Color temperature and light source

[niels123]

Obviously, a change in (the type of) light source needs adjusting the color temperature.

Just a theoretical question: imagine a subject being lit by a single light source only in a completely dark room. If you calibrate your camera to this light source and you change the subject, does the color temperature then needs to be readjusted? In other words: does the 'correct' color temperature only depends on the light source or also on the (color of the) subject?

 

[Marsu42]

Just a theoretical question: imagine a subject being lit by a single light source only in a completely dark room.

You're describing the sun and the earth?

In other words: does the 'correct' color temperature only depends on the light source or also on the (color of the) subject?

My layman's understanding: "yup". That doesn't mean that the color temperature seems subjectively correct or you get accurate color reproduction though (use a Color Checker Passport and dng profile for that).

 

[rs]

In very simple terms, yes, WB is set for the colour temperature of the light source, and it shouldn't matter what subject is lit, the WB should remain the same.

However, take into account reflected light, eg a flash of a known colour temperature bouncing off a coloured ceiling, and you're into a whole different ball game. And then of course, using the sun as a source, it's placement causes differences - blue light gets dispersed through the atmosphere, so the more atmosphere it goes through (think sunrise/sunset) to light up your subject, the less blue the light source is. And then there are other light sources with a known colour temp but a low colour gamut such as sodium lighting or some cheap LED's - there's very little you can do to correct that.

 

[niels123]

I am asking because I am trying to get 'more advanced' with my microphotography setup. I used to use two speedlites for lighting, but there is some disadvantages there. I want to switch to a lighting continuous setup. It would be nice if I only have to calibrate for the light source once and then use this color temp for all my photos.

1) first did some experiments with the Ikea Jansjo LED lights (http://www.ikea.com/nl/nl/catalog/products/80163192/). However, I have the feeling that the colors are not nearly as good as with my flashes and just moving the color temp slider in lightroom doesn't help.
2) The other option is energy saving daylight bulbs, but for a decent amount of lighting I quickly need several hundreds of watt's in energy and this may heat up my subjects too much. Is there decent, high-quality daylight LED's available. Please let me know if you hve any experience! What woudl you recommend?

 

[Marsu42]

It would be nice if I only have to calibrate for the light source once and then use this color temp for all my photos.

Color. Checker. Passport. DNG. Profile.

 

[niels123]

It would be nice if I only have to calibrate for the light source once and then use this color temp for all my photos.

Color. Checker. Passport. DNG. Profile.

I have a ColorChecker passport. The problem is however that, as far as I know, lens coatings effect the colors of your photo as well. This means that you have to use the same optics for your colorchecker photo as for your actual photos.

How do I make a colorchecker passport photo if my Field Of View equals 1.20 mm x 0.90 mm?

Obviously, this is not extremely important. Descent (LED) lighting is much more relevant, as well as suggestions for nice (LED) lighting that produces a proper homogenous nice and soft light.

 

[Marsu42]

It would be nice if I only have to calibrate for the light source once and then use this color temp for all my photos.

Color. Checker. Passport. DNG. Profile.

I have a ColorChecker passport. The problem is however that, as far as I know, lens coatings effect the colors of your photo as well. This means that you have to use the same optics for your colorchecker photo as for your actual photos.

I know the manufacturer puts a lot of weight on lens calibration, but imho just like "calibrate your monitor every week" this is due to marketing considerations, too. For wb adjustment in a studio, one dng profile for all lenses will do unless you're doing critical repro work. The main effect is to cancel out artificial lighting and ambient color reflections - and I'd use it even if you got yourself nice and proper led lighting.

How do I make a colorchecker passport photo if my Field Of View equals 1.20 mm x 0.90 mm?

Well, that's kind of a special setup

 

[Lawliet]

1) first did some experiments with the Ikea Jansjo LED lights (http://www.ikea.com/nl/nl/catalog/products/80163192/). However, I have the feeling that the colors are not nearly as good as with my flashes and just moving the color temp slider in lightroom doesn't help.
2) The other option is energy saving daylight bulbs, but for a decent amount of lighting I quickly need several hundreds of watt's in energy and this may heat up my subjects too much. Is there decent, high-quality daylight LED's available. Please let me know if you hve any experience! What woudl you recommend?

You want something wit a high TLCI (akin to the color rendition index, but accounting for the peculiarities of a tristimulus CFA). High powered daylight on a budget? Hedler's LED1000 comes to mind. Litepanales make nice aera sources, L5-Cs come with a richly filled spectrum and the defined penumbra&cuts of a Fresnel.

 

[Loswr]

How do I make a colorchecker passport photo if my Field Of View equals 1.20 mm x 0.90 mm?

Datacolor ChromaCal.

http://www.emsdiasum.com/microscopy/products/calibration/systems.aspx

 

[Zeidora]

I am asking because I am trying to get 'more advanced' with my microphotography setup. I used to use two speedlites for lighting, but there is some disadvantages there. I want to switch to a lighting continuous setup.

May I ask what problem you have with your speedlite set-up? I do a lot of macro and micro-photography (MPE 65 to about 7:1, then to stereomicrosocope, compound microscope, and scanning electron microscope), and wish I could use more flash. So I wonder whether it may be more of a question of using the flashes better.

Otherwise, yes balance the light source, and be done. Custom white-balance of camera is extremely good, better than using an external color meter; did some experiment with my Minolta colormeter III and manually entering measured color temperature to camera.

 

[privatebydesign]

The biggest problem you are running into is the actual spectral output of the bulbs. Don't be fooled by 'daylight' or high CRI figures, they are easy to get around. What you need are genuine full spectrum bulbs and the only brand that I use are the leading manufacturer of them, Solux.

Look through here http://www.solux.net/cgi-bin/tlistore/infopages/index.html and get the best for your situation, the halogens do produce a lot of heat but there are other options. Once you get them set it up, do the ColorChecker once and you are good for any subject, same exposure, same WB and same camera profile, make that an import preset and you are done.