I noticed the dubious R9 value on measurements others posted, but was waiting for more measurements to be shared before drawing conclusions. The other measurements I looked seemed at least in the very rough ballpark - I think someone shared an R9 around 20 measurement on an SBT-90 (a bit high), and R9 above 80 on a 519A (about right)
But I agree an R9 of 78 from an LED with an Ra of around 60-70 is wildly off.
The difference of a reported Ra of 61.2 from the Opple 4 compared to 71.1 from the Opple 3 also suggests much worse Ra accuracy than I was hoping for, even recognizing the fact that this is a budget instrument. I had the impression that in the few instances when Opple 3 users were able to make comparison to proper spectrometers, the results were usually only about 2-3 points different.
I am hoping this is just a correctable bug with this first batch. It seems like the new sensor with more color measurement points should be capable of improved accuracy over the Opple 3.
On a separate tangent, it’s interesting to me that Opple is continuing to use a discrete channel sensor. I understand these sensors are cheaply available, but it seems to me that a refinement of the classic DIY spectrophotometer design that relies on a diffraction grating and an imaging sensor could be possible at low cost:
I would have thought this technique could be refined enough to make a commercially viable product capable of near continuous spectral measurements using low cost components like the camera modules used in entry level smart phones. I think the main challenge is calibration. Perhaps that’s a much more difficult challenge than I realize?
agree… now that I understand the Opple 4 better, it seems clear that bogus R9 is only an issue with Low CRI LEDs, and the giveaway is that low CRI Ra that produces High CRI R9 is a symptom of Low CRI LEDs… Basically the Opple 4 cannot give accurate R9 for lights with low Ra.
otoh, with high CRI LEDs, the issues are less critical… the Opple 4 reads higher DUV by about 0.0030, than the Opple 3, but the Opple 4 adds R9 data, that I find valuable.
Both the Opple4 and Opple3 give pretty close CCT values, when testing High CRI LEDs at similar lumens output, and similar lux on the two Opple meters. I find that gratifying. See the TS10 example above as a prime example.
so, based on my last few tests, imaged above, I do think the Opple 4 has useful application for comparing High CRI LEDs to each other.
For example, Im looking forward to comparing the R9 of an LH351d (coming in the mail), to a 519a… I want to confirm that the LH351d has lower R9, and only the 0pple4 has R9 sensors. The Opple3 has no R9 data.
This last observation will cause me to return LM4. Please check your finding to see if it is same as mine. To check this you must have both LM3 and LM4 and 2 phones.
I experimented with my S21D 519a. Light on tripod, sensors fixed in position 15 ft away next to each other. No change in position or direction of either light or sensor during test.
x and y of my LM3 goes up and down but in the order of 1-3 points, 10 points AT MOST. For example x=0.3081 going up to 0.3091. I do this a lot and would sit a long time watching because some LED like 519a the Duv goes down a lot with time & heat build up. I am used to how stable the numbers are. Lot of times x stays same, and y drops 1 or 2 points at a time.
x and y of my LM4 goes up and down by 20-30 points and subsequently causing Duv to go up and down quite a bit. Check your LM4 Duv, hopefully with a stable light with stable output like Convoy S21D. FET driver may cause output to change too much and this affects Duv. There is something very wrong and very different with, at least, my LM4.
@jon_slider what’s the best way to ask for refund through Aliexpress? What’s the chance of getting our money back?
Sometimes, even when a refund is okay with the seller the shipping cost to China makes it not worthwhile. At least that was my conclusion on a couple of occasions from the US.
I received my LM4 today and wanted to share my observations:
SBT90.2 on Wurkkos TS30S 5700K
At low output levels, I get reasonable R9 and CRI readings. However, as I increase the output (5/7 in stepped mode), R9 behaves weirdly and hits 100.
LH351D on Sofirn LH351D 5000K
R9 is measured around 90, which is relatively high for this LH351D. LH351D is known to have poor R9 (one measurement I saw showed R9 of 70). In my skin test, my skin appears significantly paler under the LH351D compared to other R9080 Nichia LEDs. So, I suspected that my LH351D had a lower R9 than my Nichia LEDs. However, measurements from my LM4 disagree with my previous observations.
DUV
Calculated DUV measurements are convenient and still useful, but the numbers by itself is some what questionable. They seem to be positively biased compared to my LM2 and LM3. The DUV of my most pink light was measured -0.0073 on LM3 and -0.0079 on LM2. However, on LM4 it is measured -0.0030. Many of my previously neg duv measured lights are now measured positive on LM4.
The calculated duv are still useful in that pinkish light still shows lower duv and greener lights shows higher duv. It is just that the numbers by itself may not mean much. (i.e. poorly calibrated)
In conclusion, LM4 is not terrible, but not as useful I thought would be.
Yes, and it is quite cheap for what it does. Not to say that it shouldn’t work correctly. I think they are aimed at people checking home lighting, not flashlight nerds… so there is that. But yes, those folks would expect accuracy as well.
Then there is the question of the Chinese seller potentially allowing these to go out before they are ready. So maybe we are getting what are effectively beta units (??).
What I would like to see is a comparison to a calibrated quality spectrometer. Right now, all we are doing is comparing them to something we are used to. Not a known good standard.
Mine just arrived. I also have a V2 and V3 Opple. I need to figure out a good way to control the process. I do have mall tripods and some of the clamp adapters for the lights. I just need to figure out a good way to hold the Opple(s) in the correct orientation. So far, I have just used the older ones for quick and dirty hand held testing.
Yes, I have seen such practices. Perhaps that’s how they are able to produce so many products so quickly, by using early buyers as beta testers. Weird thing in this case is that beta testers pay for their units instead of being paid or getting free test units.
Today, I revisited the Aliexpress listing page and noticed the following announcement from Opple:
"Light Master 4 now only supports white LED light measurement. Not support monochromatic light or others, it will read wrong data.
We are preparing to launch an OTA updates of app in the future to support more light measurements.
Estimated app updated on 30th, May to fix some bugs we found, then a small iteration optimizations updating will be done in the following 30th June, 30th July. (It can only be updated once a month because App Store’s Restriction.)
Sorry for any inconvenience. If you are currently testing a reading that you believe is inaccurate, you have the option of returning the device for a refund, or choosing to keep it. In the future, we will do an OTA upgrade to make the chip reading more accurate. Thanks for your understanding."
In summary, there are issues with the LM4, and Opple is planning to release app updates at the end of May, June, and July to address these problems. I assume that the Opple can be updated through the app. Hopefully, the update will improve the usability of the LM4.
I kind of doubt that. But maybe… I would bet that they will be tweaking the (APP) software to work better with the V4 hardware .
Anyway, apparently they are aware that there are problems and are working to fix them. The penalty for being early adopters…
I received my Light Master IV today. I did some brief tests comparing a range of CCTs and CRIs to my X-Rite spectrophotometer, and the results are not promising. The R9 measurement was accurate on one light (5000K high CRI), but otherwise completely useless. CCT and Duv both differ from the X-Rite significantly more than the Light Master III. I’ll try to do a more controlled test of all three devices later tonight.
On AE I can’t order LM4 anymore. There is message that they cant ship to my address. They took it off sale, I guess after bugs which you guys found here.
I didn’t have a chance to use it but this might a good picture to load if you decide to file Aliexpress dispute. Especially that part about “wrong data.”
You may never be able to buy from them again with the same address. There is a reason the Amazon price is so much more expensive than Aliexpress. Think wisely before committing fraud.
Just ask for refund and send the device back to them.
Aliexpress is asking for evidence that the device is not working as first part of refund process. None is better than providing Opple’s own description.
Just chat with the AliExpress store. They sent me two messages without me asking for a refund. I was trying to let them know about issues with CCT and duv measurements.
"Dear customer, we are very sorry for any inconvenience. Light Master 4 is a reliable device. We spent 8 months debugging the chip and data to ensure the stability of its measurement.
Usually, it is used in lighting design. The purpose of this device is to test daily used white LED lights in the normal environment. Not support monochromatic light or others, it will read wrong data. We are preparing to launch an OTA updates of app in the future to support more light measurements.
If you are currently testing a reading that you believe is inaccurate, you have the option of returning the device for a refund, or choosing to keep it. In the future, we will do an OTA upgrade to make the chip reading more accurate. Thanks for your understanding."
“Estimated app updated on 30th, May to fix some bugs we found, then a small iteration optimizations updating will be done in the following 30th June, 30th July. (It can only be updated once a month because App Store’s Restriction.)”
I’m super excited that they’re planning an OTA upgrade!
I put the LM3 and LM4 head to head with the sensors nearest each other on the floor and connected each to the Opple Smart Lighting app on an Android phone and an iPad. They’re 2-3 metres from the roof.
Here are results for a ZebraLight SC700d in H1 mode.
I balanced the LM4 upside down on a LM3 and shifted it to make the sensors near each other. Both placed at the edge of a table.
I then put a ZebraLight SC700d on a drawer about 2.5 metres away and entered H1 mode (maximum).
I used the Opple Smart Lighting app on an Android phone and an iPad. To take the measurements I hit stop at the same time on the phone and iPad and then saved screenshots.
