Understanding the (K) White Balance option

[gauamg]

I think by now I understand the physics behind WB. Just want to confirm that the K-setting on the digital SLRs indicate the frequency it cuts out and not the other way around. As I lowered the K number I got more and more bluish tint and conversely on the upper end of the spectrum I got warmer hues. I am interpreting this as the filtering effect i.e. at the lower end of the spectrum it filtered out the reddish/orange frequency and thus gave it a bluish tint and reverse at the higher end. Does this make sense? Am I interpreting it right? (I am checking out a Nikon D7000).

Any pointer would be helpful. Thanks

[Peter Ryan]

I Arindam and welcome to CiC,

In effect yes except the filtering is designed for the camera to emulate clear white light (5,500K) so if you take an image, say under a tungsten light source (which has a redder glow) the camera will add blue to try and bring it back to a neutral white light. So if you were reading a book by light lamp the page would appear white in print and not with a reddish tinge.

In the days of film when film was either daylight or night time balanced film you had to use filters to correct for the colour of the light source. So in our example with film we would need to put a blue filter in front of the lens to correct for the colour cast. I hope this helps.

[gauamg]

Peter,
Thanks. If I am interpreting you right this is what you are saying - when I am setting a low K value I am in effect telling the camera that the light source is emitting at the lower end of the spectrum and the camera is trying to compensate to get to the white light - depending upon how far off I am from the actual light condition I will get different hues of blue. So, unlike what I thought, it is actually adding blue light instead of cutting out red light - right?

[Peter Ryan]

Yes, rather than something you use as a filter to add red or blue light it is filtering the light source you are shooting under to correct for a colour cast being emitted by that light source .

This doesn't mean you cannot use it to your advantage. When shooting sunsets (which are red/yellow) the camera tries to adjust for the colour of the light by adding blue and often you are disappointed by the results. By telling the camera the light source is actually bluish (i.e. the cloudy setting) the camera will adjust by adding red to bring the colour of the light back to neutral and in doing so it will really make your sunsets punch with colour.

[gauamg]

Yes, I did notice that. I have tried out that particular scenario and the result was truly gratifying.

Thanks again.

[blanconegro8rc]

I would like to share my six cents worth with regards to WB/Kelvin. My understanding is simple and practical. please, do correct me if I am wrong. Ok, there is only one light source. the sun. this, on kelvin, is about 5000K-5800K. since nikon's characteristic tends to be warm, My default is at 5000K. if you are looking at the range of K temp, the median is 5000K, numbers going towards your left( flourescent, tungsten, candle light) are blue or cool. that's because they're artificial. numbers going towards the right(flash, cloudy, open shade) are degrees of red/warmness. the one on your left, to correct it during film days, you will use FL-Day, 80A. Now, the one's on your right, they are warming filters! Great Idea! It finally hit me! there are three major colors. Blue, White and Red! since the official mantra of digital photography which is " you have to start somewhere", you shoot at 5000K (our earth's lightsource), assess your LCD. if its blue/cool, go to the right( flash/6000K, cloudy/7500K, open shade/8500K! ranges varies). If its red/warm, then go to the left( flourescent/3800K, tungsten/2500, and candle light/1000K). now, the advantage of cameras nowadays( mine is Nikon d200) there is the quadrant to further fine tune your white balance. and my advice to students is, if you are taking pictures of people, white balance should be for skin tone and not the white wall. I always tell them that same thing applies to quadrant what is to WB. the Blue and red thing. only this time, you bias toward magenta. remember,using the quadrant, red+magenta= pink. skin tone should be pink( " in the pink of health" ). not blue(depiction of mental imbalance in movies), not green/flourescent(depiction in comics when one is to vomit or an alien from outer space, not yellow which is like jaundice/hepatitis, and not red, which is like a roasted pig. I hope I amuse you guys. I am just trying to contribute.

[AB26]

Hi Arindam,
My advice would be to go to Photography Tutorials in the drop down menus at the top. There is an in depth tutorial on Understanding White Balance. Study the totorial and experiment with the settings.

[rpcrowe]

I alway use auto white balance and shoot in RAW so I can adjust the white balance in post processing. I most often shoot a color correction target to help me balance the color in post processing.

I have fallen in love with the WhiBal target.

http://www.whibalhost.com/_Tutorials/WhiBal/01/

Donald introduced me to this target and I think that it works a lot better than just shooting a white index card. It is a bit on the expensive side but, the more I use it, the more I like it.

By the way, I will tweak the White Balance visually on my monitor when I am unable to shoot the target. That is the advantage of having a calibrated monitor.

[bobrobert]

I wouldn't get too hung up on the technical side of things. If you post process your images then the setting of WB can be done on a large monitor as opposed to a 3" LCD. At the end of the day you are altering colour balances and your idea of what the colour balance should be like, according to your taste, should be your goal.

[FrankMi]

I alway use auto white balance and shoot in RAW so I can adjust the white balance in post processing. I most often shoot a color correction target to help me balance the color in post processing.

I have fallen in love with the WhiBal target.

http://www.whibalhost.com/_Tutorials/WhiBal/01/

Donald introduced me to this target and I think that it works a lot better than just shooting a white index card. It is a bit on the expensive side but, the more I use it, the more I like it.

By the way, I will tweak the White Balance visually on my monitor when I am unable to shoot the target. That is the advantage of having a calibrated monitor.

That is a very interesting set of tutorials Richard. It really helped me to understand the LAB system of colorspace and why getting the color white balance accurate can make such a significant difference. It also helped me to understand why I have always had problems getting a good white balance, particularly due to how easily the eye can be fooled. For those that are interested in this subject I would recommend watching the #6 and #8 tutorials in this set. Thank you Richard for posting this link!