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AWB accuracy changes with aperture setting?


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Hello all.

This is my first post on the forum.

 

Let me begin by letting you know that a little over a month ago, I got the royal "yes" from my wife to buy an M-E. As we were looking at it the store, the salesperson asked if I would be interested in a M instead, and that the wait may not be long because they had two cameras coming in for two people that preordered them, but often someone will cancel the order once the camera has arrived. My wife asked how much extra for the M, the salesperson told her (~1500 Canadian dollars), and my wife said, "Sure, go ahead and get the more expensive one, my husband will only be after it in a year if we get the M-E now." I could only sputter "Humina, humina.....um, yes please." My wife is magnificent! The first guy on the waiting list turned down the first camera which was then picked up by the second guy. So I'm now waiting for the next one to come in, should be any day, I'm told. YES.

 

Okay, so about the topic of my post, the M has a couple grey cards painted on the shutter. I assume the camera uses the light bouncing off of these to auto set the white balance. So there's more light for the camera to read when the scene is brighter and if the lens is not stepped down. Has anyone noticed if the AWB is better with wider apertures?

 

Best and thanks,

Steve

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... the M has a couple grey cards painted on the shutter. I assume the camera uses the light bouncing off of these to auto-set the white balance.

Grey cards ... :D what a cute idea.

 

No, the light bouncing off the shutter blades is used for (classic) light metering. It's white in at the center, black at the edges, and grey in-between in order to add a center-weighted characteristic to the metering.

 

 

Has anyone noticed if the AWB is better with wider apertures?

The aperture doesn't matter because the sensor for AWB is on the outside—the small round "eye" between the rangefinder and viewfinder windows.

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I see. I've read that the small sensor in the front is a brightness sensor, but not AWB.

I've suspected it might be an external AWB sensor, but I couldn't find much written about it.

But using grey cards on the shutter might be a good idea in the future.

Best,

Steve

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the M has a couple grey cards painted on the shutter. I assume the camera uses the light bouncing off of these to auto set the white balance. So there's more light for the camera to read when the scene is brighter and if the lens is not stepped down.

The light reflected off he shutter blades is used for metering, not AWB. AWB uses the data from the image sensor (i.e. the actual image data captured) so the aperture setting has no bearing on white balance.

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The aperture doesn't matter because the sensor for AWB is on the outside—the small round "eye" between the rangefinder and viewfinder windows.

 

The small eye is to estimate the aperture set for EXIF purposes. Nothing to do with white balance.

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What is the function of the light sensor in the body?

It is used for guesttimating the selected aperture, for example. Also for adjusting the brightness of the frame lines.

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AWB uses the data from the image sensor (i. e. the actual image data captured) ...

Is that so?

 

I seem to vaguely remember an article about the M8/M9's automatic white balance where the author said the sensor eye (a. k. a. 'Blue Eye') in the camera's front provides not only brightness data for estimating the aperture but also colour temperature data for AWB. However I cannot retrieve this article anymore, so my memory might be faulty.

 

Anyway—the AWB results seem to suggest there must be more than just the image data used for AWB. I'd suppose that the sensor eye provides at least some input data about the ambient light to the camera's AWB algorithms. Of course I don't know for sure ...

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The light reflected off he shutter blades is used for metering, not AWB. AWB uses the data from the image sensor (i.e. the actual image data captured) so the aperture setting has no bearing on white balance.

****

 

Does anyone know if the accuracy of AWB changes with ISO settings? In other words, has anyone noticed if darker scenes at high ISO have significantly worse AWB color matches than brighter scenes at low ISO?

 

Best and thanks again,

Steve

****

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Is that so?

 

I seem to vaguely remember an article about the M8/M9's automatic white balance where the author said the sensor eye (a. k. a. 'Blue Eye') in the camera's front provides not only brightness data for estimating the aperture but also colour temperature data for AWB. However I cannot retrieve this article anymore, so my memory might be faulty.

 

Anyway—the AWB results seem to suggest there must be more than just the image data used for AWB. I'd suppose that the sensor eye provides at least some input data about the ambient light to the camera's AWB algorithms. Of course I don't know for sure ...

That was the Digilux2
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I am quite sure the 'little blue eye' only does brightness measurement for the aperture guess and the bright frame lines for the new M. Not sure if there are any other functions to it.

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****

 

Does anyone know if the accuracy of AWB changes with ISO settings? In other words, has anyone noticed if darker scenes at high ISO have significantly worse AWB color matches than brighter scenes at low ISO?

 

Best and thanks again,

Steve

****

No, but they have different light.

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