Got a gray card, now how do I use it correctly?

JayClark79

I know I take a picture of it and save it as a custom white balance.... BUT.
1. Can I use a flash when I take a picture of the white card?
2. Does the white card have to fill the frame, just be in the frame, or just a portion of the frame?

If it has to fill the frame iv noticed its kinda hard for my camera to focus on, if i hold it out far enough for it to focus its not filling the frame?

:dunno

Id like to get the white balance right in camera, so i dont have quite as much post processing.

Scott_Quier

JayClark79 wrote:

I know I take a picture of it and save it as a custom white balance.... BUT.
1. Can I use a flash when I take a picture of the white card?
2. Does the white card have to fill the frame, just be in the frame, or just a portion of the frame?

If it has to fill the frame iv noticed its kinda hard for my camera to focus on, if i hold it out far enough for it to focus its not filling the frame?



Id like to get the white balance right in camera, so i dont have quite as much post processing.

There are at least two ways to use the gray card.

The first is to use it to set a Custom White Balance (CWB). Take a picture of it under the lighting conditions that you will be shooting. This image should fill at least the center circle of your viewfinder. Then travers the menus and use that image to set the CWB. It is not necessary to have a good focus. It can be as blurry as you like, all you are interested in is the color of the gray card.

The second way (and my preference) is to shoot RAW, Auto-White Balance (AWB) and shoot an image of the gray card. The continue the shoot. In post processing, you use the image of your gray card to set the WB of all the images shot under that lighting scenario. Why is this my preference? Because I will be adjusting the WB of the image anyway .... to my eye, the gray card is (almost) never spot on.

HTH

JayClark79

Scott_Quier wrote:

There are at least two ways to use the gray card.

The first is to use it to set a Custom White Balance (CWB). Take a picture of it under the lighting conditions that you will be shooting.

Thanks for the quick reply Scott....

So if im using flash i should use flash to take the test shot of the card correct?

And if i only fill the center circle, i should be spot metering?

Scott_Quier

JayClark79 wrote:

Thanks for the quick reply Scott....

So if im using flash i should use flash to take the test shot of the card correct?

Yes

JayClark79 wrote:

And if i only fill the center circle, i should be spot metering?

Spot/weighted/evaluative metering has nothing to do with it. But, you will get a better CWB if you get a good exposure. Your histogram should show a strong spike in, or just to the right of, the middle of your histogram.

pathfinder

If you are using flash, you will want the grey card to be lit by flash, exactly like the subject you plan to shoot.

If you shoot your grey card at two feet, and your subject at 8 feet, you MAY change the flash to ambient light ratios, and thus change the white balance in your images.

You want to shoot the grey card in the SAME light you plan to shoot the subjects in with the same amount of flash. I use a BalanceSmarter reflector at times because it is a non-specular grey and is approximately 2 feet long on a side so it does not have to be as close as an 8x10 grey card. Some folks just include a small WHiBal card in an image to use later in RAW processing.


If you use a grey card up close, you have to turn off the AF on your lens to allow your camera to fire, and then turn the AF back on. The BalanceSmarter reflector has a thin, white cross on its surface so that I do not have to turn AF off and remember to turn it back on as well. Perfectly color balanced images that are totally out of focus do not command much premium in the marketplace.


As Scott said, it is good to have a resonably correct white balance, but it may not be the white balance you actually decide to use, because yours looks better.

If I shoot a BalanceSmarter reflector in Av mode, I expect to see a perfect single spike dead center in the middle of my histogram with each of the three channels, R,G,B lining up perfectly with each other. I will also see the shutter speed the camera chose to get this exposure, and I will then have the proper exposure - ISO, shutter speed, and aperture - to shoot the camera manually as well. The grey image can then be used to set my camera's custom white balance as long as the light does not change.

If the flash is changing in its relation to ambient light as you shoot, then your WB is varying too.

JayClark79

thanks guys for your help..

i got the studio sized card which is 3.5 x 6... couldnt quite afford the 8x10 right now lol maybe in the future

i think im going to try both ways scott described and see what works better for me

Scott_Quier

JayClark79 wrote:

thanks guys for your help..

i got the studio sized card which is 3.5 x 6... couldnt quite afford the 8x10 right now lol maybe in the future

i think im going to try both ways scott described and see what works better for me

This is ALWAYS the best policy. Just because some says something is so doesn't mean that it's right for you. Take something someone says, take it out for a spin, kick the tires a bit, make sure it's right for you. And, in doing so, you will find that you've learned something as well - how to better shoot the way YOU shoot! Doesn't get any better than that!

JayClark79

Hey Scott I tried your way in Lightroom I just wanna make sure im doing it right...

In Raw... Snap a shot with the grey card in it set on Auto WB.... Then keep it on Auto WB and take more shots until the lighting changes..

Open the first pic in lightroom and use eye dropper or WHITE BALANCE SELECTOR and select the card... Then change the all the other pictures in that series to the same white balance as the one set on the card?

Scott_Quier

JayClark79 wrote:

Hey Scott I tried your way in Lightroom I just wanna make sure im doing it right...

In Raw... Snap a shot with the grey card in it set on Auto WB.... Then keep it on Auto WB and take more shots until the lighting changes..

Open the first pic in lightroom and use eye dropper or WHITE BALANCE SELECTOR and select the card... Then change the all the other pictures in that series to the same white balance as the one set on the card?

When you are shooting RAW, it really doesn't matter where the WB is set, but if you have it on AWB you stand a better chance of having the image in the camera LCD look right. The thing is, the WB setting of the camera does not have any impact on the RAW data written to the file - just to the embedded JPG (the data used to generate the image on the camera LCD).

So, yes, aside from that one small point, you have it just right. Every time the light changes, shoot another gray card and you'll be "cooking with gas!"

TonyCooper

JayClark79 wrote:

I know I take a picture of it and save it as a custom white balance.... BUT.
1. Can I use a flash when I take a picture of the white card?
2. Does the white card have to fill the frame, just be in the frame, or just a portion of the frame?

If it has to fill the frame iv noticed its kinda hard for my camera to focus on, if i hold it out far enough for it to focus its not filling the frame?



Id like to get the white balance right in camera, so i dont have quite as much post processing.

Others know more than I do about this, but I used a gray card this afternoon. My Nikon's shutter won't fire if the AF can't focus, so I understand your question here. Focus on the edge of the card by depressing the shutter half-way and holding it, then move the camera so the card fills the image. Then the shutter will trip.

Scott_Quier

TonyCooper wrote:

Others know more than I do about this, but I used a gray card this afternoon. My Nikon's shutter won't fire if the AF can't focus, so I understand your question here. Focus on the edge of the card by depressing the shutter half-way and holding it, then move the camera so the card fills the image. Then the shutter will trip.

For many cameras, this is the default configuration but many/most (all) have a menu option that allows one to trip the shutter whether the camera has acquired a focus lock or not.

I can definitely see where the tip Tony offers would work quit well if the camera doesn't see enough contrast to get a focus lock. Good tip!

DeVerm

I think flipping it to manual focus lets you shoot no matter what the focus is...

ciao!
Nick.

TonyCooper

Scott_Quier wrote:

For many cameras, this is the default configuration but many/most (all) have a menu option that allows one to trip the shutter whether the camera has acquired a focus lock or not.

I can definitely see where the tip Tony offers would work quit well if the camera doesn't see enough contrast to get a focus lock. Good tip!

It's a cat thing. Ways to skin one, that is. Going to a menu option, or going to manual focus, or - probably - several other solutions are available. Focussing on the edge with the shutter half-depressed and then moving the camera slightly just seems like a simple and fast solution.

Since I shoot RAW, and use CS4, I don't use the gray card very often. I just happen to be shooting a series of close-ups of the back and front of some objects on a background, and I wanted to minimize post adjustments and keep the background the same.

DeVerm

I have a question about this: why is it that instead of the gray card you can also use a white card and follow the same procedure in Lightroom?

I noticed that in Photoshop you have three thingies for each of black, gray and white, but in Lightroom there's just one... ?!

thanks,
Nick.

Scott_Quier

DeVerm wrote:

I have a question about this: why is it that instead of the gray card you can also use a white card and follow the same procedure in Lightroom?

I noticed that in Photoshop you have three thingies for each of black, gray and white, but in Lightroom there's just one... ?!

thanks,
Nick.

"Gray Card" is just the name for the tool, maybe because it used to be that such cards were only white. A more useful tool is one that contains a good black, a good gray, and a good white.

Why does white also work for setting the WB? Because white is also a neutral, all three channels (RGB) being present to the same extent.

DeVerm

Scott_Quier wrote:

"Gray Card" is just the name for the tool, maybe because it used to be that such cards were only white. A more useful tool is one that contains a good black, a good gray, and a good white.

Why does white also work for setting the WB? Because white is also a neutral, all three channels (RGB) being present to the same extent.

hmmm... still not clear... if it just has to be neutral, instead of understanding it, I can only come up with two more questions:

- if you have 256 levels per channel, you can create 256 different colors that are all neutral, i.e. all three channels present to the same extent... so any of those can be used then, incl black? If so, I can understand how the software uses that for the "relative" levels but there's still question no.2:

- I was under the impression that with the Lightroom white balance tool, I can click on something that is supposed to be white and it becomes white. If I click on a very light pink, it becomes white. I click on a gray, it becomes...?? I click on black??? I know I can just try that out but I like to understand this, not just be able to use it correctly ;-)

I think there are many out here that don't really understand this ;-)

thanks,
Nick.

Scott_Quier

DeVerm wrote:

hmmm... still not clear... if it just has to be neutral, instead of understanding it, I can only come up with two more questions:

- if you have 256 levels per channel, you can create 256 different colors that are all neutral, i.e. all three channels present to the same extent... so any of those can be used then, incl black? If so, I can understand how the software uses that for the "relative" levels but there's still question no.2:

- I was under the impression that with the Lightroom white balance tool, I can click on something that is supposed to be white and it becomes white. If I click on a very light pink, it becomes white. I click on a gray, it becomes...?? I click on black??? I know I can just try that out but I like to understand this, not just be able to use it correctly ;-)

I think there are many out here that don't really understand this ;-)

thanks,
Nick.

Q1 - The brighter the object, the better job will be done of generating the WB for the image and for the same reason that there is 1/2 your image data in the first stop of your histogram (thus the reason for exposing to the right). The brighter the color used to generate the image CWB, the more data to be used to generate that CWB and the more accurate it will be.

Q2 - When you use the WB tool in LR and click on anything, that color is changed to be neutral. Being pedantic about it, when you click on something that is supposed to be white, it becomes neutral ... it might become gray or it might become black; that's controlled by the exposure (how brightly rendered that object is). Pink will become the new neutral. What shade of neutral (how dark/light it is) then becomes a function of the brightness of that starting color.

So, if you click on something that should be white and it turns gray, the next step would be to either push the exposure or the brightness of the image to bring that gray up to the "whiteness" that you are looking for.l

pathfinder

Actually, the best target to use is a non-specular white - specifically the 2nd lightest white chip in a MacBeth Checker target or similar target. You want to avoid using a specular reflection, a mirror surface.

Here is a frame of a few of the color checking tools I used in discussing in camera custom white balancing tools The color checker is an Xrite color checker is this image.



Andrew Rodney says it is better to avoid the standard Kodak grey card for a white balance tool as it MAY not alway be a perfect neutral tone - it was never promoted for white balance, but for an exposure tool to measure with a reflected light meter.

Some camera instructions suggest using a known white target, some a neutral tone. In the picture above is a small bracelet device with a round circle of pure white titianium dioxide. It works well also.

I should also mention that this image is a SOOC jpg with a custom white balance from a SpectraSnap filter on a cloudy grey overcast day. Notice how well the grey scale is captured. I MIGHT have gotten away with 1/3 stop more exposure.

Notice the card with the white, grey and black sections and what their pixels read in Photoshop. Not really that black and not really that white. That is why I tend to prefer a color checker or a very white bracelet target if they are to be used for color correction after shooting in Adobe Raw converter.

DeVerm

just when you think you start to understand... ;-)))

I do understand that when you have a card that is known to be say 222,222,224 you can shoot it and adjust WB, exposure and brightness until you match it.

I also understand Scott about using the auto-WB tool in Lightroom and adjusting expose/brightness after that to match it with how it should look.

My problem is that I have read two explanations of Lightroom and both tell you to use that gray card and that you can substitute it with a white card but they make it appear that no further adjustments are needed while in fact you do need to adjust exposure/brightness after that.

I'm gonna read and test more ;-)

thanks,
Nick.

Scott_Quier

DeVerm wrote:

just when you think you start to understand... ;-)))

I do understand that when you have a card that is known to be say 222,222,224 you can shoot it and adjust WB, exposure and brightness until you match it.

I also understand Scott about using the auto-WB tool in Lightroom and adjusting expose/brightness after that to match it with how it should look.

My problem is that I have read two explanations of Lightroom and both tell you to use that gray card and that you can substitute it with a white card but they make it appear that no further adjustments are needed while in fact you do need to adjust exposure/brightness after that.

I'm gonna read and test more ;-)

thanks,
Nick.

And that's the way to do it. Trust and Verify

If you are using a true neutral in LR to set the WB, then it is true that you don't need to do anything further to set a good WB. But ... it's a big one ... getting a true neutral is very difficult and once you do, you may not like the results for any number of reasons. One reason might be that it changes the WB such that the image doesn't "correctly" reflect the scene as you saw it when you shot it. Or, like some, you like a slightly warm image. Or you like a slightly cooler image. Here's the deal, The LR WB tool will, when you click on a decent neutral, give you a good starting point.

ziggy53

If you have nothing better to use you can also photograph your own palm and use that for determining "color balance". If you know the color tones of your palm during controlled lighting, you can use that to determine a good starting point for balancing the photographs in an unknown lighting environment. As long as you shoot RAW format you can correct after the fact in your RAW converter and image editor/processor software.

Eddy

MAN ..luv this question ..thanks to Scott Pathfinder and ziggy..nice understanding of WB really appreciatethe time you all took to feed us some good info while learning this great hobby
eddy

limited60

I honestly don't know a lot on this subject (photography, I mean)....but maybe someone can correct me, or make sense of what i say:

Doesn't a "white" card turn up gray when photographed close up ....same with a black card? They all come out gray?

I thought the goal of the in-camera image processors was to average all the visual information to come up with an image that is ~18% gray--the same color a gray card typically would be.

Does this come in to play here at all?

pathfinder

You are correct, the sensor in your camera does not know what color is in front of it.

Neither does the light meter in your camera. Your reflected light meter, built into your camera, WILL expose a white page or a black page to both look like a medium 18% grey IF you allow it to, because it will not alter exposure based on the known difference in reflectance of black and white.

However, if you use a hand held incident light meter, it will give the correct exposure for both the black and the white page and render them correctly. An incident light meter measures the light falling on the subject, not the light reflected from the subject, and hence gives more accurate exposure settings. Not as convenient as the light meter in your camera, but more accurate.

That is one of the points I was making in my comments about shooting a 32 step gray scale and capturing the entire scale with one exposure without blown highlights or shadows, when shooting jpgs. To do this, requires very accurate exposure, within 1/3 stop or so.

DeVerm

Hmmm.... so how does it change things now that the Canon 7D has a metering system that does "see color"?

cheers,
Nick.

pathfinder

It doesn't change anything. The only mention of color and the light meter I can find is Canon's new "Focus Color Luminance" metering system, that measures focus, color, and luminance across 63 zones . This is taken from the review of the 7D on dpreview.com


Reflected light meters ( all of them ) are fooled because they are built around the concept that all subjects can be represented accurately by a 16% grey card. But white paper will reflect at least 4 fstops more light than black paper - so how can a meter that measures reflected light know the proper exposure. In short, it can't. That is why almost all cameras all have Exposure Compensation built into them. I note that the designer's of the 7D still included Exposure Compensation dials in the 7D, so the meter must not be absolutely correct all the time.

Whereas an incident light meter does not care whether the subject is a white cat in a snow storm or a black labrador in a coal mine, as it measures the light intensity FALLING ON the subject. The reflectivity of the subject is no longer significant to the meter.

I am not critical of the 7D, I bought one for my wife for Christmas, and I think it is an excellent camera. But its light meter will need to be used with understanding, just like all reflected light meter have to be, whether used in spot metering, central metering, matrix metering, backlit metering, or any of the other techniques manufacturers have tried to create to deal with the fundamental truth of reflective light metering - not all subjects are an 18% grey equivalent.

Try using the meter in your camera to shoot a sunlit subject in a snow field - it will almost certainly under expose your image, unless you add + exposure compensation. It will want to render the snow grey. I predict the 7D will do the same thing.

SittingElf

I have the Photovision Calibration Target system and it works better than anything I've used before primarily because it can be used pre or post processing and includes all three colors for precision... black, 18% grey, and white.
Different sizes available and includes an awesome DVD that clearly demonstrates how to obtain almost perfect WB and exposure using the system...every time!
Pricey, but well worth it IMHO. (current sale on their website until April..)

http://www.photovisionvideo.com/store/CTGY/DCT/

DeVerm

pathfinder wrote:

It doesn't change anything. The only mention of color and the light meter I can find is Canon's new "Focus Color Luminance" metering system, that measures focus, color, and luminance across 63 zones .

I got my info from a book. The 7D AF and metering are completely integrated and even got a new name: Intelligent Focus Color Luminosity metering (IFCL). I think it's the first camera that does the metering in color instead of monochrome.
That doesn't mean it works better of course but I think it's something overlooked with all that HD video and stuff.

Up til now, the only photo's I shot with the 7D that weren't metered correctly had much more wrong with them. I have this camera almost 3 months now and will soon be ready to read that book again. I keep discovering features by accident ;-)

cheers,
Nick.

JohnBiggs

Draw an X in the center of your grey card with a sharpie. Focus problem solved.

I use http://www.bhphotovideo.com/c/product/330874-REG/Lastolite_LL_LR1250_EZ_Balance_Grey_.html for my grey card.

pathfinder

That Lastolite screen was also sold as the BalanceSmarter and I agree, I find it quite effective, fast because you don't have to disarm AF and remember to turn AF back on, and very accurate. It works well in Photoshop for a know neutral as well.