Lightroom 3 White Balance Sample Size

Hello,

Under LR3, is that slider named "Scale" under white balance eyedropper sample tool do change WB sample area or is it just... a loupe, nothing more? Other words, does sampled area become wider if I move Scale to the right? If that is not it's purporse, is there a way to control sample size of WB eyedropper tool?

Thanks.

view image at 100%, or 300%.

The sampled area doesn't change with movements of the Scale slider. All the slider does is zoom in to give you a closer view in the loupe.

So, tool use only one pixel? No way to average it over an area?

I don't know the exact sample size but I did a quick search and found this thread on Adobe Forums: http://forums.adobe.co​m/thread/511892

I also checked the LR3 User Guide and here's how it describes the Slider on page 102:

Scale Slider
Zooms the close-up view in the Loupe.

coldplug wrote in post #10559859
So, tool use only one pixel? No way to average it over an area?

Thx.

PixelMagic wrote in post #10559908
I don't know the exact sample size but I did a quick search and found this thread on Adobe Forums: http://forums.adobe.co​m/thread/511892

I'm pretty dissapointed about this LR "feature"

I disagree. First, the Scale slider appears only when the eyedropper is inabled, it is not the zoom slider. Second, the sample grid displayed together with the eyedropper clearly displays a larger area of the image. The WB calculation is calculated from all the pixels in the sample area. In LR2 the sample was 5x5 pixels at 1:1 zoom but increased when the display size was reduced. Now in LR3 the sample size is still somewhat dependent on display size and at 1:1 can be varied with the Scale slider from 5x5 (25 pixels) to 17x17 (289 pixels) and is slightly larger at zoomed displays.

I'm doing some additional research; I don't think the sample is 1 pixel; if I had to guess I'd say its either 3x3 or 5x5 by default.

tzalman wrote in post #10562627
I disagree. First, the Scale slider appears only when the eyedropper is inabled, it is not the zoom slider. Second, the sample grid displayed together with the eyedropper clearly displays a larger area of the image. The WB calculation is calculated from all the pixels in the sample area. In LR2 the sample was 5x5 pixels at 1:1 zoom but increased when the display size was reduced. Now in LR3 the sample size is still somewhat dependent on display size and at 1:1 can be varied with the Scale slider from 5x5 (25 pixels) to 17x17 (289 pixels) and is slightly larger at zoomed displays.

There are so many conflicting information about this feature on the web. After some playing with tool it seem to me that it does not do any average, because if it do, there will not be so dramatic WB change when I move mouse only one pixel over my grey card... and moving Scale fully to the right does not slow down wb changes for one-pixel mouse movements over WB grey card.

Still confused and still searching for correct information Thanks all who help me on this topic.

By the way, Adobe Camera Raw... it looks there is no even that Scale.. there you can't change any setting for sampling grey color..... of course in Photoshop you can easy select how big you want to be the sample area, but in ACR/LR?? Hm.....

I don't think anyone confused the Scale slider with the Zoom feature. The original question was whether the scale slider affects the sample size of WB Tool dropper. I found several references that claim that the the slider doesn't affect the WB sample area.

The LR3 User Guide is largely silent except to say the following:

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HTTP response: NOT FOUND | MIME changed to 'image/jpeg'

tzalman wrote in post #10562627
I disagree. First, the Scale slider appears only when the eyedropper is inabled, it is not the zoom slider. Second, the sample grid displayed together with the eyedropper clearly displays a larger area of the image. The WB calculation is calculated from all the pixels in the sample area. In LR2 the sample was 5x5 pixels at 1:1 zoom but increased when the display size was reduced. Now in LR3 the sample size is still somewhat dependent on display size and at 1:1 can be varied with the Scale slider from 5x5 (25 pixels) to 17x17 (289 pixels) and is slightly larger at zoomed displays.

PixelMagic wrote in post #10562664
I just looked at Martin Evening's LR2 book and it states that the slider does adjust the sample size:

HTTP response: NOT FOUND | MIME changed to 'image/jpeg'

This is what mostly intrigues me, this is located on official adobe web!! But according to my testing with WB card this does not look to me be true... still confused!

I have changed my mind after some testing. The two screen shots below show an image enlarged to 1:11 in order to be sure I am on the same pixel each time (indicated by the yellow arrow). The 5x5 takes in only grey, the 17x17 takes in a lot of red which should drastically influence the WB. It doesn't. Both times the WB is 4700. The Scale slider has no effect on WB.

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Ah ha...that's my observation too which certainly conflicts with Martin Evening's assertion. The center pixel is always selected regardless of size change in the slider. Here's a Flickr thread that also discusses this finding: http://www.flickr.com …iscuss/72157604​319799563/

tzalman wrote in post #10562877
I have changed my mind after some testing. The two screen shots below show an image enlarged to 1:11 in order to be sure I am on the same pixel each time (indicated by the yellow arrow). The 5x5 takes in only grey, the 17x17 takes in a lot of red which should drastically influence the WB. It doesn't. Both times the WB is 4700. The Scale slider has no effect on WB.

I just did a further test. Assuming that the eyedropper behaves the same with a tif as it does with a CR2, I created a 30x30 grey square (85%/85%/85%) with a single off-color, bluish pixel in the middle (46%/47%/90%). When the blue pixel is not in the 5x5 grid the readout is 85/85/85, as should be, and clicking causes no change in Temp and Tone values which remain 0/0. When the blue pixel is in the middle of the grid the readout is 87/87/86 (far from the actual color of the pixel) and when clicked the correction is +3/-7. When the blue pixel is anywhere else in the grid the readout is still 87/87/86 and the correction remains +3/-7. Conclusion: the eyedropper does indeed average out the 25 pixels in the grid. 24 greys and 1 blue gave the same results no matter where the blue was.

So it's 5x5 pixels average. Better than one pixel for sure, but still not enough in my opinion because when I have color noise I cannot get consistent results. Every click on WB card give much different WB setting. Ah, that's the life