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  #1  
Old November 21st, 2006, 03:42 AM
Pat Yuen Pat Yuen is offline
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Default Cus. White Bal. White card or Gray card better?

I'm in a discussion with another photographer who claims that it is absolutely more accurate to get a white balance reference from a white card instead of a gray card. My contention is that you can use either but a gray card will be more accurate as is stated in every Canon DSLR manual. Every reference I have seen regarding white balance recommends the use of a gray card.

I'm hoping to get some clarity on this from Chuck Westfall, Michael Tapes, and Doug Kerr as to the technical reason why gray is more accurate than white when it comes to white balance.
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  #2  
Old November 21st, 2006, 11:23 AM
Don Lashier Don Lashier is offline
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I've read this also, but my informal tests show little if any difference. But it does make sense as things can get a little weird at sensor saturation. I suspect a better distinction is that balancing off a grey card is safer, while using white is a little risky.

- DL
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  #3  
Old November 21st, 2006, 12:29 PM
Asher Kelman Asher Kelman is offline
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WhiBal being waterproof, having standard continuous color throughout its thickness, having qaulity control is a standard that works every time.

Just don't use it wrongly to get rid of color cast you prposely add as a color gel over your lights!

Always take the WhiBal reading before adding the colored gel or colored light effect!

If you need to, the WhiBal card can be sanded to rejuvinate it. I have never found this necessary.

Asher
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  #4  
Old November 21st, 2006, 01:17 PM
Ron Morse Ron Morse is offline
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I have found the WhiBal to be a great help with colors as long as it is within the flash zone in my aquarium shots.
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  #5  
Old November 21st, 2006, 01:35 PM
Dave New Dave New is offline
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Grey card or white card, the important thing to remember is to not overexpose the card. If you shoot a white card a stop or so underexposed, it will look remarkably like a grey card ;-).

The other important thing to remember is that most traditional grey cards (like the ubiquitous Kodak card found in many photo emporiums) are not very accurate for color balancing. They were designed, rather, to give an accurate exposure index, but were never intended to be used as a color reference, and frequently have undesirable color casts, and/or metamerismic effects under various lighting sources.

That's why you'll hear folks here (and elsewhere) recommend things like Gretag MacBeth color checkers, or to get something that will stand up to field use, the WhiBal. If you use a GM color checker, you should note that the paints used will age with time and exposure to light/heat, and the card should be replaced every couple of years, to avoid long-term color shifts.

WhiBals appear practically indestructible. I have my doubts about the longevity of the black sticker, but Michael Tapes has indicated that replacement stickers are easy to obtain.

I have a GM color checker I use in the studio for various things, but never bother to carry it in the field. Instead, the WhiBal is my constant companion.
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  #6  
Old November 21st, 2006, 02:00 PM
Don Lashier Don Lashier is offline
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Quote:
Originally Posted by Pat Yuen
My contention is that you can use either but a gray card will be more accurate as is stated in every Canon DSLR manual. Every reference I have seen regarding white balance recommends the use of a gray card.
Actually, the Canon manual (and Chuck iirc) has always recommended using a white surface. In my experience this works fine as long as you don't overexpose. The Canon instructions do say "shoot the white object so that a standard exposure is obtained. If it is underexposed or overexposed, a correct white balance might not be obtained". I assume this means to expose so that the white comes out mid grey. If just including the card in a standard shot this probably won't be the case.

- DL
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  #7  
Old November 21st, 2006, 03:26 PM
Pat Yuen Pat Yuen is offline
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Although the Canon manual talks about doing custom white balance with a white card, every one of them includes a hightlight that reads: ""Instead of a white object, an 18% gray card (commercially available) can produce a more accurate white balance."
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  #8  
Old November 22nd, 2006, 08:15 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Pat Yuen
Although the Canon manual talks about doing custom white balance with a white card, every one of them includes a hightlight that reads: ""Instead of a white object, an 18% gray card (commercially available) can produce a more accurate white balance."
That's because many 'white' objects are not very uniformly white throughout the visible spectrum. Paper often has optical brighteners built in and will exhibit fluorescence in proportion to other (shorter) wavelengths. Paper and plastic can also yellow with time.

A gray card may not be exactly gray, and since we attempt to estimate a white point, extrapolating from black and gray towards white will magnify the deviations at the gray level. Also, accuracy wil deviate from batch to batch.

A WhiBal is at least checked to be within a small tolerance range at the different levels, just like a BabelColor white reference is superbly neutral and of high reflectance when produced. Gray cards have unspecified manufacturing tolerances for neutrality, because they are intended for reflection percentage, not for neutrality perse.

Bart
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  #9  
Old November 22nd, 2006, 08:21 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Don Lashier
I assume this means to expose so that the white comes out mid grey.
You'll get a closer estimate of white, when you 'over-expose' relative to medium gray exposure. When shooting (at least with Canons) Raw at ISO 100 and higher, you can at least 'over-expose' 2 stops safely without clipping because the camera models I've seen tested have some 3 stops of headroom before saturation. For ISO 50 a +1 EV is save, because it has a 2 stop headroom.

Bart
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  #10  
Old November 22nd, 2006, 02:45 PM
Herman Teeuwen Herman Teeuwen is offline
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> since we attempt to estimate a white point, extrapolating from black and gray towards white
> You'll get a closer estimate of white

Hi Bart,

Isn't the actual white irrelevant? The 'only' thing the camera needs is a scaling factor for each RGB channel to adjust RGB response. Any oject that is perfectly neutral (middle gray or white) will do the job.

Herman
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  #11  
Old November 22nd, 2006, 03:16 PM
Don Lashier Don Lashier is offline
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Quote:
Originally Posted by Herman Teeuwen
Isn't the actual white irrelevant? The 'only' thing the camera needs is a scaling factor for each RGB channel to adjust RGB response. Any oject that is perfectly neutral (middle gray or white) will do the job.
Exactly, but I think what Bart was trying to say was that theoretically the accuracy may be slightly better with higher exposure (rgb values). I've got a card with four neutrals on it including white, black, and two greys, and find no practical difference between balancing using any of the four although the black seems slightly more variable (not surprisingly). Note that the manufactuer no longer sells the four pane version but just a grey card.

- DL
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  #12  
Old November 22nd, 2006, 06:02 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Herman Teeuwen
Isn't the actual white irrelevant? The 'only' thing the camera needs is a scaling factor for each RGB channel to adjust RGB response. Any oject that is perfectly neutral (middle gray or white) will do the job.
Tests of 'nearly' clipping whites and 'truely' clipping whites reveals that the last 1/3rd stop before clipping, isn't neutral on an otherwise 'neutral' camera response curve, one color channel may/will clip sooner than another (and it varies with ISO setting). In addition, in an attempt to determine 'White' balance, wouldn't it intuitively make more sense to sample 'white' rather than 'gray' or any other color (from my tests I know it does)? The least it would achieve is sampling a 'white' one attempts to characterize.

Another issue will be to e.g. determine the difference between a white shirt being illuminated by a Reddish lightsource, versus a Reddish shirt being illuminated by a 'White' light source.

Bart
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  #13  
Old November 22nd, 2006, 06:44 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Don Lashier
Exactly, but I think what Bart was trying to say was that theoretically the accuracy may be slightly better with higher exposure (rgb values).
Yep, I can only test so many cameras but, to exclude the ones not tested, one needs to allow room for non-linear response between the R, G, and B channels. I can't exclude the (unlikely) possibility, except when near clipping/saturation where it becomes almost a given. However, in general white subjects will be rendered as white.

So far, Digicams have proven to be quite linear in their (Raw) response to luminance. That would suggest that 'White' has a similar ratio of input/output channel response, albeit not necessarily equal for all channels. Anything not white (R=G=B, and higher than average), being converted to white, will introduce a color cast at that rightness level.

Bart
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  #14  
Old September 2nd, 2010, 02:36 AM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Don Lashier View Post
Exactly, but I think what Bart was trying to say was that theoretically the accuracy may be slightly better with higher exposure (rgb values). I've got a card with four neutrals on it including white, black, and two greys, and find no practical difference between balancing using any of the four although the black seems slightly more variable (not surprisingly). Note that the manufactuer no longer sells the four pane version but just a grey card.

- DL
I was looking up what we have written on gray cards.

I was reminded of Don Lashier an active member of OPF, always ready to share his experience.

Unfortunately Don passed away as most of you know. Losing a friend or family member is always painful. It was May 5th 2008 and at 63 and tragedy to be taken so young when one is hopefully enjoying the fruits of one's labor. He was a great photographer and most helpful to everyone.

I support the idea of using neutral objects that are not too bright as Bart has pointed out, since clipping of one color can occur before the others. Knowing one can get good samples of how incident light is being reflected by a neutral surface is useful. In absence of a card reading, one can get close by using the whites of the eyes, black pupils, grey concrete, a white shirt and the like. I simply experiment and then pick the spot that gives the closes to natural appearance as possible. Then I'd go on to fine tune that by eye.

The important thing is to only use color cards before one adds colored gels or the sunset sky changes the colors or else one removes the effect one seeks.

I'm glad that Don's ideas still stimulate me to think about how I approach photography.

Thanks Don,

Asher
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Last edited by Asher Kelman; September 2nd, 2010 at 09:38 AM.
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  #15  
Old September 2nd, 2010, 06:32 AM
Doug Kerr Doug Kerr is online now
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Hi, Asher,
Quote:
Originally Posted by Asher Kelman View Post
I support the idea of using neutral objects that are not too bright as Bart has pointed out, since clipping of one color can occur before the others.
Probably a good idea, especially if the shot with the target is metered.

Quote:
In absence of a card reading, one can get close by using . . . black pupils . . .
Really? For white balance?

Best regards,

Doug

Last edited by Asher Kelman; September 2nd, 2010 at 09:37 AM.
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  #16  
Old September 2nd, 2010, 07:27 AM
Kevin Stecyk Kevin Stecyk is offline
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Quote:
Originally Posted by Doug Kerr View Post

Really? For white balance?
I wouldn't rely upon pupils to give an overall white balance. While the pupils should be black, nobody will notice if the values are r,g,b 5,3,3. Others just see dark.

If I had to rely upon just the pupil, then I'd simply adjust color balance to taste. I wouldn't be fussed that it isn't accurate. Rather, I would be concerned that it is pleasing.
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  #17  
Old September 2nd, 2010, 09:43 AM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Kevin Stecyk View Post
I wouldn't rely upon pupils to give an overall white balance. While the pupils should be black, nobody will notice if the values are r,g,b 5,3,3. Others just see dark.
Kevin,

The idea of course now is to get within range of pleasing very fast. I try using the presets for various light sources. I also check out using whatever I can find close to neutral and use these too in separate layers and then compare. Think of the complex lighting in the 2cd floor lounge at the Colburn School, (post #37), that you helped with color correction. Were you corrections global or regional and fused from layers?

Asher
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  #18  
Old September 2nd, 2010, 10:01 AM
Kevin Stecyk Kevin Stecyk is offline
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Quote:
Originally Posted by Asher Kelman View Post
Kevin,

The idea of course now is to get within range of pleasing very fast. I try using the presets for various light sources. I also check out using whatever I can find close to neutral and use these too in separate layers and then compare. Think of the complex lighting in the 2cd floor lounge at the Colburn School, (post #37), that you helped with color correction. Were you corrections global or regional and fused from layers?

Asher
I used my usual practice where I sample a few points and use curves to adjust. I don't use those eyedroppers. I don't even know how to use them. So for your picture, I just used curves to make global adjustments and then blendifs to restrict the changes to certain areas. If you look closely, you'll notice that there are color casts further down the room.
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Old September 2nd, 2010, 01:27 PM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Kevin Stecyk View Post
I used my usual practice where I sample a few points and use curves to adjust. I don't use those eyedroppers. I don't even know how to use them. So for your picture, I just used curves to make global adjustments and then blendifs to restrict the changes to certain areas. If you look closely, you'll notice that there are color casts further down the room.
Not to get too far off grey cards, but in that correction, you ended up with a nice result. However we removed the wall colors in the process. I went back and just added on camera flash and discovered that even that could overcome much of the discrepancy between 3 color sources: window light, fluorescent light plus incandescent light. Ideally, in an indoor architectural panorama like this, one should have gray card in every single shot and correct the color before stitching. In future, I'd do both: use electronic flash and tiny grey cards everywhere one can clone out!

Asher
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  #20  
Old September 2nd, 2010, 01:56 PM
Nill Toulme Nill Toulme is offline
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I've recently been surprised at how easily I can get "in the ballpark" by clicking on something black.

Nill
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  #21  
Old September 2nd, 2010, 11:32 PM
Michael Tapes Michael Tapes is offline
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Quote:
Originally Posted by Nill Toulme View Post
I've recently been surprised at how easily I can get "in the ballpark" by clicking on something black.

Nill
The problem with clicking the WB tool on Black, is that the resolution down there in tre mud with the noise make good WB very problematic. As discussed before, one wants a very neutral reference, whose exposure brings it up into the light gray region to maximum resolution between the R G and B points. Like a WhiBal or Passport. Both feature highly neutral bright gray surfaces.

BTW...in a pinch the white of eyes can get a reasonable starting point.

Michael Tapes (glad to be back :>)
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  #22  
Old September 3rd, 2010, 06:00 AM
Doug Kerr Doug Kerr is online now
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Hi, Michael,

Quote:
Originally Posted by Michael Tapes View Post
glad to be back
Glad to have you back!

Best regards,

Doug
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  #23  
Old September 3rd, 2010, 06:29 AM
Kevin Stecyk Kevin Stecyk is offline
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Quote:
Originally Posted by Asher Kelman View Post
Not to get too far off grey cards, but in that correction, you ended up with a nice result. However we removed the wall colors in the process. I went back and just added on camera flash and discovered that even that could overcome much of the discrepancy between 3 color sources: window light, fluorescent light plus incandescent light. Ideally, in an indoor architectural panorama like this, one should have gray card in every single shot and correct the color before stitching. In future, I'd do both: use electronic flash and tiny grey cards everywhere one can clone out!
My question about throwing gray cards everywhere would be why? Why bother?

Even when using your on-camera flash, I suspect that as you looked down the room, you found color casts creeping in everywhere again.

Are you attempting to scientifically reproduce colors everywhere? Or are you attempting to reproduce the feeling and ambiance of the setting? If it is the latter, curves will get you there. Just use your artistic judgement.

If you have a bunch of gray cards everywhere, won't they counteract each other? That is, when you use one card to set the white balance, won't it adversely affect your previous setting?

Again, if I were shooting an indoor location, I'd try my best to have one indoor light source. Your flash and outdoor might not be too different--though I am not sure. But if you can eliminate your multiple indoor light sources, I suspect that much of your differences will disappear.
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Old September 3rd, 2010, 06:52 AM
Michael Tapes Michael Tapes is offline
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Quote:
If you have a bunch of gray cards everywhere, won't they counteract each other? That is, when you use one card to set the white balance, won't it adversely affect your previous setting?
Yes, but for certain applications, like professional architectural photography, the multiple gray card technique allows one to white balance different parts of the scene differently by making multiple raw conversions (in Lightroom you could use Virtual Copies), and "blending" the various sections together using masks in PS.

Some people need that. And I emphasize some.
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  #25  
Old September 3rd, 2010, 07:52 AM
Kevin Stecyk Kevin Stecyk is offline
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Quote:
Originally Posted by Michael Tapes View Post
Yes, but for certain applications, like professional architectural photography, the multiple gray card technique allows one to white balance different parts of the scene differently by making multiple raw conversions (in Lightroom you could use Virtual Copies), and "blending" the various sections together using masks in PS.

Some people need that. And I emphasize some.
Never having used multiple gray cards and having to blend in several conversions, whether performed in RAW or PS, I don't know the amount of effort involved. Though, I am sure the effort is considerable to make the blends seamless.

If I were going to the trouble of using several gray cards sprinkled around a panoramic room, I would spend the additional effort to use the gray card, take my shot, remove the gray card, and reshoot with the exact same settings. Next location, and repeat. I would *hope* to eliminate the cloning. Just use your gray card settings on your live shots.

Since I have never done architectual shots with or without gray cards, I am out of my depth.
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  #26  
Old September 3rd, 2010, 09:15 AM
Nill Toulme Nill Toulme is offline
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And Michael we're glad to have you back! Hope all is well with you and yours.

Mind, I would never suggest that this (i.e., clicking on black) is any sort of substitute for a WhiBal or the like. It's more of a last ditch desperation kind of thing. The surprise to me has been that it has worked so well to get me a good starting point in badly out-of-color images lacking a decent neutral white.

Speaking of which, clicking on "whites" often tends to be more problematic for me, in fact, now that I think about it. I frequently can click on different sections of the same "white" shirt or player jersey, for example, and get wildly varying (and highly inaccurate) WB's from it.

Nill
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  #27  
Old September 3rd, 2010, 09:32 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Kevin Stecyk View Post
My question about throwing gray cards everywhere would be why? Why bother?
Hi Kevin,

It's a scenario typically encountered in architectural photography, but it can also occur in other situations (e.g. shooting partially under a tree canopy).

In architecture there are different styles of photography. In general there seems to be a preference with USA based photographers to use lots of added artificial (filtered) lighting (and/or transparent colored filter sheets on windows) to control color reproduction and light distribution. Apparently European photographers tend to prefer dealing with existing light (because the architect designed it that way).

Especially in the latter scenario it may be difficult to match furniture color with the other color schemes around in a photograph. We humans do the correction automatically/mentally within a narrow viewing angle, so picture showing a larger scene can be shockingly confrontational.

Some of the mix between e.g. outside daylight and interior tungsten (or fluorescent or LED) light should be maintained but the difference must often be attenuated/controlled. Getting back from shooting a scene, and sitting behind the computer, sometimes others do the postprocessing, can be a daunting task, hence the need for some mind joggers and reliable references. It requires skill and knowledge to do it well, but it always helps to have a known reference handy.

Some customers are very critical about their interior's colors, and can withhold their approval to use the image. I know of an incident a photographer had with a designer about the color of a lampshade. The photograph showed a different color from what the designer had in mind when he chose the material. As it turned out the photographer was right, and the designer was wrong (he forgot how the lampshade looks with lamplight falling through it, instead of the fabric only reflecting light from the outside!!!). So one may need to be able and adjust afterwards, to match expectations, anyway.

All I want to say is, sometimes things need to be spot-on, sometimes things need to represent the ambiance, sometimes it's a mix. It will help to have the possibility to adapt to every possible situation, especially afterwards. Good references help to get 'good' color.

Cheers,
Bart
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  #28  
Old September 3rd, 2010, 10:20 AM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Bart_van_der_Wolf View Post
Hi Kevin,

It's a scenario typically encountered in architectural photography, but it can also occur in other situations (e.g. shooting partially under a tree canopy).

In architecture there are different styles of photography. In general there seems to be a preference with USA based photographers to use lots of added artificial (filtered) lighting (and/or transparent colored filter sheets on windows) to control color reproduction and light distribution. Apparently European photographers tend to prefer dealing with existing light (because the architect designed it that way).....

Some of the mix between e.g. outside daylight and interior tungsten (or fluorescent or LED) light should be maintained but the difference must often be attenuated/controlled.
Bart,

Thanks for pointing this out! This, to me, is most important! I seek the feel of perfect architectural simplicity for spaciousness with enough of the ambience of the real light bring back a feeling of humanity. So, in a way, this place is vacant but inviting for your use, so "Please rent ime and use it for your own pleasure and purpose."

Thanks for the extra insight.

Asher
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  #29  
Old September 3rd, 2010, 10:45 AM
Asher Kelman Asher Kelman is offline
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Quote:
Originally Posted by Michael Tapes View Post
Yes, but for certain applications, like professional architectural photography, the multiple gray card technique allows one to white balance different parts of the scene differently by making multiple raw conversions (in Lightroom you could use Virtual Copies), and "blending" the various sections together using masks in PS.

Some people need that. And I emphasize some.
Hi Michael,

Thanks to you we have a well organized forum structure in OPF! You set us up so well and gave us a jump start for which we'll always be grateful. That was a generous labor of love to this community!

Also I am very pleased with the Gretag Macbeth color reference card, grey cards and WhiBal™, Eye One™ computer monitor spectrophotometer for my Eizo monitor. These are the basis for all my work and I'm grateful for you setting me up too for a color managed workflow!

More so, it's a delight for you to pop in as I know running Raw workflow.com is a 30 hr a day job, LOL!

Yes, I can give excess praise to a friend, but now the simple ungarneshed truth! The WhiBal™ is to me the simplest and most reliable reference for accurate color I have used. I even use it when using gels. I take a reading before the gel is added and then use that previous image of the card as the reference for subsequent images with the gel to get just that pure color effecting change not the temp of the lights.

Folk may not know you are also a talented and avid photographer! Hopefully we'll see more of your work!

Asher
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