gray balance before taking photos and GTI N8 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 75 Old 06-15-07, 12:01 PM
kenyee
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gray balance before taking photos and GTI N8

I've been getting more into photography lately and acquired a whibal white balance card (http://www.rawworkflow.com/products/whibal/index.html).

What's interesting is that the resulting picture doesn't look like the room according to my eyes. The autowhitebalance picture (394) looks more like what I see because of the yellowish ambient lighting in the room.

391 is a picture of the room after I used manual white balance and whibal (that's the GTI N8 on the projector wall from the Simple Grey thread on avsforum in case you're curious). GTI N8 is a certified "neutral munsell N8 gray" that is sold at photography shops like Adorama and B&H Photo, and since we're after the perfect gray screen, I decided to use that as the front projector screen for my Panny AX100.

393 is a picture of the room after I did manual white balance using the GTI N8. What's interesting is that this more reddish than the whibal calibrated image which seems to imply that N8 is not a perfect gray. I'm very impressed w/ how the whibal adjusted the white balance cleanly.

Any color experts care to comment on why GTI N8 can't be used to white balance a camera?

p.s., sorry about the blurriness of the photos...they were taken at 1/4sec because of the low lighting at night.
p.p.s., this means if you're taking photos of your projector screens and you have any ambient lighting, you should be doing a manual white balance to take an accurate picture of your screen (I think).
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gray balance before taking photos and GTI N8-dscf0394.jpg  

gray balance before taking photos and GTI N8-dscf0391.jpg  

gray balance before taking photos and GTI N8-dscf0393.jpg  

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post #2 of 75 Old 06-15-07, 07:35 PM
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Re: gray balance before taking photos and GTI N8

kenyee,

Welcome to the Shack!! It's great to have you here!!

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post #3 of 75 Old 06-15-07, 07:55 PM
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Re: gray balance before taking photos and GTI N8

Welcome back mech, and same Kenyee... great to see you.

This is a very interesting post. Maybe we can get the Calibration and Screen Shot standards thread going here that nobody was interested in elsewhere.

I'll have to get a white balance card myself. What I was doing was setting my internal light meter before shots, but this may be better to get a representation of exactly what I see. I usually take enough pictures to fill my memory card and then sort through them for the ones that look the best and closest to what I see on the screen. Most look nothing like what is up there.

Good topic!
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post #4 of 75 Old 06-15-07, 08:10 PM
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Re: gray balance before taking photos and GTI N8

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wbassett wrote: View Post
Welcome back mech, and same Kenyee... great to see you.

This is a very interesting post. Maybe we can get the Calibration and Screen Shot standards thread going here that nobody was interested in elsewhere.

I'll have to get a white balance card myself. What I was doing was setting my internal light meter before shots, but this may be better to get a representation of exactly what I see. I usually take enough pictures to fill my memory card and then sort through them for the ones that look the best and closest to what I see on the screen. Most look nothing like what is up there.

Good topic!
Thanks Bill! It was a very rejuvenating vacation!! Now I've got a lot to wade through!

I'll reply more on topic later (tomorrow).

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post #5 of 75 Old 06-21-07, 10:30 PM
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Re: gray balance before taking photos and GTI N8

kenyee,

Can you label those photos? Is the top one 391? Thanks! Also I ordered a whibal card today. How long did it take till you received it? Kinda wish I would have had it before I went on vacation...

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post #6 of 75 Old 06-22-07, 05:30 AM
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Re: gray balance before taking photos and GTI N8

What camera and how does it reference white? Could be abias in the camera or there may be other settings for the white point.

Looking for me, just google my username. I have used the same one for most sites for many years.
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post #7 of 75 Old 06-22-07, 08:29 AM
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Re: gray balance before taking photos and GTI N8

mech: top one is 394, 391 is 2nd one, 393 is last (you can right click and select properties to see which file is which). I bought my WhiBal from B&H photo and it took less than a week. Let me know how you like it. Be careful mixing light sources...last weekend, I white balanced for interior lighting and took pics w/ the window in the background and the sunlight in the window was blue because the camera was adjusted for incandescent when I told it to white balance on the WhiBal so I had to crop out pics w/ windows in the background :-)

lcaillo: the camera is a Fuji F30 set on auto white balance. All cameras I've tried suck at auto white balance indoors because there are so many lighting temps that are possible (tungsten, incandescent, HMI, fluorescent, etc.). There are actually multiple fluorescent temps now as they compact fluorescent makers try to get closer to sun light temps.
post #8 of 75 Old 06-22-07, 09:43 AM
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Re: gray balance before taking photos and GTI N8

The N8 and the whibal look fairly similar. Maybe a bit more of a green push in the whibal picture.

When I get mine in a week or so we'll know more.

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post #9 of 75 Old 06-22-07, 05:12 PM
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Re: gray balance before taking photos and GTI N8

The N8 picture definitely looks "warmer", so that makes me wonder if GTI did that deliberately (would make skin tones "glow" more). The N8 screen looks reddish in that picture (which is very odd because you'd think if I pointed at it and said "that's grey", it would be grey). The steam heat pipe in the corner is definitely reddish in that picture, but is painted with beige high-temp paint spray that you can buy from Home Depot. The beige paint on the wall is definitely beige and has no reddish tint to it in real life, even if it looks relatively warm in the N8 picture.

So for actual colors of the objects, the WhiBal one probably is more realistic. However, under the ambient light, everything does have a yellowish tone like the autowhitebalanced pic.

Of course, then I'm viewing this on an uncalibrated monitor (although it has been pretty accurate when I compare photos w/ what people say they took), so who knows? All this calibration stuff is pretty complicated :-)
post #10 of 75 Old 06-22-07, 06:40 PM
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Re: gray balance before taking photos and GTI N8

In MSPaint the pipe gives me these RGB values:

In DSCF0391 171-164-148 Whibal
In DSCF0393 183-170-161 GTI N8
In DSCF0394 193-173-140 Auto

On auto mode there's quite a jump between the RGB values. Keep in mind that there's nothing scientific about this. I could have been off a few pixels (more than likely I was off many!) on each selection. With the N8 you still see a somewhat large drop between the Red and Green but very little between the Green and Blue. And the Whibal has an even smaller drop between Red and Green and then the big drop to Blue. You'd think there would have been a little more similarity there. I'm gonna write it off to poor pixel selection between the samples though. But I do plan on plugging away at this more when my Whibal card shows up. Should be here by Wednesday.

kenyee,

Did you get the GTI N8 paint from B&H as well?


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