exposure and white balance (grey card and white card)


sglion

New Member
Dec 11, 2009
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#1
Hi,

As far as I have understood, white balance setting is due to the nature of light, as a white card is used for custom white balance setting.


exposure is what the camera decides will be the best for a given photo. So if its a white curtain on sunlight and shot is for inside, it might think the curtains could be overexposed and try to reduce the exposure level, and the camera tries to make it 18% Grey and set its exposure.

So how using a gray card is exposure fixed? like using a white card to set the white balance, how is the exposure set ?
 

sglion

New Member
Dec 11, 2009
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#2
I mean is it such that the metering is locked/based to that 18% grey card, and after that refocus and shoot ?
 

IsenGrim

New Member
Jan 28, 2008
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#3
grey/white card has nothing to do with exposure.

its for white balance.

what is white balance? it has nothing to do with exposure. it just means your white/grey card will appear white/grey in your image.

your white card can be blue if you shine blue light on it. right? then you can choose to either, let it remain blue, or use white balance to correct it to white.

(or you can use white balance to correct away from white, make something white look yellow for instance)
 

catchlights

Moderator
Staff member
Sep 27, 2004
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Punggol, Singapore
www.foto-u.com
#5
grey/white card has nothing to do with exposure.

its for white balance.

what is white balance? it has nothing to do with exposure. it just means your white/grey card will appear white/grey in your image.

your white card can be blue if you shine blue light on it. right? then you can choose to either, let it remain blue, or use white balance to correct it to white.

(or you can use white balance to correct away from white, make something white look yellow for instance)
all along (since the heyday of film photography) photographers being using gray card for getting correct exposure.
 

IsenGrim

New Member
Jan 28, 2008
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#6
all along (since the heyday of film photography) photographers being using gray card for getting correct exposure.
learnt something new today. i think its something i take for granted given the instant previews on digital cameras now adays.
 

sglion

New Member
Dec 11, 2009
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#7
catchlights, Thank You.
 

daredevil123

Moderator
Staff member
Oct 25, 2005
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lil red dot
#8
Hi,

As far as I have understood, white balance setting is due to the nature of light, as a white card is used for custom white balance setting.


exposure is what the camera decides will be the best for a given photo. So if its a white curtain on sunlight and shot is for inside, it might think the curtains could be overexposed and try to reduce the exposure level, and the camera tries to make it 18% Grey and set its exposure.

So how using a gray card is exposure fixed? like using a white card to set the white balance, how is the exposure set ?
Simple. Once you get the exposure metered on the 18% grey card, just use the metered values and set your camera to M mode.
 

Abbot Man

New Member
Aug 4, 2009
181
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gallery.me.com
#9
Simple. Once you get the exposure metered on the 18% grey card, just use the metered values and set your camera to M mode.
Can also do exposure lock; after metering you can lock the expousure without the need to go M mode. Check your camera manual for the AE-L button.
 

Abbot Man

New Member
Aug 4, 2009
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gallery.me.com
#10
all along (since the heyday of film photography) photographers being using gray card for getting correct exposure.
The 18% reflectance of the grey card represents the middle grey tone between black and white and is used as the standard for metering systems..
 

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