[jjbuzard]

I have a Pentax K10D and I am trying to manually adjust the white balance on my copy stand, I am using 4 EIKO 250W 4800 K bulbs. (I have the same results using AQWB)
I have followed the instruction in the book and the test shots of my neutral test card come out gray. if I shoot a page with color, the color is ok, but the white part of the page is gray. What is going on?

[/IMG]

[jimH]

Would exposure be the issue here rather than white balance. The light meter reads white as medium gray 18% gray. Your exposure looks like a 18% grey card. IMO To get white, increase the exposure by several stops. I may be wrong but that's my take on the issue.

[Marc Sabatella]

Jim is not wrong. A piece of white paper is *supposed* to come out gray if the meter is working properly. Completely colorless gray if you've got the WB right (as opposed to an orange-tinted gray as you'd get with utomatic white balance), but gray nonetheless. The proper way to shoot this type of subejct is to first meter of an 18% gray card - available at most photo stores - and use that exposure for your image. Actually, to get the white to be *completely* white, you'd probably need to add another third of a stop or so from there, since meters are typically calibrated to around 13%, not 18%.

[jjbuzard]

OK that makes sense, but if I am shooting on "Auto" and AWB is the setting why can't the camera get a better white by itself, there are 3 - 5000k settings, I assume (hate that word) I am supposed to customize each one for my use, so what am I looking for when I try to set each one? Am I looking for a pure white in the viewer as I set it? All I see are shades of blue, green, etc as I adjust, or am I looking for a match on the gray card?
Thanks for your help!

[jimH]

OK that makes sense, but if I am shooting on "Auto" and AWB is the setting why can't the camera get a better white by itself, there are 3 - 5000k settings, I assume (hate that word) I am supposed to customize each one for my use, so what am I looking for when I try to set each one? Am I looking for a pure white in the viewer as I set it? All I see are shades of blue, green, etc as I adjust, or am I looking for a match on the gray card?
Thanks for your help!

In my experience, no matter which camera you are using, if you meter on white the resulting exposure will be under exposed by about 2 stops or about 18% gray, that's how meters are made.

When metering choose an object to meter on that is more of a neutral shading. This is true especially if you are using a spot metering mode, more so than an average metering of the entire scene.

Just be aware of how the light meter works. So chose the multi zone metering when you are shooting a normal scene on Automatic, in fact if you are using the "green" Auto mode, you will have pretty good luck by setting both the focus point and the metering to the auto or "green" settings also. Good luck!

[SOldBear]

...but if I am shooting on "Auto"

First off, as some posters wrote, this is a metering issue, not white balance.

"Auto" is what the problem is.

The light sensor in the camera measures light reflected from the scene back to the camera (reflective light), not light falling on the scene (incident light). How much light reflected back from an object depends on its reflectivity. The light sensor does not know the object's reflectivity so it assumes the average 18% and set the aperture/shutter speed accordingly.

This is why when taking photos of snow/sand/beach (more "white"), you need to add 1-2 stops (e.g. setting EC) and when taking photos of dark objects, you need to subtract 1-2 tops. The best way is to measure incident light, but this is not always possible.

This is a great reading on metering:

Guide to Good Exposure

Edit to add:

This is one of my posts: White Car with Black Tires

If I set the meter according to metering off the white body, in the photo, the body will come out gray, and the tires will be very very very black (no details). If I set the meter according to metering off the black tire, in the photo, the tire will come out gray, and the body will be washed out.

[jimH]

OK that makes sense, but if I am shooting on "Auto" and AWB is the setting why can't the camera get a better white by itself, there are 3 - 5000k settings, I assume (hate that word) I am supposed to customize each one for my use, so what am I looking for when I try to set each one? Am I looking for a pure white in the viewer as I set it? All I see are shades of blue, green, etc as I adjust, or am I looking for a match on the gray card?
Thanks for your help!

One more thought on the Auto White Balance: The camera has to make a lot of assumptions about the scene and lighting to arrive at a correct white balance. That is why sometimes the white balance is off a bit or a lot. If you are working in difficult lighting conditions, it would be good to carry a gray card with you and take a shot of the gray card under the lighting conditions you are working with and then adjust the white balance manually on the picture of the gray card. Good luck!

[jeffkrol]

I have a Pentax K10D and I am trying to manually adjust the white balance on my copy stand, I am using 4 EIKO 250W 4800 K bulbs. (I have the same results using AQWB)
I have followed the instruction in the book and the test shots of my neutral test card come out gray. if I shoot a page with color, the color is ok, but the white part of the page is gray. What is going on?

[/IMG]

AWB (auto white balance) should be named ANB (auto neutral balance)....
In your sample the white is 132,133,137 R,g,b.... White is up to you and exposure...
MEAN is 119, median 128.... Camera mean is what counts w/ the meter.

[Marc Sabatella]

OK that makes sense, but if I am shooting on "Auto" and AWB is the setting why can't the camera get a better white by itself

Because AWB is not about *exposure*, it is about *color* - or more particularly, *hue*. You might think of gray and white as different *colors", but they are actually the exact same hue; just different *values* (lightness or darkness) of that hue. WB is about hue; exposure is about value. So AWB has done it's job perfectly; you can stop thinking about it all. You need to turn your attention to exposure, and that's what the meter is for - not the WB system.

If the next question is why didn't the meter figure out, the answer is, the meter has no way of knowing the difference between white and gray. A white piece of paper in dim light and a gray piece of paper in brighter light look *exactly* the same. Surprising to us humans, who can tell the difference based on how our wide open our irises are due to ambient light, and indeed, it would be theoretically possible to design a camera meter similarly, but in practice, that's just not how it is historically done. It's been an age-old problem in photography, and the way it was solved the better part of a century ago - by inventing the 18% gray card and calibrating camera meters so they would get the values right if you meter off that - is the ways most professional cameras still work.

[jjbuzard]

Thanks again to everyone that has replied, I have alot of info to digest and I am sure that armed with this info I will solve my copy stand problem, I read the directions that came with my gray card and they said to use the gray card on a light stand, BUT I didn't listen.

So my question now is what am I looking for when I manually adjust the the White Balance. Is it just hit or miss or will I be able to see the change on the screen?

I will report back.

[Rico]

jjbuzard are you shooting some sort of white card to adjust the white balance manually. Proper exposure as mentioned will yield better results. When taking a reading you will see a difference on the screen after the adjustment is ok'd.

[flyer]

To get your exposure right, put your gray card in front of your subject, put your camera on spot meter and manual exposure, and meter off the gray card by pushing the green button. Now, as long as the distance between your subject and light remains fairly constant, you shouldn't have to do anything else to your exposure. If the distance between your subject and the light changes, then you have to do the same thing again. Note that the exposure won't change if you move the camera around, it will change only if the distance between the subject and light(s) changes.

[ma318]

Here is what I would do in your situation (assuming the camera is already on the copy stand)

1) Set the white balance:

- set the camera's WB setting to custom and then set the camera to "P" mode
- aim the camera at the gray card, press the "WB button" and shutter simultaneously


2) Set the exposure:

- put camera in manual mode
- select your aperture
- aim your camera at the gray card and hit the green (or AEL if your camera do not have a green button) button to let the camera set the correct shutter speed

Now you are ready to shoot.

[jimH]

To get your exposure right, put your gray card in front of your subject, put your camera on spot meter and manual exposure, and meter off the gray card by pushing the green button. Now, as long as the distance between your subject and light remains fairly constant, you shouldn't have to do anything else to your exposure. If the distance between your subject and the light changes, then you have to do the same thing again. Note that the exposure won't change if you move the camera around, it will change only if the distance between the subject and light(s) changes.

Well said Yves!

[Wheatfield]

One click.
This is an exposure opportunity.