Color cast / white balance

[dr_zero]

This came up on another thread where someone thought this was what I was talking about so I though I would start this so people could see better what we were talking about.

So as not to re-invent the wheel here are some good links

http://www.cambridgeincolour.com/tutorials/white-balance.htm
http://www.kenrockwell.com/tech/whitebalance.htm
http://www.ronbigelow.com/articles/white/white_balance.htm
http://www.shuttermom.com/whitebalanceexplained.htm

If you get out one of the old Kodak hand books it has a pretty good tutorial on light sources and film and the filters you need to try and compensate.

http://www.lightingmagic.com/flmlitqa.htm

http://www.aapvrf.cornell.edu/photo.htm

Filters are tools that help to balance and enhance color and contrast in pictures. The kind of light we use and the way light is reflected off the surface of an object, will determine its saturation (the way color and tonality look and feel), in the photographs we make.

The following list of filters is a guide for students and faculty in the college when color conversion, color correction and contrast are needed to achieve the best quality results in their photography work.

Filter Factors

Because filters absorb or subtract some of the light passing through a lens, exposure needs to be adjusted (increased) - by either shutter speed or aperture - to compensate for the loss of light.

Thus, if a filter has factor of 2x, you must double the exposure time either by slowing the shutter speed down by 1 stop or opening your aperture by one stop. A filter with a factor of 4x would require a two stop adjustment, a factor of 8x, a three stop adjustment and so on. For example, a filter with a 2x factor would change an exposure of 1 /125th @ F-11 to 1/60th @ F-11. Because filters have different densities, they have different factors.

Finally, if the camera you are using has a built-in meter, the correct exposure will be indicated because the meter is reading the light through the filter. Please be aware that the cameras available in the Knight Visual Resources Facility do not have light meters. Exposure settings must be manually adjusted.

Conversion Filters for Color Films:


Color films are balanced for specific light sources. Using a color film with an incompatible light source requires a filter to adapt the film to the color of the light source. For example, exposing daylight balanced film under tungsten light will yield an image with a warm "yellow" cast. By using an 80A (blue) filter you can convert the film to the light source and get acceptable color balance. Conversely, using tungsten balanced film in daylight yields a cold "blue" cast. By using an 85B (orange) filter you can convert the film to the light source and get acceptable color balance.



You can use the following guide to convert films for use with different light sources.



80A (blue): filter factor is 4x or 2 stops. Use to convert daylight type films for use with tungsten 3200 K lamps - for slides or prints.



85B (orange): filter factor is 1.5x or 3/4 stop. Use to convert tungsten 3200 K films for daylight use.



Color Compensation Filters When Using Ordinary Flourescent Lights

These filters will help correct color rendition when shooting under flourescent lights. Without compensation filters, daylight balanced films will take on a greenish cast, and tungsten balanced films will have a bluish cast when exposed under flourescent lights. Warm white or cool white bulbs are the most common examples of institutional flourescent lamps. Use the following filter/exposure guide as a starting point when shooting under flourescent light.

Warm white type ( bulbs have a subtle pink-purple tint ):


Use 40 magenta & 20 cyan when shooting daylight film. Filter factor is 2x or 1stop.

Use 50 magenta & 40 yellow when shooting tungsten film. Filter factor is 2x or 1 stop.

Cool white type (bulbs have a subtle blue-green tint ):


Use 40 magenta & 10 yellow when shooting daylight film. Filter factor is 2x or 1 stop.

Use 60 red when shooting tungsten film. Filter factor is 2.5x or 1&1/3 stop.

Correction and Contrast Filters for Black & White Photography.

Often, the results we get on film when photographing outdoors do not look the same as the actual scene. Correction filters will have the effect of changing the way a film responds to light so that the tonal values approximate the way the eye saw them. A good correction filter is the K2 yellow. The K2 has a factor of 2x or 1 stop.

Contrast filters change the relative values in a scene so that tones which would normally be interpreted as the same shade of gray ( in black & white ), will separate more clearly in terms of brightness. A good example of a contrast filter is the #25 red. This filter dramatically darkens blue skys, making clouds stand out, and reflective surfaces more brilliant. The #25 red has a factor of 8x or 3 stops.

Polarizers

A polarizing screen is useful in both black & white and color photography. The polarizer will darken skys, reduce glare and reflection off non metallic surfaces and penetrate haze. Polarizers have a factor of 2.5 or about 1&1/3 stops.

 

[boBQuincy]

If there is some balance of Red, Green, and Blue the white balance may be able to correct it. If there is no balance, such as a scene lit entirely by lights with red filters, there is no G or B to add to the mix. This kind of lighting can not be corrected, it will always be red.

Pirates of the Caribbean is an example, many scenes can not be corrected to a decent white balance nor should they be, the scene was lit with red and that's how it should look.

Stage shows and concerts can present a similar issue, they may be lit with red on one side and blue on the other, with no green present. Such a scene can never be balanced for white.

 

[DizzyV6P]

Just to add some examples. Some pictures just can't be fixed simply because the spotlight is using a red filter on that particular part of the stage. In this example, this lady rocker was right under the red-filtered par can lights. This particular venue is notorious for bad and uneven lighting so this was the best I could do given the situation. All taken in Raw

This next picture, the rocker was under the yellow par-can light that's mixed w/ the red par-can light. That's why the colors are more even.
Same Band, Same venue, just 8 feet away. Proper lighting makes a HUGE difference!

 

[MICKEY88]

Just to add some examples. Some pictures just can't be fixed simply because the spotlight is using a red filter on that particular part of the stage. In this example, this lady rocker was right under the red-filtered par can lights. This particular venue is notorious for bad and uneven lighting so this was the best I could do given the situation. All taken in Raw

This next picture, the rocker was under the yellow par-can light that's mixed w/ the red par-can light. That's why the colors are more even.
Same Band, Same venue, just 8 feet away. Proper lighting makes a HUGE difference!

one way to deal with pics like the first is to turn it into a B&W ,

 

[jann1033]

red or not i really like the first better ( over all, not strictly lighting) and agree, think it would look good monochromatic due to the halo effect of the hair
the thing is if you are using digital and raw why not just adjust the channels pp and forget the color filters?
just playing, sure you could do better and will be happy to remove if you want but to me this could be a really good photo in b&w

for some reason when i export from lightroom it darkens just a little, you could just make out the shape of the leg til i exported so it didn't look like "disembodied guitarist" like it does on my screen now lol

 

[dr_zero]

red or not i really like the first better ( over all, not strictly lighting) and agree, think it would look good monochromatic due to the halo effect of the hair
the thing is if you are using digital and raw why not just adjust the channels pp and forget the color filters?
just playing, sure you could do better and will be happy to remove if you want but to me this could be a really good photo in b&w

for some reason when i export from lightroom it darkens just a little, you could just make out the shape of the leg til i exported so it didn't look like "disembodied guitarist" like it does on my screen now lol

Looks great!

Oh the filters info was mainly for film shooters.

 

[DizzyV6P]

LOL. Thanks. I actually did turn it into B&W just to see how it looked. I'll post up my version when I get home

 

[dr_zero]

I like the look of the original but if was trying to look more like the second I might try something like this. Just a quick attempt here

 

[DizzyV6P]

Here's my BW version.

The band is currently on tour right now, but I've been asked to do another shoot for them when they come back into town. Should be fun

 

[ALittleDisneyFan]

I recently purchased a 40D and I'm stumped on the warming issue. Everywhere I read, people say to shoot in raw and fix later. Well - when I'm just snapping photos of my daughter I don't have time to sit and fix, convert, then enhance... I've read about the Kelvin temps, but still unsure on what a good temp for indoor is. Any advice? Any advice for outside temps? I recently had a maternity shoot and the outdoor photos were impeccable, but I can't remember what temp I had it on.... (i also shot raw for that.. since I was unsure of this all). Thanks!

 

[dr_zero]

I recently purchased a 40D and I'm stumped on the warming issue. Everywhere I read, people say to shoot in raw and fix later. Well - when I'm just snapping photos of my daughter I don't have time to sit and fix, convert, then enhance... I've read about the Kelvin temps, but still unsure on what a good temp for indoor is. Any advice? Any advice for outside temps? I recently had a maternity shoot and the outdoor photos were impeccable, but I can't remember what temp I had it on.... (i also shot raw for that.. since I was unsure of this all). Thanks!

Well Im going to get bashed for this but try the preset auto setting and see how they do first you might like them. (dont forget to check your white balance first)

There is nothing wrong with using the auto feature on your camera.

When you get to a point where you can play some then try shooting in the areas where you are normaly going to be taking pics and then try the fixing in the computer and maybe you can come up with a preset that will work for general shots.

Here are two good links about the d40 and may answer your questions better

http://www.kenrockwell.com/nikon/d40/users-guide/index.htm
http://www.kenrockwell.com/nikon/d40/users-guide/menus-shooting.htm

White Balance

I leave my WB at AUTO. See also How to Set White Balance and White Balance Examples.

Trick: to fine-tune (make warmer or cooler) each setting individually, after selecting it in the menu, press OK (or click right) to get to the +3/-3 trim setting. + is cooler (bluer) and - is warmer (more orange). This delicate, but critical, adjustment is missing from the D50, and it was my biggest complaint about the D50.

The WB settings are:

Auto (A): I use this all the time. It makes its best guess for WB. It's usually very good. Indoor tungsten can be too orange unless you have some bright tungsten light also in the image. If you do, it removes the orange and compensates completely. If not, the D40 only partly compensates and you get a nice warm image instead.

Tungsten (hanging light bulb icon that's easy to confuse with the sun icon): This makes the picture very blue. Use this only for deliberate Arctic freezing effects, or under conventional tungsten light bulbs.

Fluorescent (glowing tube icon): Used to make crappy fluorescent light look less crappy. These settings rarely work; use the preset setting for better results.

Direct Sunlight (sun icon): Use this in direct frontal sunlight. Use other settings for shadows or indirect sunlight.

Flash (lightning bolt): I never use this. It's almost the same as direct sun. I'm told it's really for studio strobes, since the Auto mode compensates magically for flash if you use it on-camera. The reason to use this is if you use a different trim value for your strobes than you do for sunlight.

Cloudy (cloud): Warmer (more orange) than the sunlight position. I use this in shade, too.

Shade (house casting a shadow): very warm (orange). Use this for sunset shots and deep shade.

Preset (PRE): You use this setting with a white or gray card to get perfect color matching.

I use this in bizarre artificial light that I wish no make look natural, or to get exact color with my studio strobes. An Expodisc makes this easier, but even without an Expodisc or white card I shoot off anything neutral, like a piece of paper or a T shirt.

Any light weird enough to need this setting won't care about small inaccuracies in the neutral reference.

To set this:

1.) Ensure your card or other neutral object is in the light representative of the light on the subject.

2.) Select PRE via the menu button (or the Fn button and spinning the dial).

3.) Press OK (or click to the right).

4.) Select Measure and click OK (or to the right). (The Use Photo option is a backwards bow to Canon's convoluted setting method. Canon Jihadists used to brag about this. It does the same thing, but requires twice as many steps. Ignore this option.)

5.) Select YES.

6.) Point your camera at the card or neutral colored thing and press the shutter.

7.) If the LCD says "data acquired or the viewfinder flashes "Gd," you're set. Shoot away!

8.) If the display flashes "unable to acquire" or the viewfinder flashes "no Gd" then repeat from step 2.).