The reason why you're not seeing the color temperature reading change is because you have the Lumu Power installed backwards. The diagram at the top of the screen shows you that you need to have the flat side facing the light source.

Hi, Here we are having issues with Lumu too, and really slow communication and return process, still waiting ... :(

Hi everybody,
it's Marko here from Lumulabs.

We recalled PhotoJoseph's unit and sent him a new one. His unit displayed some small error. We will check it extensively to find the reason and make sure it doesn't happen again.

I'm sure Joseph will make another review with his new Lumu Power.
However, we tried to replicate the accuracy test and documented it on our side as well. CHECK IT OUT https://support.lu.mu/hc/en-us/articles/115004257809

It's our standard practice to immediately replace the unit if the user reports
- bad accuracy
,- physical damage happened to device or
- is getting some other strange behaviours.
With the new Lumu Power we had approx. 0.6% of cases like that.

We also always refund the money to any user
- not satisfied with device,
- doesn't find it useful in his/her workflow and even
- not specifying any particular reason.
This happened in approx. 0.5% of cases with the new Lumu Power.

Both statistics are well below industry standard.


Thanks for your attention and
With Lumulove,
Marko.

So far im pleased with the outdoors exposure accuracy. I'm still playing with it and doing a lot of testing. Loving it!

Hi Joseph and everyone else,
accept my apologies for the late reply.

1) MEASURING ORIENTATION
You have to use flat side to measure Color Temperature and Illuminance. And dome side to measure Ambient and Flash exposure. Be aware of the small pictogram on top of each screen - it tells you which side is measuring in particular mode. You can of course plug your Lumu Power in your iOS device in either orientation.


2) ACCURACY
Lumu Power uses state-of the-art color sensor from AMS (formerly MAZeT) http://www.mazet.de/en/products/jencolor/true-color-sensors/item/385-as73210.html and state-of-the-art photodiode from Hamamatsu https://www.hamamatsu.com/jp/en/product/category/3100/4001/4103/S1087-01/index.html.
Each light meter has color sensor calibrated with 7 different light sources and photodiode calibrated for response and offsets. Calibration is automatic, each device has it’s own serial number, all unique raw data along with the calculated calibration contants and matrices are saved to the web servers.
@Joseph You can factory restore your Lumu Power in the general app settings.

The thing is - this is the light meter built from the ground up, and it just came in the hands of thousands of people. We made lots of test, but there can be bugs, especially in the version 1.0 firmware and software. Lumu Power hardware is solid though.
We recently found that the Ambient Exposure measurements can get confused under specific types of lights, we also found the way to calculate calibration matrix for color measurements even better.
Both of these two things, along with others, will be updated automatically with the firmware upgrade through the iOS app. Our work on enhancing the capabilities or accuracy of your Lumu Power never stops until it is absolutely perfect. It’s the main reason behind setting up a system where each light meter can have firmware and unique Serial number dependant calibration contstants upgraded over the air.


3) CHANGING THE LIGHT METERING INDUSTRY
The next two things which were the main motivation behind creating Lumu Power:
- Light meter which combines color temperature, illuminance, ambient and flash exposure metering - it has never been done before.
- App which is constantly improved, changed, new features added or removed - everything based on the user feedback. App which is made to be used - it has never been done before.


4) MANUAL
We don’t have a manual yet, but we are working on it.
Fixing bugs and hardware manufacturing have been our main focus during the last months. Also, we weren’t quite sure how much of the app will users understand without the manual.

Since the beginning of this project, we spent a lot of time to make our Light Meter app as simple, self-explanatory and intuitive as possible. We are aware that there is a room for improvements. And when one starts using a completely new device, it helps to have a set of starting points.

I invite you to explore the app as much as possible. Don’t be afraid, you can’t anything break or make wrong. Then send us the feedback about your experience - what gives you problems, which features you do not know the purpose of? Write directly to me mu[at]lu.mu.
With your help, we will make our app more useful. And will be able to prepare the most relevant features manual and how-to-use real world examples. We care deeply about how to make your photographs better and your life easier.

A brief overview of the functionalities, to start you exploring:

a) “Home Screen” (where all the different Modes are listed)
- The Gear icon in the top left corner: takes you to the app “General Settings”. Here you can
- see the info about your Lumu Power, additional calibrate it or factory restore it
- customize which Modes are visible on the Home Screen
- turn off “Auto app open” (= pop-up message when your Lumu Power is inserted into the iPhone)
- set app to Dark Theme
- set measuring button to “CONTINUOUS MEASURING” in all Modes. Measuring button function will change from “hold to measure” to tap to START/STOP measuring.
- Pencil icon in bottom right corner: takes you to all the saved measurements.

b) On each Mode Screen:
- on top of the screen, you can see small pictogram - it tells you which side of the Lumu Power is measuring in this specific mode
- with the top right icon, you access Mode-specific Settings
- with bottom right Pencil icon, you save the last measurement

c) ILLUMINANCE Mode
- AVG icon in the bottom left will plot the graph of the measurement and calculate average illuminance in real time. For this option to be visible, you have to set “CONTINUOUS MEASURING” to ON in the app General Settings.

d) PHOTO AMBIENT Mode
- You have to tap on the photo parameter (APERTURE / EXPOSURE / ISO) to choose and measure it. The remaining two parameters are locked and you can adjust their value by swiping them left-right or tapping on the < > arrows.
- Bottom left icon gives you the option to set exposure or filters compensation if you use them.
- Drop down menu on top of the screen reveals additional “MULTI” and “PINHOLE” submodes.
- If you tap on the top right icon, it will get you into Settings for this mode and here you are able to set maximum aperture or minimal shutter time app will display. 

e) PHOTO FLASH Mode
- You operate it similar to the PHOTO AMBIENT Mode.
- After you measure a flash, you can adjust parameter values with swiping. App will automatically recalculate all displayed parameters.

f) PHOTO SPOT METERING Mode
- uses iPhone’s camera only, no need for Lumu Power hardware
- you select and adjust photo parameters the same as in the PHOTO AMBIENT Mode

g) CINE/VIDEO Mode
- in this Mode you always measure APERTURE
- tap on FPS or EXPOSURE to manually insert the values and swipe ISO to set its value

h) COLOR TEMPERATURE Mode
- Currently showing GREEN/MAGENTA shift in standard colorimetric scale. Additional options to display it in Adobe or other standards will be added with future app updates.
- Drop down menu on top of the screen reveals “FILTERS” submode, where you can measure a color difference of two different lights.
- FILTERS Submode: you can tap on the number to select and measure each light separately. You can tap again on the selected light and you can input Color Temperature manually. App returns you the necessary color filters to use with the 2nd light. 

i) CHROMATICITY Mode
- currently only showing reading in CIE 1931 color space, more options will be added in the future app updates


Thanks for all the additional comments or questions,
With Lumulove,
Marko.
CPO

Ok ...hoping for feedback on those results... thanks for testing...just received my Lumu

I've been watching this Lumu Power reader for close to a year now and I would love to pick it up for the pre-order price of $229 before Monday. After watching this video, I'm on the fence, I was really hoping it was accurate.

Ok - this is what I did. White-balanced and set my GH5's exposure using a Lastolite grey card. Took a photo and bought it into Lightroom. The Lumu identified the temperature as 3820K with no green shift. Lightroom had the temperature at 3800 with a shift of +14 to magenta. (A Luxi with Cinemeter II app gives 3420K) If I use the dropper to set the white balance, it changes to 3750 which a shift of +15 to magenta. For photo ambient, my Sekonic suggested an aperture of f2 for an ISO of 500 and shutter speed of 1/50s. The Lumu suggested f1.8, which is perfectly fine.

Great show @PhotoJoseph
I been using Photo Pills that is a great app that has golden hour, where the sun is, time laps calculator, DOF and much more. http://www.photopills.com/

Arrgghh. I started watching this video, got so excited that I ordered the Lumu. But by the end of the video it looks like it doesn't work. I need my money back!

Jospeh, great show as always! Here is the link to the video I put together about a year ago where I go over some of the best iPhone apps for filmmakers. There have of course been many more created since I released the video, including color metering apps like Lumu, but the list still has some relevant apps that are helpful.
https://youtu.be/nAHMqn0VCfY