Re: Why Cat needs vertical pupil and Octapus needs horizontal pupil?


This topic has been of great interest to me over the years. And it is my
belief, it has to do with how and what an animal has to do to get food to
survive and also to avoid capture (to become food!). I have seen the other
comments in this thread already discounting ANY relation, and feel that is
not the case. NOTE: it is hard for me to type all of this out instead of
verbally communicating... I am not a fast typist by any stretch of the

Also let me state that I am not a trained / schooled optical engineer but I
have spent many successful years (25+) engineering optical and
electro-opto-mechanical systems and wish to comment on this particular
thread. I present my observations on the iris comment/question and where
this lead my research and ultimate success in developing a single lens
stereoscopic camera system or simple to implement depth enhancement

So here goes my view(s) on irises:

The iris in an eye (or camera) can have a very interesting effect on the way
images are displayed on the retina or a film plane. In fact I have several
patents (and two pending, others applied for) on imaging systems using this
very process, and allot of my research has been with animals and irises in

If an iris is mostly vertical for example, the resultant image on the retina
or film plane, will have a higher resolution in the horizontal direction.
For animals with that particular orientation, they are typically ground
hunters: that is they need to catch "their dinner" running across there view
field horizontally, i.e. cat catches mouse. Other creatures whether sea,
land or air typically meet this criteria. A frog and other land / water
creature have very complex irises due to the nature of dual index of
refraction (air and water) and the need to operate in either or both at the
same time, and of course eat or be eaten.

Horizontal irises are typically used to gain resolution in the vertical
direction... and so on.

Iris shapes are essentially simple passive optical filters for the animals
survival, arrived via natural selection, and random biology/mutation as
well. But ultimately the best eye wins in the long run.

And there are some very interesting shapes like horses (round but a
feathered edge on one side) and cuttlefish (horizontal with a cusp in the
center). The horses iris may allow them to increase image sensitivity
towards the rear of the animal, that is often the most likely place a
predator approaches from, and is probably why horse get "skittish" when you
approach from behind as well. Cuttlefish have a curvy shape again to
increase vertical and diagonal resolution.

Note that horses have extremely high "monocular" vision and a very small
"binocular" or stereo vision. Humans are a mix of both, about 60 degrees of
both, i.e. 60 monocular, 60 binocular, 60 monocular ~ 180 degree field of
view. Pigeons have sight like a horse... More on this later... I always
found it interesting that flounder (and a few other flat fish), which have
two eyes on one side, have very good depth perception, although there
intraocular distance is relatively small. Unlike most other fish which have
eyes on both sides, and relatively poor depth perception (stereo), like a

In fact an iris is a perfect place to do image processing, i.e. "optical
Fourier transforms" using spatial light modulators or more simply just
shaped holes (iris apertures) in camera lenses (or human eyes for that
mater). By having and using unique iris shapes, also pre-computes (in the
optical domain) images for use by the brain. Humans (and several other
animals / mammals) have the "CPU" power to process images in very special
ways, and some animals / insects need all the help they can get, having as
little as 100 synapses to be called a brain. ( I know several politicians
that meet this requirement, but that is another news group!)

Also note, there are several animals that use both the shapes of there
irises and motion to process information. Dolphins being one. But because
of their high intelligence and the fact that they use a multitude of sensory
inputs, sonar, temp, smell, they are very complex to observe and isolate
sensory functions especially sight.

The study of irises lead me to depth enhancement technology....

After long hours of looking at the need to make a single lens stereo camera
lens I used the following animal example...

Most birds have a round iris because, like humans, can get there food (and
be eaten) from all directions. A pigeon has little or no eye image overlap
in which to create a stereo image pair, so it bobs its head up and down to
gain better depth information in order to feed on the seed (or uneaten
french fries or popcorn in the park!) it finds. A human can do the same
thing (bobbing or moving the head) using one eye only. You can gain depth
perception by moving you viewpoint from one location to another (no big leap
of faith here). But what is interesting is that due to several factors most
of the population is not sensitive to the very small amounts of motion it
require for use to gain depth in this way. In fact when we walk, our eyes
move (and shake) due to being well connected to our spines...legs...our
feet. Our brain has a natural filter to remove these vertical shifts from
our daily lives, i.e. when we walk, or run etc.

Now by simply moving the iris inside a camera lens you can trick the brain
into seeing or enhancing depth of a standard moving image. The speed, and
motion must be controlled in a particular way to produce the effect. Also a
normal distribution of people see the effect, some more than others by about
80-20. That is 80% seeing depth, 20% seeing nothing or no depth
enhancement. Our studies have shown people with just one working eye from
birth have seen depth for the first time using this technique. From here
you can let your imagination run wild. But do not expect this process to
replace true 3D. While the depth effect is noticeable, it is not as fake
looking and also does not produce the distorted 3D effect these other
processes create. But on the flip side it is easy to produce and can be
edited with all of today's studio gear. Commercial television is about to
start using this technology - I hope! The company I helped created this
technology for won all best new technology awards at this years (2005) NAB
show, so now it is a race to get this to market ASAP... this has been a 10+
year development project, and I sure hope it pays off! We are in the
process of product introduction now, TV commercials should follow soon, 3

I firmly believe nature provides us with abundant examples of design (in all
disciplines, optical, mechanical, electrical), and the study of it will lead
(and has lead) to many new and innovative ideas.


Aron Bacs

P.S. I hope you can understand my relating depth to the iris question. It
is clear in my mind, but even after all these years, I still have a hard
time conveying this information to others.

<youzpalang@xxxxxxxxxxxx> wrote in message
> Hi:
> 1-Why in daylight cat needs a vertical (vertical slit) pupil?
> 2-Similarly, why octapus needs horizontal pupil? It is said that it is
> for better viewing of the horizontal ocean floor, how does this work if
> that is the case?
> 3- Some animals like insects and frogs have weired shape (e.g. zigzag
> shape) pupils, what is their puprpose?
> In general what role the shape of pupil has in visual sensory systems?
> I was considering field of view.
> thanks