Why not square lenses???

[Battou]

They're not in any of my cameras.

nor mine

 

[Moglex]

Actually, looking at that again, I suspect Vader meant to ask why mirrors and sensors aren't round.

The answer to that would presumably be that whilst making lenses round is the most sensible/efficient method of doing things for several reasons, we are far more likely to want a rectangular result than a circular one.

The point at which it becomes sensible to change format is at the mirror/film plane/sensor/focusing screen. There would be no advantage to making those circular and the design and manufacture would be a lot harder and lead to unnecessarily larger equipment.

 

[nymtber]

Glass is ground and polished round. a typical (sperical) lens is just that, part of a perfect sphere. both grinding and polishing are much much easier with a round lens, and therefore thats the way most are done, ROUND. After polishing, the lenses can be shaped to darn near any shape needed for a job, square, star shaped (to a certain extent)...Ive been making optics for 8 months now, its an exciting and not so easy job. I make aspheres, which help with chromatic abbervation, and also cost quite a bit more!

I cant give away how I do stuff, but i will say since most of our polishing is done rotating, round objects kinda work better than square. Like I previoiusly said, we can shape the lens AFTER its polished to tolerance Well, I cant, but other people in the shop can!

hope that helps a bit too!

 

[Mike_E]

Alex_B here is a link to the aluminum story.. http://physicsworld.com/cws/article/news/20033

it's not new but gives cause to hope.
mike

 

[Thom K]

Optically it would not work, because the light is a cone. What I need to ask, is why not circular sensors?

 

[Alex_B]

Optically it would not work, because the light is a cone. What I need to ask, is why not circular sensors?

because then we had circular images, which are hard to frame.

a square lens would work by the way if the curvature would be rotational symmetric.

 

[Alex_B]

Alex_B here is a link to the aluminum story.. http://physicsworld.com/cws/article/news/20033

it's not new but gives cause to hope.
mike

But it is not alumin(i)um!!! transparent aluminum is a star trek invention and will never work since it is a metal.

that article is old, and the idea even older. they talk about alumina, which is aluminium oxide. aluminium oxide is not aluminium, just as sapphire is not aluminium, although it contains aluminium atoms.

the hardness of alumina has nothing to do with the properties of the metal known as alumin(i)um


(sorry I took this personal, but I have been working on alumina for the recent 4 years )

 

[VADER1775]

Actually, looking at that again, I suspect Vader meant to ask why mirrors and sensors aren't round.

The answer to that would presumably be that whilst making lenses round is the most sensible/efficient method of doing things for several reasons, we are far more likely to want a rectangular result than a circular one.

The point at which it becomes sensible to change format is at the mirror/film plane/sensor/focusing screen. There would be no advantage to making those circular and the design and manufacture would be a lot harder and lead to unnecessarily larger equipment.

You are right my friend. That is what I meant, Why are they not round? Thanks for pointing that out.

 

[Mike_E]

But it is not alumin(i)um!!! transparent aluminum is a star trek invention and will never work since it is a metal.

that article is old, and the idea even older. they talk about alumina, which is aluminium oxide. aluminium oxide is not aluminium, just as sapphire is not aluminium, although it contains aluminium atoms.

the hardness of alumina has nothing to do with the properties of the metal known as alumin(i)um


(sorry I took this personal, but I have been working on alumina for the recent 4 years )

Not a problem. In what aspect may I ask?

Btw, I wouldn't have a problem with a clear sapphire lens.

It's sure that something needs to give in the materials department if the major companies are to keep driving the markets with higher resolving power.

 

[Moglex]

But it is not alumin(i)um!!! transparent aluminum is a star trek invention and will never work since it is a metal.

that article is old, and the idea even older. they talk about alumina, which is aluminium oxide. aluminium oxide is not aluminium, just as sapphire is not aluminium, although it contains aluminium atoms.

the hardness of alumina has nothing to do with the properties of the metal known as alumin(i)um


(sorry I took this personal, but I have been working on alumina for the recent 4 years )

I have a feeling that if they ever do start using glass made in part from aluminium we will indeed be talking about 'aluminium' and 'silicon' lenses.

And probably 'silicone' lenses to boot!

 

[Alex_B]

Not a problem. In what aspect may I ask?

Simulating surface properties and adhesion properties of oxides.

I have a feeling that if they ever do start using glass made in part from aluminium we will indeed be talking about 'aluminium' and 'silicon' lenses.

And probably 'silicone' lenses to boot!

good comment If we use improper terms, then we should do it with all consequences

 

[abraxas]

Sheesh, I'm really high right now,... but I was just thinking, if there were square lenses, wouldn't we have to have square eyes?

nite-nite.

 

[Thom K]

On the subject of circular sensors, take a rangefinder or a point-and-shoot for example. The issue is much simpler becuase there aren't mirrors and prisms to get in the way. With a circular sensor, you would maximize the capturable content, and then you could crop the circular image into a rectangle. The advantage would be that you could choose any size of crop, rotation would not matter, and you could get better composition with the extra content afforded by a sensor that captures more. It's hard to put into words, sorry.

 

[John_05]

Wow.....I didn't expect to get such thourough and technical (and quantity) responses to this thread but great explanations. It all makes sense especially the aperture which I hadn't though about.

Next up, I'm making a round monitor to hang on my wall

Or, just order one......

 

[Garbz]

That's just dumb. The human eye has a larger horizontal field of view than a vertical. A circular monitor makes no sense.