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set white balance with a grey card?
Hi all
Although I am a beginner, I think I have a basic understanding about the need to have white balance set to suit the prevailing light when taking pics with my 60D. However, i bought a pretty helpful book on the Canon 60D that included a grey card to use to set white balance ??? Yep, a GREY card to set WHITE balance!!! Obviously this must be right, but the book doesn't explain how setting the grey balance is the same as setting the white balance, and I have not (so far) read anything about setting the grey balance in anything I have read. So I am mystified - can anyone explain this? Thanks in advance David |
#2
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set white balance with a grey card?
On 2011-05-11 19:36:03 -0700, David Ross said:
Hi all Although I am a beginner, I think I have a basic understanding about the need to have white balance set to suit the prevailing light when taking pics with my 60D. However, i bought a pretty helpful book on the Canon 60D that included a grey card to use to set white balance ??? Yep, a GREY card to set WHITE balance!!! Obviously this must be right, but the book doesn't explain how setting the grey balance is the same as setting the white balance, and I have not (so far) read anything about setting the grey balance in anything I have read. So I am mystified - can anyone explain this? Thanks in advance David Yes, you use a Grey card to set white balance. You are not setting the "grey balance". Depending on the photo-editing software you are using you should have a custom "white balance" tool, along with the usual list of standard settings. The idea is to have a neutral grey card placed in your scene, under the lighting you will be shooting in. This reference shot can be taken at the beginning of the set on images, or at the end. I use a WhiBal reference card. http://mtapesdesign.com/whibal/ Take a look at their user guide PDF, and video tutorials. http://www.whibalhost.com/_pf_sitefi...rGuide_V10.pdf http://www.whibalhost.com/_Tutorials/WhiBal/01/ -- Regards, Savageduck |
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set white balance with a grey card?
On Thu, 12 May 2011 12:36:03 +1000, David Ross
wrote: Hi all Although I am a beginner, I think I have a basic understanding about the need to have white balance set to suit the prevailing light when taking pics with my 60D. However, i bought a pretty helpful book on the Canon 60D that included a grey card to use to set white balance ??? Yep, a GREY card to set WHITE balance!!! Obviously this must be right, but the book doesn't explain how setting the grey balance is the same as setting the white balance, and I have not (so far) read anything about setting the grey balance in anything I have read. So I am mystified - can anyone explain this? Thanks in advance Yep, in simple terms the camera needs to be told that what it saw was something that reflected Red Green and Blue in equal proportions. It doesn't specifically matter what the colour of that object is though logically it is going to be something grey or off-white. Some whites will reflect blues more strongly causing the white balance to be off. -- AnthonyL |
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set white balance with a grey card?
David Ross wrote:
Yep, a GREY card to set WHITE balance!!! Obviously this must be right, but the book doesn't explain how setting the grey balance is the same as setting the white balance, and I have not (so far) read anything about setting the grey balance in anything I have read. So I am mystified - can anyone explain this? What's the difference between a grey object and a white object? *None!* Same object, but it will show up as grey or white depending on the amount of light and the context. If other objects close to it are illuminated with the same amount of light, it will be grey. But if all nearby objects have 1/64th as much light, the "grey" object will be white. And likewise, if that "grey" object has 1/1000th as much light on it as do nearby objects... you'll see it as black! What is needed to calibrate color balance, which is perhaps incorrectly called "white balance", is an object that reflects red, green and blue equally... and sufficiently to provide an accurate measurement. Generally any object that has a reflectance of more than perhaps 5 to 10 percent (a grey card is 18 percent) will work. And that includes a "white card" with 90 percent reflectivity. -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
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set white balance with a grey card?
On Thu, 12 May 2011 19:30:39 +0200, Alfred Molon
wrote: In article , David Ross says... However, i bought a pretty helpful book on the Canon 60D that included a grey card to use to set white balance ??? I've used grey cards in a number of cases to get accurate colours: http://www.molon.de/suche/?s=grey%20AND%20card I've just started experimenting with the SpyderCube http://spyder.datacolor.com/product-cb-spydercube.php It enables me to make full use of NX2's one-click ability to set black, white and grey points respectively. It's too early for me to have reached any conclusions about it. Regards, Eric Stevens |
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set white balance with a grey card?
7On Thu, 12 May 2011 07:54:16 -0700 (PDT), David Dyer-Bennet
wrote: On Wednesday, May 11, 2011 9:36:03 PM UTC-5, David Ross wrote: Hi all Although I am a beginner, I think I have a basic understanding about the need to have white balance set to suit the prevailing light when taking pics with my 60D. However, i bought a pretty helpful book on the Canon 60D that included a grey card to use to set white balance ??? Yep, a GREY card to set WHITE balance!!! Obviously this must be right, but the book doesn't explain how setting the grey balance is the same as setting the white balance, and I have not (so far) read anything about setting the grey balance in anything I have read. So I am mystified - can anyone explain this? Any "neutral" color card will work; you have to expose it properly. What's needed is an exposure where all three color channels have data -- no channel is "clipped" (off the top or bottom). White balance is all about the relative exposure of the three channels. So, white will work, grey will work. So long as they're precisely neutral tones. Black would work, if the light was bright enough. They all come out grey with suitable exposure. I'm not sure why they prefer grey to white (the choice of card with that book). If you fill the frame with the card, the AE system will expose them all the same, so it doesn't matter. If you put the card as one small item in the frame, though, a white card is more likely to be exposed so at least one channel clips, whereas a grey card is less likely; that could be the reason. Or maybe they want to use the same card for other uses, like local exposure measurements; grey is the standard for that. I use the Tapes Whi-Bal card by setting it in the scene before my series of shots, and then using the card in the image to set my white/neutral/black points in Photoshop. Works a treat. -- Tony Cooper - Orlando, Florida |
#7
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set white balance with a grey card?
AnthonyL wrote:
Some whites will reflect blues more strongly causing the white balance to be off. Often a problem with white paper. Worst are those whiteners (often in cheap paper) that take UV light and return it as blue. Due to the way our eyes work, bluer is often seen as white(r) because a neutral white will be yellowish in comparison. -Wolfgang |
#8
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set white balance with a grey card?
On 2011-05-17 08:54:36 -0700, Wolfgang Weisselberg
said: AnthonyL wrote: Some whites will reflect blues more strongly causing the white balance to be off. Often a problem with white paper. Worst are those whiteners (often in cheap paper) that take UV light and return it as blue. Due to the way our eyes work, bluer is often seen as white(r) because a neutral white will be yellowish in comparison. -Wolfgang Hence the need for a spectrophotometer calibrated, neutral grey card for establishing an accurate WB. ....and not all grey cards are equal. Just because they have told you it is an 18% grey doesn't meant that it actually is. However for the most part any grey card at approximately 18% is going to give you more accurate results than a white target, which as you have stated, can leave you with a color cast. Using a white target for WB can also lead to very blown highlights. A clean white card target is useful for setting a "white" point, not a "white balance." those are two different things. The same goes for setting a "black" point using a "true black" target. -- Regards, Savageduck |
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