I reread this thread in full again. This is a lot of info to digest! I think I "got" a lot more on the second pass, particularly in studying the links on CCT, the Kruithof curve, and googling blackbody radiators. Thanks all for your patience. Now I have a few keeper points:
1. All objects emit light radiation and are natural blackbody radiators
2. CCT measures the radiation level of each blackbody radiator
3. Artificial light sources mimic natural blackbody radiators imperfectly. The spectrum of colors may not be smooth and follow the curve of a natural blackbody radiator. The colors graph often has big spikes.
4. The color spectrum of natural daylight, from some of the graphs I looked at, is not a straight line. It's a curve with a small peak in the center, and the entire curve is upward sloping, lower at the warm colors and higher at the cool colors.
5. Light emitted by natural blackbody radiator may not always be pleasing to the eye. For any CCT, the Kruithof curve shows that pleasing light colors are obtained only within a certain range of illuminance levels. But the Kruithof curve was found empirically and hence may vary from individual to individual.
Human health perspective? No reasons, unless you are going to use them in your ambient home lighting.
Yes, this is EXACTLY my purpose, ambient home lighting. It's winter now, there was a post in this thread on seasonal affective disorder, my wife has at times had trouble sleeping, my 1 year old is not a great sleeper, and dealing with 2 kids has thrown my wife and I's sleep cycle rhythms off in the last few years too. So yes, whether it's proven or not, I would like to mimic natural light as much as possible, to capture any ancillary benefit regarding seasonal affective disorder and circadian rhythms. (Err on the side of health and good sleep.)
As has been pointed in the past Anders, Solux bulbs DO NOT match natural sunlight, they match the blackbody curve at 3000, 3500, and 4000K within the visible light spectrum AND sunlight when it is at these color temperatures which is for a short period of time in the morIning and evening DOES NOT match the blackbody curve.
Thanks for this clarification. I think my summary at the top of this post are now consistent with what you are saying here.
So technically, to mimic real daylight, we would actually have to have a lighting solution that changes CCT throughout the day, peaking midday just like natural sunlight. Instead, what we actually have in our homes and offices is a solution at one fixed CCT, which the sun gives us just one or two times during a normal day. So we just have to choose, do we want it to always be a cloudy morning? Or do we always want it to be a sunny day in the shade? etc etc. From a human health perspective, I wonder which choice is better. This sort of reminds me of typical space shows/movies where the computer changes the time and it goes from looking out the window at nighttime to suddenly looking out the window at sunny daylight.
Of course, generally for photography, except for taking pictures of small items, a continuous light is rarely used in the studio beyond a modelling light and you use strobes for the actual photos so I am not sure what you are trying to accomplish? Can you give us some more insight?
I am not talking about studio photography here, which is perhaps what you are thinking of. That is an entire model of photography that requires different lighting. Think candid photography of authentic moments, rather than formal portrait photography in a studio.
I am trying to achieve a home lighting situation where flash of any kind is not required for home photos of my kids in action. This gets into the aesthetics of photographs, but essentially if ambient lighting is sufficient, some photographers prefer to avoid flash. While sophisticated flash solutions can make the lighting seem more natural, I am trying to craft a solution where flash simply becomes unnecessary. Again, it's just my personal photography aesthetic inclination (but one I know a segment of photographers share).
However, keep in mind for photography, as they go up in color temp, they go down in efficiency as they are using a filter to accomplish this.
It looks like I didn't quite realize how much the efficiency drops. (
link). Should have read the specs in more detail.
Ok, so the higher CCT Solux bulbs are basically filtering out a lot of the spectrum to achieve the blackbody curve at the higher CCT so you'd need more bulbs to get the same illuminance levels?
I assume the 4700 on Esko's chart looks so flat because it's a log chart, but that the shape of the 4700's color spectrum should be the same as the others.
Related to the efficiency issue is the Kruikof curve. If I am going to use a cooler CCT, the Kruikof curve requires higher illuminance (and energy usage) in order to achieve pleasing light colors (assuming the Kruikof curve is true). A warmer CCT allows more energy savings because pleasing colors can be achieved at lower illuminance.