Gray Cards

[marc_matteo]

This is a photo 101 question BUT, I have never used an 18% gray card so what

is it really for, is it needed, and how do you use it? I am mainly a wedding

photographer. I shoot in raw with a Canon 40D and 5D. I find my images to be

very well balanced with very little I need to do in photoshop. Does this card

really make a difference?

[steve_parrott]

The Whi Bal grey card I use is very helpful to me. I also do weddings, and always include

the grey card in the first shot of a series whenever possible. Sometimes my assistent will

hold the card, and I have also had the subject hold the card in front of their face for the

initial shot. I tell them exactly what the purpose of the card is, so I can be sure the color is

accurate. When people are paying to get good photos, they don't mind holding the card

for the first shot. I shoot in RAW, use Capture One to process. In the white balance section,

all I have to do is click on the grey card in the photo, and the white balance will set itself

correctly. I then use the same color temp and tint settings on subsequent photos taken

under the same conditions. Even a grey card cannot totally fix a mixed lighting situation

though, such as mixed flash and flourescent lighting... but it will help.

[picturesque]

Before digital cameras, a gray card was used for exposure, not white balance, since with film, white balance was not an issue. Obviously you can use the gray card for white balance, as explained above. However, for exposure, you should first understand that exposure meters, whether handheld or in-camera, or whether incident or reflected, compare the information it gathers to a middle gray value in order to end up with an exposure suggestion. Middle gray is the standard by which EV is determined.

 

So to use one, you put the gray card in the same light as the subject and meter it (normally with a reflected meter). The result should be a good starting point for the EV of the scene. Whether it makes a difference for you is dependent on how YOU use the card.

[errol young]

Nadine. As I understand it, white balance was always a film issue. That is why you could buy tungsten and outdoor slide film. For the processor, an image of a gray card could be very useful in getting the CMY balance.

 

Errol

[picturesque]

Errol--from that perspective, you are right. I was just referring to the fact that one usually brought a gray card along (back in the film days) to help determine exposure, and not to set white balance, since the film itself set the white balance. I do recall using the card as the first frame of a set series of photos, such as for prom photos, where the printer used the card to set exposure and color balance for the entire roll, to save the effort for each frame.

[colinsouthern]

[C/P from a relevant post I made in the DD Forum this morning]

 

Essentially, what we're trying to do here is present the RAW converter with a reference. If, for example, you shine a red light on a white or grey piece of paper then it'll take on a red "cast" - if you use a blue light then it'll take on a blue "cast". So - if you're in ACR in you use the WB tool and click on your grey/white card the program samples the 3 R,G, and B channels and if it finds something like Red=220, Blue = 200, Green = 200 then it says (to itself) "A-Ha! ... this image has a red colour-cast, and will adjust the entire image accordingly so that R, G, and B on the grey/white card all equal the same value.

 

As a side note, the way it does it is quite interesting - you might think that it scales the appropriate axies so that the relevant points are all equal, but it doesn't - it actually re-defines the colorimetic interpretation data (ie it "tweaks the definitions that it has for what shade of RG&B the numbers represent for that particular make/model of camera, whereas if you to WB correction in PS then it reverts to scaling the axis (so you won't get the same issues if big WB shifts are required) - another good example of why it's nearly always best to make any corrections that you can in ACR - but I digress!

[frank_myers2]

A more useful tool than a gray card in the digital world is the expodisc. It creates a white balance reference in any lighting situation and is very simple to use. It comes in two types standard and portrait (slightly warmer).

 

http://www.expodisc.com/

[colinsouthern]

Frank Myers wrote:

 

"A more useful tool than a gray card in the digital world is the expodisc."

 

I've got two of them - and to be honest - I'm not 100% sold on them for 3 reasons:

 

(1) You have to point the camera with the disc towards the source light, not the subject - this isn't always as easy as getting someone to hold a grey card in the scene.

 

(2) Setting a custom WB in-camera takes a lot longer if the situation & lighting are changing rapidly - again a grey card is much faster because you deal with the results in post-processing.

 

(3) Unless the source light is "clean" and well-defined, it's possible to get a tainted reading (which I've managed on many occasions).

 

Don't get me wrong - I WANT to like them (as I say, I've got 2 of them) - and I certainly think they have their place - but I do think using a grey card is always faster in changing conditions, and can be more accurate in situations where the light-source isn't "clean".

[rayt]

"A more useful tool than a gray card in the digital world is the expodisc. It creates a white balance reference in any lighting situation and is very simple to use."

 

Not quite. The problem with the Expodisc is that it white balances with the light reaching the lens, the light refelected from the subject. If your subject is predominately red, say a red sweater, your resulting white balance will be too blue. Other colors suffer the same problem and will render the white balance off by having too much of the opposing color.

 

A gray card reflects the light using a known, neutral, color source. Therefore you are white balancing with the actual light falling on the subject, not the tainted light being reflected from the subject.

 

Use the Expodisc if you like and as long you understand fully the shortcomings of the product, you can do OK. But a true reflective target is always better as it it a known color.

 

Attempting to white balance with light that is skewed by a color is an excersize in frustration.

[William Michael]

I use a grey card for (digital) white balance and (sometimes) for exposure.

 

Especially for white balance in outdoor portraiture or mixed lighting.

 

When using a grey card for white balance, I will still take the first shot of every series with the grey card and a skin tone side by side in shot: as I did at the beginning of any series using film.

 

For inanimate objects I will often use the Kodak Professional colour patches, as well the grey card in the first frame of a series, for reference.

 

(A `series` = being under the same lighting conditions.)

 

I am not sure if this technique would make work easier for others more talented than I with computer Post Production, but it certainly does for me, and it is an undisputed source reference point to have in the first frame: I like `undisputed`.

 

WW

[fotografz]

If you go through the trouble to shoot a reference card wouldn't it be just as easy to set a

custom WB while you're at it?

 

I have to do this with my Leica M8 because the AWB sucks on that camera, and in really low

Tungsten the camera's Tungsten setting also sucks.

 

The various custom WB saving feature on the 1DMKII which is then added to the exterior WB

selector is a great feature and a monster time saver in post.

[William Michael]

>>> If you go through the trouble to shoot a reference card wouldn't it be just as easy to set a custom WB while you're at it? <<< (MW)

 

I think this refers to my post, if so I was not explicit enough to convey the correct meaning.

 

Please read the first three sentences of my previous post as meaning:

 

`I use a grey card to set a custom white balance in the camera and (sometimes) for ascertaining exposure.

 

Especially I use it to set custom white balance in outdoor portraiture or where there is mixed lighting.

 

Even when using a grey card to set the custom white balance, using a digital camera, I will take the first shot of every series with the grey card and a skin tone side by side in shot: as I did at the beginning of any series using film.`

 

***

 

And please read the last sentence thus:

 

`I am not sure if this technique would make work easier for others more talented than I with computer Post Production, but it certainly does for me, and it is an undisputed source reference point to have in the first frame: I like `undisputed`. This point refers to viewing on different monitors.

 

 

WW

[colinsouthern]

Raymond Thompson wrote:

 

"Not quite. The problem with the Expodisc is that it white balances with the light reaching the lens, the light refelected from the subject. If your subject is predominately red, say a red sweater, your resulting white balance will be too blue."

 

Umm - No. With an Expodisc you don't use reflected light from the subject - you go and stand where the subject is, and point the camera back towards the light source - take a shot - and then set a custom WB based on the shot.

 

If you're shooting a number of shots under the same light then it works well - but if you're shooting under changing conditions then it's heaps slower than a grey card.

[steve_parrott]

Well... to me.. and I emphasise to ME, setting a custom white bal in camera is a ROYAL

PAIN IN THE BUTT. Just too many steps and time consuming. In wedding circumstances,

time is a very precious and sometimes almost non-existent luxury. The way I see it, you

have to shoot the grey card in the first place, why not just do it for one shot and be done

with it for that series. It is quick and easy to reference it in post production for white

balance. To set a custom white balance in camera, I still have to shoot the photo with the

card in the scene, then have people standing around while I go through the asinine multi

step button pushing to set the custom setting in camera. I feel this is an area where the

camera manufacturers, or at least Canon, have really let the photographer down. Setting a

custom WB in camera should be a fast, one button exercise. So for me it works best to

take one shot of the card in the scene and be done with it. One click on the card later in

the RAW processor, and the WB is set. Quick, simple, accurate.

[colinsouthern]

"I feel this is an area where the camera manufacturers, or at least Canon, have really let the photographer down."

 

Perhaps they could give us a dedicated Custom WB Record button instead of the print button ;)

[amy_elliott3]

I have an expodisc as well and think it does the job - just about as well as my old wb

solution, the Pringles lid.

 

To the op - if as you say, your images are consistently well-balanced and you're not

spending a lot of time in post fixing them I wouldn't worry about it. I only do in mixed light

situations that are particularly ugly - not usually the case with weddings. There's often less

light than we'd like - but it's not usually "conference room with windows" bad.

[frank_myers2]

I think Colin is right, both in how to use an expodisc, and in his assessment that if you are in a situation where there are a lot of mixed light sources or changing light it is more of a pain than a gray card.

 

I find that evening receptions are the place where white balance seems to be difficult - fluorescent lights, dark outside so no sunlight, and DJ lights colored and white...If I can white balance with the expodisc to the primary light source, with a gel on my flash, my results are more consistent with the least amount of hassle.

[marc_matteo]

I'm so glad I brought this up! It seems like I have my own little forum going on. Thanks for all your info. I'll start experimenting with this.