white balance

[dioptic]

Hello,

This is my first post to the forum---I hope I do it correctly.

I'm lucky enough to have a 20D and recently took some pics in a room with flourescent lighting. The camera was set to "AWB" which I thought would adjust for the lighting but didn't work so well. Any tips or advice for next time?

Thanks.

dioptic

[intechpcx]

I have become a recent proponent of using the custom white balance whenever possible. I was playing around with it after reading some of the hockey threads the other night and was shooting indoor shots. Without the flash and using AWB or the Incadescent light setting, the pictures came out with the typical yellow tint. However, after setting the custom white balance using a white wall as the reference, the color came out considerably better. If you'd like, I can post 3 pictures showing all three modes and the color differences.

[robertwgross]

I leave my camera set to AWB a lot, but I find that it will miss the white balance quite a bit in a fluorescent-lit scene. If I set it to fluorescent white balance, then it will get it right, or if I set it to custom white balance, it will get it right. I find dim fluorescent lighting to be the hardest, partly because the spectrum is screwed up narrowly with cheap fluorescent tubes. There are newer fluorescent tubes that have a much broader spectrum and are somewhat closer to daylight.

The other light that is difficult would be Mercury Vapor. Sodium Vapor is bad also, but they are not so common anymore.

---Bob Gross---

[dioptic]

intechpcx,


Thanks for the information. Yes, it would be great to see the three photos.

Thanks.

dioptic

[Cadwell]

Custom white balance is invaluable when shooting indoors in available light. If you don't want to do custom white balance, then shoot in RAW and be sure to photograph at least one frame with something white in it under those lighting conditions. You can white balance correct this shot using the white object as a reference and then clone the condtions to the other shots in post processing.

[scottbergerphoto]

If you are shooting Raw, use the eye dropper in ACR to click on an area of white that still has detail (not neutral grey). You can fine tune that selection using the Temperature (blue - orange) and Tint (green-magenta) sliders.
If you aren't shooting Raw, open up the image in PS, and create a Levels Adjustment Layer. Click on the middle eye dropper to select the Gamma and click on a neutral grey tone.
Scott

[intechpcx]

Here are three shots I took on lunch today. They were all taken with the same exposure settings changing only the White balance settings. I used a closer picture of the whiteboard that you see in the shots to set the white balance for the custom WB.

This was with the White Balance set on AWB:
http://www.themillersweb.com/AWB.JPG

This was with the White Balance set for florescent light:
http://www.themillersweb.com/Florescent_WB.JPG

This was after I set the Custom white balance:
http://www.themillersweb.com/Custom_WB.JPG

[dioptic]

intechpcx,

I see. Thanks for the information. You don't have to spend all day in that little cubby-hole of an office, do you?

dioptic

[Jon]

Fluorescent's miserable to balance for. There are a number of different types of fluorescent lights (cool white, warm white, daylight, . . .), but they all rely on excitation of an electroluminescent compound, so they all exhibit, to varying degrees, a discontinuous spectrum (not all wavelengths will be there, unlike light from an incandescent bulb). Because of this, custom white balance is your best bet. If that's really not possible, try the fluorescent WB setting.

[intechpcx]

intechpcx,

I see. Thanks for the information. You don't have to spend all day in that little cubby-hole of an office, do you?

dioptic

Yes unfortunately that is my little 8'x10' hole in the world that I get to work from every day. Why do you think I got into photography. I need something to keep me in touch with the real world. :lol:

[Hydro]

Going out today to try some basketball shots for the first time. I got a gray card (actually a pop-open fabric with white on one side and gray on the other) but would like some input on how to set up correctly at the gym. Should I take the CWB photo shooting down on it, or should it be facing the lighting from the floor, or what? Does it matter?

Any thoughts greatly appreciated.

[dhbailey]

You want to hold the gray/white card so that it will be illuminated in the same manner as the subjects you want to shoot. Hold it in front of the camera, turn off autofocus, with the card turned upward if the light will primarily be coming down from the ceiling. Then take the picture and follow the procedure for setting custom white balance, then take a test shot and see how it turns out. Don't show up one minute before the game begins and attempt to get good results -- show up early enough so that you can set the custom white balance and take some test shots AND get yourself situated in a good position so that your camera won't interfere with the other spectators and will still allow you to get great shots.

Oh, yes, be sure you either have a trusted friend sit right in front of you to ward off errant passes or sit far enough back that you'll have time to react and protect yourself and your camera.

[Theaterbuff]

What setting on the AUTOWB would one use on the 20D, for sunsets or sunrises??

(I prefer to use the AUTOWB settings whenever possible)

[robertwgross]

For sunrises, I tend to stick my camera on the Daylight setting. Then the unusual colors of sunrise will show up more. Sort of like a poor man's Velvia.

---Bob Gross---

[dioptic]

These are all good tips. I'm having trouble following the directions in the manual. Would anyone be good enough to spell it out for me? Don't be afraid to treat me like a third grader.


Thanks.

dioptic

[intechpcx]

These are all good tips. I'm having trouble following the directions in the manual. Would anyone be good enough to spell it out for me? Don't be afraid to treat me like a third grader.


Thanks.

dioptic

Well I can tell you how it's done on the 300D, I'm not sure how similar it is to the 20D. On the Rebel you first take a picture on AWB in the lighting you'll be working in that has a pure white covering as much of the center as possible. Then in the menu you select custom white balance and choose the picture you just took. It will load the settings from that picture using the white in the middle as its reference. Exit the menu and switch from AWB to the Custom WB setting and you're all set.

See if that matches up pretty closely with what your manual says. Like I stated, I have a 300D so the process on the 20D may be different.

[aam1234]

Well I can tell you how it's done on the 300D, I'm not sure how similar it is to the 20D. On the Rebel you first take a picture on AWB in the lighting you'll be working in that has a pure white covering as much of the center as possible. Then in the menu you select custom white balance and choose the picture you just took. It will load the settings from that picture using the white in the middle as its reference. Exit the menu and switch from AWB to the Custom WB setting and you're all set.

See if that matches up pretty closely with what your manual says. Like I stated, I have a 300D so the process on the 20D may be different.

I read somewhere that the procedure in the 20D manual is wrong and the above is the correct way. The difference is the starting point. In 20D manual it says to start by choosing CWB then follow the steps (taking the pic, etc...), but the correct method is to start by taking the pic in AWB then switch to CWB. I hope this information is correct, has anybody heard of something similar.

[Jon]

I read somewhere that the procedure in the 20D manual is wrong and the above is the correct way. The difference is the starting point. In 20D manual it says to start by choosing CWB then follow the steps (taking the pic, etc...), but the correct method is to start by taking the pic in AWB then switch to CWB. I hope this information is correct, has anybody heard of something similar.

It doesn't matter what setting you use; the conditions under which it was taken are recorded in the image data and can be used to adjust to achieve a good colour balance. THe D60 manual notes that default CWB is sunlight, and doesn't tell you to use any particular mode. I'd halfway expect that using AWB might be more problematic than the others, however. Just a nagging uncertainty that the exact corrections applied to any JPG may not be fully-recorded, not from any definite knowledge.

[Marvinspu36]

I just took some pictures this weekend in my church. We have 1000 watt theatrical lights which light up the stage. I shot the pictures from about 70 feet from the stage using my 20D and 580EX flash. I took one picture using AWB. Then I went up on the stage, put my white card on a music stand, and took a photo of the white card using AWB. Then I selected Custom White Balance from the menu, pressed the set button, and selected CWB as my white balance mode. The difference between the AWB photo and the CWB photo were significant. The AWB photo was darker and very yellow (our theatrical lights have a pinkish gel), while the colors on the CWB photo were very true and vibrant.

So, it appears that you can take a picture of the white card using AWB. I haven't tried the same thing using a gray card. That is next.

I would highly recommend purchasing a white and gray card. They aren't that expensive, and will give you consistant results. Also, you can use the gray card to set exposure compensation. Take a picture of the gray card and there should be a stong line in the middle of your histogram if the picture is exposed properly.

[robertwgross]

I think you will find it difficult to set an accurate custom white balance in a situation like this with theatre lights and a 580EX strobe flash. The reason should be clear. When you are back seventy feet, the theatre lighting will dominate the exposure. When you are up close to the card on the stage, then your strobe flash will dominate the exposure. Your custom white balance is likely to be right for one but not right for the other.

If the strobe flash is going to dominate, then you ought to set for Flash white balance. If the theatre light is going to dominate, then you ought to set up a custom white balance.

---Bob Gross---

[glangston]

ExpoDisc is a product I recently came across. It works as a lens cap to. Pretty much whereever you are you just take the lens off AF and shoot with this white disc on the camera. Then you go to Custom White Balance and select this gray frame you've just produced. It works with flash too.

The drawbacks are it is $80-120 as it comes in several sizes.

http://www.expodisc.com/

Custom white balance improved my photos a lot over AWB.

[dioptic]

Gee, thanks for all the thoughful replies. Taking good pictures can be complicated!

dioptic

[dioptic]

The owner's manual (page 51) that comes with the 20D is wrong regarding Custom White balance.

Here is the way it should go.

1. Have the camera set to AWB.
2. Take a picture of someting white (make sure the whiteness fills the focus field)
3. In "Menu" select "Custom WB"
4. Find the shot you just took in # 2 above.
5. Push "Set" on the dial.
6. Clear "Menu"
7. Change AWB to the custom symbol (two ramps facing each other)

Don't forget to reset to AWB when you are finished using the "custom" setting.


dioptic

[Marvinspu36]

I think you will find it difficult to set an accurate custom white balance in a situation like this with theatre lights and a 580EX strobe flash. The reason should be clear. When you are back seventy feet, the theatre lighting will dominate the exposure. When you are up close to the card on the stage, then your strobe flash will dominate the exposure. Your custom white balance is likely to be right for one but not right for the other.

If the strobe flash is going to dominate, then you ought to set for Flash white balance. If the theatre light is going to dominate, then you ought to set up a custom white balance.

---Bob Gross---

Yes, mixed lighting does make it a little more difficult. I was actually only 50 feet from the subject, not 70. The 70 feet was a typo. The photo I took with CWB actually came out pretty good, as far as color is concerned. It was much much better than the image I took with AWB. Since I was still close to the flash's working range (190GN/f4=47.5 feet), I took the white balance picture with the flash turned on and flash exposure compensation set to +1. I stepped back from the white card as far as I could to take the white balance picture. My main reason for posting was to show the steps for setting custom white balance. Guess I would have been better off just putting them in a list.

Thanks for the tips. I do appreciate them, and will keep them in mind.

Best Wishes

[Jon]

The owner's manual (page 51) that comes with the 20D is wrong regarding Custom White balance.

Here is the way it should go.

1. Have the camera set to AWB.
2. Take a picture of someting white (make sure the whiteness fills the focus field)
3. In "Menu" select "Custom WB"
4. Find the shot you just took in # 2 above.
5. Push "Set" on the dial.
6. Clear "Menu"
7. Change AWB to the custom symbol (two ramps facing each other)

Don't forget to reset to AWB when you are finished using the "custom" setting.


dioptic

And you know Canon is wrong how?

First, using any WB setting (including CWB) for the initial picture, you're applying a previously-defined set of parameters to that picture. From that, the CWB setting routine can determine what changes to the parameters need to be applied in storing the new CWB settings. If you use AWB, the CWB compensation routine has to pick these up "on the fly", while if you use a "canned" setting, they're constants which have been previously recorded. Note that Canon specifically states that default CWB is normal sunlight.

Second, you want to shoot a normally-exposed picture, which should average out to 18% grey. If you use a white object, it may, or may not, be pure white. If you use a photographic 18% grey card like Kodak's, it's neutral, and your exposure will be right on the money, as well as matching the exposure setting you'll use in your actual photo session. If you use a white object, and try to adjust so it's properly exposed, you risk blown-out highlights, and it will be that much more difficult to get a true reading from which to get final CWB settings.

[dioptic]

Jon,


When I say Canon is wrong I meant that the step-by-step directions are wrong in the manual. Your point about using a grey card is well taken.

Thanks.

dioptic

[intechpcx]

I'm not sure I agree with you Jon (regarding the 18% gray vs white). From reading the manual (again for the 300D) the calculations made for the Custom White balance are done using the White as a reference point. The 18% gray estimation is what is used for Auto white balancing because it is the best approximation for the reasons you stated. The camera uses it because it has no real reference point as obviously it doesn't know what color is supposed to be what. The whole point of Custom white balance is that the the user is now giving the camera that reference point by specifying what color white actually is under the given circumstances, hence the reason that the manual calls for a picture that includes white in the center of the photograph. Taking a picture of a gray card or something of that nature is going to cause gray to appear as white in your photos because that is what the camera is expecting.

As far as exposure, The manual does state that you have to be careful not to over or under expose. You probably want your picture to include more than just the white object, just make sure the white object is in the middle (See my examples above).

Now I'm a novice, so maybe I'm misunderstanding something here, but this is the description straight out of the Canon Manual.

"With a digital camera's white balance setting, you can compensate for the color temperature so that the colors in the image look more natural. The subject's white color is corrected and used as the basis for adjusting the other colors. The Camera's <AWB> feature uses the image sensor for auto white balance.

With custom white balance, you shoot a white object that will serve as the standard for the white balance. By selecting this image, you import its white balance data fro the white balance setting"

I do agree with you that the WB setting you use for the reference shot probably doesn't matter. Again I too would have to assume that the camera understands the RGB and temperature settings it used and bases the CWB settings off that.

Jon, if I'm missing something, can you please explain what it is that I'm missing. If I'm not understanding this correctly I'd love to expand my knowledge.

[Jon]

I think your misunderstanding comes down to your one sentence here:
Taking a picture of a gray card or something of that nature is going to cause gray to appear as white in your photos because that is what the camera is expecting.

The point of CWB is to ensure that a perfectly neutral colour is reproduced correctly. This may be a white (R:255, G:255, B:255) or a grey (say, R:128, G: 128: B:128). So CWB assumes that the subject you photographed has R, G, abd B channels that are the same. It doesn't try to set the white level based on the neutral colour sample, just the relative adjustments the camera will apply to the input colour channels based on the readings. If a grey card (using the arbitrary values selected above) photographed under the existing light conditions produces a R:96, G: 144, B: 128, the camera will apply a 128/96 or 1.33x adjustment to all red channel values from 0 to 255. It'll apply a 128/144 or 0.89x adjustment to all green channel values from 0 to 255. And it'll apply a 128/128 or 1.00x adjustment to all blue channel values from 0 to 255. Now R:128, G:128, B:128 isn't 18% grey, which is used for determining exposure, but it will be acceptable in colour balancing, since R=G=B..

The problem with using a white object as your target is that at both ends of the luminosity curve (approaching black and approaching white) it becomes difficult for the unaided eye to determine whether the subject is "pure" black or white; you'll tend to perceive it as a pure colour even if it's off by a bit (same reason we don't have the trouble identifying colours under different lighting conditions - the brain applies AWB). And with a white subject, unless you're careful to underexpose the target, you risk blowing out the highlights, thus forcing everything to R:255, G:255, B:255 even though the actual values recorded might be (if the sensor could handle these values) R:255, G:295, B:287. Note: shooting RAW won't eliminate the potential for this; you may increase the number of recordable steps between black and white, but overexposure is still overexposure; the recorded values for R, G, and B of any particular grey would increase accordingly.

A photographic 18% grey card, which is designed to produce consistent exposure results regardless of the spectral sensitivity of the light meter used, or the spectral distribution of the light used, has the requisite R=G=B values as otherwise you might get different meter readings depending on the nature of the light meter you're using (Selenium, CdS, Silicon, etc.) or the light under which you're using it.

[Jon]

Jon,


When I say Canon is wrong I meant that the step-by-step directions are wrong in the manual. Your point about using a grey card is well taken.

Thanks.

dioptic

Actually, their directions will work just fine, even if they differ from those in, say, the D60 manual (where the white balance setting used to capture the "standard" image is not even specified). It actually doesn't matter what white balance you're using; what's important is that there be a known correction factor associated with that original white balance. The procedure outlined in the 20D manual moves the steps 4 & 5 from the D60 manual (your step 7) in front of steps 1, 2, and 3 from the D60 manual (your steps 2-6). This has a potential operational advantage in that it ensures the user has set the camera to CWB, and doesn't forget to select CWB after setting the new standard. It's a shift from the D60, DR, and 1DMkII manuals which don't specify, at all, what mode the base shot should be taken in. But it won't affect your results.

[ChrisN]

Ok. I have read what everyone has said, and I have to admit that I am still a little baffled by what I am reading.:o

Point 1. I am using a Canon DRebel 300D
Point 2. It says in the manual to center a "white" object, not "Grey"

What still baffles me is whether I should purchase the 18% grey card or just bring along with me a white piece of paper.

Has anyone actually set custom white balance with a 300D and 18% grey card? What was the result? Sorry if I am being daft, I am just trying to figure this all out and hope I don't waste a ton of money in the process.

Thx in advance

[gcogger]

Grey cards work fine. With a white target, you could over-expose either the R, G or B channels without knowing (you won't get the over-exposure warning on reviewing the pics on the camera if only one channel is 'blown'). Obviously, if any of the R, G or B channels are over-exposed, the white balance measurement will be totally wrong. Also, a 'white' sheet of paper can often have a slight colour cast that's hard to notice.

So, to summarise the summary: try to use a decent photographer's grey card for white balance! As an example, Calumet do grey cards that are fairly cheap, don't change colour under different lighting conditions, and are made of tough plastic.

[gcogger]

I just noticed that someone suggested using the Kodak 18% grey card for white balance. According to a certain 'guru' (OK, Ethan Hansen :) ) the Kodak grey cards can take on different colour casts under different lighting conditions and therefore are a poor choice for white balancing. It's better to get something designed for setting white balance (rather than exposure, which is what the Kodak card is designed for).

[intechpcx]

OK GC, you lost me now. Wouldn't you want the color of the card to change under different lighting circumstances? Afterall that's the whole point of white balance is that colors appear differently under different lighting situations. I can't understand how using a gray card as the WHITE reference cannot have an adverse affect. Can you explain that to me. I would expect that if you set the white balance by telling the Camera that 18% gray is actually white, then all the white in your photo will look 18% gray. I must be missing something, please explain.

[robertwgross]

It really does not matter whether you use a white card or a gray card, as long as you have a usable exposure. What is important is that the card be a pure white or pure gray, and not have any tint at all. Many sheets of white paper appear pure to the naked eye, but they may have a tint. That will cause just a little error in a custom white balance setting.

---Bob Gross---

[intechpcx]

OK, so I'm still not understanding why it wouldn't make a difference if you use a white or gray for the reference on the white balance. So I decided just to try it both ways and see what happened. So, I composed a frame with a fairly flat field (my china cabinet against a white wall with some candle holders and a clock on the wall). First I used a gray card as the reference for the WB and then took a shot. I did the same with the white card. When I compare the two, there is a difference. Looking at the histograms, the second one (white card) shifted to the left compared to the first. To the naked eye, there is a definite difference, in gray card result the whites look more yellow-ish than in the white card shot. Both had the exact same exposure settings and the same light conditions. Additionally, both of the reference photos had all the same settings, I took them both on full manual to ensure that. So the only thing that changed was the color used for the WB balance.

Now that said, the changes from one to the other were not very drastic. The histogram shift was only slight, but enough to notice. The colors again were noticable to the naked eye when compared side by side, but both looked like good shots and both were definitely better than the AWB control shot I took. I don't know what this means, which one is correct but there's a difference (for what it's worth). Ultimately this thread has gone on so long I'd say try the same experiment yourself and see which result you like best.

[Vega$50]

Ok. I have read what everyone has said, and I have to admit that I am still a little baffled by what I am reading.:o

Point 1. I am using a Canon DRebel 300D
Point 2. It says in the manual to center a "white" object, not "Grey"

What still baffles me is whether I should purchase the 18% grey card or just bring along with me a white piece of paper.

Has anyone actually set custom white balance with a 300D and 18% grey card? What was the result? Sorry if I am being daft, I am just trying to figure this all out and hope I don't waste a ton of money in the process.

Thx in advance

You don't have to spend a lot of money on this....use a white coffee filter, get a grey card and try both methods and see what works out for you. I will tell you that you WILL see a difference in your pictures. The coffee filter method works for me so I stick with it.

[Jon]

OK, so I'm still not understanding why it wouldn't make a difference if you use a white or gray for the reference on the white balance. So I decided just to try it both ways and see what happened. So, I composed a frame with a fairly flat field (my china cabinet against a white wall with some candle holders and a clock on the wall). First I used a gray card as the reference for the WB and then took a shot. I did the same with the white card. When I compare the two, there is a difference. Looking at the histograms, the second one (white card) shifted to the left compared to the first. To the naked eye, there is a definite difference, in gray card result the whites look more yellow-ish than in the white card shot. Both had the exact same exposure settings and the same light conditions. Additionally, both of the reference photos had all the same settings, I took them both on full manual to ensure that. So the only thing that changed was the color used for the WB balance.

Now that said, the changes from one to the other were not very drastic. The histogram shift was only slight, but enough to notice. The colors again were noticable to the naked eye when compared side by side, but both looked like good shots and both were definitely better than the AWB control shot I took. I don't know what this means, which one is correct but there's a difference (for what it's worth). Ultimately this thread has gone on so long I'd say try the same experiment yourself and see which result you like best.

If I'm reading what you said correctly, you found a shift in the histogram when you shot a white card as opposed to shooting a grey card, using a constant exposure.

Or do you mean that when you metered the scene, then photographed a white card and set white balance from that, then photographed the scene with CWB you got a histogram and colour shift over what you saw when you did the same thing only with a grey card?

In either case, the colour differences could/would easily be caused by an off-white white and/or overexposure of the white card when taking the CWB standard.

If the first, the histogram shift would be from the white, rather than grey card in the pictures being compared. If the second, overexposure of one or more channels of the white card could cause miscalibration of the colour correction, thus a slight histogram shift.

In general, exposing your reference so that a white card shows as white will give you problematical results (a result, as several of us have said, of blow-out in the highlights). If you meter so the white shows as a mid-tone, your grey card's going to be seriously underexposed, and that can cause similar problems due to the values the computer has to work with being too small.

[intechpcx]

Jon, what I did was compare two identical photos using different custom white balance setups. To setup the white balance for the first photo, I took a reference photo of the Gray card and used that for the shot. For the second photo, I first took a reference photo of a white card and used that for the custom white balance setting. So I'm comparing to shots that don't have the cards in them, the shots are identical in all ways except how I set the white balance for each (or more specifically what color I used in the reference photo for the white balance setup). The histogram shift I see is between those two pictures (not the reference photos) therefore the color of the card in the reference photos has nothing to do with it.

Now as I've said, I'm no expert but thinking about this logically I would think if anything is going to cause blowout it would be the grey card. Now follow my thinking here. The camera is expecting you to provide it with a white reference from which it can set the white balance (as stated in the manual). It is going to correct color temperature based off that. So in any given seen, white is going to appear brighter than gray , would you agree? So if you shoot white, it is going to set the colors settings to a certain point. However, if you tell it that white is actually darker than it is (by telling it gray is actually white by shooting a gray card), the camera will now over compensate in its settings.

For the record, as tedious as this thread may be seeming, I appreciate all of you hashing it out with me. In the end, I just want to understand all this as best I can because that is what will improve my skills as a photographer.

[gcogger]

I think you're getting confused between white balance and exposure.
If you take a shot of a white object to set the custom white balance, you are not telling the camera how bright the white object is. You are telling it how much colour correction to do to ensure that the R, G and B values are the same. Those corrected RGB values could be 50, 50, 50 or they could be 255, 255, 255.

[René Damkot]

With theatre lights its very easy: Set WB to tungsten or K, somewhere between 2800-3300 K according to taste. Put a yellowish color filter on your flash, so it also emits 'tungsten like' light. (I use a Lee 205). Bingo....

[Jon]

Now as I've said, I'm no expert but thinking about this logically I would think if anything is going to cause blowout it would be the grey card. Now follow my thinking here. The camera is expecting you to provide it with a white reference from which it can set the white balance (as stated in the manual). It is going to correct color temperature based off that. So in any given seen, white is going to appear brighter than gray , would you agree? So if you shoot white, it is going to set the colors settings to a certain point. However, if you tell it that white is actually darker than it is (by telling it gray is actually white by shooting a gray card), the camera will now over compensate in its settings.

No, as gcogger said, what it's going to do is look at the central part of the image and say "Ahah! That should be R=B=G, but it's not. So I'll adjust R, G, and B (well, only 2 of them) so that it is, and apply that correction to everything." It doesn't say "That's white, so it should be R=255, G=255, B=255". One thing, though. If you adjusted the exposure so the white card was a real white, you might have overexposed the white card, in which case CWB can't be relied on to function correctly. If the camera thinks that one or more channels need a different adjustment than they actually do, you could get a histogram shift (which would show up as R, G, and B histograms not lining up correctly when you look at them in your editor).

Were you using manual exposure? Were the shutter and aperture readings for both of the comparison shots the same?

[jimsolt]

At the risk of oversimplification, isn't white balance about the color temperature of the light hitting the subject. It would seem that a pure white at whatever the intensity of the light hitting it will most accurately reflect (pardon the pun) the color of the light hitting it? All the "cautions" of proper framing, tilting, not pure white, etc., are of course valid, but the object is to measure the color temperature of the light, not the exposure. That is a different question, and that is where the gray card comes in. It has an 18% reflectivity, about the same ammount that the camera meter compensates for and that is an excellent tool for exposure, not white balance. The tri-color cards, white, gray, and black are for exposure, not white balance. White balance is the color of the light.
As to the "normal daylight" referred to earlier . . . what is that? I have a chart that measures daylight in it's various forms from 3400K (1 hr from dusk/dawn) to 5500K (sunny around noon) to 6500-7500K (overcast sky) to 9000 - 12000K (Blue sky). As one might suppose, that is a significant range and would have a significant effect on the appearance of the photograph. This would affect the photograph regardless of the exposure which could be right on, over or under, but with a color cast in each case if the white balance is not correct.
Yes, you can fiddle with this in RAW and achieve some marvelous results, but the assumption is you would start with reality for most photographs.
Jim

[gcogger]

Yes, white balance is about the colour temperature. The camera works this out by looking at the ratio of R, G, B values in a neutral object. This object can be white or grey since we don't care about the absolute RGB values, just their relative values.. The reason to use grey is that with a white object you're more likely to over-expose the object and clip one of the channels.

[Marvinspu36]

According to the Canon 20D manual, Page 52:

"Instead of a white object, an 18% gray card (commercially available), can produce a more accurate white balance."

I assume since if you are using autoexposure, the camera will be more apt to not overexpose the image. Overexposing the image will render an inaccurate white balance. Also, as mentioned above, if you where to use a white card, you would have to use a photo white card, not just any "white" object.

Also, according to the Canon manual, you can take a picture of the gray card (or white) using ANY white balance setting. The step just before taking the picture of the gray (or white) card is to "set any white balance setting (see page 50)". The camera knows what it is set to and will correct for it.

I suppose what it boils down to in the end is: If using a photo white card works for you, then use it. If using an 18% gray card works then use it. In the end, they both should provide you with accurate results if you properly expose the image.

[hmhm]

Here is the way it should go.

1. Have the camera set to AWB.
...

Says who? From my own experiments, it makes absolutely no difference what white-balance mode you're in when you take the CWB "reference shot". And if you think about it, it _shouldn't_ make any difference. The camera will apply whatever WB mode is in effect when generating the .jpg or the thumbnail, but that has no impact on the image's subsequent use as a CWB reference shot.
-harry

[DieselGirl]

How much of my field does the white object I am attempting to set my custom white balance to have to take up?

In other words, if I see a white coffee mug from afar and it only takes up, let's say 25% of my entire photo, can I use that object to set my white balance to?

Does it need to be bigger? If so, how much bigger?

[DieselGirl]

Says who? From my own experiments, it makes absolutely no difference what white-balance mode you're in when you take the CWB "reference shot". And if you think about it, it _shouldn't_ make any difference. The camera will apply whatever WB mode is in effect when generating the .jpg or the thumbnail, but that has no impact on the image's subsequent use as a CWB reference shot.
-harry

I agree. It doesn't make a differnce what mode you are in when you take the reference shot.

[Jon]

How much of my field does the white object I am attempting to set my custom white balance to have to take up?

In other words, if I see a white coffee mug from afar and it only takes up, let's say 25% of my entire photo, can I use that object to set my white balance to?

Does it need to be bigger? If so, how much bigger?

It needs to fill the partial metering zone at a minimum. And I wouldn't use a shiny surface, especially with curves. Too likely to pick up a reflection from some off-colour object or light source.

[aam1234]

It needs to fill the partial metering zone at a minimum.

Hi Jon,

Do you think there is an added benefit if the white "object" covers the entire frame.

Thanks

[Marvinspu36]

I don't mean to belabor the point, but it is best not to use some random white object to set white balance if you want accurate color balance. It is best to use an 18% gray card. This is also what is recommended by Canon. See my post above. You can buy them from just about any photography shop for around $10 for a pack of two 8" x 10" cards. Or you can buy a set from B&H photo for $15 that has 18% gray on one side, and photo white on the other. :)

[DieselGirl]

Thanks John. One more thing, define "fill partial metering zone". Thanks again.

[Jon]

Partial metering zone's roughly the biggish circle in the center of your finder. You'll find a more precise definition in your manual, and it'll be shown on the CWB page thereof. but essentially, that's what you have to fill with your neutral object.

[jimsolt]

I don't mean to belabor the point, but it is best not to use some random white object to set white balance if you want accurate color balance. It is best to use an 18% gray card. This is also what is recommended by Canon. See my post above. You can buy them from just about any photography shop for around $10 for a pack of two 8" x 10" cards. Or you can buy a set from B&H photo for $15 that has 18% gray on one side, and photo white on the other. :)

What do you suppose the "photo white" side is intended for?

Jim

[intechpcx]

Jon, that was the explanation I needed. Thanks for detailing that.


Diesel Girl, I'm not sure which camera you have but on the 300D there are 7 focus points. I've found I do fine if the white object borders or covers the central 5 points.


AAM, I've actually seen some poor results when taking a picture of nothing but white. Probably an overexposure problem that results in washout of the colors that would impact the white balance calculations.

[Hydro]

I have been attempting to set the CWB for shooting basketball. The local camera shop recommended a "Lastolite EZ Balance Ref 12", which was kind of a spring loaded pop out fabric pad with white on one side and grey on the other. First question is (and apologies for asking) but the 85 f1.8 lens won't focus on the card. Should I use a different lens so I can achieve focus? How important is it? Then I should take the shot using manual or whatever mode will allow a normal exposure?

Secondly, I have been using the white side. Sounds like I should be using the grey side. My results have been mixed so far, but all three gyms I've shot in have been different. I have been shooting in RAW and making some adjustments in PS Elements 3, and have managed to squeeze out a few keepers------but I need to get this CWB thing wired.

Sorry for the newb questions in a thread that features some very technically savy photographers, but I'm hoping someone will indulge me.

[gcogger]

Use manual focus to stop the camera trying to auto focus - precise focussing is unnecessary. Yes, the grey side is probably the better choice. Just don't under- or over-expose it too much. The grey card should be reasonably bright in the image for best results.

[Jon]

Yeah, that's the catch in using something that fills the frame and is uniform - there's nothing to focus on. Go manual focus, or step back so the outside edge of the target hits one of the outside Af sensors. The lens shouldn't make too much difference if you have good-quality lenses from the same manufacturer. Canon, in particular, tries to ensure that all its lenses have the same colour rendition.