Confused beginner to WB

[davidr]

I anyone could explain the use of WB to me I would be grateful. I have read the articles and posts etc but do not understand how the cards work.

If I hold them against my subject what exactly am I referencing and why? Am I referencing the value of the reflected light from the card and measuring the effect the color temperature of the light has on pure white, gray and black and if so why these three colors? How does adjusting these values enable me to get correct skin tones etc. If I see someone under artificial light their skin has a cast which reflects that color of light as will the card so how does it remove a cast if that is its intention. Couldn't I just use color sliders in photoshop to remove any unwanted casts.

I am very confused and really anxious to learn but cannot get to grips with the concept any help would be much appreciated.

[MichaelT]

A quick guide. (Full gudie to happen within 2 weeks).

In all cases the camera must know the color of the light stiking the subject inorder to product the correct color in your final image. The camera (in auto WB mode) then tries to guess and set the WB correctly. It usually comes close in Daylight and misses mostly indoors.

For RAW workflow...
By having a WhiBal shot as a reference you have ythe exact color of the light recorded by your camera because WhiBal reflects ALL color equally, and so the camera records the "gray card" as reddish, or blusish or whatever, based on the lighting. Within C1 or other RAW software, you click on the WhiBal light Gray card and the software calucaltes the proper White Balance for the image. Then you apply this WB setting to all other shots taken with this same kind of lighting and they will have perfect WB setting as well.

For JPEG workflow...
Same system, except you use the darker gray card and use the middle eyedropper in levels or curbed to set a gray point in the image. This can be saved and applied to other images. Not nearly as accurate as in RAW but it gives you a starting point.

In either workflow you can use the Black and White cards to establish the Black and White points of the image to establish proper dynamic range (more on this in the full guide.

As far as adjusting the slider in PS to get the WB right...
1 - It is time consuming
2 - It take more than adjusting 1 slider
3 - There are only very few people who can do this accurately
4 - It is almost impossible to do quickly and accurately even if you are good.

Shooting a proper Gray Card is the only way to assure a proper white balance, and we think that the WhiBal in addition to be equal to or better than any cards out there is the most convenient card around, based on colors, size, coinvenience, duarability etc.

More later. Have to catch a plan to Denmark :>)

[davidr]

Quote from site FAQ.

WhiBal works in the following way. The Gray cards in the WhiBal have been engineered such that they will always reflect exactly the colors that are bounced off of them. They are precisely neutral. ****So if the light is a bit orange they will precisely reflect that orange light to the camera.****

The **** bit was confusing me, as I felt this meant the grey card would have an orange cast. Having read Robin Myers article where he states as the lighting changes, the grey will appear to remain grey, there will be no color cast to the grey helped me figure out what the card was actually doing.

[amumford]

Well I think what is meant is that the Grey card *will* be orange as the camera see's it, however to the eye it remains grey under any lighting since your "eye" will adapt to the surrounding lights colour temperature.

So actually both statements are correct although seemingly contradictory - the difference is in the viewing instrument, in one case human vision which auto white balances in any lighting and in the other case a camera/film system which records the actual colour of the light faithfully but then needs an accurate reference subject so that the colour temperature can be balanced to neutral.

[davidr]

I see thank you. This is what I think I understand so far.

The camera does see the light as Orange and our final image would have this cast. The camera tries to guess at the correct setting if we guide it with various white balance settings but often it is not accurate enough.

Shooting Raw enables us not to worry about the cameras white balance setting as we can place a neutral grey card in the scene which has a flat spectral response whatever the light shone upon it, in other words remains grey.

This reference point then enables the software to readjust the tones across the whole image to this mid grey point. As it is the software that is setting the white balance and not the camera, different RAW software will react differently and have different requirements for their neutral grey setting some prefer a light grey card some a dark grey card.

The mid grey point value will be higher or lower depending on the temperature of the light shone upon it. The higher the temperature the higher the grey values for example 220R 220G 220B for bright sunlight outdoors and perhaps nearer 112R 112G 112B for illumination by low power indoor lights.

[ratz2plt]

This reference point then enables the software to readjust the tones across the whole image to this mid grey point. As it is the software that is setting the white balance and not the camera, different RAW software will react differently and have different requirements for their neutral grey setting some prefer a light grey card some a dark grey card.

I believe he said that you use the Light Gray Card for RAW and the Darker Gray Card with the middle eyedropper in levels or curves for JPEG.

So my question is for the RAW and Light Gray Card you use the white eyedropper in levels or curves right?

[ratz2plt]

I believe he said that you use the Light Gray Card for RAW and the Darker Gray Card with the middle eyedropper in levels or curves for JPEG.

So my question is for the RAW and Light Gray Card you use the white eyedropper in levels or curves right?

Sorry davidr I owe you an apology. I guess you and I were right. You do also use different cards for different converters. I am also trying to figure out the specifics. I understand how it works just not the specifics yet. Just ordered mine today.

[MichaelT]

I see thank you. This is what I think I understand so far.
This reference point then enables the software to readjust the tones across the whole image to this mid grey point. As it is the software that is setting the white balance and not the camera, different RAW software will react differently and have different requirements for their neutral grey setting some prefer a light grey card some a dark grey card.

The mid grey point value will be higher or lower depending on the temperature of the light shone upon it. The higher the temperature the higher the grey values for example 220R 220G 220B for bright sunlight outdoors and perhaps nearer 112R 112G 112B for illumination by low power indoor lights.

David,

You are getting closer.

1 - First both Photoshop CS and C1 both want the lighter card. I do not know of a RAW converter that would want the darker value.

2 - In your exam,ple you are missing a key point. In Blue light the Gray card will NOT read such that R=G=B, in fact the B value will be higher, because the light was blue and the gard reflected exactly what it saw based on it flat spectral response. So the number will never be 112/112/112/ It they were you would aready have perfectly WB'd image. Only AFTER clicking on the WhiBal will the R/G/B numbers be equal.

Make sense??