 Bunny Snow |
setting the correct white balance via kelvin temps Please explain what my results mean, as I’m trying to understand how to set the correct white balance using temperature on my Canon20D? I set Custom Function 01 to 1 (change quality). The AF-WB button was set to K, and in the menu I set a variety of color temperatures. The temperatures began at 5200K (IMG_2322), 5000K (IMG 2323), 4900K (IMG 2324), 4700K (IMG 2325), and so on with the color of light coming closer and closer to the white of the white foam core poster board, and the histogram moving closer to the very right side of the screen. At 3500K (IMG_2331), highlight alert (the over exposed areas began to blink on the small photo with the histogram display. These areas have so much exposure, that only white is exposed, no detail, according to Rob Sheppard’s Magic Lantern Guide for the Canon EOS 20D. I have not uploaded my images, but it is easier to describe what was seen if I use the image number here. I could see the shades of color becoming lighter and lighter as the histogram move further and further to the right, seeing the raw images on the monitor was even more profound. IMG_2322 was something like a pale mustard shade (the general shade of the paint on the ceiling and walls of the room). But, the white foam core poster board was the whitest shade available and I was told it was stark white. IMG 2331, 3000K, began flashing dark on the left side of the screen. The histogram appeared to be to the furthest right side of the screen. For the sake of comparison, I wanted to see more temperatures, to see what would happen. IMG 2332, showed even darker flashing on the left side of the screen, and I couldn’t readily tell from the camera that the histogram was further to the right, but on my computer monitor in the EOS Viewer Utility software, it definitely moved further right. With IMG_2333, ¾ of the left side of the screen was flashing a very dark shade of black. I suppose if I continued this experiment, I would burn out more and more detail, with the continually lower and lower Kelvin settings. But, first, I want an explanation: I turned off AF, and focused manually, as best I could. But the aperture settings were all the same –f11@3.2; 100, ISO. The times of the day when the images were taken changed from the first (IMG_2322) at 12:58:38 to the last (IMG_2333)at 13:31:06. The first image was a pale mustard shade (the approximately shade of the walls and ceiling), and IMG_2333 was definitely white. Recall, the poster board was said to be stark white. Do I assume that my correct setting for the color temperature is just before the screen began flashing? Please, help me understand what I’ve done. Thanks.
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Jon Close |
I think sample pics would help. I don't think you should be seeing such dramatic differences in the histogram from changing the white balance. The histogram measures exposure. White balance should have little or no effect on exposure. Are you sure the ISO and shutter speed were not changed as well? Setting the white balance to a particular K° is most effecient when shooting under studio lamps that are known to be rated at a particular color temperature. Otherwise, to set the white balance using a calibrated 18% gray card or white foam core poster board, follow the procedure for Custom White Balance (p.51-52). If that isn't quite right, then apply White Balance Correction (p.53) to get your white subject to appear white without any color cast.
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Bunny Snow |
Thanks, Jon, for replying. I checked and every exposure was exactly the same with shutter and aperture. However, those readings were not necessarily correct. I was trying to measure the color of light on the white foam core, not take an accurate image. I set the focus to manual and only used window light as it indirectly entered the livingroom window at that time of day. The entire viewfinder was filled with foam core. The same data are on each image number, with only time of day varying: The exposure that was set did not reflect the light in the room. However, I measured the ambient light from indirect window light, not from any flash equipment. I manually focused on a label in the corner of the foam core and moved the tripod, so that the entire white area was covered by the lens. I'll download some images a bit later, as I have to take my housekeeper home. Thanks, for your suggestion, Jon.
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Bunny Snow |
Hi Jon, Looking over my settings very carefully, I noticed a difference, which may explain why IMG_2322 (light mustard color) was noticeably different than the other images: the white balance was set to flash. Whereas, with all the other images, the white balance was set to COLOR TEMPERATURE. Novice as I am to digital, I didn't know one reading from another. But since the flash didn't go off on the first one, I changed that individual setting to Color Temperature and all that follow are also set to Color Temperature. The various temperatures were taken between 13:10:36 and 13:31:06 on October 5, 2006. I'm not certain that I can say what I learned, but there is a big difference having the setting on Flash and Color Temperature, even though the flash did not go off. What is the best way to download the various images without taking too much space? Should I purchase a premium web site and display the information with the various color temps, there? Or, should I download several here? Please, advise. "Bunny"
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Bunny Snow |
Date: 10/05/06, Time 12:58:38. There is an important factor with these, which I learned about after the previous communication and that is, the exposure was not always accurate. That can, and does, make a big change in white balance temperature. And, for comparison, after doing these mentioned previously, I'll illustrate with others carefully focused manually, and then, carefully metered. Firstly, however, I'll download those images cited above. ~Bunny
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Bunny Snow |
Shooting Date/Time 10-05-06 12:58:38
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Bunny Snow |
I cannot figure out how to upload and need help. This is the url of my the light captured for the first image. C:\CANON D20\SELF-PORTRAIT with CANON 20D\WHITE BALANCE TEMP MEASUREMENT\IMG_2322
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Bunny Snow |
IMG_2323.jpg
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Bunny Snow |
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Bunny Snow |
White balance set to color temperature, 4900K Date & Time 10-05-06 13:12:58 All other data is the same, as above.
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Bunny Snow |
IMG_2330.jpg
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Bunny Snow |
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Bunny Snow |
All settings remained the same. The WB was set to the color temperature of 3500K.
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Bunny Snow |
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Bunny Snow |
I want to emphasize that no processing occurred, only resizing.
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
I'd like to know if the histogram on a 20D change function to double as a white balance check. But, histograms do change depending on the amount of color in a scene. Even a properly exposed dark scene will have a histogram over to the left if it has lots of blacks and dark colors. And when setting a custom white balance, it's recommended to use the sample shot as one that's exposed right before highlight warnings start to flash. a preset white balance for flash will make a picture lean towards yellow from sunlight temps, because many flashes,(hot shoe and built in) tend to have more blue in them. So are you trying to figure out what a color temp in the 3000's does or when you use them, or something else?
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George R. Stewart |
First of all that 'url' as you call it is the location of your file on your local computer. Now why is your camera set to f 11 with 3.2 seconds of exposure? You would generally use such a 'stop-down' for a landscape shot on a bright sunny day when you want Everything to be in focus, on a tripod. I see you are in 'aperature priority' so the camera is holding to that f-stop and lenghtening the exposure time to 3.2 seconds. Your camera is strangling for light! Tell you what, put that camera into 'manual' mode. It isn't like a manual transmission on a car, the Canon software inside with provide you with all kinds of data in your viewfinder. Get the red lettering to where it says '0' not 2/3 or -1. That will tell you the camera is happy with your aperature/shuttertime settings. You will learn to use those other settings when you want to make adjustments to the effect you want to covey with your picture. If anything get it off aperature priority, that's for manipulating your 'what's in focus' priorities, such as taking a picture of a person behind trees or something...you'll want that slightly blurred so to won't look like antlers on the person in the 'portrait'. As for the white balance...5000K is supposed to signify daylight, but not too bright I would suspect. I set my computer monitor to 5000K...its dimmest setting because I work in a dark room. I suspect a camera set to the same conditions would aid in getting the photo to come out reasonably correct on a printer if everything was set to the same temperature. Put the camera on 'Auto' pretend to take a picture with a half shutter press then switch the camera to 'P' mode and see if your white balance doesn't swing back up to past 5000K. I believe it your aperature that's giving you problems. Good Luck Bunny
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George R. Stewart |
As for the histograms...you want to keep the pixels from crawling up the walls of the histogram. That is the Extreme left & right, the very edges of the histogram box, that signifies under and overexposure, those are the pixels that blink. Once again, Best of Luck!
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Bunny Snow |
Hi George, Thank you for responding. I know the uses for aperture priority. It's my favorite mode, as long as I'm on a sturdy tripod. And, you are correct, I didn't need it for these shots because depth of field was not needed. Do you think that Program would have better White Balance readings? Does the long exposures of Aperture Priority throw off white balance? It shouldn't have anything to do with it, I should think. As long as the exposure is accurate and the pixels in the histogram are not flashing, it should be fine. I tried not to play with my exposure compensation because I did not want to throw more confusion into the picture. I wanted everything to remain the same so that I could see what was, or was not occurring. Today, I plan to use the different scenarios for the different WB settings. (i.e. Shade WB for open shade. Cloudy for early morning and late afternoon light, or cloudy conditions, etc. And, in those images something will fill the inner circle of partial metering for me to set my white balance. If these don't come out better, I may just go out a buy that expensive ExpoDisc filter. Thanks for the explanation with the pixels in the histogram blinking. I knew that it had something to do with overexposure, from experience. Back to the drawing board again...so to speak. Thanks everyone for your input.
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George R. Stewart |
You're not telling me you deliberately wanted to take a 3.2 second exposure? Astrophotography maybe, I'm not able to imagine such a need. Night photography? I don't think one worries about that, in a disco? Maybe to most definitely..depends. As I, aka newbie here, presently understand white balance if there's not a true white object in the picture the camera will make assumptions on just what the white balance should be, primarily in 'auto' mode. But auto mode comes in handy for emergency shots. If you really aren't intending to stop your camera down to f 11, then yes put the camera into Program 'P' mode. When you got into your menus and play with the white balance levels the camera will adjust all the other settings. And I think you can put the camera back to auto-focus as well. You will likely need your focus lamp on as well for a solid colored object such as a piece of styrofoam. Take it in to a photo store maybe they'll let you compare it to a calibrated piece of white that costs how much $60 $70 dollars? Good thinking Bunny! The Webmaster emailed me to notify me you wrote so this is a very decent place. Thanks Web-Master.
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Andrew Laverghetta |
check out what Jon mentioned in his post. I guess if you're trying to understand what's going on then this is alright, though I would check out the manual as stated. If you want to use a certain type of lighting, take this white sheet that you're using, take a picture, and go to the menu and set Custom White Balance, then it will ask you to select a photo (that you have already taken). Select the photo where that white sheet fills the frame. Then, go to the part on the top of the camera where you set white balance and set it to the one that seems to have two triangles and something small in between. Then you're color balance should be accurate. Also, if you have a raw converter installed in photoshop, just take ANY picture in ANY number of situations and mess around with the different white balance settings in Photoshop. Even if you have to download a trial of Photoshop CS2 and get the plug-in, this is what really helped me. You can look at a RAW photo that you shot and apply any one of the white balance settings and see how the photo will come out. For instance, if you take a photo using daylight outside and you set the white balance to tungsten it will look blue. For your tests as well, do you have any stray light from tungsten/indoor lamps? Are you using DIRECT sunlight coming in the window? If it's not direct then it's going to look a little blue because of the blue in the blue sky.
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
". (i.e. Shade WB for open shade. Cloudy for early morning and late afternoon light, or cloudy conditions, etc. And, in those images something will fill the inner circle of partial metering for me to set my white balance." BR> That's sounding like you intend to set white balance for the preset white balance. And that's not something you do. You just set the camera to a preset wb for the light you're in. It's sounding like you're snowballing this into something much bigger than it needs to be. Try going back to the beginning. What is it you most want to know, or are confused about? Is it the preset wb, or how to use and set the custom wb, or setting the actual color temp on the camera for white balance?
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Bunny Snow |
Bunny
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