I'm a bit fuzzy headed about gray cards.

I had overexposed an image and someone suggested I use a gray card to meter the light for proper exposure. I searched what a gray card is and didn't quite get the point. An article said that the gray card is used to set your 'custom' white balance in a certain type of light, but, if you're shooting RAW you can just click something white in the image and set it that way, or scroll the image temp til it's proper. So i'm missing something because these little colored cards are specially made and essential for photographers evidently.

So I watched this video, still no answer. http://www.prophotolif​e.com …ra-meters-and-histograms/

Then I read this article. still no answer http://www.the-digital-picture.com/Reviews/Gr​ay-Card-Review.aspx

Am i not comprehending something?

There's a lanyard with Black/Gray/White cards on bhphoto for $30. I'd like to know if they're necessary before I spend that type of money. All i'm trying to do is get proper/perfect exposure.

Thanks!

You're confused because the article is poorly written. And because the grey card can be used for two things - determining exposure and determining correct color (white) balance.

To determine the WB you take a shot of a gray card that you can buy for $30 or a piece of free white or gray paper, like a business card and use it for the camera to determine custom WB right then or adjust your shots to this white/gray in post-processing for correct WB.

To determine exposure you meter the light off this card, put it in same light as subject, point the camera and lock exposure or set it manually. It works because the camera expects to see the majority of what you're photographing to be gray, and it exposes to see that 18% gray. So if you take a picture of snow and the camera meters snow, it'll make it gray. Same with black, it'll make it dark grey.
So you can use a $30 gray card for that or make one yourself and use it for an important photoshoot, alternatively you can just work with your camera and dial in positive exposure compensation for overly white scenes and negative for black ones, check histogram and picture on viewfinder, adjust, rinse, repeat

For exposure, I use this as a starting point almost all the time: Need an exposure crutch?

Somewhere back in time, Kodak engineers determined that the median brightness of a scene was 18% gray (according to lore...another story says 12% but Ansel Adams convinced them to use 18% gray because his Zone System; but let's not bother with this detail, to keep the story simple). And thus the 18% gray card was born. Thus, if your scene was 'average', the 18% card would represent an integration of the various brightness levels, and your reflected light meter conveniently uses that gray level for its own 'proper exposure' calibration. So the 18% gray card very conveniently is a surrogate to use instead of reading a white bridal gown or a black tux, and then having to use some Exposure Compensation.

There are 'gray cards' on the market which are NOT 18% gray, and are intended for use ONLY for providing a neutral (equal values of R-G-B) gray for White Balance. These should not be used for Exposure metering unless you first know precisely their deviation from 18% tonality!

There are 18% gray cards on the market which are both neutral in color and also are proper tonality for metering purposes. PhotoVision targets, Douglas Grey Card, and Kodak Gray Card are examples of this.

Often times, you simply do not have a proper 18% gray card, and using techniques like PhotosGuy's post is a good surrogate. After all, you always have the palm of your hand, and it generally never tans to change tonality. Again, popular lore says the palm is +1EV above 18% gray, but many of us have spotmetered our palms and compared to gray cards, and discovered that the actual difference is +1.3EV or some other value, so you should keep in mind that if you meter your own palm, but then decide to have the bride hold up her own it can end up some other value which is fractionally different from your own -- but at least you are 'in the ballpark'

That's all wonderful information, thanks everyone. I have not had the time to try it yet.

I ran into a photographer at work (I work at a hotel) and asked him for his take on the gray card. He said to take a photograph of a white paper (while the exposure needle is at 0) set that as custom white balance and your done. Take photos while the needle is at 0 and your exposure should be proper. Make sense to any of you? It's surely not as in depth/advanced.

TomCross13 wrote in post #12320297
That's all wonderful information, thanks everyone. I have not had the time to try it yet.

I ran into a photographer at work (I work at a hotel) and asked him for his take on the gray card. He said to take a photograph of a white paper (while the exposure needle is at 0) set that as custom white balance and your done. Take photos while the needle is at 0 and your exposure should be proper. Make sense to any of you? It's surely not as in depth/advanced.

I have done testing with randomly chosen white printer paper, and I have found that using the wrong white paper can throw off your White Balance setting by 600K. This is because paper manufacturers can often coat the paper with optical brighteners in order to make a 'whiter' looking brighter paper.

White glossy photo paper from Kodak is quite neutral, but you may have to be careful about the glossy surface

I used a piece of old white poster board to set my custom white balance under white flourescent lighting at 0EV. Took a photo again of the white poster board and it still came out as gray, i ignored it. I partial metered my hand and the needle went to +1EV. As the article said it would.

Put a model car on the white posterboard with a black velvet backdrop at 0EV, this is what I came up with. This is the first photo I ever took that didn't need major adjustments in PP, how's it look to you guys?

After photographing the model car, I put my 70-200L on the table, the EV didn't change and I didn't need to adjust shutter speed or aperture, I put my black flip flop on the table and didn't need to make any adjustments, it was as if the EV was set to where it needed to be for any color object, Is that correct?

http://tomcrossshots.s​mugmug.com …LHj/0/X3/i-pDbDLHj-X3.jpg

Ok, that worked well. The WB is good. Slightly bluish, but it's very slight and most people wouldn't see it.

I understand from this that in M you metered off your hand and set the camera so the needle was on +1. That was good, but, as Wilt noted in his post, the +1 is a rough guide, and I think you will need to make it +1.5. I say that because you wrote that the board is white, but in the photo it is grey, about 1 stop below white. However, the subject you chose was a very difficult one because the reflections on the fender and the door frame are even brighter than the white board (they are what is known as "spectral reflections") and are already blown out entirely. Giving an additional 0.5 stop of exposure would have increased the size of the blown out area. This is a constant problem with metallic subjects and the best solution is more diffuse lighting.

Now I'm "a bit fuzzy" about what you did.

If you mean that you metered a light object and then a dark object and there was no change in the position of the "needle", then something is seriously wrong. If, OTOH, you mean that once you have set the exposure in Manual by using your hand then you don't have to change that setting as long as the light doesn't change, no matter what the color of the subject is, then yes, that is correct.

Ill do it again, bear with me, almost there.

Its my night time now, good night

I've been making a couple of mistakes. First, while setting custom white balance shooting a white card I didn't have my meter at 0ev so my initial image was either over or underexposed to begin with. So my custom white balance was off as well. Second, I was over exposing to bring out the shapes in the shadow areas of subjects, rather than just saying there's no light - let the shadow be a shadow.

Last night I went to the park and got a photo of a heron

Byte size: ZERO | Content warning: NOT AN IMAGE

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

TomCross13 wrote in post #12328846
I've been making a couple of mistakes. First, while setting custom white balance shooting a white card I didn't have my meter at 0ev so my initial image was either over or underexposed to begin with. So my custom white balance was off as well. Second, I was over exposing to bring out the shapes in the shadow areas of subjects, rather than just saying there's no light - let the shadow be a shadow.

That shouldn't have been a serious mistake unless it it was very far off. The instruction to set the needle to 0 is to prevent adding so much EC that the image is overexposed to clipping. And in a very underexposed image the low signal/ noise ratio could affect the calculation of the CWB.

I hate to beat a dead horse. I understand setting white balance using white card & gray card now. However, there's an added bonus. Is the camera seeing the 18% gray accurately- now comes white balance correction. Anyone care to explain? My feelings won't be hurt if not but there doesn't seem to be any good youtube videos.

Are you asking about using the gray card to set the white balance? It's pretty simple -- if the card is actually a neutral gray then in the lighting that you are shooting you can take a shot that centers on the card, tell your camera to use it as a WB target (your manual will have specific instructions) and then set your camera to use a Custom White Balance. Or, if shooting Raw, you can put the camera settings off till post processing -- shoot the gray card and then in PP use the WB eyedropper to select the card which will set the WB then you just apply that setting to all the images that were shot in the same lighting.

Both ways work, although it can be helpful to get the camera properly set to start with.