On TV: Why is Purple Blue?

[Chuck Hildebrandt]

I've been noticing this for years now -- whenever I've watched the LA
Lakers, or Minnesota Vikings, or Northwestern Wildcats, or any team that has
purple as a team color, their uniforms appear blue on television. I noticed
it again on Sunday when I was watching the Vikings/Bears game. I see it
again tonight with the Colorado Rockies.

One weird aspect of this is that the graphics the networks use to denote the
team's colors definitely appears as purple -- but the uniforms themselves
appear as blue.

This doesn't occur in photographs, as pictures in magazines or the newspaper
from the very same game yield a purple color for the uniforms. The
purple-uniform-as-blue thing happens only on TV.

What is it about the electronics of television that causes this to happen?

Thanks.

Chuck

 

[Sir Charles W. Shults III]

This is because CCD cameras that are typically used for television now are
sensitive to other wavelengths and can create false colors. One way to see this
is to aim a TV remote control (infrared type) at your webcam. You will see a
bright bluish white light from it, although it is IR and not visible to the
human eye.
In the real world, there are unseen sources of IR and also there are dyes in
our clothing and everyday items that can fluoresce IR, similar to UV/dayglow
colors.
Added to the camera's sensitivity for IR, the colors tend to pick up a blue
cast.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Richard Crowley]

"Chuck Hildebrandt" wrote ...

I've been noticing this for years now -- whenever I've watched the LA
Lakers, or Minnesota Vikings, or Northwestern Wildcats, or any team that
has
purple as a team color, their uniforms appear blue on television. I
noticed
it again on Sunday when I was watching the Vikings/Bears game. I see it
again tonight with the Colorado Rockies.

One weird aspect of this is that the graphics the networks use to denote
the
team's colors definitely appears as purple -- but the uniforms themselves
appear as blue.

This doesn't occur in photographs, as pictures in magazines or the
newspaper
from the very same game yield a purple color for the uniforms. The
purple-uniform-as-blue thing happens only on TV.

What is it about the electronics of television that causes this to happen?

1) The color sensitivity of the red and blue imaging filters/chips.
2) The wierd man-made dyes used in modern fabric.

There was an extensive discussion of this over on one of the television-
related sci. newsgroups several months ago. (Except that it was the
weather-girl's purple pant-suit!)

Silver-halide-type film cameras use "negative"/"subtractive" filters
(yellow, magenta, cyan), where video (and electronic still cameras)
use "positive"/"additive" filters (red, green, blue). One theory is
that those "negative" filters have a broader bandpass and don't
miss the wierd (aneline dye?) colors in the "plastic" fabric.

 

[Bob Myers]

"Chuck Hildebrandt" <mcmlxi@enteract.com> wrote in message
news:62f536370cadcae1d1aeb0159f05c97d@news.teranews.com...

One weird aspect of this is that the graphics the networks use to denote
the
team's colors definitely appears as purple -- but the uniforms themselves
appear as blue.

Accurate reproduction of color imagery via electronic means is a
topic that can fill a book - and has! - but in somewhat simplified
terms there are two major problems here:

1. Both the image source (in this case, the camera) and the
display (a CRT) may be "speaking" in terms of RGB values,
but may not be using quite the same red, green, and blue (although
these ARE supposedly standardized by the broadcast television
specifications) or how much of each is supposed to be combined
to make "white." This will alter the appearance of the color as
displayed vs. what the camera "intended."

2. No three-primary system can ever cover the entire range of
colors perceivable by the human eye (due to the nature and
overall shape of the "color space" in which they must be represented).
Further, none of the three primaries used - either by the camera or
in the CRT - is fully saturated, which additionally restricts the range
of colors which can actually be reproduced correctly. Truly
saturated purples and yellows are difficult if not impossible to
produce in the typical RGB system.

In addition, the color encoding system used in television ("NTSC"
encoding) imposes additional limits, and also some unique problems
in obtaining accurate and repeatable colors. The reasons are a bit
much to go into in a short posting, but again really accurate purples
wind up being difficult to convey properly. You CAN get a reasonably
good purple out of the system - as evidenced by what you're seeing
in the network-generated graphics - but keep in mind that THOSE
are artificially created by a system that can be biased in favor of
greater saturation of these colors, rather than a good balance and
accuracy overall.

If you'll forgive the plug, I cover this in reasonable detail in my book
"Display Interfaces," which has sections both on color in general and
on the system used to encode color for broadcast television. (It's
part of the SID-Wiley series on display technology, published by
John Wiley & Sons.)


Bob M.

 

[Charles Schuler]

"Chuck Hildebrandt" <mcmlxi@enteract.com> wrote in message
news:62f536370cadcae1d1aeb0159f05c97d@news.teranews.com...

I've been noticing this for years now -- whenever I've watched the LA
Lakers, or Minnesota Vikings, or Northwestern Wildcats, or any team that
has
purple as a team color, their uniforms appear blue on television. I
noticed
it again on Sunday when I was watching the Vikings/Bears game. I see it
again tonight with the Colorado Rockies.

One weird aspect of this is that the graphics the networks use to denote
the
team's colors definitely appears as purple -- but the uniforms themselves
appear as blue.

This doesn't occur in photographs, as pictures in magazines or the
newspaper
from the very same game yield a purple color for the uniforms. The
purple-uniform-as-blue thing happens only on TV.

What is it about the electronics of television that causes this to happen?

You have received some good responses. And, lots of males are in a category
known as red-green color blind.

 

[Mark Carroll]

In article <uf8ab.6747$kg.5660@twister.tampabay.rr.com>,
Sir Charles W. Shults III <aichipREM@OVEcfl.THISrr.com> wrote:

This is because CCD cameras that are typically used for television now are
sensitive to other wavelengths and can create false colors. One way to see this
is to aim a TV remote control (infrared type) at your webcam. You will see a
bright bluish white light from it, although it is IR and not visible to the
human eye.
(snip)

Wow, you're right. (-: I tried it last night with our digital camera.

-- Mark

 

[Bob Myers]

"Charles Schuler" <charlesschuler@comcast.net> wrote in message
news:jVydnQtn3rqhvPeiU-KYgg@comcast.com...

You have received some good responses. And, lots of males are in a
category
known as red-green color blind.

Something like 8% of the male population - this condition is linked to
a missing gene on the X chromosome, so for it to affect a female it has
to be missing on both Xs. However, this results in the inability (or
reduced ability) to distinguish red and green; it would not account for
differences in perceived color between a television image and the real
world.

Bob M.

 

[Charles Schuler]

Something like 8% of the male population - this condition is linked to
a missing gene on the X chromosome, so for it to affect a female it has
to be missing on both Xs. However, this results in the inability (or
reduced ability) to distinguish red and green; it would not account for
differences in perceived color between a television image and the real
world.

You could be correct. However, there is a psychological compensation factor
that blurs this issue. Those with this deficiency can, in certain
environments, fill in the missing data by using brightness and contrast and
context. It's not as simple as most think.

 

[Don Klipstein]

In article <jVydnQtn3rqhvPeiU-KYgg@comcast.com>, Charles Schuler wrote:

You have received some good responses. And, lots of males are in a
category known as red-green color blind.

Actually, there are two "red-green" forms of colorblindness, both of
which very disproportionately affect males.

One is deuteranopia, where reds and greens look alike in hue but without
red objects looking darker than they should. The other is protanopia,
which is sometimes known as "red blindness" because it makes red objects
look darker than they should in addition to making reds and greens similar
or somewhat similar in hue.

- Don Klipstein (don@misty.com)

 

[Don Klipstein]

In article <3f6a3ae4$1@usenet01.boi.hp.com>, Bob Myers wrote:

"Charles Schuler" <charlesschuler@comcast.net> wrote in message
news:jVydnQtn3rqhvPeiU-KYgg@comcast.com...

You have received some good responses. And, lots of males are in a
category
known as red-green color blind.

Something like 8% of the male population

Including the mild/partial forms known as protanomaly and deuteranomaly.
The severe forms (protanopia and deuteranopia) affect more like 1% of the
male population.

- Don Klipstein (don@misty.com)