Difference between light "quality". Led's vs. Incandescant

Joined
Sep 21, 2009
Location
South Burlington Vermont USA
In addition to co-owning a performing arts academy in Vermont, I photograph dance and theater at various venues on the east coast. I've noticed that when shooting shows that use a lot of LED instruments, color is a lot more saturated compared to when incandescent fixtures are used, often to the point of blowing out even at a good general exposure level. The vibrancy of the color as captured by the camera's sensor seems greater than what's seen with the eye. My gear has good dynamic range (Nikon D810 and D750) but it makes post processing much harder (sometimes impossible) than shooting when conventional incandescent fixtures are used.

Can someone explain the physics behind the difference? I'm trying to figure out of it's a function of the light itself, a design issue with the sensor, etc? I've asked this question in pro photo communities but no one seems to know.
 

sk8rsdad

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Aug 15, 2008
Location
Ottawa
There are two relevant parts of the system, the LED emitter and the camera CCD.

LEDs are narrow band emitters. They produce very specific frequencies of light. As an aside, white LEDs cheat this by using a (typically) blue emitter to stimulate a phosphor which in turn produces a broader spectrum of light.




The camera's sensitivity to RGB light is determined by a Bayer filter which allows only certain frequencies to reach the sensor. Some frequencies pass through the filter easily while others are reflected off.



Depending on the frequency of the LED, and sensitivity of the Bayer filter, a disproportionate amount of the red, green, or blue light produced by the LED may get through the filter.
 

SteveB

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Joined
Mar 20, 2004
Location
Brooklyn, NY
Recall as well that what your eye and thus the camera is used to, is incandescent lighting that is filtering, using color filters, to only the wavelength of that color desired, with often a huge loss of efficiency, and thus intensity.

LED's can be designed to be extraordinarily "punchy" in certain colors, with fixtures designed for R&R as example, having a lot of emitters in the Red, Blue, Green and possibly Amber colors. Thus they are significantly brighter and more saturated in those particular colors, then a comparable incandescent with a filter. They can be dimmed of course, but the relative intensity might be set by the lighting designer, who's eyes are better able to see the contrast and might be OK with the look. The camera may have trouble though.
 

Ric

Active Member
Joined
Sep 15, 2008
Location
Werribee, Victoria, Australia
I'd also point out that as we've got new tools to use with lighting we've changed the way we use the lights and colour.
I.e. we've never been able to have as deep and saturated blues in use for long periods of time. This was due to the gel burning out, and it not being practical to have half the rig in a single deeply saturated colour to achieve the brightness needed. Now that we can have a whole rig in a single colour at the press of a button then we can finally achieve some of the looks that were desired with incandescent and gel, but were not practical to achieve.