Subject. I do care about eyes (ish), so I have the “Night light” setting enabled almost always (Windows and android). But when I edit photos, I tempted to reduce color temp on them, and results looks cold for other people. How to keep the right color balance?
I was wondering why Adobe chose to have color temperature compensation be the B-channel of the LAB spectrum, as it does not look at all like the kelvin spectrum. Does the B-channel compliment Kelvin colors particularly well, or did they just do that because LAB can approximate human vision well? It can capture a wide range of colors and change colors without changing lightness, so I would have picked it too, but I wouldn’t have named it Kelvin because it doesn’t look anything like Kelvin and I’m pretty sure LAB is not based on Kelvin.
I know there’s already threads about this topic and I read them and there was some amazing answers about physics and history and ways to improve your photography but they never really touched on why the B-channel was used except one person who was guessing it was used because it approximated human vision.
Here are the threads I have already checked:
White balance color space
What is color temperature and how does it affect my photography?
EDIT: I was talking with Michael C and he says that Lightroom goes from blue to amber and I was wondering if I could get a second opinion because I’m color blind so I wouldn’t know for sure. I increased the temperature on this image to max. It appears yellow to me, not as dark as the amber from Kelvin, so is it just me?
I was wondering what does color temperature do to your pixel’s RGB/LAB values when you adjust it.
I get that things get more yellow or more blue in the case of temperature, but what equation is Lightroom/Camera RAW using? Is it simply 1-uping the B-channel values for every pixel when you move the temperature up a notch?
My other question is this: I noticed that changing the temperature and tint significantly changed the gray values when I converted my photo to black and white and worked in that space. Other color tools actually add color instead, like color grading, so it’s no longer black and white, it gets a cast, and some don’t work at all, like saturation. So does that mean that the A and B values of LAB influence luminance values in black and white? I’m guessing that yellow would make things brighter? Is Lightroom changing L values or does it preserve them and generate a preview on top where color values influence gray values?
I’m trying to program a photo software and maybe one day a camera app so I’m interested in what is specifically going on.
I’ve been searching for weeks for what Lightroom and Photoshop use to determine your image’s color temperature. People have said a lot about the kelvin scale and how to white balance, but this isn’t exactly what I’m looking for.
I noticed that from picture to picture the starting color temperature has different amounts depending on the warmth of the image. What is it doing to determine that starting amount? Is it an average of all the LAB B-channel values, or a ratio between how many values are yellow vs. blue? If it’s all from the camera and the RAW file, then what is the camera doing to determine its color temperature values?
I’m hoping to start programming a photo editing software and maybe one day a camera app so I’d like to know the math of how the computer makes its decisions regarding color temperature.
I got a Macbook Pro 2019 with Intel Core i9 Processors and it seems to heat up and get the fans spinning even with very low cpu usage.
For Example, today when I was on a video call, Both my fans were spinning quite loud and my CPU Temperature was at 57deg Celcius. When I looked at Activity Monitor, my CPU was 97.44% idle.
Is this a problem with the computer or is this normal?
I have an HP Proliant ML110 G9 Server.
Added an HP Smart Array P420 PCI-E card to have real hardware RAID on the server. Everything works fine, but I noted that the P420’s processor was extremely hot (I realized by touching the sink). Added an extra cooling and temperature seems to be ok now. I’m not using the HP cooling kit for PCI-E line, it’s a home-made cooling solution.
The problem is that I cannot find a way to monitor the controller temperature.
- HP ILO is not showing me information about P420 controller sensors.
- Embedded HP SSA detects the controller well, but no shows temp readings.
- Tried SSACLI utility with same results.
- BIOS, ILO and P420 firmware are up to date.
- Using the ssacli command ctrl slot=3 show I get this:
Smart Array P420 in Slot 3 Bus Interface: PCI Slot: 3 Serial Number: PGKLH0ARH5U16J Cache Serial Number: ABLAA0BRD4XD9X RAID 6 (ADG) Status: Enabled Controller Status: OK Hardware Revision: B Firmware Version: 8.32-0 Rebuild Priority: Low Expand Priority: Medium Surface Scan Delay: 3 secs Surface Scan Mode: Idle Parallel Surface Scan Supported: No Queue Depth: Automatic Monitor and Performance Delay: 60 min Elevator Sort: Enabled Degraded Performance Optimization: Disabled Inconsistency Repair Policy: Disabled Wait for Cache Room: Disabled Surface Analysis Inconsistency Notification: Disabled Post Prompt Timeout: 15 secs Cache Board Present: True Cache Status: OK Cache Ratio: 25% Read / 75% Write Drive Write Cache: Enabled Total Cache Size: 0.5 Total Cache Memory Available: 0.3 No-Battery Write Cache: Enabled Cache Backup Power Source: Capacitors Battery/Capacitor Count: 1 Battery/Capacitor Status: OK SATA NCQ Supported: True Spare Activation Mode: Activate on physical drive failure (default) Number of Ports: 2 Internal only Encryption: Not Set Driver Name: hpsa Driver Version: 3.4.20 Driver Supports SSD Smart Path: True PCI Address (Domain:Bus:Device.Function): 0000:03:00.0 Port Max Phy Rate Limiting Supported: False Host Serial Number: USE445ZDWS Sanitize Erase Supported: False Primary Boot Volume: logicaldrive 1 (600508B1001C2873F3D9BA3495546FF6) Secondary Boot Volume: logicaldrive 1 (600508B1001C2873F3D9BA3495546FF6)
According to SSACLI official user guide that command should return temperature readings but is not doing it.
Any suggestion will be helpful
Thanx in advance!
The question is indirectly touched upon in EU regulation No 261/2004 (the main regulation on compensation for missed or cancelled flights):
(j) “denied boarding” means a refusal to carry passengers on a flight, although they have presented themselves for boarding under the conditions laid down in Article 3(2), except where there are reasonable grounds to deny them boarding, such as reasons of health, safety or security, or inadequate travel documentation;
In other words: Airlines are allowed to deny boarding for health reasons without engaging the compensation rules defined in the regulation. Technically, that doesn’t mean there isn’t another rule somewhere else but clearly the intent of the EU legislator was to preserve the airlines’ ability to deny boarding for health reasons. And if you are prevented from entering the airport by a third party, the airlines would simply consider you a “no-show“.
Two other things to note:
- I don’t know about the situation in Bulgaria but it is often recommended not to use public transportation or even leave your home at all if you have mild flu or cold symptoms and do not know whether it’s Covid or not.
- Many airlines and other transportation operators have enacted special rules to encourage people to book trips even when they are not sure they will be able to travel. It could be worth calling to see if they are prepared to make an exception to their usual terms and conditions.
First of all, I am making a couple assumptions which are not explicitly written in the question but I consider very likely to be true (because that’s how it works in Rimworld). When any of these are incorrect, please drop a comment and also update the question.
- Your game world is tile-based. So you don’t need temperature at arbitrary points, just on a tile-based resolution.
- The game world is a rectangle with a limited width and length.
- Heat spreads slowly across tiles, not instantly.
- You already know how to detect clicks on tiles and derive the tile coordinates in your click event.
Under these premises I would actually not rely too much on what Unity can do for me and rather roll my own solution in form of a cellular automaton.
I would create one new gameObject “TemperatureSystem” with a script of the same name. That script has a private two-dimensional array of float’s with the same size as the game tilemap. This array represents the temperature of each tile.
The script would also offer a public method which allows other scripts to read the heat at a specific tile. This method should be used by other game mechanics which take heat into account. I would also add another public method to increase or decrease the heat value of a specific tile. This is for objects which change heat, like heaters or air conditioners. Such an object would in most cases only change the heat of the one tile it is on and then rely on the TemperatureSystem to dissipate the change to the surrounding.
The Update-method of my TemperatureSystem would then derives the new heat value of each cell from the old value of itself and the old value of its neighbors.
Create a copy of your heat values (the new values).
Iterate over the old heat values and:
- Calculate the heat difference between this tile and its right neighbor by subtracting the neighbor heat value from its own heat value (use the old values, not the new ones)
- Determine the amount of heat being transferred between the tiles by multiplying that value with your desired rate of heat spread and Time.deltaTime. You might modify the heat spread multiplier depending on the materials of the two tiles. So some materials might work as heat insulators while others might work as heat conductors. But remember that the heat taken from a tile should be equal to the heat given to another. Otherwise you violate conservation of energy.
- Change the heat values in the new array by subtracting that amount from the current tile and adding it to the neighbor tile
- Repeat steps 1-3 for the lower neighbor
Replace the old heat values with the new ones.
By the way: There are a lot of other applications for cellular automatons in tile-based or block-based games. You can, for example, use them for:
- Air pressure in a space vessel
- Flow of liquids
- Spreading of fire (where you usually work with spread probability instead of constant spread rate)
- Plant growth
The colors along the color temperature axis were “chosen” because they are the colors black bodies radiate as they increase in temperature. This includes everything from heated metals to the surfaces of stars, including our Sun. Almost all of the strong light sources found in nature emit light somewhere along or very close to the color temperature axis. We designate the colors along this line based on the temperature to which a black body must be heated in order to glow at that color.¹
We use the temperature scale created by Sir William Thomson (1824-1907), 1st Baron Kelvin, OM, GCVO, PC, PRS, FRSE. Addressed by his royal title as Lord Kelvin, he was a mathematician and scientist who create a temperature scale that places the “null” mark at absolute zero, the theoretical temperature point where all molecular motion will cease, and uses units the same size as the Celsius scale. 0 K is equal to -273.15°C. 0°C is equal to 273.15 K.
For most of human history, even primitive artificial light sources like torches and oil lamps emitted light along the Kelvin temperature scale. This is because most of the fuel sources don’t actually glow very brightly as they burn, but the gasses and vapors that are emitted from the fuel source as it is heated burn and glow very brightly. Early electric light sources used metals heated to glowing temperatures to produce light. Since the metals used are very close to being black body radiators, they also emit light along the color temperature scale. These are what we call incandescent light sources.
In the modern world, though, we deal with a lot of light sources that are not natural and do not fall on the Kelvin scale. The axis that is more or less orthogonal to the color temperature axis is the Magenta ←→ Green axis. This is often called a “tint” or “hue” adjustment. This is represented in the illustration above by the lighter grey hashes along the color temperature axis. Many artificial light sources, particularly those designed primarily to use low amounts of energy, are quite a distance away from the colors emitted by black body radiators on the Blue ←→ Amber color temperature axis.
So in addition to adjusting color temperature to compensate for our light source, we must also compensate along the tint axis. Many cameras call this white balance correction.
For instance, in addition to having a color temperature of about 3700 K, traditional fluorescent bulbs also emit a green tint along the green←→magenta axis and need correction in the magenta direction. On the other hand, many of the popular LED stage lights found in small clubs are also at about 3700 K but have a decidedly magenta tint that requires compensation in the green direction along the green←→magenta axis. Both types of light are the same basic color temperature but look very different without compensation on the green←→magenta axis that is approximately orthogonal to the blue←→amber color temperature axis.
Beyond doing color correction in two dimensions instead of just one, there’s also the issue that many artificial light sources don’t emit the full spectrum of visible light.
Most natural light sources do. The sun, as seen from the Earth’s surface on a clear day, may be centered on about 5500 K, but there is at least a little bit of the entire visible spectrum in sunlight. The Sun emits even more electromagnetic radiation than what we can see and measure from the Earth’s surface. The Earth’s atmosphere reflects and absorbs some of the energy radiated by our sun, and lets what we call visible light pass more easily. (Of course the reason we call it “visible light” is because we have evolved to be visually sensitive to the wavelengths of electromagnetic radiation that the atmosphere we evolved in allows to pass most easily!)
When using only artificial light sources that do not give a broad spectrum of light, there are certain colors we can’t reproduce. This is because there is no light the proper wavelength(s) to reflect off our subject for that color. Custom White Balances come in very handy for such lighting. In such cases, we might also have to use an HSL (Hue-Saturation-Luminance) tool in post processing to remove a color cast.
¹ It should be noted, however, than no individual star is a perfect black body radiator, just as no metal or other material is. As the Wiki article for “Black Body” points out several times, we model stars as if they are black body radiators. It also notes that in the case of supergiants and main sequence stars, it’s rather remarkable that we can get away with treating them as such. “It is perhaps surprising that they fit a black body curve as well as they do, considering that stars have greatly different temperatures at different depths.”
My iMac fans started blowing at full speed for sometime so I rebooted and ran diagnostics and received an ambient sensor error, image attached below.
I had been considering adding an SSD in addition to my 2TB internal HDD and so decided I would add the SSD and replace the sensor whilst I was there. The sensor I bought
After carefully replacing the sensor (I’m a PC technician by trade) at first boot the the fans were still blowing at full speed..
So I reset SMC by unplugging the iMac and waiting, same result. I then reset PRAM a few times, same result, fans still blowing at full speed. I then decided to run diagnostics again although the test just displayed ‘starting internet recovery’ for more than an hour so figured it might be hanging, and rebooted.
Booted back into OSX and fans were quiet and have been for 10 days, although today on booting up the fans were on full and have been ever since despite rebooting a few times, I can’t believe it! What is going on here??
It’s nothing to do with the SSD I cloned the existing HDD to the SSD and used the proper OWC sata cable kit, the original hard drive hasn’t be changed merely cloned then wiped.
Thanks in Advance