Colour rendition of LED lighting

[paulears]

Not really sure people understand what I'm moaning about. Over christmas, part of my role is to take stills and video - of pantomime. Stills wise, I've always used Pentax cameras, because I have a decent collection of glass. I'm not interested at all in video from them - I hate DSLRs for video. I take the shots as and when I can, and I dropped my Pentax K100 that I was very happy with. I replaced it with a K5, and the pictures don't match - not remotely the same. A shot with the K100 at a certain point one night looks quite like what my eye sees, but the K5 looks very different, and no adjustments make it look the same, and I cannot adjust it in Photoshop without bringing up the noise far too much. When I use my JVC cameras (250's) they're pretty truthful, but what ITV shot on XDCam looks wrong, when broadcast. Looks nice - don't get me wrong, but we all know what full blue and red from an LED fixture look like. It's magenta. Maybe different fixtures may be a bit bluer or redder, but to the eye, magenta is magenta. It is NOT to many cameras.

 

If you get a chance, Gary - point your Panasonic at magenta from an LED source and see what colour it sees. I bet it's 'wrong'. I don't think it's any deliberate ploy by the manufacturers, just that they don't build or test them on saturated colour, just white within the range of around 3000K to 7000K. If they can white balance to those colour temps, that's job done. The TV people are only concerned with white balance - never RGBCMY only sources. None of the cameras I grabbed for the test hit the marks on the vectorscope - some missed by a mile. I'm not suggesting any kind of proper standard is required, but if you have a video camera that captures decent images at HD - pictures that look good, surely it should have the ability to be able to record magenta as magenta?

[Judge]

I know what you are saying Paul. I lit a show in January that was lit entirely with LED - trees, buildings, all kinds of stuff. I took stills with my Olympus E-M1 and compared it with shots taken with a Nikon D700, and Canon 60D and some kind of Sony and they were all utterly different, and this would not have happened it another lightsource had been used. I have to say the the Nikon handled it best and the scenes looked much more natural, but I think that if I spent enough time writing a RAW colour profile especially for the Olympus I could have gotten it a lot better. Of course the bigger sensor of the D700 helps. And you are right in suggesting that sensors are not designed to properly capture single saturated colour, but really up till now there has not been any real reason for doing so, and the ones that do are probably more by happy accident than design.

[bigclive]

I guess that the cameras are using sensors with narrow wavelength detection of the primary colours. If the LED source used exactly the same wavelengths then everything would be fine. But LEDs often have a close band around 470 nm for blue, but that all depends on the fixture. Some might have a completely different "shade of blue". If the camera sensor didn't match the narrow band of the LED source closely it could look very dark.

 

I suppose the answer there is to have a camera with a wider band of sensitivity in each colour area, or allow more advanced calibration that cpould boost the gain on a mismatched colour. However, that would get very messy with multiple light sources.

 

When I first started using blue LEDs in TV props the results were very odd. Often manifesting as a surreal glow round the illuminated object. Fortunately they were mostly sci-fi props, so they added an extra visual element to the effect.

 

Oh look. I've found a short where I did some VERY dubious custom LED stuff with a lot of blue LEDs. The action starts about 10 minutes in.

 

This production used some odd electronics. A fully animatronic internally illuminated ###### that got near totally censored and other items like the "groin light", "butt crack light", "welly lights" and so much more. Sadly the planned use of mass pyrotechnics in the office got limited by the use of a studios actual offices, and all I was allowed to do was a "photocopier going berserk" gimmick.

 

Keep in mind that this was done well before LEDs became mainstream in TV and film.

 

Yes, that is an implied instance of necrophilia at the end.

 

Telly-safe soft porn flick.