Beware AWB....!

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#2
Well that is marked difference..........though under a brolly would be the epitome of shade!

I am getting the EM1.2 and in the past with Canon have found AWB fairly reliable. So apart from the above quite extreme change how trustworthy overall have you found the AWB???
 
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Alan
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#3
There will always be scenes which confuse the camera and no camera will get it right 100% of the time so I suppose the thing to do is to learn how the camera and its AWB work and why, learn what in what situations it could be confused and why, work with it and correct it when required.

And a PS.
One advantage CSC's have here is that you'll see the WB before you take the shot and can adjust it if you want by selecting a different setting like sunny or cloudy or setting it yourself by doing a custom WB or setting it in "K" or whatever system your camera has.
 
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OP
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Dave in Wales
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#4
Well that is marked difference..........though under a brolly would be the epitome of shade!

I am getting the EM1.2 and in the past with Canon have found AWB fairly reliable. So apart from the above quite extreme change how trustworthy overall have you found the AWB???
You have to keep your eye on it, couple of examples below.......

The wall is actually light yellow.
P4190001-2 copy
by Dave in Wales, on Flickr

This one is a screamer, I couldn't believe my eyes. The tank is actually brown with rust.....see below...same tank.
P5180556
by Dave in Wales, on Flickr

P6180135-2-Edit-Edit
by Dave in Wales, on Flickr
 
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Nod

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#6
Auto anything can (and often does!) fool the camera. Knowing when such issues are likely and how to avoid them is all part of the fun!
 
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#7
The difficulty which AWB faces is that it's not intended to replicate the colours as they were when photographed, i.e. the spectral frequencies and brightness emitted by each coloured surface, but to try to match the AWB of the human eye and brain, including the failures of the human AWB.
 
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#8
Camera E-M1 Mk II set to AWB.
P7060350 copy
by Dave in Wales, on Flickr

WB set to 'shade' gives actual colour.
P7060354-2-Edit
by Dave in Wales, on Flickr
You have to keep your eye on it, couple of examples below.......

The wall is actually light yellow.
P4190001-2 copy
by Dave in Wales, on Flickr

This one is a screamer, I couldn't believe my eyes. The tank is actually brown with rust.....see below...same tank.
P5180556
by Dave in Wales, on Flickr

P6180135-2-Edit-Edit
by Dave in Wales, on Flickr
shoot in raw then you won't have any problems
Looks like for interiors (i.e. mainly where daylight does enter into the equation?) I will have to keep my WiBal Card to hand more often than I needed to with the Canon.................but as mentioned above I do shoot raw so have the most control of potentially needed WB corrections!
 
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#9
With subjects like that, AWB really struggles. It works along basically the same lines as auto-exposure, which looks at the entire scene, scrambles all the bright and dark tones into a porridge, assumes this will even out to a mid-tone, and sets an exposure which puts that tone in the middle of the histogram. AWB assumes that when all the colours are mixed up, they will even out to neutral grey.

In the same way as auto-exposure has difficulty with subjects that are predominantly light or dark, so AWB is prone to errors when subjects contain a lot of one colour so algorithms are overlaid to ignore or down-weight them. Systems may also look for the brightest area, assume that is clean white, and use it as a reference. There are numerous of other variations that may be factored in, such as a large area of blue at the top of the image is likely to be a sunny sky, or a large area of green at the bottom is probably grass. Things like focal length and focusing distance can also be used to give the system a clue about the subject. In the past, some cameras had a little window on top that attempted to read the colour of the prevailing light, which seems like a good idea as that's the main determining factor, but it hasn't caught on.

Given the potential for getting white balance hoplessly wrong, it's amazing how clever most modern cameras are at getting it there or thereabouts. However, if you want accurate and consistently accurate colour, use one of the presets (daylight, flash, shade etc), or do a custom white balance, or - the easy option - correct it manually in post-processing.
 
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#10
Auto anything can (and often does!) fool the camera. Knowing when such issues are likely and how to avoid them is all part of the fun!
Absolutely. This is why constant advice is posted to shoot in manual, and to know and understand what you are doing and to make changes to settings as required. Cameras will let you down all the time.
 
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#11
I don't usually agree with shooting in manual unless there's a specific reason to do so as it's often too much of a faff to adjust and keep an eye on everything. At least in the semi auto modes like Aperture and Shutter the pressure is relieved a bit and you can allocate more time and concentration to framing and taking the shot.

Personally I use aperture priority with auto ISO unless there's a specific reason to do something else for example when the light drops causing the shutter speed to drop to 1/60 or slower as this is usually too slow for me so I normally then switch to manual and dial in suitable aperture and shutter settings and let the ISO float as appropriate.

I shoot raw most of the time so I don't worry too much about WB although forgetting what the scene should look like could sometimes be an issue. The only time I set a WB myself is when shooting JPEGs which is rare for me or when I know someone is going to want to see the results on the back of my camera immediately and in those rare instances I don't want to have to explain why everything is (for example) too yellow and that it'll be ok once I've "developed" the picture.
 
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StewartR

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#12
This is why constant advice is posted to shoot in manual.....
Sorry, but that's rubbish.
..... and to know and understand what you are doing and to make changes to settings as required. Cameras will let you down all the time.
But this is good advice.

If I understand how / when / why my camera's exposure meter can be fooled, I can easily apply exposure compensation to correct for it. That's far better than going fully manual.
 

Nod

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#13
Sorry, but that's rubbish.
But this is good advice.

If I understand how / when / why my camera's exposure meter can be fooled, I can easily apply exposure compensation to correct for it. That's far better than going fully manual.

:plus1:

I rarely shoot manual, generally using P mode (or equivalent) and often shifting away from the cameras' suggested settings. When I feel (or see) that it's necessary to dial in some EC, I do - very occasionally using the bracketing options.

WB is almost always set to auto but a quick chimp if I think there's a chance that the camera's stuffed up its guess usually shows that the WB is out so I can reshoot if necessary.
 
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#15
I used to demonstrate to people in classes how AWB could be fooled by taking a pic of a yellow register filling the whole frame, and the image came out as white/grey. I always said to people, if you are in consistent lighting situation, choose the appropriate WB preset, especially if you are shooting in Jpeg. But always remember to change back to AWB as a default, ;) becasue you don't know what situation you may pick

I try to do that as much as I can unless I'm in a situation where the lightning conditions change quickly, in and out of steets and squares on holiday for example. Even if you shoot in the RAW format, getting a more accurate WB at capture may negate further colour correction, or at least minor changes.
 

GTG

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#16
I found that Fuji get it right, at least the X-T1 I used to own seemed to.
 
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#18
AWB is just a starting point to give you some sort of reasonable preview. Every single time you need to set it to the correct white colour or at least to something that roughly looks right.

The examples just highlight the fact that camera meter system just isn't expecting such subjects and is treating it as something else. Something green is likely to cause a major magenta shift and vice versa. Yellow - to blue. And so on.
 
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