RAW pictures and white balance?

plierouge

Member
Hello!

This question is not specific to Sigma, but since this forum is very active, I should have a response to something that has been bugging me for months!

From what I understand, photographing is RAW mode is the best since the end user has maximum flexibility of its final pictures. He can control every aspects of the picture, including colour saturation, contrast, sharpness, white balance... this last one is what I don't fully understand. Why do we have to select a white balance setting in the camera when shooting RAW if the idea is to do all the adjustments in a post-production software? Also, I always thought that a RAW picture was an unprocessed image, exactly what the sensor has captured. I made some test pictures selecting different white balance settings in the camera and shooting in RAW mode and the white balance of the pictures were all different. I understand that this in normal in JPEG mode since the camera applies settings to the pictures, but I was not expecting this for a RAW image. I guess I am missing something...

Thanks for any enlightenment!

Sébastien
 

notalent

Active Member
Hello!

This question is not specific to Sigma, but since this forum is very active, I should have a response to something that has been bugging me for months!

From what I understand, photographing is RAW mode is the best since the end user has maximum flexibility of its final pictures. He can control every aspects of the picture, including colour saturation, contrast, sharpness, white balance... this last one is what I don't fully understand. Why do we have to select a white balance setting in the camera when shooting RAW if the idea is to do all the adjustments in a post-production software? Also, I always thought that a RAW picture was an unprocessed image, exactly what the sensor has captured. I made some test pictures selecting different white balance settings in the camera and shooting in RAW mode and the white balance of the pictures were all different. I understand that this in normal in JPEG mode since the camera applies settings to the pictures, but I was not expecting this for a RAW image. I guess I am missing something...

Thanks for any enlightenment!

Sébastien

For one thing, you have the opportunity to set a custom white balance by shooting a reference card. Though I'm not sure whether it's best to use white or grey card for this. Look in the SD14 manual for how to do this. It's very easy.

Regards,
 

Guest .

Banned
Hi Sébastien,

the point is, that shooting raw means that you do not lose any image information within the cam's interior image procession!

I.e. the camera indeed records a WB-information, but does not change anything with your raw-file. The complete colour information remains unchanged is still is available with any RAW, you shoot. It is nothing more than an additional information, which then is utilized by your RAW-converting software on your PC.

When going jpg-in cam, the camera itself uses its WB-findings and saves colours, making use of its WB-info. This then is a lossy process ... colours really are changed and saved and colour information really goes lost.
Sure, you can rebalance JPG-pictures on your PC ... you simply cannot do it without losing image information!

In other words .... having your cam "deciding" on a wrong WB setting with going RAW, nothing is done which you could not correct with your computer without any losses. The RAW-file remains unchanged. :)

See you with nice pictures

Klaus
 

OyvindS

Well-Known Member
Re: WB in RAW

Hi Sebastian

I have to answer specific to SD14, which is the camera I know.

Klaus has a good explanation about the RAW/JPEG difference above. I just like to add a few things.

The reason you get different results I suppose is because the PP program reads the in camera WB setting, and adjust accordingly. So let say it was midday, the Overcast and Shade WB sould be to yellow, and the incadescent WB would be too blue. The AWB would depend on the scene, how good the camera was at guessing the K temperature.

When you shoot in RAW, it is believed that the RAW file, in the RAW part, only use a flag to indicate the camera WB setting. The RAW developer should read this, and adjust accordingly. You should then be able to freely change the WB and receive the same result as if you had chosen that WB originally.
However, there may be more to it:
1. A while ago, a user at another forum compared the RAW part of identical images, shot with different WB settings. The difference in the file suggested that ther was more than a flag set.
2. Also, several users at another forum have claimed that just changing a WB yields different result than if this WB was used in the first place. It may be that this problem was connected with using AWB in camera.
Sorry, can't find links right now, dpreview is down.
I have not verified this personally.

You could try to change the WB of your test shots to the same WB, and compare for yourself.

You ask what the point is to set the WB, if the idea is tó do all adjustment in PP? Well, I like to try to shoot my images so I get to do as little adjustment as possible.

There is an important descision to make regarding WB.
Do we want to correct the images to "neutral"? Or do we want to capture the actual color of the illuminant?
There are areas where the WB should be balanced to neutral (like indoor and product shots etc.), but often the feeling of the image is lost if it is brought to "neutral" (Like when you set to shade/overcast, or do a Custom WB.
Coming from film based cameras, I like to use one WB setting. I almost always leave my camera on SWB (sunlight), which should roughly equal Daylight slide film.
An alternative to this is to do a Custom WB on a gray plate, at midday, and use this CWB "always". Some users at another forum use this method and are very satisfied.

kind regards
Øyvind

ps: If you are considering the SD14, my SD14 compendium may be of use:
Please, Log in or Register to view URLs content!


Hello!

This question is not specific to Sigma, but since this forum is very active, I should have a response to something that has been bugging me for months!

From what I understand, photographing is RAW mode is the best since the end user has maximum flexibility of its final pictures. He can control every aspects of the picture, including colour saturation, contrast, sharpness, white balance... this last one is what I don't fully understand. Why do we have to select a white balance setting in the camera when shooting RAW if the idea is to do all the adjustments in a post-production software? Also, I always thought that a RAW picture was an unprocessed image, exactly what the sensor has captured. I made some test pictures selecting different white balance settings in the camera and shooting in RAW mode and the white balance of the pictures were all different. I understand that this in normal in JPEG mode since the camera applies settings to the pictures, but I was not expecting this for a RAW image. I guess I am missing something...

Thanks for any enlightenment!

Sébastien
 

kakou

Active Member
When you shoot in RAW, it is believed that the RAW file, in the RAW part, only use a flag to indicate the camera WB setting. The RAW developer should read this, and adjust accordingly. You should then be able to freely change the WB and receive the same result as if you had chosen that WB originally.
However, there may be more to it:
1. A while ago, a user at another forum compared the RAW part of identical images, shot with different WB settings. The difference in the file suggested that ther was more than a flag set.
2. Also, several users at another forum have claimed that just changing a WB yields different result than if this WB was used in the first place. It may be that this problem was connected with using AWB in camera.
Sorry, can't find links right now, dpreview is down.
I have not verified this personally.
I remember those links at dpreview and I agree, there is a difference more than just setting a white balance flag.
 

Arvo

Well-Known Member
Can someone point to these links?

Can someone send me some raw files, shot in identical conditions (studio, tripod recommended - otherwise it is impossible to compare) with different WB setting? AWB doesn't count - this "flag" (actually decoding matrix) is not constant. CWB (matrix) is constant unless you set it next time.
 

notalent

Active Member
Can someone point to these links?

Can someone send me some raw files, shot in identical conditions (studio, tripod recommended - otherwise it is impossible to compare) with different WB setting? AWB doesn't count - this "flag" (actually decoding matrix) is not constant. CWB (matrix) is constant unless you set it next time.
I could imagine that the color temperature tables (white balance) in SPP and the camera firmware might not match exactly, depending on which version of each is in effect at the time of post processing.

But one would expect the latest firmware and the latest SPP to be the same. If not, then perhaps the right hand does not know what the left hand is doing at Sigma.
 

Arvo

Well-Known Member
I'm fairly sure that SPP uses (calibrated) WB matrices from camera. The latest SPP does add some other correction, esp for highlights, but "base" color balance is tightly related to camera/sensor. I think these matrices are not contained in firmware, but are programmed into camera flash at calibration time.
 
Top