I’m thinking of getting some 12V MR16 GU5.3 LED spotlights (yes I’m technically in the wrong forum but I decided it didn’t matter since my question is generic) from AliExpress. The sellers claim these come with Sharp Zenigata which have decent CRI (80 or higher) and a highish CCT (5000K or higher which I prefer). I know from research a while before Zenigatas are available in this sort of range so it’s possible they’re telling the truth. (Unlike those who claim they have XP-E cool white and CRI above 80, except Cree doesn’t offer cool white with high CRI in the XP-E or XP-E2 range or much anything besides XT-E and XB-D as far as I’m aware.) But it would still likely be difficult to verify since I suspect other Chinese and Taiwenese LED producers make similar design COB LEDs so the LEDs aren’t distinct enough. And I’m not sure if I can even look at the LED properly without destroying the spotlight.
I don’t have anything testing equipiment since I’m just a hobbyist. I can obviously get a good idea of the colour temperature etc. But since I’m choosing these in particular for the highish CRI, what’s a good way to test the CRI beyond just looking at different colours and seeing how they render compared to other lights. Skin (e.g. both sides of your hand) seems to be a common recommendation, although I guess it depends on the precise colour of your skin. But any other suggestions on how I can best test the CRI?
AFAIK without some sophisticated equipment there is no way to measure CRI. However in most cases these lamps are easily opened so you can check the led inside.
Check out the Philips Endura 10W MR16 LED bulbs. Over 400 lumens, 80 CRI, 4000K, valid specs. I have around 40 of the 3000K (490 lumen) bulbs installed in my house.
That Philips bulb is extremely inefficient for a 80 CRI source. They are pushing their lumileds but competition has moved forward. For example bridgelux has sm4 led that delivers 360lm@85°C/3000 °K/80CRI/ at 4,25W and even when you add driver losses bulb using this led could get away with approx. 5W for these lumens at hot 85°C…
Not once you get optics and driver losses involved. Also the Philips bulbs put out the most light of any MR16. It’s the only one that can replace a 50W halogen bulb. Doing lots of light in the MR16 form factor is a real challenge. The Philips bulbs actually contain a tiny fan. And it has real, confirmed specs and UL/CSA/FCC certifications. I tested LOTS of bulbs before settling on the Philips bulbs (search My adventures in LED home lighting for “Philips”)
4000K is a little too low for me. Even 5000K is a bit low but there doesn’t seem to be anyone offering higher CCT that I have reason to believe really may be high CRI.
It’s going to be dimmer than 50W but I purposely ensured there are a lot of lights so I think they should still work.
Will share the links later since I’m on an iPad. But just do a search for MR16 Sharp 8W and probably 9W (theres one supply who claims this altho doubt it’s really any diff) and you should find them. There are about 4 or 5 suppliers but so far only two have offered to sell me a single one to test. There are more 5W ones if you don’t need it that bright. Some suppliers claims their Cree XP-E is high CCT 80+ CRI but Cree only has 4300K for 80+ except possibly XB-D and XT-E as far as I know.
If you can spare the money you could invest in a colour checker. Lights of higher CRI should distinguish the colours of the chart better than lower CRI lights.
Unless I read it wrong, colour checker is a digital screen display. What I’ve been looking for is a poster size wall chart of the complete colour scale with all its values (preferably in matte) that I can shine my lights on to compare tints and CRI visually.
I thought of a simple diffraction grating. But unless the LED is totally crap, I’m not sure whether it would really help me tell if the CRI is likely to be as expected.
I’m not trying to say that philips bulb is not up to the specs or doesn’t produce lot of light but merely that it is possible to make much more efficient bulb with up to date components. MR16 form factor in it’s standard dimensions is very limited regarding cooling capabilities (without fan) and IMHO reasonable top for it is 35W halogen equivalent at approx. 4-5W of led power. Although using more smaller power bulbs is much more efficient and these bulbs if decently designed and build could easily achieve advertised life times for leds…
Unfortunately most of led manufacturs are concentrating on leds in 2700-4000 K range for use in incandescent/halogen bulbs replacements and only few of them are offering high CRI in light temperatures above 4000 K namely japan producers as Citizen, Sharp and Nichia…
There is something called the colour checker passport, which is a booklet with physical colour charts. It goes together with some software. The original idea is using it for photography, when you take a picture, you also take one (with the dame settings) of the colour chart so you can calibrate your monitor/prints with the real chart next to it. It is also a usefull chart to check your colour rendering.
Yeah thats what I mean. Some of the AliExpress sellers claim their light have high CRI high CCt but the claims are questionable since they also claim it uses Cree XP-E which only goes up to 4300K with high CRI (above 80). The XB-D and XT-E do go to 80 with higher CCT at least according to the datashee and Cree website but not one seems to use them on AliExpress. Some of the Taiwanese LED manufacturers like Edison and possibly Epistar may be have high CRI high CCT LEDs but those are a bit more iffy IMO particular since I expect there are even more Chinese clones.
In terms of MR16 GU5.3 12v 7W or so, so far all I’ve seen are ones which supposedly use Sharp Zenigata which do come with high 5000K 80+ CRI so it cold really be that unlike those who claim it for their Cree ones. It may be partially to do with voltage. Zenigata for 7W-10W is 12.3 or so forward which is a little high but maybe with a decent buck driver its not that hard. For Citizen and a few others I looked at they tend to be designed for line votage usage so fairly high forward voltage i.e. the chip uses a lot in serial rather then parallel. There are some Citizen MR16 12V in the 5W range on AliExpress
