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COLOR BIAS, Que es?

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Old Saturday 24th October 2009, 00:40   #1
xmeecosmic
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COLOR BIAS, Que es?

I have not been able to come across a good definition of color bias, or at least one that I could practically comprehend.

Consequently, what is color bias, why does it or does not occur, and when and when isn't it optically important/significant?
Also, it wouldn't hurt to explain what warm,cool, and neutral signify.

Please go slow as I am only an ex-MSW who never had to take an economics course and obviously never a mechanical engineering course.
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Old Saturday 24th October 2009, 01:34   #2
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http://www.lintuvaruste.fi/hinnasto/...ulars_GB.shtml

Possibly the best discussion of "color bias" can be found in the short discussions of "color rendition" in the above link. It is an english translation of the Binocular Reviews from the now defunct Finnish Birding Magazine, "Alula." The reviews were written by Kimmo Absetz. (IMHO, these reviews are worth preserving as "Reference Standards" on how binocular reviews should be done.)

With that editorializing out of the way, I think that "color bias" usually is the result of a consensus of opinion among the people who use the specific binoculars in question because there are always some people whose eyesight or interpretation of what they are seeing is different from others. For instance, I own at least 9 Nikons. The general consensus (and it agrees with Kimmo Absetz's assessment) is that Nikon has a color bias toward Red. I don't see this color bias myself. To me, they have the most neutral of color biases. I can easily see the yellow color bias that my old Leitz 7 x 42 Trinovid is notorious for, and there even seems to be a hint of it in my more modern Leica 7 x 42 Trinovid. My little Zeiss 8 x 20 Victory does seem to have a slightly blue, cool, color bias as Absetz notes. I can't comment on Swarovski because I have had very little experience with them.

I wonder if visual phenomena like these are scientifically measurable or if they are subjective interpretations of our brains and our optic nerves, which are connected to our brains after all!

Cordially
Bob

PS: In the link above, click on the review: "Leica 10 x 42 Ultravid Challenges the Elite 10 Power Binoculars" to see a more extensive comparison with other Brands.

Last edited by ceasar : Saturday 24th October 2009 at 01:54. Reason: Grammar
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Old Saturday 24th October 2009, 10:22   #3
Sancho
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Quote:
Originally Posted by ceasar View Post
I wonder if visual phenomena like these are scientifically measurable or if they are subjective interpretations of our brains and our optic nerves, which are connected to our brains after all!
I can´t help wondering that also, Bob...what we interpret with any of our senses needs processing inside the skull. We debate about art, literature, politics etc., because we interpret data differently, and I reckon it must be the same with what we see through binos...especially as we´re talking about subtle differences in wavelenghts, etc. Have you ever taken statements from a number of witnesses to an incident, say an accident or a fight? This happens in my school sometimes, and I´m amazed by the huge variation in accounts from different people who all saw exactly the same thing. Each one believes they are relating the incident accurately, but there are as many different interpretations as there are people. I reckon if you lined up twenty birders and ten "alpha" binos, you´d get the same kind of variation in interpretiation. I don´t even trust my own eyes anymore, when I try to compare two optics I´m sure primary deciding factors are subjective ones (I mean for for ornery folk like me, not for optical experts...)
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Old Saturday 24th October 2009, 10:49   #4
end4
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I have not been able to come across a good definition of color bias,
good working definition: "it's in the eye of the beholder" =:
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Old Saturday 24th October 2009, 12:55   #5
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Thanks all for your responses but...
what and why is it that is in the eye of the beholder?

Last edited by xmeecosmic : Saturday 24th October 2009 at 14:08.
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Old Saturday 24th October 2009, 13:07   #6
etudiant
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Eye of the beholder is very appropriate.
The color perceived by each individual eye differs, as anyone can test by simply looking at something first with one eye and then with the other.
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Old Saturday 24th October 2009, 14:04   #7
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Color bias is how an image differs when viewed through optics as compared to when viewed with your naked eye.

If a binocular has a yellow bias images will look more yellowish when viewed with them compared to without them.

Warm or cool would be bias toward the warm and cool colors, warm being red, orange, and yellow, and cool being green, blue, and violet.

As far as why it happens and why it is optically important (or if it is), check these threads.

Colour balance - is it really that important?

What determines our color sensitivity as looking through bins?

Mike
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Old Saturday 24th October 2009, 14:13   #8
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That is a good definition of color bias Mike!
Bob
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Old Saturday 24th October 2009, 14:18   #9
xmeecosmic
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Thanks Mike for the clear and concise definitions along with the links. I now have a basis of understanding and will follow-up on the other threads.
For a while, I thought that I would have to consult the Metaphysical Forum or the Paranormal Forum to experience the answers.

How then optically does one binocular, say the Sky King (as it has been reported in BF) control color bias/or have less issues with it than an other binocular say the ZRS'?
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Old Saturday 24th October 2009, 14:37   #10
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I agree with Mike. The way you perceive color with the naked eye may be subjective, but the change imposed by optics with non-linear light transmission on the colors that reach your eye is not. That can be measured and photograghed. All binoculars have non-linear light transmission. Usually there is a peak in the light transmission somewhere between 550nm (yelow/green) and 650nm (red) accompanied by a roll off in transmission in the blue/violet. The location of the peak determines the exact color of the color bias and the difference in transmission between the peak and other colors determines the strength of the bias. In modern multi-coated binoculars the peak is minor and broad so the color bias is quite mild, like a very weak color filter. The weakness of the bias in modern optics probably accounts for the different subjective impressions people report. It's easily overwhelmed by the varying colors of light at different times of day and different weather conditions, but the light transmission curve of the binocular does not change from person to person.
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Old Saturday 24th October 2009, 15:03   #11
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Thanks Henry for even more clarification. Measurable, Quantifiable, Optically Objective, largely controllable through multi-coating, consistent light transmission curve but since the color bias is weak and viewing conditions may vary, people may experience it differently.
i think that I am starting to get a handle on it.
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Old Saturday 24th October 2009, 16:05   #12
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Here's a link to some of Ron's (Surveyor) measurements of binocular light transmission which show the non-linear transmission across different colors.

http://www.birdforum.net/attachment....6&d=1254939832

The photo method I concocted is designed to show what the color bias of different transmission curves actually looks like.
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Old Saturday 24th October 2009, 16:42   #13
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Hi Henry,

Does your camera lens have a specific bias when you measure and photograph?
Will it amplify or diminish the binoculars bias? Any optical device can have a bias.

Ultimately the computer, monitor and software you view it on will screw it up completely. Or the film you view it on will show it differently. But, I understand your intentions. Most people see a yellow bias in Swaro bins. Ok... it's yellow.

When all other lighting is controlled the bias comes from the glass. Or the coatings. Or the glue used to bind some glass. Or the plastic used in some elements.

In top end bins the bias is most likely specific and for a purpose. In cheaper bins maybe not.

Your explanation shows what the bias is by the light transmission peak. But that is just the measurement of something. What actually caused it to measure this way?

Maybe I'm wrong.

Cheers
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Old Saturday 24th October 2009, 17:05   #14
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Hi,

To supplement Henry’s comments.

I have attached a CIE color report. This is the industry standard for CCT (Correlated Color Temperature) or “color bias” to the Standard Observer, or “average observer”. These numbers are derived from mathematical analysis of the transmission curve.

Of course, the individual may be far more sensitive to the green or red sides of “average", thus the different perceptions of color.

Best
Ron
Attached Files
File Type: txt ColorSample-2008_1_2-2.txt (782 Bytes, 134 views)

Last edited by Surveyor : Saturday 24th October 2009 at 17:08.
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Old Saturday 24th October 2009, 17:49   #15
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Hi Surveyor,

I understand the CIE system is a metric for measuring color. You can accurately measure any color... I'm asking when you view through something what is making the color shift. I want to know what causes the bias in the system. Not the end measurement of the color.

So, what component is causing the color bias? I'm sure it's lots of things.

Cheers

Last edited by oleaf : Saturday 24th October 2009 at 17:51.
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Old Saturday 24th October 2009, 17:55   #16
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Quote:
Originally Posted by oleaf View Post
Hi Henry,

Does your camera lens have a specific bias when you measure and photograph?
Will it amplify or diminish the binoculars bias? Any optical device can have a bias.

Ultimately the computer, monitor and software you view it on will screw it up completely. Or the film you view it on will show it differently. But, I understand your intentions. Most people see a yellow bias in Swaro bins. Ok... it's yellow.

When all other lighting is controlled the bias comes from the glass. Or the coatings. Or the glue used to bind some glass. Or the plastic used in some elements.

In top end bins the bias is most likely specific and for a purpose. In cheaper bins maybe not.

Your explanation shows what the bias is by the light transmission peak. But that is just the measurement of something. What actually caused it to measure this way?

Maybe I'm wrong.

Cheers
oleaf,

The camera and monitor bias shouldn't matter since the photo method is comparative, not absolute. Light from the same piece of paper is photographed directly and then after passing through the binocular optics. The difference between the two is the color bias imposed by the binocular.

As for the cause of the bias in the optics, I would say it's virtually all in the coatings. There may be a little extra light loss in the glass at the extreme ends of the visual spectrum, but most optical glass has nearly linear transmission from the far violet to the far red. The only serious exception I know of is a single type of strongly yellow tinted glass used in the eyepieces some Russian binoculars. I've owned examples of uncoated binoculars which show dim images, but very little color bias and I've owned some examples of binoculars which underwent coatings changes (Nikon E series and Swarovski Habicht Porros) in which the very same optical design and glass types show very different color biases from nothing except a change in coatings. The only examples I know of color bias caused by lens cement come from the Canada Balsam in old binoculars deteriorating.

Top end bins usually claim to provide natural unbiased colors, which I think is certainly the best thing for birding.

Henry

Last edited by henry link : Saturday 24th October 2009 at 18:40.
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Old Saturday 24th October 2009, 18:16   #17
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Hi Oleaf,

Typically, this is more subjective than I want to get into. Color perception is too dynamic for me to try to understand. I only want to quantify differences in optic equipment and not perceptions.

Color bias is caused by to many things to list, such as color influence of nearby objects, moisture in the air, atmospheric pressure or any metric that can alter refractive properties of the light path, the source lighting color temperature, etc. Optics acts as a fixed filter, with a static transmission shape.

An interesting experiment for those who wish to see a perceptual experience. Go to the local Wally World and buy enough Daylight or Sunlight (5000-6000K) compact fluorescent bulbs to completely change out one room of your house. Most house lighting is around 2800K. If you try this, let me know how long it takes you to change them back. I did this because I thought it would be a good way to change the white balance for photos in my optics test photos.

Best
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Old Saturday 24th October 2009, 20:49   #18
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Hi guys,

I really do understand the color influences of external forces. Part of my job is as a photographer so I really understand lighting temperature. I'm interested in the constant bias of the optical device. Why it's yellow, or red, or blue. I've always thought Nikon had it right with the LXL. That to me is most neutral.

I'd like to know why Nikon chooses red, Meopta yellow, Swarovski yellow, Zeiss blue.
What their philosophies are. Yellow is for hunters... but for what purpose. More contrast or brightness on crappy weather days?

Cheers

Cheers
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Old Saturday 24th October 2009, 21:03   #19
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Guys,

I gotta say discussions like this are very interesting. Color bias can make or break a very expensive optics purchase. And it's interesting to hear how some can see it and some can not. If you bird in the woods a lot it's tough to see a bias. If you bird on overcast, low ceiling days in the open it's easier to see.

Cheers
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Old Sunday 25th October 2009, 01:18   #20
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Similar to Oleaf's question as to why certain binocular manufacurers choose a particular color bias, I had read on BF that someone had stated that the majority of binoculars that are produced transmit a red/yellow bias. Is this the case and is that deliberate-if so, why would that be?
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Old Sunday 25th October 2009, 01:06   #21
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Quote:
Originally Posted by oleaf View Post
Hi guys,

I really do understand the color influences of external forces. Part of my job is as a photographer so I really understand lighting temperature. I'm interested in the constant bias of the optical device. Why it's yellow, or red, or blue. I've always thought Nikon had it right with the LXL. That to me is most neutral.

I'd like to know why Nikon chooses red, Meopta yellow, Swarovski yellow, Zeiss blue.
What their philosophies are. Yellow is for hunters... but for what purpose. More contrast or brightness on crappy weather days?

Cheers
I think part of the answer may lie with haze penetration. Binoculars sometimes classified with a yellow or red bias also perform better at haze or fog penetration. I have found binoculars manufactured out of Japan fall into this "hazer" category. This is one area where binoculars are different from cameras. With cameras, you can easily attach a U-V filter. Not so with binoculars. So, again in my humble opinion, I think the optical manufacturers build haze penetration into some binoculars, knowing a significant market share of users will observe in haze intensive environments.

Just my humble opinion. I do not have any test results or stats to support my opinion.

...Bob
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Old Sunday 25th October 2009, 01:41   #22
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For my eyes, the slightly warm color bias does a better job of contrasting the more subtle earth tone colors, browns, greens, grays, tans, etc. I think one reason why the Swarovski EL is so popular with hunters is this very reason. Not only does it do a good job with game animal colors it also does a good job at rendering brighter colors of the more colorful avian inhabitants. I always viewed it as using different colored sunglasses for various conditions. I personally do not like something like a Zeiss FL nearly as much as I do the Swarovski EL or the Steiner Peregrine XP
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Old Monday 26th October 2009, 19:29   #23
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I think part of the answer may lie with haze penetration. Binoculars sometimes classified with a yellow or red bias also perform better at haze or fog penetration. I have found binoculars manufactured out of Japan fall into this "hazer" category. This is one area where binoculars are different from cameras. With cameras, you can easily attach a U-V filter. Not so with binoculars. So, again in my humble opinion, I think the optical manufacturers build haze penetration into some binoculars, knowing a significant market share of users will observe in haze intensive environments.

Just my humble opinion. I do not have any test results or stats to support my opinion.

...Bob
Kentucky USA
Bob, that's a good point. I do remember some of the aftermarket fog lights for car use yellow light for better penetration. I also have seen Steiner's advertisement that indicates warm bias is better for hunting. I am not a hunter. So I don't know how true that statement is.
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Old Wednesday 28th October 2009, 14:54   #24
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A few quotes from a world reknowned optician

( Zeiss coats each glass according to it's own unique index value. It requires constant monitoring by skilled technicians, as well as adjusting the formula. Some (evaporant) produce a so-so coating, other, more expensive materials produce a very high transmission coating. )

(as lenses come off the production line, they are multi-coated on production coating machines, without regard to glass type or index. This results in a nice rainbow of colors (reinforces in the purchaser's mind that, by golly, I got a real multicoated (lens) here). Unfortunately, that rainbow tells me right away that the coatings are not optimal, just average, and, believe it or not, sometimes they can be worse than no coating at all.)

(High index glass is the hardest to coat properly, it wants 4 or even 5 layers, whereas pretty much all the popular eyepieces I've seen use typically 3 layers, or even only one layer for very high index flint elements. This results in a yellowish tint to the image,...)

Last edited by edz : Wednesday 28th October 2009 at 14:54. Reason: sp
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Old Wednesday 28th October 2009, 15:17   #25
xmeecosmic
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Individually and cumilitively the responses have been very helpful in my beginning to understand about color bias. Thanks so much.
From what has been said, if I have it correct, some optic manufacturers deliberately include some slight bias in an attempt to optimize viewing under certain circumstances.
My next question then would be is "neutral" ever a desired state? If so, why and when?

Last edited by xmeecosmic : Wednesday 28th October 2009 at 15:20.
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