CRI and Kelvin co-relation

LuckyStudio 13

LuckyStudio 13

The Tapeless One
Is there any co relationships between Kelvin Temp and CRI ? Somebody was saying that if a CFL bulb has high temp, the CRI must be high also in order to push out the light in that temp. Which doesnt really make sense to me.

Also, any adverse effect when using a mogul to medium socket adapter color temp wised ?
 
I advise that you peruse the already excellent depictions on Wikipedia.com
there is no point in repeating them here.
Basically. There is a relationship between CRI or Color Rendering Index and Color temperature but it's not a very useful relationship. Color meters measure color temperature in ºK. the history of the Kelvin scale is interesting but also widely depicted. CRI is newer and takes advantage of advances in the science of colorimetry. It maps the exact color of a light source on a spectral graph and the unit of measurement is NOT kelvin.
CRI is helpful in zeroing in on one visible spectrum of light that will display the widest possible separation or differentiation of colors (hence the name).
Keep in mind that in video, your camera is calibrated to lock in a neutral white balance. Theoretically, 100CRI. in theory, pure daylight is 5,500ºK unfortunately it's not 100CRI and I can assure you that it does not result in the most pleasing flesh-tones if that's what you are photographing.
There used to be a fluorescent tube ( not CFL) that was called Chroma 50. This was 100CRI.
Not sure what the CFL equivilant might be.
 
In the world of lighting (by itself), there is no relationship between color temperature and CRI. In the world of cameras, there can be one.

When not considering a camera and how it perceives things, you can have low CRIs in any color temperature and high ones as well. This is just at the level of spectrophotometric test equipment which is what is used to measure CRI and color temperature.

However if your camera's sensor isn't good at a particular color temperature or conversely is better at a certain color temperature then for you color temperature could be an issue in CRI.

I often tell people that color temperature is a measure of where white light falls on an axis between red and blue bias. More toward red and its like tungsten or 3200K type light. More toward blue and its closer to daylight / 5600K type light.

The other scale used in measuring light is the green / magenta axis and that indirectly measures CRI--although its not the whole story. If a light of a particular color temperature is a bit too green then its CRI will be lower than one that falls in the middle of the green magenta axis.
 
Any correlation between color temperature and CRI is purely coincidential. They measure rather different things and the things that affect color temperature don't necessarily have anything to do with CRI and vice-versa.

An extremely rough analogy would be that color temperature is like the key that a piece of music is performed in, and CRI is like whether they are playing in tune or not.

A mogul to medium socket adapter is a simple mechanical gadget. What sort of "adverse effect" are you concerned about?
 
Well if that is the case, why should we bother to look for light source that have high CRI along with the color temp that the source puts out ? Why cant we just use any 5600k bulb ? i am worried that introducing a Y adapter to a mogul-med socket adapter will have affect in the flow of electricity and will ultimately have effect in the color temp of the light source.
 
LuckyStudio 13 said:
Well if that is the case, why should we bother to look for light source that have high CRI along with the color temp that the source puts out ? Why cant we just use any 5600k bulb ?
Click to expand...

I don't think I understand your question. You always want CRI as high as you can get. I would think for the most obvious reason: the higher the CRI, the "flatter" the "frequency response" of the light, and the more accurately all the colors will be illuminated.

You would chose color temparature based on several factors. If you are supplementing existing illumination, you would certainly want your supplementary light to be the same color temp as the ambient light to avoid the obvious effects of different color light (unless that is some special effect you are going for.)

If you continue to think there is any correlation between color temp and CRI, you will continue to be confused. They are independent variables.

You are correct that "CRI must be high also in order to push out the light " makes no sense. You have only to go outside in the city at night and see the high-pressure sodium-vapor street lamps to completely blow that theory out of the water. Forget it. It is nonsense.

LuckyStudio 13 said:
i am worried that introducing a Y adapter to a mogul-med socket adapter will have affect in the flow of electricity and will ultimately have effect in the color temp of the light source.
Click to expand...

You didn't mention any Y-adapter in your original question. Yes, a Y-adapter presents the possibility of doubling the load on the power source and wiring. That could mean overloading socket, switch, cables, circuit-breakers, generators, etc. But it has nothing to do with mogul to medium socket adapters.

If you managed to load down the power source so that the voltage droops, then incandescent lamps may droop to lower color temperatures just because that is how incandescent lamps work. But that is only coincidental with overloading the power source. If you deliberately reduced the power source (as with a dimmer), it would have the same effect.

A Y-adapter does not "affect the flow of electricity" any more than a power strip or extension cord with multiple outlets "affects the flow of electricity". Consider getting your information from more informed sources.
 
Got all the "info" from an employee from the Electrical Dept of the local hardware store :D He was trying to convince me that even though tht 6500k CFL globe does not have the CRI listed, it must have high CRI in order to be illuminating at 6500k. Which doesnt make sense to me, because I know of diff fluro tubes with same color temp that have diff CRI.
 
Yeah, that's total nonsense.

Color temperature is the relative red to blue. CRI is the accuracy of how it represents colors, and is usually attempted to be corrected by adding plusgreen or minusgreen gels. Totally different, unrelated concepts.
 
A bulb goes on the mogul form factor for a couple of reasons:

1). It has a higher wattage use and therefore current flowing through the socket. Therefore they want a bigger socket to handle that current

2). The bulb is probably also physically bigger and needs a larger socket to handle its weight.

Thus I wouldn't use a mogul to medium adapter and Y adapter too if the bulb is really big and bulky and is a higher wattage, especially something in the 200w range. CFL bulbs for instance are usually available in medium base up to about 105w. After that they go to mogul because they are getting pretty big physically and their power usage is bigger too.

On the other subject, I'd offer a different opinion about why CRI might not be listed on the bulb in a hardware store: because its low enough that its nothing to be proud of so they didn't bother ;-).
 
You must log in or register to reply here.
Back
Top