16

I know that there are "gray cards" sold that help with exposure/color correction, but as I'm on a tight budget I'd like to make my own. Is this possible?

Also, are there other objects (paint sample cards for instance) that can be used for color correction?

15

Gray cards are super cheap (e.g., $2.49) - I wouldn't bother. :)

  • I've also seen grey-keyrings available quite cheaply, and you'll always tend to have them on you - they're more suited for calibrating white balance, however. – Rowland Shaw Jul 16 '10 at 16:04
  • With shipping price included, this costs me $60. – Aquarius_Girl Mar 22 '12 at 12:33
9

Spot-meter the palm of your hand (be sure it's lit appropriately, however).

Seriously.

It, or a Caucasian face, will meter about 1 stop brighter than you need, which means it's easy to compensate for.

5

As far as I know, you need a gray card for exposure measurement and white balance correction. If you are only interested in custom white balance, you may use a white piece of paper that is lit under the same condition as your subject. Sometimes, you may even use a thin piece of paper (white toilet paper) you put on your lens and take a picture you will later use for your in-camera or for RAW post-processing custom white balance.

I do not know how a white piece of paper may help you in exposing properly, but I guess you may step up and get the same results.

Here you may find more info on this subject, including the stepping up the exposure and using the white card instead of a gray one: http://photography-on-the.net/forum/showthread.php?t=58677

  • You can use a sheet of white paper for color balance, but you have to make sure it's pure white, and not "bright white", which means they've probably added a touch of blue to it. Black paper will also work, along with any neutral tone from pure white to pure black. Grays work best but the others will do. As far as using white for exposure, you can do it, but the camera will try to make white into a neutral 18% gray so you have to open up two stops if I remember right. – Greg Feb 25 '11 at 2:42
5

You can use the color sample cards from paint companies. Just walk to the paint isle in local hardware store, paint store, Home Depot and such, and pick some of the sample cards, including some whites, grays, reds, greens, yellows, oranges, and blues. Experiment with them, and write down notes on the back of the cards for future use. You will be amazed, how you can create special effects, color corrections, compensations, etc.using those cards. Follow your camera user manual to create closeups of the cards for future use. Use custome white balance option in the camera. You can create different light effects, e.g. a moon lit landscape in broad daylight, or sunrises/sunsets with pleasing colors, or snow scapes with beautiful blues or purples. Just remember, the color you will see in the photograph as a result will be complementary to the color of the card you used. For example, if you used blue card, the result will have a colorcast of orange of the same intensity, if you used red card, you will have a green colorcast in the photo, if you used a purple card, you will have a yellow color cast, or vice versa, and so on.

4

Be aware that there are gray cards that are only designed for exposure and not for white balance. These, along with the fore-mentioned paint color strips and other DIY solutions, are not guaranteed to be color-neutral.

Drop a couple bucks and get one designed for white balance if the accuracy is important to you.

2

You probably bought one by now - but just in case... I printed out a gray card because I needed one quickly. I think this is the best one can do.

0

Behr makes a paint called Legendary Grey that is extremely close in color and shade to a grey card. I painted a small piece of plywood and have used it for exposure and color balance with no problems.

0

An oldie, but a goodie. I want to expand a bit on Al Graham answer.

White balance and middle gray are two totally different things and need different tools.

I. White balance

First of all, the white balance is in reality not a white balance, it is a gray balance. Let me explain.

Any color will turn more or less white given sufficient exposition on the sensor. I am pretty sure we all have experience with some overexposed white sky.

So, you can have a real white point on your image (r255g255b255) but the starting color of that zone could have been any color on the original subject.

Now, when you modify a curve, grabbing it from almost the edge make a tiny adjust in a big shift of the curve (red dot). You have more control, and smoother changes if you adjust the curve from the center (cyan dot).

enter image description here

A lot of cheap "gray cards" are not really gray, it is a bit hard to have a really neutral color.

In my experience, whenever possible, the best white balance target is the main light itself. And I am talking mainly on artificial light and specially defused one.

  1. I use "sun" as the starting point for these settings. Close the diaphragm of the camera (f22), set the camera to the lowest ISO (let's say ISO 100) and take a picture of the softbox. Avoid burned zones.

  2. Now use this image as the white balance target. You are telling the camera that this is the light that is supposed to be white.

This method gets a bit more complicated when you have different light sources or when it is a single spot.

Use then a white target, for example, white paper rated with some whiteness level. It can be your seamless background or an inkjet paper. The closer the whiteness number to 100 the better. Use only matt paper. A glossy one can reflect something from around.

Shot this white targets underexposed so they are close to middle gray on your target photo.

Avoid any paper that has some time on the shelf, because paper turns yellow after some time due to oxidation. Avoid paper that has to be on direct sunlight because it can be burned the same way. I prefer a "fresh" white paper than an old "pro gray target".


II. Middle "gray"

This can be a bit more tricky but at the same time, you have many more options to play with.

To have an exposure reading you could:

  • Use an incident light lightmeter (The ones with a white dome).

  • There are some domes that can be attached to either a smartphone or even a camera itself to act as a lightmeter.

  • Use the histogram.

  • Use the palm of the hand (pretty much inaccurate because there are many skin tones, even in the palm of the hands).

  • Use some zone system to measure the scene.

  • Rely on the auto-exposure values, using the shutter priority mode on your camera, and replicate that on a manual mode.

  • Using a cheap gray card.

  • Using a white paper as a reference and readjust the values.

I must say that almost any method must be tested and calibrated.

As I am a fan of DIY let me explain how to use a simple white piece of paper as a gray card.

  1. Take a close up of a white paper on the defined light condition using an auto exposure mode. (Use continuous light)

  2. Viewing the histogram you should see a clear zone in the middle of the graph. If the paper was uniformly lit, the graph should be narrow.

enter image description here

  1. Now, change the settings on the camera to overexpose the exact same shot, let's say 3, 4, 5 steps. If you had, for example, a shutter speed of 1/200s, overexpose using 1/25s. The point is to push this graph to almost the extreme right of the histogram without burning it.

enter image description here

You can do this to the dark side, doing the inverse. Make some tests, use the aperture for fine tunning your tests, for example to 2 2/3 or 3 1/3 exposure changes.

You will now know that if you use a similar simple white paper, you can overexpose an auto mode reading 3 stops more to have an accurate reading for example.

After these tests, you now will know, not only a way to use a simple piece of paper, but you have a method of knowing the dynamic range of your camera. You could find that your camera has better dynamic range and you can push the reading more stops.

But I must say that using a card to measure exposition is sometimes not the best method, because it is strongly dependant on the angle of incidence of the light.

For example, if the light is a frontal one, it will bounce a lot of light, if the light comes from a side it will receive a lot less light, but a 3D subject, like a person's face, will receive a lot of light on that side of the face.

Putting the card on an angle is necessary, probably in a middle angle between the light and the lens.

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