White Balance With Different Objects

[pbjef]

<p>I have an 18% gray card for pre-setting white balance. Its a thick piece of cardboard. I've seen people use a white sheet of copy paper, a device they attach to the front of the lens and even a thick sheet of toilet paper. Of all of these is any better than the other?</p>

[bobatkins]

<p>Nope. As long as it's a neutral object (reflects all colors equally), your white balance should be set properly.</p>

<p>The 18% gray card may actually be the best since it's actually designed to be neutral, but I've often used a sheet of white paper and it seems to work just fine.</p>

[pbjef]

<p>Thanks Bob, I shouldn't have read your profile. I'm intimidated now.</p>

[derek_kennedy]

<p>I cut myself out a 'card' from a thin sheet of white plastic so that I can put it in my camera bag and not worry about it getting wrecked. Roughly 4x6 inches.</p>

[ben_goren]

<p>Jef,</p>

 

<p>If Kodak made your 18% gray card, it’s an excellent tool for gray balancing. Not the

absolute best, but well within the margin of error. As a bonus, it’s perfect for setting

exposure.</p>

 

<p>“White” paper is about the worst choice possible. The substrate is usually yellowish,

and paper manufacturers compensate by adding fluorescent dyes that absorb ultraviolet light and re-emit it as blue light.</p>

 

<p>Polystyrene has a flat, neutral spectrum superior to most commercial photographic gray balance

tools. It usually has 85-90% reflectivity, which is perhaps ideal for gray balance purposes (though, obviously, not for exposure). Solid packing foam and disposable coffee cups are (almost always) made from polystyrene.</p>

 

<p>Many super-expensive scientific targets, designed to have 99.5% (or even more) reflectivity equally across the

entire spectrum, are made from PTFE. You can buy PTFE at your local plumbing supply store as a roll

of tape for a couple bucks.</p>

 

<p>Cheers,</p>

 

<p>b&</p>

[pbjef]

<p>Wow ... didn't know there was so much to think about. Not sure where my card was manufactured although I did buy it from a reputable camera shop in my town.</p>

[JDMvW]

<p>My old Kodak 18% gray card has 100% white on the back which would work fine for white balance (although it was originally, I think, more for low light). There <em>were</em> color temperature meters however, and some people did use what were called <a href="http://en.wikipedia.org/wiki/Mired">decamired</a> filters to achieve WB even back in film days.</p>

[ben_goren]

<p>Jef,</p><p>This is just barely scratching the surface, to be honest. But don’t worry —

you’ll know when (if ever) you have to worry more about it.</p><p>If you can’t find out who made your gray card, I’d have two suggestions. First and best, if you

have any friends / club members / <i>etc.</i> who have a spectrophotometer, have them measure it.

That’ll tell you if the card is any good, but, more importantly, it’ll get you an impromptu

hands-on lesson about the subject and more.</p><p>Otherwise, genuine Kodak gray cards are like twelve bucks for a pack of an 8″ ×

10″ and a few 4″ × 6″s. They’re cheap enough to be disposable,

so you don’t have to worry about being gentle with them or losing them. And they hold up as

well as any other piece of heavy cardboard, so you’ll probably go years before buying another

package.</p><p>Cheers,</p><p>b&</p>

[bobatkins]

<blockquote>

<p>“White” paper is about the worst choice possible.</p>

 

</blockquote>

<p>I wouldn't quite go that far. Red, Green or Blue paper would be much, much worse! I actually did some testing comparing gray cards with white copy paper and the results were pretty similar. The white paper had a slight blue bias, but very slight. If a true neutral tone was RGB (142, 142, 142), white paper read something like RGB (142, 143, 149), the excess blue coming from the whitener in the paper which converts UV to blue via fluorescence. Under the same conditions, polystyrene measured RGB(142,144, 140) which is slightly closer to the gray card than the white paper.</p>

<p>If I wanted a good white balance and I wasn't carrying a gray card, I wouldn't hesitate to use a sheet of white paper as an acceptable substitute. I've also been known to use my LowePro Trekker photo backpack as a color reference, since it's pretty close to a neutral gray! A polystyrene coffee cup would also work.</p>

 

[jay a. frew]

<p>I use a piece of white terry-towel (half of a golf towel). It works well enough with my EOS 40D "custom white balance" setting, in mixed light conditions (for me that is almost always indoor lighting with flash). I always shoot in raw mode, so, I adjust white balance with my computer software.</p>

<p>The texture of the towel also tells me, quite quickly, if I have overexposed (texture begins to disappear).</p>

<p>I can throw it over the subject's shoulder, drape it, toss it on the floor - whatever (easier for me to "deploy" than a grey card - which I also own, but, never use).</p>

<p>It is cheap, easy to replace, can crumple-fit into any camera bag I own...and...it does double-duty as a towel. That last item is important, since it seems that I need a towel more often than I need a white balance tool.</p>

<p>;~))</p>

<p>Cheers! Jay</p>

[lex_jenkins]

<blockquote>

<p>"A polystyrene coffee cup would also work."</p>

</blockquote>

<p>Ditto. My Nikon D2H has a white balance sensor in the prism which is finicky. Works great in daylight and incandescent light as long as it's bright enough. But the prism sensor is balky in dim lighting and most artificial lighting - the cycling of fluorescent and metal halide lamps throws off the sensor. A white styrofoam coffee cup over the lens for through-the-lens white balancing has worked in a pinch several times. The downside is that the cycling of fluorescent and metal halide lamps will ensure several photos from each session will be way off neutral no matter how you attempt to set a custom WB.</p>

<p>Regarding white vs. gray cards for WB, eh... my experience has been about equal for both. Many "gray" cards have a distinct color cast visible to the naked eye, and even the Kodak cards can shift with age. These were designed for metering, not white balance. In ye olden dayes when I did video for community access stuff we used white cards. Generally speaking I still get more neutral results by white balancing from an ordinary sheet of white paper than from my Kodak gray card.</p>

[Wayne Melia]

<p>Lex's response triggered an issue I've wondered about....<br>

Is it better to use a lighter object than a medium toned (grey) object? It is called "white" balance. Thanks in advance for replies.</p>

[Ed_Ingold]

<p><em>Is it better to use a lighter object than a medium toned (grey) object? It is called "white" balance. Thanks in advance for replies.</em></p>

<p>With auto exposure, the camera will make every effort to render a subject which fills the viewfinder as 13-18% grey. This includes a "white" target. This action places the exposure in the same part of the tone curve imposed on the RAW image, avoiding unexpected color shifts in that regard.</p>

<p>The important issue is whether the target reflects all visible wavelengths the same. An high-quality grey (or white) target based on pigment coatings (e.g., X-Rite nee' Gretag-MacBeth) come close to this criteria, and are priced accordingly ($50-75). Cheap targets don't come close, and are often not grey at all, rather printed with CMYK inks with a glossy finish , suitable for checking exposure only.</p>

<p>Color Checker charts (X-Rite) can be used to set both the tone curve and white balance simultaneously, for the best color accuracy. The X-Rite "Passport" kit is an highly effective combination of targets and software specifically for this purpose. X-Rite charts are either flat or semi-gloss to reduce the effect of specular reflections.</p>

[sarah_fox]

<p>Gee, I'm gonna get flamed for this one...</p>

<p>I'm with Bob on this one. A white piece of paper (auto-exposed medium gray) works quite well, as long as it's a good piece of paper (new, bright, white, and not "brightness enhanced"). Almost any target will have its particular "issues." Plastics and wood products can yellow. White cloth can yellow and can even be "brightened" the same way as some papers. CMYK-printed gray cards have metamerism issues.</p>

<p>In the end, all of these issues pale by comparison to variations in light color from different directions. Unless you're shooting an entirely monochrome scene, there will be objects or fields of differing colors that will produce casts in the light color reflected from different directions. Photograph Pat Boone (opposite of Johnny Cash -- a guy who liked to dress in all white) standing on a grass lawn, under a blue sky, with a beige umbrella slung over one of his shoulders, and you're going to see variations in the apparent color in the ripples and wrinkles of his clothing, depending on which direction each patch of clothing is oriented. Actually this looks very natural. If you were to neutralize the color casts, it would look quite strange. I would contend, therefore, that it is difficult to PRECISELY characterize light color in any ordinarily complex situation. In the real world, there's a bit of wiggle room in white balance, and proper white balance is best fine-tuned in postprocessing anyway. Exceptions would exist for situations such as copy work.</p>

<p>At the risk of sounding sloppy and getting burned as a heritic, I often don't even use a neutral target or custom WB. I often use a WB preset to get close to the mark and then fine-tune WB in postprocessing by neutralizing color in objects I want to appear white. (Note here: I also shoot in raw.) For instance, if I were a wedding photographer, I would really want the bride's gown to look dead-on white (unless it's an intentionally ivory colored gown or something). If it's some other formal event, there are a lot of white shirts that should look white. I pick those items out opportunistically in postprocessing (usually in DPP) that I want to look white or otherwise neutral (e.g. gray), and I find frames where those items are substantially away from the right side of the histogram. (No, I don't nail perfect exposures every time, which makes me... honest.) I take my WB readings off of a sampling of those items and then apply the same correction across all frames shot in that lighting environmnet. The result? Nobody has ever complained about my WB, so I guess I do OK.</p>

<p>More heresy: I'm not sure you want to entirely nullify color casts even when you can. Let's say you're photographing a couple having a romantic dinner by candle light. Doing the "right thing," you shoot for a light temp somewhere around maybe 3000K. I guarantee you the picture will look cold, and there will be nothing romantic about it. The same often applies when shooting under tungsten. Sometimes the tungsten color is important. On the other hand, if you were to use a daylight balance when shooting under tungsten or candle light, the pic would look quite unnaturally orange. I contend that the best WB often lies somewhere inbetween daylight and fully corrected. It's a judgment call that can only be made in postprocessing. One technique I sometimes use is to overlay a color corrected layer over a daylight-balanced layer and then to adjust the opacity of the top layer for the right look.</p>

<p>Just how crazy is this practice of not shooting WB targets or using custom WB settings? How nuts is it to relegate all this to postprocessing? Well, film photographers have effectively been doing it for eons, and the labs have somehow managed to do the necessary fine-tuning of WB using nothing but the image on the negative. Somehow good, or even adequate, lab technicians have managed to achieve pleasing WB this way since before I was born. This whole issue of getting exact, dead-on WB using high-dollar color targets is a recent problem. I contend that if we do what's already been done with film processing in labs, we'll be just fine.</p>

<p>Finally, I do often use custom WB settings in weird lighting situations, using neutral targets. A great neutral target is a piece of photographic paper whose brightness isn't enhanced with UV-fluorescent brighteners. For instance, Epson's Premium Presentation Paper Matte (formerly Enhanced Matte) is a no-no. Their Premium luster or glossy papers are very neutral and are not enhanced. They make good targets if you hit them with a very light touch of matte spray. Aluminum is also a good target if it is not shiny. Even corroded aluminum is quite neutral in color. The dull side of a sheet of aluminum foil isn't too bad. Crinkle it and/or hit it with some matte spray, and it's even better.</p>

<p>As to the question of whether gray is better than white: Both should work the same. The only difference between gray and white is that one is brighter than the other. The color balance is the same. The utility of an 18% gray card is that you can meter off of it, but that has nothing to do with WB.</p>

[silverdae]

<p>I think it all depends on how color critical your work is. I've shot basket ball games where I know the final output is going to be 4x6 at the most, or more likely ending up in a non-color correct album or book, so I've been know to swing around to the white-ish walls of the gym, set a white balance, and call it good. It knocks off the obvious color cast in the images, but doesn't get it perfect. Now if I'm shooting portraits outdoors, I usually go for auto WB- Its close to right, it is too time consuming to set for each scene, as someone mentioned, reflections can change the "whiteness," I like to set the white balance to what feels right in a portrait, not necessarily what is right, and I shoot raw, so I have that luxury. If I'm shooting critial pieces, I set the white balance using a rather pricey target, then include the target as I change my lights around so I can guage it again in post if I need to. </p>

<p>So no, one isn't better than the rest. One may be more appropriate than the rest, but not necessarily better.</p>

[kevin_delson]

<blockquote>

<p> The white paper had a slight blue bias, but very slight. If a true neutral tone was RGB (142, 142, 142), white paper read something like RGB (142, 143, 149),</p>

</blockquote>

<p>I did the same with pretty much similar results.<br>

If I'm off by 50-100 kelvin, do I really care?..No.<br>

It is far easier to carry a rolled up piece of paper than a still 8x11 grey card,</p>

 

[janisok]

<p>all very helpful</p>

[rashedahmed]

<p>White offset papers (that we use for office printing) has blue in it.Sometimes yellow.So, use a gray card to be in a safe side.Make a custom WB from it and later shoot the white paper in the same lighting.You will get the answer.</p>