18% grey or white card for white balance setting

[shingfan]

what is an 18% grey card?....and how white should a white card be?....when setting white balance...which is more convenient to use?......so..when setting the white balance....should i put the paper very close to the camera...or use long focal lenght?....any difference?

 

[Digital Matt]

Either one will work fine. An 18% grey card is used for determining proper exposure, and for calibrating a meter. Meters always give recommendations to make your exposure 18% grey, or "middle" grey. The meter has no idea what your subject matter is. It's up to you to decide how to expose based on the meter.

As for white balance, all you need is a neutral tone to balance off of. White balance is a term that comes from video, and somehow has made the transition to digital still photography. A grey card works just as well as a white card. You need to have the card illuminated by the same light that is hitting your subject, or chosen scene. If you are shooting a model, have them hold the card. If you are setting a custom white balance, depending on your camera, you may have to fill the frame, or it might let you select a spot in the photo to wb from. I don't know what camera you have. If you are planning to set the white balance in software later, it doesn't have to fill the frame. You'll just click on it with an eyedropper to select WB.

 

[shingfan]

so i can grap a piece of regular printing paper and it should do a fine job acting as a white reference?.....does it matter if there has folding line.......or it is not that critical and it doesnt need to be perfectly smooth surface when evenly spread color?....i'm thinking of putting a couple pieces of printing paper in my camera bag to use for setting white balance if this is okay in your opinion...but of course...they are too big to fit in the bag so i'll need to fold them...so when i use them...there will be folding lines...wonder if it matters

 

[Digital Matt]

I wouldn't recommend using a piece of paper, because it's not totally opaque. You want something opaque, so no other colors show through it. A piece of white foamcoare or mat board is probably smarter. Folds and creases don't really matter. You want something to represent neutral color in your scene.

 

[ladyphotog]

Why not just buy a gray card, you can get one for about 10 bucks.

 

[shingfan]

well....three piece of printing papar stacked is probably opaque enough?........or maybe white cardboard?.....i like to put it in the camera bag and carry along easily.....how about focal length?.....does it matter?......better if the card board is farther or closer to the camera?

well....i'm not sure what a grey card is....i'm a newbie....and if i can get something to do the same job for free at home....i would save the $10...lol....

 

[ladyphotog]

well....three piece of printing papar stacked is probably opaque enough?........or maybe white cardboard?.....i like to put it in the camera bag and carry along easily.....how about focal length?.....does it matter?......better if the card board is farther or closer to the camera?

well....i'm not sure what a grey card is....i'm a newbie....and if i can get something to do the same job for free at home....i would save the $10...lol....

You will use a gray card many times for different situations and you will always have it if you take care of it.

This is a gray card:
http://www.kodak.com/US/en/motion/products/tools/card.shtml

 

[Digital Matt]

Focal length doesn't matter. The paper has to be clearly visible under the same lighting conditions as your subject.

 

[ksmattfish]

Gray cards are a specific tone. Unless they also say they are color neutral, they may not be. The standard Kodak gray card (at least the older one I have), for instance, is not color neutral.

This place sells color neutral gray cards.

http://secure.netsolhost.com/664583...vc?Screen=CTGY&Store_Code=CI&Category_Code=GC

 

[shingfan]

when using this grey card...do i need to also include the white and black area in the exposure?....

how much is it different from just using white paper?

 

[ksmattfish]

how much is it different from just using white paper?

You can white balance with anything that is color neutral. The problem is that the human eye is not very good at determining if something is color neutral or not, so you need to know for sure whether the paper is color neutral.

 

[shingfan]

what is the meaning of color neutral?....

 

[Digital Matt]

what is the meaning of color neutral?....

Having no color cast. Usable as a reference point. If for instance, you white balance off of a red card, your camera or software will shift the color to make that card neutral, which will in turn shift your white balance to very cyan. You need something that has no color, which is pure grey, or white.

 

[shingfan]

o...i see.....i understand that with white card...there might be contamination and might introduce a bit of color cast........but black card....it is completly black and doesnt reflect any color cast....why is it not a good idea to use black card?....i'm just trying to understand the physics i hope you dont mind

 

[Christie Photo]

what is an 18% grey card?....and how white should a white card be?....when setting white balance...which is more convenient to use?......so..when setting the white balance....should i put the paper very close to the camera...or use long focal lenght?....any difference?

A grey card reflects 18% of the light falling onto it. The back of a grey card is white. I always shoot both... grey side first. The card should fill the entire image. After shooting the grey card and setting my exposure, I set the white balance. I then shoot the white side and double-check my exposure. I look for a thin line on the histogram, straight up and down, all the way to the right but not going off the graph. Once I have achieved this, I reset the white balance.

Maybe I'm an obsessive-compulsive type.

Pete