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Grey card / calibrating a camera


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Grey card / calibrating a camera
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chucker
 
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2007-03-19, 01:12

In fixing someone else's images, the main part of which being making the white balance remotely humane (awful, awful camera output ), I've been reading up on white balance, and now I'm curious: what, if any, non-SLR digital cameras allow you to calibrate the white balance using a grey card (or a random grey or white sheet of paper)? Is this a standard feature these days that most people just never discover, or is this typically only found on SLRs?
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TMT
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2007-03-19, 02:56

At least you can always choose between daylight and tungsten presets, which is good enough in most cases, or set it to automatic, where the camera searches for the brightest parts in the image, assuming them to be white and adjusting the images automatically (with terrible results sometimes).
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chucker
 
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2007-03-19, 02:58

Quote:
Originally Posted by TMT View Post
At least you can always choose between daylight and tungsten presets, which is good enough in most cases, or set it to automatic, where the camera searches for the brightest parts in the image, assuming them to be white and adjusting the images automatically (with terrible results sometimes).
Yep, I'm aware of presets and automatic white balance… I was just wondering if something mid-end (e.g., PowerShot S3 IS, or DMC-FZ8) likely has a way to manually define a white balance these days.
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ast3r3x
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2007-03-19, 06:33

I haven't heard/don't know much about the adjustments on cameras, but adjusting it on the final image isn't too hard when you have a known white, black, and grey. I do believe that yo have to adjust it for every location though, you can't just adjust it once and be like "well my white balance is set."

I don't get why you'd adjust the white point unless it was consistently off by a lot. If you're serious about color you can always tweak it later in photoshop to make it perfect. Especially if you're willing to use a grey card, it makes it a lot easier to correct later.
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chucker
 
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2007-03-19, 07:27

Quote:
Originally Posted by ast3r3x View Post
I haven't heard/don't know much about the adjustments on cameras, but adjusting it on the final image isn't too hard when you have a known white, black, and grey. I do believe that yo have to adjust it for every location though, you can't just adjust it once and be like "well my white balance is set."
Yep, that's very easy to do, but my fear is that cameras throw a lot of image data away based on their white balance assumption.

This all came to me when I analyzed a bunch of images from a friend which all suffered one and the same horribly, horribly low color temperature. Using the white from a woman's blouse in one of the shots helped me get a much more accurate white; applying this same setting to all images helped tremendously. However, the images still felt like they were lacking large parts of the color spectrum: I had merely shifted what parts were covered (to more accurate averages), not enhanced them.

Maybe this wouldn't be as much of an issue when the camera supports RAW, but I'll frequently be getting stuff from people who certainly won't want to support a camera that even supports TIFF (let alone bother with setting the camera up properly before shooting).
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trevo
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2007-03-19, 07:44

Hi chucker, most cameras these days have manual presets for white balance. My camera phone has white balance presets! While semi-professional DSLRS have presets and the option to manually select your kelvin temperature for the perfect white balance.

A grey card is used to get the correct exposure. Not commonly used for white balance.

A grey card is what the world would look like if you took all the colours in the world and supposedly put them into a blender, the result is 18% grey. All camera's light meters are 'set' to 18% grey.

When a camera's shutter release (that button that takes the photo) is half-pressed the camera's light meter reads the scene your about to take a photo of. If you were taking a photo of snow which is obviously lighter than grey your metered exposure would be under-exposed (it's taking the white light of snow and making it 18% grey). In this situation you would purposely over-expose unless you want your snow looking dirty.

Vice versa with scenes at night. Sounds kind of funny, under-expose (make darker) for night time shots where it's already dark and over-expose (make lighter) for things like snow which are already bright.

A lot of cameras now have smart light meters that guess that your shooting at night time and of course exposure settings for snow, fireworks, night time, etc. AND wb presets like flash, tungsten, fluorescent.

Hope the layman terms were okay

edit: In the days of film, you would use a grey card for exposure and filters for colour balance

tungsten is an orange/red tinge so you would put on a blue filter to bring the temperture back down to normal

Last edited by trevo : 2007-03-19 at 08:38.
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julesstoop
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2007-03-19, 07:45

My Olympus SP 510UZ does have a manual white balance 'recording' option.
We own a cheap DV-camera as well, which also has this feature.
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trevo
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2007-03-19, 07:53

Quote:
Originally Posted by chucker View Post
Maybe this wouldn't be as much of an issue when the camera supports RAW, but I'll frequently be getting stuff from people who certainly won't want to support a camera that even supports TIFF (let alone bother with setting the camera up properly before shooting).
I don't quite understand what your saying here. You could shoot with tiffs and not waste any time editing the good ones AND HAVE THE OPTION!!!! to fix up the bad ones that you can't bring your self to throw away.
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chucker
 
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2007-03-19, 08:19

Quote:
Originally Posted by trevo View Post
Hi chucker, most cameras these days have manual presets for white balance.
I'm aware

I'm more asking how commonly today's consumer cameras have the ability to select a specific point in an image for white balance calibration.

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A grey card is used to get the correct exposure. Not used for white balance.
From what I read, with digital photography, grey card are frequently used for both exposure and white balance.

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Hope the layman terms were okay
I think "that button that takes the photo" was pushing it. In any case, your knowledge seems focused on analog photography, which is of little concern to me. I appreciate the explanations, but as some quick queries on the web will confirm to you, grey cards are indeed frequently used these days for white balance.
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trevo
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2007-03-19, 08:22

edit: I've just thought about it and that makes perfect sense. Using a grey card for WB has never popped up at school or work and I don't know anyone that uses a card for this purpose, not that I think it's a bad idea. Back to your question, I only know that some of the higher-end cameras do offer a manual define option for WB

atm I am only shooting digital with a D200. I was trying to make a point with the analog part

edit: damm chucker your so fast at replying when i'm refining my post

Last edited by trevo : 2007-03-19 at 08:36.
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chucker
 
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2007-03-19, 08:30

If you insist.

http://www.rawworkflow.com/products/whibal/index.html
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Having a "GrayCard" reference is the best assurance that the digital pictures that you capture will have the ability to be properly White Balanced.
http://www.cambridgeincolour.com/tut...te-balance.htm
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(Custom white balance uses an 18% gray card as a neutral reference.)
http://www.stevesforums.com/forums/v...264&forum_id=9
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I am getting annoyed with carrying a small piece of white paper to do my white balance with. Can anyone recommend a good gray card and maybe a place to buy it online?
http://www.the-digital-picture.com/R...rd-Review.aspx
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I find my white balance results to be excellent when using the Gray Card.
http://www.photoxels.com/tutorial_white-balance.html
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By pointing the camera at a white or gray card (angled so that it is reflecting light from the room) as a neutral reference, filling the screen completely with it, then pressing the White Balance button (or set it in the menu), the camera does its WB calculation.
http://www.outbackphoto.com/workflow/wf_65/essay.html
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To finish, we just need to move the Levels adjustment layer that contains the correct color balance over to the image without the gray card.
And so on.
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TMT
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2007-03-19, 15:35

I don't have my canon ixus here at the moment, but my girlfriend's leica d-lux has the option; you can save even two manual values.
I think it is quite common, but often hidden in the menu, and most people with smaller consumer cameras anyway tend to take more snapshot-like photos, and leave the settings most of the time in automatic mode.
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turtle
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2007-03-19, 16:03

chucker, to answer you first question, my wife's Canon A620 has custom WB setting as an option to you. I'm not sure where on the scale it fits, but not bad for a point and shoot.

Also, you are right about Grey Cards being widely used now in digital photography to correct WB errors. I've been through a good portion of class about how it will simplify the life if you shoot in RAW/TIFF. However, with something like custom WB on the Canon point and shoot you would have to wait until post production to correct the WB.

As odd as this is, I've never learned about using a Grey Card for proper exposure. I understand it's where the idea came from, but it isn't taught in digital classes anymore.

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