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Esteemed Contributor
Posts: 3,078
Registered: ‎06-11-2013

Re: Custom White Balance kinda sucks

Waddizzle, he's nudging the gray card slightly more left in each frame to determine how far is "enough" before the camera gets a good enough sample to work.

 

In the three thumbnails, the left image has the center of the frame dominated by green, gray card is to the right.   The camera takes the green as the gray card and the magenta white-balance is the result.  In this sample the gray card seems to hold no sway over the white balance.  It's not close enough to center.

 

In the next frame, the edge of the gray card cuts through the center of the frame so it's basically half green / half-gray.   You can see the camera actually sampled a little bit of both.  So the white balance is off as badly as the first test, but it's not enough to fully correct.  This tells you that the camera isn't sampling one magic pixel... it's sampling an area.  But how big is that area?

 

In the third frame, the gray card is slightly more left and finally the gray card works (the camera appears to be ignoring the green).  

 

Another way to think of this is... how big of an area in the center should you use?  If the gray card were as large as a cocktail coaster would it be big enough?  Would it need to be the size of a dinner plate?   Lens focal length and distance from the card would certainly be a factor but what he's determined is that the gray card does not need to occupy most of the frame... if it covers that area around the center AF point then it's probably big enough to work.

 

In every-day use, you probably want to be a little generous on the gray card area just to make sure you don't slip up (better to have a little more area than you need... than to have a little less area than you need.)  But I certainly get the idea.

 

It looks like the two of you are basically in agreement... and stuck on terminology.   i.e. if the gray card is in the middle then it's good enough.

 

Tim Campbell
5D III, 5D IV, 60Da
Respected Contributor
Posts: 1,813
Registered: ‎02-26-2015

Re: Custom White Balance kinda sucks


Stonius wrote:

There are three captures from video of a person that happens to be me on the bottom row.

 

Directly above each of them, are three subtly different photos that show the image that was selected for custom white balance and used in the image below. The subtle difference lies in the fact that the white piece of paper moves incrementally to the left.


The white balance is taken in the center 1/3, top to bottom and left to right. What you are using for white balance needs to be in the middle, not on either side.

 

Honored Contributor
Posts: 5,427
Registered: ‎08-13-2015

Re: Custom White Balance kinda sucks


TTMartin wrote:

Stonius wrote:

There are three captures from video of a person that happens to be me on the bottom row.

 

Directly above each of them, are three subtly different photos that show the image that was selected for custom white balance and used in the image below. The subtle difference lies in the fact that the white piece of paper moves incrementally to the left.


The white balance is taken in the center 1/3, top to bottom and left to right. What you are using for white balance needs to be in the middle, not on either side.

 


Exactly.  The metering system is circular, and centered in the frame.  Nudging a grey card across the frame proves what?

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Honored Contributor
Posts: 5,427
Registered: ‎08-13-2015

Re: Custom White Balance kinda sucks


TCampbell wrote:

Waddizzle, he's nudging the gray card slightly more left in each frame to determine how far is "enough" before the camera gets a good enough sample to work.

 

In the three thumbnails, the left image has the center of the frame dominated by green, gray card is to the right.   The camera takes the green as the gray card and the magenta white-balance is the result.  In this sample the gray card seems to hold no sway over the white balance.  It's not close enough to center.

 

In the next frame, the edge of the gray card cuts through the center of the frame so it's basically half green / half-gray.   You can see the camera actually sampled a little bit of both.  So the white balance is off as badly as the first test, but it's not enough to fully correct.  This tells you that the camera isn't sampling one magic pixel... it's sampling an area.  But how big is that area?

 

In the third frame, the gray card is slightly more left and finally the gray card works (the camera appears to be ignoring the green).  

 

Another way to think of this is... how big of an area in the center should you use?  If the gray card were as large as a cocktail coaster would it be big enough?  Would it need to be the size of a dinner plate?   Lens focal length and distance from the card would certainly be a factor but what he's determined is that the gray card does not need to occupy most of the frame... if it covers that area around the center AF point then it's probably big enough to work.

 

In every-day use, you probably want to be a little generous on the gray card area just to make sure you don't slip up (better to have a little more area than you need... than to have a little less area than you need.)  But I certainly get the idea.

 

It looks like the two of you are basically in agreement... and stuck on terminology.   i.e. if the gray card is in the middle then it's good enough.

 


Thanks, Tim.  I get the part about nudging the grey card.  

 

I fail to see how that yields insight into how large,or small, of an area that the metering system needs to accurately sample a grey card.  The target needs to be in center of the frame, and of variable size.  Not moving like an eclipse across the frame.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
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