Newbie Q about white balance/gray card

My PowerShot G3 has a custom white-balance mode that works by pointing the camera at a white card OR a gray card. I'm wondering, wouldn't it need to always point at a white card, to know what white looks like? If I point it at a gray card, seems like it would try to compensate for that being white and just mess up everything. ...???

confused,
Eric

--
Themepark: a full-service web application and design company
'great web sites, delicious corn dogs!'
http://themepark.com

If you think about it, gray is just a darker white. White contains all colors in equal amounts, so does gray. The amounts are just lower. So the only thing gray does is make the camera look at a darker "scene." So, the only problem with using a gray card would be if it had color cast to it or the light illuminating it was too dim to allow the camera to get a good measurement. The bottom line is that gray is not a color in the sense of red, blue, or green. So a gray card should work as well as a white one as long as the gray is not too dark.

Does this give you a better understanding?

Dewdrop

pnoeric said:

My PowerShot G3 has a custom white-balance mode that works by
pointing the camera at a white card OR a gray card. I'm wondering,
wouldn't it need to always point at a white card, to know what
white looks like? If I point it at a gray card, seems like it would
try to compensate for that being white and just mess up everything.
...???

confused,
Eric

--
Themepark: a full-service web application and design company
'great web sites, delicious corn dogs!'
http://themepark.com

Click to expand...

Hi Dewdrop1

I understand about White Balance, indeed I constantly carry around with me a portable white balance dog for calibration. And yes, I agree with your post about gray, for the purpose of white balance, being just another form of white.

However a number of pro's seem to recomend gray instead of white. Do you have any idea why?

Dave

Dewdrop1 said:

Does this give you a better understanding?

Dewdrop

pnoeric said:

My PowerShot G3 has a custom white-balance mode that works by
pointing the camera at a white card OR a gray card. I'm wondering,
wouldn't it need to always point at a white card, to know what
white looks like? If I point it at a gray card, seems like it would
try to compensate for that being white and just mess up everything.
...???

confused,
Eric

--
Themepark: a full-service web application and design company
'great web sites, delicious corn dogs!'
http://themepark.com

Click to expand...

Click to expand...

David Barkin said:

Hi Dewdrop1

I understand about White Balance, indeed I constantly carry around
with me a portable white balance dog for calibration. And yes, I
agree with your post about gray, for the purpose of white balance,
being just another form of white.

However a number of pro's seem to recomend gray instead of white.
Do you have any idea why?

Click to expand...

Don't hold me to this, but I'd like to speculate. Perhaps a pro can confirm my theory. Since gray is a neutral color, it can be used for white balance which I've already said. However, since the matrix metering of cameras (film included) assumes an 18% gray average for a scene, having such a card would allow the photographer to set the exposure using the gray card. Place the card in the same light which is illuminating the subject, point the camera at the card, press half way, hold the button, compose the shot and shoot. Of course, you can read the shutter speed and aperture settings off the LCD or EVF and use them to set the camera manually. This would be useful where the scenes you are shooting contain large bright or dark objects which would offset the exposure forcing you to use exposure compensation. Furthermore, the EV might be different for each shot. So being able to get a good meter reading (going back to the "old days") would be very helpful. By the way, in the days when cameras didn't have their own metering system, I used an exposure meter and took the reading off the palm of my hand (I'm a white person - this wouldn't work for all races.). It wasn't perfect, but I found it was close enough and I didn't need to carry a card with me. Also, I was shooting in black and white which is more tolerant than color.

I hope I haven't missed the mark by too much. The bottom line of what I'm trying to say is that a gray card is useful for both white balance and exposure settings, whereas, a white card is only useful for white balance.

Okay??? (Pros - be kind to me, I'm trying to help but please correct any misleading statements I might have made.)

Dewdrop

I'm no pro, but this what I have heard. If you have a film camera, you MUST use a Gray card. If you have a digital camera, you can use either. BUT, the gray card is preferred. Apparently the "white" cards have a "shine" to them and can trick the camera in certain conditions because the shinyness is reflecting MORE than it should be. Using the gray card, there is no apparent additional reflective coating, thus consistant picture through any lighting condition.

Makes sense, but ..... don't blame me. I use a gray one now when I need to set my WB.

--
Mr. Pickles

Hi Dewdrop, Mr. Pickles

Hopefully someone will confirm what you guys have written. I'm particulerly interested in Mr. Pickles statement! It gives me much more confidence in my White Balance Dog, who although being white also does not have a reflective surface!

He's 120 pounds and is easy to focus on at any time to make custom white balance.

Dave

Mr. Pickles said:

I'm no pro, but this what I have heard. If you have a film camera,
you MUST use a Gray card. If you have a digital camera, you can use
either. BUT, the gray card is preferred. Apparently the "white"
cards have a "shine" to them and can trick the camera in certain
conditions because the shinyness is reflecting MORE than it should
be. Using the gray card, there is no apparent additional reflective
coating, thus consistant picture through any lighting condition.

Makes sense, but ..... don't blame me. I use a gray one now when I
need to set my WB.

--
Mr. Pickles

Click to expand...

Mr. Pickles said:

I'm no pro, but this what I have heard. If you have a film camera,
you MUST use a Gray card. If you have a digital camera, you can use
either. BUT, the gray card is preferred. Apparently the "white"
cards have a "shine" to them and can trick the camera in certain
conditions because the shinyness is reflecting MORE than it should
be. Using the gray card, there is no apparent additional reflective
coating, thus consistant picture through any lighting condition.

Makes sense, but ..... don't blame me. I use a gray one now when I
need to set my WB.

Click to expand...

Now I'm confused. You don't set white balance on a film camera. You buy film which is already balanced for the light you are shooting in or you use filters. You must use a gray card for both film and digital to set exposure if you choose to do it that way. A white card would be too bright, shine or no shine, and your shots would be underexposed. So, if you heard that a gray card is used to set white balance on a film camera, I'd sure like to hear about it. I would also like to know which film cameras have a WB setting.

As to using a white card to set WB for a digital camera, I agree that you should not use a glossy card, but one that is flat white. After all, the gloss could reflect the sky or some other nearby bright color. So, in that sense, a gray card is better, but only if it isn't a glossy gray.

Dewdrop