. Quality, familiar brand movie lights hold their value and usually last longer than knock-offs too.

[Patrick Neary]

Hi-

 

I've been using 2 FloLight panels for the last year and they are great- rugged and very versatile.

 

I also carry a bunch of those little white rechargeable "home security" led lights from Costco ($20 for 2-pack) and other than a slight green spike they are also great. Stick a piece of velcro on the back and you can put them anywhere, they are quite bright and have two power level settings and last forever on a charge.

 

A friend has a couple lowell blenders and sorry to say those things are awful. Cheaply made, flicker like crazy every time I've tried to use them, and the battery holder is a disaster. A good idea not well executed.

[Mathew Rudenberg]

I finished a shoot recently where Art Dept would occasionally mix LED christmas lights in with the old school ones.

 

It was pretty easy to tell the difference - the LED's flickered and we couldn't find a shutter angle that would eliminate that flicker.

 

I did, however. find that it was only the plug in (AC) LEDs that flickered, the battery powered LEDs we had on set did not. I suspect this is due to the sine wave cycle of the AC power/ not having a great transformer on cheap christmas lights, however I didn't take the time to test them or anything, we just stopped using the LED models.

[Dave Kovacs]

Tim,John- You're right, you get what you pay for. Dp'ing alot of low budget stuuf, I've learned which corners to cut and which one not to cut.

 

Patrick, Matthew- Thanks for the tip. I'll go by Costco and pickup some of those small fixtures. Last week, I watched a

mid-level budget film with B-list actors that had a scene where an actress enters her dark apartment. The room was illuminated by one of the LED wire scupture reindeers. It was flickering like crazy!!! I'm thinking ' somebody did not test cheap LED reindeer lamp'.

 

I read this article about the EPA and the switch from the 120hz standard to 150hz, and now back to 120hz.

http://www.optoiq.com/index/display/article-display/1176614052/articles/optoiq2/photonics-technologies/news/technology-products/lasers-__sources/2010/3/so_-what_about_led.html

 

Perhaps this may have added to the problems with flicker.

[JD Hartman]

"A friend has a couple lowell blenders and sorry to say those things are awful. Cheaply made, flicker like crazy every time I've tried to use them, and the battery holder is a disaster. A good idea not well executed. ", not at all surprising, considering the source.

 

Flicker on the cheaper LED panels and holiday lights would come from poor filtering in the power supply (AC ripple). If you've any electronics experience, this may be eliminated with additional filtering capacitors and or a filter choke in the power supply (if it's a traditional linear supply).

[John Sprung]

The KISS method of powering LED's would be to throw a bridge rectifier across the incoming 60 Hz AC, giving you 120 Hz pulsed DC. The suggestion of going to 150 Hz betrays ignorance of the fundamentals.

 

 

 

 

-- J.S.

[Dave Kovacs]

The KISS method of powering LED's would be to throw a bridge rectifier across the incoming 60 Hz AC, giving you 120 Hz pulsed DC. The suggestion of going to 150 Hz betrays ignorance of the fundamentals.

 

 

 

 

-- J.S.

 

Can that type of modification be done with a soldering gun, or this beyond the 'I got my gear from Radio Shack' skill set?

[Phil Rhodes]

It's not the end of the world as tasks go, but you don't want to mess with mains if you're in any way unsure.

[John Sprung]

It's well within the Radio Shlock skill set -- but you get better prices and selection from Digi-Key:

 

http://www.digikey.com/

 

http://ordering.digikey.com/video.aspx?PlayerID=25003088001&width=750&height=650&videoID=82296308001&WT.z_tz_fr=Lighting&WT.z_lt_cat=Video&WT.z_lt=60-Watt Light Bulb using LEDs&WT.z_ref_page_id=lighting_hp&WT.z_video_source=TZ Lighting

 

 

 

-- J.S.

[Hal Smith]

LED at the most basic level are a rectifier, feed one with AC and you'll get pulsations. The only way to avoid this is indeed to feed them with DC, either from a battery pack or a well filtered source of rectified AC. I'd start with a industrial "brick" power supply, they're cheap on eBay. The transformer types are more reliable in rough service but they are quite a bit heavier than chopper (inverter) supplies.