Since when is purple blue?

Started Sep 14, 2011 | Discussions
Marker
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Since when is purple blue?
Sep 14, 2011

Am I the only one who has this problem? When I shoot something with purple in it on my D300, it comes out blue - not even close to the actual color. Other colors in the frame are fine. What gives?
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Leonard Migliore
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Got a sample?
In reply to Marker, Sep 14, 2011

Marker wrote:

Am I the only one who has this problem? When I shoot something with purple in it on my D300, it comes out blue - not even close to the actual color. Other colors in the frame are fine. What gives?

I don't generally see this but some flower colors can give you trouble because they're fluorescent. Could you post an example?

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Leonard Migliore

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Island Golfer
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Re: Since when is purple blue?
In reply to Marker, Sep 14, 2011

Absolutely! And, I thought it was me. It is the worst when the color is extreemly vibrant purple in bright sunlight. I kept trying to correct them in Photoshop. But, no luck. I finally deleted them all. I would love to hear anyone's solution to this issue. I have always thought that it might have something to do with the camera having improperly calibrated white balance.

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truview

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nikons52
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Re: Since when is purple blue?
In reply to Marker, Sep 14, 2011

Marker wrote:

Am I the only one who has this problem? When I shoot something with purple in it on my D300, it comes out blue - not even close to the actual color. Other colors in the frame are fine. What gives?
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I generally get pretty good purples...

Best,

Don

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olyflyer
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Re: Since when is purple blue?
In reply to Marker, Sep 14, 2011

Marker wrote:

Am I the only one who has this problem? When I shoot something with purple in it on my D300, it comes out blue - not even close to the actual color. Other colors in the frame are fine. What gives?

Use manual WB. AWB is fine in many situations but almost never as accurate as manual WB, not even in bright sunlight.

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tenrec
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Re: Since when is purple blue?
In reply to Marker, Sep 14, 2011

I have long noticed this problem with digital cameras, and for a long time I thought that they simply could not reproduce purple properly. I still find that my D200 has this difficulty, but I have figured out a solution. I always get the problem when I use matrix metering and follow the camera's recommendations. When I see this happening, I switch to manual metering, either spot or center-weighted, and the problem goes away. I think the matrix system frequently tends to overexpose purple, especially deep purple, and renders it as lavender or some other light shade.

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jkjond
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Re: Got a sample?
In reply to Leonard Migliore, Sep 14, 2011

Florescent - is that true?

I know film photographers used to use filters in order to photograph bluebells, which are notoriously different in photographs to what the eye sees. I'd expect digital photographers to suffer similar probs, though not something I've followed. I thought it was a UV issue, but not as simple as just using UV filters to correct.

How 'they' know, I've no idea, but I've read that bumble bees see flowers as very different colours to humans. It stands to reason that film/digital/human/bumble bee eyes and brains will each have a different take on colour.
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Alnitak
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Re: Got a sample?
In reply to jkjond, Sep 14, 2011

I had this issue a couple of years ago with a D200. Had to PP blue to purple. Did some research, and seem to remember reading something like that there is no purple in the digital world...it's not recognized. I even noticed it on the (digital) TV when they were broadcasting the Minnesota Vikings. Their purple uniforms looked blue. I can't remember all the reasons, and what you need to do to correct, but it is a common problem. Google it.

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Tony Beach
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Re: Since when is purple blue?
In reply to tenrec, Sep 14, 2011

tenrec wrote:

I think the matrix system frequently tends to overexpose purple, especially deep purple, and renders it as lavender or some other light shade.

Yep, for tricky colors metamerism: http://en.wikipedia.org/wiki/Metamerism_%28color%29 is a definite issue, and exposure as well as WB become critical. Even when you shoot RAW, when you try to apply EC to a file containing these tricky colors, you can end up with metameric failure.

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Marker
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Re: Got a sample? Here's one from my old Fuji S2
In reply to Leonard Migliore, Sep 14, 2011

I could not take this picture with my D300.

I'll post some recent ones with the problem in a little while.
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lock
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I have no issues if I choose specific WB
In reply to Marker, Sep 14, 2011

E.g., with sunlight, I choose the WB accordingly. Also, I have adjusted the AWB because it clearly contained too much green/blue: A4/M3.

I now have no issues with purple colors using any WB setting. If you wish I can upload some examples.

Btw, be aware of the picture control settings if you shoot jpg. With vivid the color error tend to get worse.

lock

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Marker
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Samples
In reply to Marker, Sep 14, 2011

Ok, here we go. The first of each of these two shots is out of camera except for resizing. The second has been adjusted with a 25 point slide to the right on "hue" in Photoshop. In each case, the second version best represents reality. Is this a Nikon problem? A problem with just my cameras? or a problem with CMOS censors? (except the Canon people don't seem to experience it and they have CMOS censors) My old Fuji S2 didn't have this issue and it used a CCD censor.

Thanks by the way for all the suggestions thus far. It's just disappointing to realize your high end gear has an Achilles heel.

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lock
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Flash
In reply to Marker, Sep 14, 2011

Did you use flash in the first ? If so, what Wb did you use ?
How about the second, what was the WB setting ?

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Marker
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Re: Flash
In reply to lock, Sep 14, 2011

Yes, flash on both with white balance at default. However, I took your advice and changed the WB as you suggested and it warmed up the image, but the purple still came out as blue.

Just to mention, I experience the same problem when I shoot without flash, indoors or out.
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sportfish
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Re: Got a sample? Here's one from my old Fuji S2
In reply to Marker, Sep 14, 2011

MARKER...i think the answer is really simple here.
you need to take a pre test white balance shot.
preferably with an 18% grey card. works every time for me.

regards sportfish

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Tony Beach
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Re: Samples
In reply to Marker, Sep 14, 2011

It's interesting that after you adjust the hue in the first shot, the Windex bottle and the bag of whey protein diverge dramatically away from one another. It's clear that the camera has recorded different colors and that they made it into the profile as different colors. Have you tried shooting RAW with a WB reference in the shot?

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malch
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Re: Samples
In reply to Marker, Sep 14, 2011

Marker wrote:

In looking at these two shots, I think at least some of the colors are way off in the second shot. I've been using Windex for many years and I've never seen it that color.

The first shot is much closer to the Windex I've used.

However, I do think your white balance is off in the first shot. I assumed that the countertop is neutral and adjusted the image based on that. The Windex still looks believable but the bag became significantly more purple.

If you want to better understand what's going on here, I highly recommend reshooting that scene with a Whibal or other grey card in the frame. Be sure to shoot RAW so you can correct the WB nicely after the fact.

Bottom line: I think most of your problem is white balance but I'm certainly willing to believe there are some strange artifacts present generated by a combination of the flash spectrum and the funky materials and dyes used in the making of the purple plastic bag.

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L Bourdillon
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Re: Flash
In reply to Marker, Sep 15, 2011

Marker wrote:

Yes, flash on both with white balance at default. However, I took your advice and changed the WB as you suggested and it warmed up the image, but the purple still came out as blue.

Just to mention, I experience the same problem when I shoot without flash, indoors or out.

Often I'll see much the same thing - blue not violet (purple?). And on any RGB sensor camera.

This could be due to the original "creation" of the color. From the visual aspect, violet can be formed in two ways: a mixture of red and blue, or a true color spectral line in the violet.

If the color has two lines (i.e. red and blue) the RGB sensor can usually reproduce this effectively. Many man-made dyes for clothing, etc., are mixes.

However, with a true violet line, the RGB sensor has only the blue pixels receiving (limited) information and the color is too blue.

Interestingly, the violet color in most flowers is a single violet line - and, many flying (pollinating) insects have vision the peaks in the violet-to-ultra-violet.

Larry

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stanginit
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white balance
In reply to Marker, Sep 15, 2011

the auto wb is not perfect.

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Leonard Migliore
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That sounds correct
In reply to L Bourdillon, Sep 15, 2011

L Bourdillon wrote:

Often I'll see much the same thing - blue not violet (purple?). And on any RGB sensor camera.

This could be due to the original "creation" of the color. From the visual aspect, violet can be formed in two ways: a mixture of red and blue, or a true color spectral line in the violet.

If the color has two lines (i.e. red and blue) the RGB sensor can usually reproduce this effectively. Many man-made dyes for clothing, etc., are mixes.

However, with a true violet line, the RGB sensor has only the blue pixels receiving (limited) information and the color is too blue.

Interestingly, the violet color in most flowers is a single violet line - and, many flying (pollinating) insects have vision the peaks in the violet-to-ultra-violet.

Very nice explanation; looks like the only way out would be to have the red filter leak a little UV.
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