Bi-Color looses half the brightness, but only on some lights

[Eric Coughlin]

Why is it that so many companies that off bi-color lights do so in a way where the light is half as bright when at full daylight or tungsten, but then other companies, such as Litepanels and Arri, are more like 90% as bright at daylight or tungsten?

You'd think if several companies have figured how to make bi-color efficient, that the rest would follow suit.

It's often that I'll find a light which looks good on first glance, until discovering the bi-color option is 50% as bright at the temptures you're most likely to use it at, which then makes you consider the daylight only version, which in turn makes you not want the light at all.

 

[morgan_moore]

I had a chat with the lupo people.. whose lights have the 'same' lumens whatever colour Temp. WOndering why thier 5200k fixture is no brighter.

It seems there are two 'clamps' in the brightness 'pipeline'

The first clamp is obviously the max brightness of the 'globes' - the second 'clamp' is the wattage delivered through the electronic ballasts, and the ability to dissipate heat in the mechanics of the fixture.

Now lets be a fixture designer..

Lets assume you are making a bi-colour with a set of white globes and a set of yellow globes.

As a designer you sit at a wall with your design.

To allow all the globes to burn at max power (which will gie maybe 4300k) you need enough ballast and heat sinkage to burn everything on full.

You get a light that has a variable out put being A at 3200, B at 4300, and C at 5200 and only in condition B are you fully utiliszing the heat sinks and ballast.. or in other words at 3200 and 5200 you are not fully using the heat sinks and balast.

But this light has headline grabbing lumens at 4300 - 50% brighter than many other fixtures.

Now choose the other design crossroads.

Design the light to fully utilise the ballast and heat disipation but not burn all the globes at full whack at the same time.

Sensible to use light that offers consistent lumens across the colour range but doesn have a headline grabbing 4300 figure.

Two design approaches.. you choose which you want (both are available) and buy it

--

In the case of the LUpo - they could put all 5200 globes in the housing.. but if they did it would need bigger heat sinkage. The 'clamp' in the lupo design is not the brightness of the globes but the ability of the fixture to dissipate heat. So the 5200 version is throttled to have the same lumens as the bicolour version.

 

[morgan_moore]

Of course if you are shooting 'blacked out' like lighting a studio the 'brightest at 4300' fixtures may present the best value.

Personally Id go for 5500k only fixtures as I dont find it a problem to chuck on a CTO in the very few situations where they key needs to be 3200.

I rarely use 3200 on the camera.

Actually I think I have a perfect mix being some 5500 fixtures and some variable fixtures. As I suaally key at 5500 but might want a warm hair light etc

 

[morgan_moore]

-

 

[nyvz]

Yeah it just comes down to emitter-limited power or driver/controller-limited power. Interesting to think bi-color lights that are driver-limited have twice the emitter power of emitter-limited units. Makes me impressed with low-cost driver-limited lights like my 100W falconeyes bicolor units and kind of curious to hook up a 200W driver to it to get it to go to 200W at 4300K... though I suppose they may only be tested to handle the heat of 100W of power.

In the end I think this is just a matter of cost and design and market. With the cost of emitters dropping and the convenience of being able to adjust color temp without changing output, seems like every manufacturer should be doing this or at least have a controller mode that allows constant output during color adjustment and a mode that allows highest output.

 

[puredrifting]

Heck, even my cheapo Kamerar Brightcasts use SMDs, not lame LED bulbs. These SMDs produce the same light output across their color spectrum. Why aren't all panels using SMDs?

 

[J.Brown]

I wouldn't want a light that changes output when I use different colour temperatures. That would be an unpredictable fixture I'd hate.

On the other hand all good bi-colour panels I've tried have a slight bump at around 4200 kelvin and that's okay because it doesen't really matter.

 

[cpreston]

I think for a company like Arri it is all about longevity and reliability in relation to the heat sink. The cheaper manufacturers probably don't really care. They just set-up a variable resistance dial, attach some diodes, and let it rip.