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D200, color purple.........

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Steve47416

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Hi,

Shot this Iris flower in my studio but could not get a true purple. The flower looks blue. I shot a gray card and imported the WB, hardly any change from he original. The flash color temp is specified at 5600K. The only way I can get it closer is to raise the color temp above 7500K. I used to have the same problem with the D100. Could someone explain to me why in NC 5600K in daylight and 5600K in flash renders different color balance, I thought color temp is color temp. Any ideas?
Comments are welcomed.
Steve Provisor











 
This has been discussed before...

Basically, the sensor array in your camera has a set of coloured filters in front of monochrome sensors, one for (appoximately) red, green and blue.

Now, it depends upon the filter characteristics as to what colour frequencies will be detected by the sensors underneath.

Remember that the electromagnetic spectrum is a continuous range but the sensors will see only small parts of that, and do your eyes. Both will "see" colours differently or not be able to see certain colours at all.

In fact, CCD sensors are actually quite sensitive (natively) to a far wider range of light wavelengths than the eye, so cameras have to have strong ultraviolet and infrared filters. Some of the purpleyou see may come from a wavelength cut off in the violet end of the spectrum. Some digital cameras may be able to pick that wavelength up, others won't, as the D200 seems not to.

It's not a fault with the camera.. every camera has to compromise in this respect.
 
It appears purple to me on my monitor, but it is subtle. A plus adjustment on hue in Photoshop gives a lovely purple. The orange spot becomes more lemony though. There is also a hue adjustment in the menu for your camera if you want out of the camera strong purples.
 
This purple to blue shift is interesting and it's been discussed for a lot of cameras. Prominent with my D70 in mode II. Hope these links work:

http://72.14.203.104/search?q=cache:117vNhl2rpkJ:www.nikonians.org/cgi-bin/dcforum/dcboard.cgi%3Faz%3Dread_count%26om%3D4706%26forum%3DDCForumID71+nikon+%22purple+to+blue%22+shift&hl=en&gl=us&ct=clnk&cd=4

http://72.14.203.104/search?q=cache:Sit7cfxIJC4J:forums.dpreview.com/forums/readflat.asp%3Fforum%3D1034%26message%3D14426189%26changemode%3D1+nikon+%22purple+to+blue%22+shift&hl=en&gl=us&ct=clnk&cd=1

http://72.14.203.104/search?q=cache:NLnJ-o7UlPcJ:www.nikonians.org/cgi-bin/dcforum/dcboard.cgi%3Faz%3Dread_count%26om%3D15086%26forum%3DDCForumID84+nikon+blue+purple+shift&hl=en&gl=us&ct=clnk&cd=30

Take a look. Some have suggested it's bit intentional to avoid skies looking purple at all, which would detract from sales.
 
D200 has pretty good anti-IR filter, unlike the D100.

--
Thierry
 
Hi Steve,

Have you tried to select only the "Blue" or "Magenta" channel in Hue/Saturation, as to avoid adjusting other color channels? Another possibility is to use a selective mask around the petals themselves. Not great when you have to manually change a lot, but it works in a pinch.
 
I've had success using L.A.B. The ways the colors are separated - A channel has green/magenta and the B channel has yellow/blue, it's trivial to correct these minor issues with purple without harming other colors or the overall balance.
 
This was a shot someone else posted in an older thread. I used L.A.B. to make the modification. I made the greens a bit more yellow due to personal preference, but it could have just as easily been made the same.

The original:



The "purple fix":

 
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