Lighting quality question CRI

Re: Lighting quality question CRI

John K Jordan

This is a can of worms with a great deal of controversy. One of the biggest arguments: the CRI rating does not take color temperature into consideration. Google will show you that many people who tell you CRI is all-important are those selling light fixtures and those selling their lighting consulting services. Search for and read what people say in the film and video industries where color is important. (you can search for something like "how important is CRI") Read the wikipedia article: https://en.wikipedia.org/wiki/Color_rendering_index

CRI numbers were not even commonly advertised for lighting elements until LEDs became popular. I always wondered if they are used mostly for the advertising value to get the consumer to buy one over another, just like lumens. (remember, the lumens number printed on a light element package may have very little to do with how much light reaches the subject)

Do a test. Acquire at least two sources, one with a high CRI and one lower. Evaluate both in a dark room. Use a high quality light meter to insure the same amount of light reaches the subject. Look at unfinished and finished wood. Look at paint color charts. Compare black and dark blue socks. Put your favorite person under each light. View photographs and artwork. See what differences you can detect, especially with some dark time between tests. For an additional test, evaluate two different sources side by side with the same CRI number.

My opinion: the eyes are incredibly adaptive to both brightness and color. We have been happily using a variety of light sources for a long time in our shops, homes, and businesses (and museums/galleries), some of which would today be given a CRI rating of less than 50. For shop use, how often are you critically evaluating colors? For the occasional need to evaluate color you can use actual daylight. But not during a spectacular sunset.

For me, brightness is more important than a CRI number.

JKJ

Great response

not a great response

Bill Tindall, E.Tn.

First the easy one:

" some of which would today be given a CRI rating of less than 50." What, other than a sodium lamp has a CRI less than 50? Crappy T12's that many hated were 60-70.

My brother-in-law is a retired lighting engineer for GE. His job was to advise businesses on lighting. CRI was most certainly an important factor when he advised lighting for new or existing installation. A high end clothing store got the best CRI lamps available, meat counters red biased lamps , etc.

Years ago there were great differences in CRI of T12 lamps. If any are old enough do you remember people complaining about fluorescent lighting and how it unfavorably compared to incandescent? Some varieties of vintage T12 lamps has parts of the color spectrum missing and it bothered some people, including myself.

It is not easy to find crappy CRI lamps today. The readily available T8 and T5 lamps are at least CRI 85, as well as later generation LED lamps. Early generation LED lamps had colors totally missing and correspondingly poor CRI rating. A high CRI LED rating is a good indication the fixture is a late generation LED. Savvy shoppers avoid early generation LED fixtures which is why manufacturers include this specification on their quality fixtures.

That said, what is good enough? I agree with your advice here. Test and see. Or make a good guess that you have never worked under a source better than CRI 85 (other than sun light and incandescent) and declare that 85 is good enough.

it was my response, anyone can make their own

John K Jordan

>>>It is not easy to find crappy CRI lamps today.

That is closely related to my main point. Almost any should be fine for almost any application.

Some long fluorescent bulbs were tested at around 50 CFI according to what I read. I can try to find them if needed. I do have "colorful" memories of the horrible photos I got in the 60s/70s under industrial fluorescents even with the so-called fluorescent filters, and the sickly feeling I got from working under them for too long.

JKJ

Re: Lighting quality question CRI

Tony-Memphis

While color is very subjective, there are standards. Regardless, what looks good to some, may not be good to others. Anyhow, I'm certainly no expert. My wife is an artist and color is very important to her. She prefers the higher CRI bulbs for sure. We have been using those (what was available) for many years. We did some experimenting and it is obvious that some bulbs are 'better' than others.

For my shop, however, I do not focus on the CRI. I need light and lots of it these days! I have no idea what CRI my shop bulbs are ( I use a mix of bulbs anyway). I do have to take stain samples into the house to check color in place. Amazing how much difference there is between the shop at night, shop during the day, house lights, etc.

There is a lot of good info out there on the subject. But again, its really up to you and what pleases your eyes. Just be aware that there are differences if color is important to you. 'They' recently changed to LED's in our office - they picked the most awful color bulbs that were available. We all complained and moaned. 6 months later, we are used to the new normal and don't care anymore. The color might actually be 'better,' but it was a lot different than the old bulbs.

Re: Lighting quality question CRI

Larry Clinton At Frankfort, (Central) Indiana

Another important issue ~ What are you wanting to achieve?

Bill is absolutely correct in his statements about CRI, however sometimes viewing a wood finish in perfect lighting CRI fools you into thinking it will look great in a home setting.

Most homes do NOT have 90+ CRI in the area the finished product will be displayed! When I try out a stain or finish, I try to view it in the same / similar lighting it will find it's final resting spot, I have some Halogen (high CRI bulbs on the ceiling of my shop, windows I can use to view in sunlight and Florescent varying in color temperature & CRI, often the "color shade" appearance changes fairly substantially under the various light sources.

Even if I know what is the current light source where the object will live, I try to achieve a fair balance that looks ok under the various illumination as many of us are changing the light sources to the newer Led's with higher CRI's.

As an former Engineer many of the products we made were used in automotive applications. Some with illuminated through translucent graphic decals. Several years ago we had to purchase a machine that measured color temperature and CRI accurately to duplicate the GM samples supplied to us. Also we had to measure the color of graphics applied and/or material color. As I recall the machine cost very near 6 figures!