We have just had new lights put in our house. The old halogen down-lights we used to have were always blowing the lamps or, oddly enough, unscrewing themselves from the fixture and dangling down into the room on two wires. We thought it was one of the family pranking us until we watched the globe get hot and cold in succession and twist around in the bayonet socket until it popped free.
Well, now we are on to LED lights and our electrician assures us we’ll get thousands of hours out of them. I’m not so concerned about that as long as they stay in the ceiling.
Well, what a photographer really wants to know about these things is how they will affect the image on a digital sensor – i.e. what is their white balance? I’ve devised a test to find it out and to compare it to other fittings round the place that still have older fluorescent or incandescent globes. ( Yes I heard you wince when I suggested mixed lighting, but we did not want to cut more holes in the ceiling for replacements. The studio strobes are 5300ºK and when I shoot in there they do the job well.)
Mr Fujifilm cameras have a custom white balance setting and also a Kelvin setting. The rear LCD screen can be set to give a visual of both the intensity of the light that the lens sees but also the colour temperature on that Kelvin scale. So I place the camera on a tripod, focus on a scene that is washed by the test bulb, and slowly go up and down the K scale until I can replicate the same thing I see with my eye. That’s the temp of the light.
The other way makes use of the decoding of a RAW image on Adobe Camera Raw in Photoshop or Photoshop elements – I suspect you could also do it with Lightroom. You illuminate a white card with the test lamp, take a custom white balance shot, save that WB and then use it to take several more. RAW shots. When you feed them into the decoder section it will say what the K temperature was.
I’ve just tried both and came up with about 3200º K to give a natural image on the subsequent JPEG. Of course as they are dimmable, you get some variation when they are off the top of the range. Almost like the days of the the old photo-floods but with no heat! And no need for blue filters in front of the lens.
Still not going to replace strobes for dance and portrait, but I would actually be tempted by an LED setup if I was only doing small still life and product and wanted to save money.