Gray card

[aam1234]

Is this gray card worth it. (http://www.amazon.com/exec/obidos/tg/detail/-/B00009R7B0/ref=wl_it_dp/104-7395758-8057569?%5Fencoding=UTF8&coliid=I1M3V4RUCC35OO&v=glance&colid=2CJ0LJKLKCO3S)

[robertwgross]

It depends.

My gray card didn't cost me anything.

A couple of years ago, I purchased the book: National Geographic Photography Field Guide. Just inside the front cover and just inside the back cover... gray cards.

If you are trying to do an exposure test, then a gray card makes sense. If you are trying to do a custom white balance, then you can use a gray card or a pure white card. I find the white works easiest for me.

---Bob Gross---

[aam1234]

It's for custom white balance. Find it a bit pricey for basically a gray paper, so I'll take your advice and use a regular white paper/card.

Thanks Bob.

[sdommin]

Don't dismiss these cards so easily. A true, photographically pure gray card is not easy to make, especially one that is printed in the back of a book. If you want to do custom white balance, a "real" gray card would be more accurate than a piece of white paper. White papers vary in their color, too.

[spelchek]

Just out of interest, how grey should a greycard be??

I guess that different effects, different shades of grey work better, but what sort of shade of grey would the 'experts' reccomend as an all round, standby greycard.?


The cards in the url were a lot darker than i thought they'd be.


edit --> on rereading thru the thread.. i guess my questions have pretty much been answered..

but can i ask one more.. what effect does using a white card have as opposed to a grey card? Will whites be whiter?? greater contrast between lights and darks??

[Jon]

The grey card was originally used for setting exposure, since a normal scene has an overall reflectance of about 18%; thus metering on a grey card when the subject deviates from the norm (sun on snow, interior with window for instance) will give you the nominal exposure for the light. Using a white card for that situation would give you an underexposure. However if the light levels are very low your meter may be able to take a reading off a white card, which you would then adjust appropriately, where it wouldn't be able to get a reading off the grey card.

A secondary use in film, and an increasingly common one with digital, is for determining colour corrections. Since the 18% grey card is neutral any colour imbalance on the recorded image will be due to the light. For this purpose, either white or grey cards can be used. They do have to be neutral, and Canon suggests that a grey card will be more accurate than a white "object "(possibly since the exposure will be more "correct" from a grey card than from a white, possibly since you may noit be aware of colour casts on "white" paper) for this.

[PacAce]

... and Canon suggests that a grey card will be more accurate than a white "object "(possibly since the exposure will be more "correct" from a grey card than from a white, possibly since you may noit be aware of colour casts on "white" paper) for this.

I wonder if it's because with a white card, there's a possibility that it might get blown if the exposure isn't right and hence lead to false colors if it's used as a neutral reference point.

[Jon]

Could be . . . if you tried to adjust so the white was correctly exposed. If you just meter the white and don't apply any compensation it'd reproduce as a mid-tone.

[robertwgross]

White papers vary in their color, too.

And that is why I wrote "pure white card" and not "white card".

---Bob Gross---

[spelchek]

And that is why I wrote "pure white card" and not "white card".

---Bob Gross---

I take it that a 'pure white card' is best purchased from a photography shop??

[robertwgross]

It depends on what you intend to use it for.

Photography shops often sell the standard Kodak Gray Card, but I have never seen them sell a white one.

I use a piece of white foamboard, and part of it shows as white. Then I have a piece of gray tape wrapped around it one way, and it is pretty close to 18% gray. Then I have a piece of black tape wrapped around it the other way. When I shoot this for exposure, I get three perfect spikes on my histogram. If I zoom in so that only the white part shows, then I get a white card for balancing purposes.

---Bob Gross---

[snibbetsj]

I bought a set of cards from www.warmcards.com (http://www.warmcards.com/) and use them anytime I shoot people. They make my post-processing go much faster. They also include a white card and a gray card in the package. I find if I can get the color balance correct in the camera it makes for so much nicer photos.


Bob Gross: I've got that same book and use it when I'm shooting landscapes. It's pretty good in a pinch.

Merry Christmas
:)

[Jon]

It depends on what you intend to use it for.

Photography shops often sell the standard Kodak Gray Card, but I have never seen them sell a white one.
---Bob Gross---
Flip side of the Kodak 18% grey is a white card.

[aam1234]

Flip side of the Kodak 18% grey is a white card.

Looked at the Kodak in the link above but it doesn't say it has a white back. Do you think it does.

[Jon]

Unless they've changed them drastically in the past "few" years, it does.

[HJMinard]

Looked at the Kodak in the link above but it doesn't say it has a white back. Do you think it does.

The link says:

One side of the card has a neutral 18-percent reflection which can be used indoors to aid in measuring the average reflection for a typical subject. You can also use this side of the card outdoors by increasing the exposure 1/2 stop above the calculated exposure. The other side of the card has 90-percent reflection for use at low-light levels.

The 90 percent reflection side is white.