Very interesting thread--thanks Tim, AG.
Timely too as was just reviewing a recent article in Nature on curing
color-blindness in primates---also an editorial a week ago in the NEJM.
So perhaps we eventually can "upgrade" our own sensors.
http://www.nature.com/nature/journal/v461/n7265/full/nature08401.html
Approximately 8% of men have a loss of or defective opsin--usually the
long or middle wavelength one---thus are "dichromats" like the
monkeys in the Nature article. They were able to deliver a wild-type
human L-opsin gene to long and middle-length cones via a
replication defective adeno-associated virus injected
sub-retinally---resulting in trichromatic vision in the
monkeys!!---still appeared to work after 2 years.
One might have predicted that even if the hardware were fixed, the
brain would not process the signals well (analogy to congenital
cataracts must be fixed quickly for normal vision to be established)
but that was not the case.
Sooo, theoretically if this process is safe and effective one might
choose an upgraded "sensor" by creation of tetrachhromacy--
why not add another opsin like in the European starling and see flowers
the way they are supposed to be seen by starlings and bees?
Nah--would be instantly dissatisfied with all current gear.
Mike
Tim, excellent post !!
During 1977 - 78 I subscribed to Scientific American, I may have had
that article 'though I lost many of the monthly issues ....emmm, only
six remain in my library. During those years I made an attempt to go
to the States to study biochemistry. I didn't win the grant, long
story.
I do have some serious works on perception, just yesterday I read one
here, about tinnitus (I'm very worried about my new audio monitors ...
:-) )
<http://www.pnas.org/content/early/2009/12/15/0911268107.full.pdf+html?si
d=7e5a21bd-942e-4e1c-9582-5b924ba5a791>
This also relates to an old post of Chuck regarding hearing loss.
Cheers,
Fernando
2009/12/31 Tim Hughes <timhughes@xxxxxxxx>:
> Ken, a couple of comments:
>
> People interested in the human perception issues of color, might
enjoy
> reading the long popular article by Edwin Land (Polaroid fame), which
> appeared in Scientific American.(Edwin H. Land, "The Retinex Theory
of Color
> Vision," Scientific American, Vol. 237, No. 6, pp. 108-128, December
1977.)
> His theory of color perception is termed "Retinex theory".
> here are a few related simplified links:
> http://people.msoe.edu/~taylor/eisl/land.htm
> http://www.wendycarlos.com/colorvis/color.html
> http://en.wikipedia.org/wiki/Color_constancy
> http://www.wendycarlos.com/colorvis/retinex.html
> http://color.psych.upenn.edu/brainard/papers/retinex.pdf
> http://www.rowland.harvard.edu/organization/land/theory.php
>
> One interesting thing is the brain can do a surprisingly good job of
> reconstructing a full set of colors from a display screen, even if
only 2
> types of carefully chosen color pixels are used, in place of 3.
>
> There are so many variations on the more than tri-color camera sensor
matrix,
> which have been suggested and patented. A very interesting variation
but for
> color screen display use, is using RGBW. (W = white)
>
> Some of the Fuji and other >3 color sensors land up with
non-rectangular
> pixel layout. This can mean the resolution is highest on a diagonal
not
> horizontal and vertical axis. This is a slight disadvantage
apparently, as
> we percieve better sharpness, if the resolution is highest on the
horizontal.
>
> A dificulty with the Foveon sensor, is not just their execution and
having to
> have a different dematrixing software/hardware, which is more
expensive
> because of lower volumes,but the RGB absorbtion curves have very
broad
> overlap with one another, making it much harder,to seperate the
colors
> accurately. This tends to magnify the noise despite the inherent
advantage of
> not throwing away more than 2/3 of photons, as in the normal 2D
filter
> sensor. Using another type of vertical filter in a stackerd sensor,
as you
> suggest, could theoretically retain this photon (noise) advantage, if
it were
> practical to make.
>
> The human eye is similar to the Foveon sensor in that the absorbtion
> spectrum of the different Rhodpsins in the eye are very similar, with
huge
> overlap making the brains job much tougher, in sorting out the real
colors.
> This is an example of why the eye is a rather imperfect, but highly
optimised
> design, despite what old creationists used to claim about godly
design
> perfection in the eye!
>
> see curves here: http://www.wendycarlos.com/colorvis/conecurv.jpg
> and discussion of opsins here :
http://en.wikipedia.org/wiki/Rhodopsin
>
> Tim Hughes
>
> --- On Mon, 11/16/09, Ken Norton <ken@xxxxxxxxxxx> wrote:
>
>> From: Ken Norton <ken@xxxxxxxxxxx>
>> Subject: [OM] Pixel Wars - The Next Generation
>> To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
>> Date: Monday, November 16, 2009, 5:09 AM
>> A shameless plug alert.
>>
>> We have a new article posted on Zone-10 which is predicting
>> future
>> development of sensors in our digital cameras. I'm sure a
>> few things in it
>> may seem a little futuristic, but isn't that the purpose of
>> a prediction
>> article? However, each and every technology mentioned in
>> the article is
>> found through patent searches and some slick detective
>> work.
>>
>>
http://zone-10.com/cmsm/index.php?option=com_content&task=view&id=461&Itemid=1
>>
--
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