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Old June 7th, 2010, 01:34 AM   #1
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LCD Colour Difference

Hi All

Here's one for you guys to figure out. Doing indoor shoots on both my HMC72's and my buddy's DVX100's at weddings, when someone in a purple dress (hopefully female!) is on the dance floor, her dress appears blue in both the EVF and the LCD instead of purple!! The final video is correct, dresses are purple and correctly colour balanced.

With shoulder-mount cameras where you have one eye on the EVF and one to see where you are going, the difference is noticeable all the time cos one eye sees a blue dress and the other sees a purple dress.

Any genius know why? It's only on indoor shots under artificial lighting so maybe the corrected colour balance is only applied to the signal after it's fed to the LCD and EVF...I really don't know!!!!

Like to shed some light on this ?? Don't LCD screens like purple????

Chris
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Old June 8th, 2010, 12:48 PM   #2
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I'll try to keep this simple...

The dress you see is from reflected light; thus white light is filtered (subtracted color) from the reflection and absorption of colors from the dress. The viewfinder uses additive color; where red blue and green sub-pixels add together to make the color you see. The two are very different systems and if we tried to see every color possible, each system has limits and can not reproduce some colors.

Worse yet, I can't say how good are the red, blue, and green filters in the LCD. Maybe there's some bleed through to other colors for some if not all of the colors. Thus the red may not be 100% pure red and may have a tiny amount of blue or green in it or it may be in the other colors.

Another problem is that the LCD is NOT a calibrated source. Just change the view angle and the results change. Likewise, a minor adjustment can shift the results. It's possible to apply color mapping to the viewfinder and improve the color reproduction, but it's just a low cost viewfinder, not a calibrated monitor.

Last of all, and this is likely the most important, the color balance of the dance floor and the color balance of your viewfinder may not match. The dance floor may be a 3200 degree K lighting and the viewfinder may be set to 6500 degrees K. There's not as big a difference between outdoor 5600 degrees K and the viewfinder vs. indoor and the viewfinder.


Bob Diaz
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Old June 8th, 2010, 04:01 PM   #3
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Wow, no wonder I have such a hard time getting colors correct. Would an external monitor solve those problems?
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Old June 8th, 2010, 05:11 PM   #4
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I've also read that LCD's have an interesting time with the color purple, also how DLP has an issue with gold and light green.
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Old June 8th, 2010, 06:00 PM   #5
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Quote:
Originally Posted by Bob Diaz View Post
I'll try to keep this simple...

The dress you see is from reflected light; thus white light is filtered (subtracted color) from the reflection and absorption of colors from the dress. The viewfinder uses additive color; where red blue and green sub-pixels add together to make the color you see. The two are very different systems and if we tried to see every color possible, each system has limits and can not reproduce some colors.

Worse yet, I can't say how good are the red, blue, and green filters in the LCD. Maybe there's some bleed through to other colors for some if not all of the colors. Thus the red may not be 100% pure red and may have a tiny amount of blue or green in it or it may be in the other colors.

Another problem is that the LCD is NOT a calibrated source. Just change the view angle and the results change. Likewise, a minor adjustment can shift the results. It's possible to apply color mapping to the viewfinder and improve the color reproduction, but it's just a low cost viewfinder, not a calibrated monitor.

Last of all, and this is likely the most important, the color balance of the dance floor and the color balance of your viewfinder may not match. The dance floor may be a 3200 degree K lighting and the viewfinder may be set to 6500 degrees K. There's not as big a difference between outdoor 5600 degrees K and the viewfinder vs. indoor and the viewfinder.


Bob Diaz
What Bob says. Purples, especially dark purples, are often on the edge of color gamut. For many devices, and many color spaces. In this case, your viewfinder is just out of gamut. Not a big deal.

The viewfinder is there as a composition aid. It's supposed to be in the ball park color wise, but it's not supposed to be something by which you make color judgments.

IOW, what you are seeing is perfectly normal. Don't let it bother you.
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Old June 8th, 2010, 06:26 PM   #6
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Hi Guys

Very much appreciated!! Nope it doesn't bother me at all...admittedly the first time I noticed it I was worried that something had gone amiss with the white balance but I simply ignore it now.

The resultant footage, of course, is always correct and the actual illusion is more apparent with a shoulder mount camera as your right eye is viewing a different colour thru the EVF to what your left (hopefully open) eye is actually seeing!!

I purely was looking for a technical explanation and Bob did exactly that...thank you!!

Chris
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Old June 12th, 2010, 11:23 PM   #7
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Originally Posted by Paul Digges View Post
I've also read that LCD's have an interesting time with the color purple, also how DLP has an issue with gold and light green.
You're not kidding. My logo is purple. Designing it was driving me nuts cause I could never really see purple on my monitor.
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Old June 13th, 2010, 02:19 AM   #8
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Ha...mine's purple too!

In any case, the Panny's all have TERRIBLE LCD's. They are IMHO not even good enough for critical focus let alone true color representation. I have used the HMC-40, HMC-150, HPX-170 and the HVX-200. An external monitor helps see the colors better and is mandatory if you do manual focusing. (although I am liking the focus assist when I can't squeeze a monitor into the gig)

Best thing I've found is get a good white balance card, get the exposure right and the camera does a decent job of taking care of the colors. Never a major hassle to tweak in post if those rules are followed.
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Old June 13th, 2010, 08:15 AM   #9
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Well, at least my logo and graphic have no purple whatsoever!! I figured that it must be the inability for the LCD to display purple correctly when my buddy in Green Bay asked about the very same problem he was having on his DVX 100!! Must be a common Panny LCD issue.

Yep the camera does a perfect job on balance even with mixed lighting...I actually carry a small white board in my case (about 12" x 9") and it does an excellent balance if there is nothing white around..however at weddings the bride is highly visible and makes a perfect candidate for white balance until you get one with an ivory dress!!

I find that I can leave my cams on auto at the reception and as long as you zoom onto something pure white the auto-WB will correct within about 3 seconds.

Chris
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Old June 13th, 2010, 02:53 PM   #10
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This kind of thing takes me back to my (film) wedding days when you'd have a bride in a white dress and her mother in a shocking cerise outfit, this - in stills photo speak - caused a 'crossed curve' whereby the cerise next to the white of the brides dress would be so bright that it would cause the shadowed areas with in the dress to appear green i.e. the opposite colour (hence the cross curve, green being opposite to magenta, which is close to cerise).

White cats on red pillows where also a popular thing for Joe Public to photograph too.
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Old June 13th, 2010, 10:20 PM   #11
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I noticed this a while back and got freaked out. Purples are blue and vice versa... but the video was always correct. Glad to know this is common!
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Old June 14th, 2010, 11:36 AM   #12
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The same colour shifting has happened to me few days ago. A stunning red bouganvillea has been rendered in my HMC151 LCD as blu!!! I contacted Panasonic but no response (at this time)
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