Temperature of Light and White Balancing

LED Temperature

I am sure most folks when they are picking out what LED bulbs, usually buy LEDs by colour and go via marketing jargons like Warm White, Cool Day, Warm Yellow etc. These terms usually represent the output colour of your LEDs. Some of you would know that there is a standard way to represent them in terms of colour temperature with units in Kelvin(These would be mentioned on your bulbs). Let’s explore what those are today.

LED Temperature White Balancing

The temperature of colour is a weird way to represent information. Colour has no “heat”. So why use temperature as a measurement unit for it? It all goes back to a concept known as a black body radiator. In simple terms, it’s a theoretical material which emits radiation(aka light) when heated to different high temperatures. For example, think of a metal(which is a somewhat close real-life black body), when it’s heated to say 1500K has a particular glow in the red/orange range. Now when you start increasing the temperature of this material, the colour slowly starts to change white(Bluish tinge). So hence temperature Kelvin is used in relation to the colour of light. The temperature range can go from 1500K – 10,000K+. 1700K range corresponds to candle-flame-orange light & 6500K is clear sunlight on a bright day. So you have a huge range of LEDs to choose from based on what you want.

Temperature and White Balancing

Now let’s come to photography of this light. Where it’s all relative to your settings. Open your mobile camera and go to the manual mode in your camera you will see there is something known as White Balance on the settings, This is also measured in Kelvin. This setting is telling your camera sensor what pure white light is. Let’s say you put the WB setting on the camera as 5000K and take a photo of an object. So any light source in your scene with a colour temp of 5000K will appear white on your image whereas any light source lesser than that will appear Yellow and anything above will appear bluish. It’s as simple as that. Now if slide up your white balance to say 6500K setting you will see more things looking yellow (if the scene lighting is at say 5000K). Knowing this concept will help you take killer pics and set the lighting mood for your camera. Take a look at the picture for seeing how an image will come out for the same lighting scene shot with different WB settings.

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Raspberry Pi Pico W Analysis

Raspberry Pi Pico W
Raspberry Pi Pico W
Raspberry Pi Pico W
Raspberry Pi Pico W Teardown

A couple of days ago, Raspberry Pi Foundation released their new board Pico W for $6 which is an extension of the basic Pico board with wireless capabilities. It’s a big deal in the maker/hobby market because of the price. Now there is a good competitor to the ever-popular ESP32 series because of the wireless option. The board comes with WiFi for IoT applications.

Pico W contains the RP2040 chip which is a Cortex M0+ chip(one of the best in the class chip for the price of <$1, check posts of last year for detailed analysis on this chip) and to enable wireless capabilities they have partnered Infineon and used their CYW43439 dual-purpose wireless chip. It can do WiFi(2.4GHz) and Bluetooth 5.2. Currently, only WiFi is enabled on firmware but BLE support I am sure will soon follow. CYW43439 contains a dual-processor M3 and M4 for handling each of WiFi and BLE stack with a single physical antenna section handling both. Although it contains those processors, they are not application processors and are merely there for handling communication(Unlike Nordic’s BLE series). It needs a host controller to handle the application and transmit the data via high-speed SPI to it. If you check the PCB layout you can find the BGA wireless chip under the metal casing(Mostly for passing certification tests of EU and FCC) for the radio module with a dedicated crystal and 2.4GHz PCB antenna coming out of it.

I am sure folks from Arduino are starting to feel the heat with Rpi launching much cheaper boards. One thing it has going for it is its availability. I don’t know how on earth Rpi Foundation is able to have chips available in these days of shortage. It seems to be the only major brand out consistently having chips and boards. I do believe one key factor for that is the professional/industry is not using RP2040 in major products. It’s a decent chip but has its flaws(No Flash Memory, poor low power performance etc). Overall it’s a good maker board as an ESP32 alternative.

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