camera lenses

cracked · December 20th, 2003, 04:14 AM

why are pictures squared if camera lenses are round? ive just always wondered this. sorry if it sounds like a stupid question.

drew

XxCowOfChaosxX · December 20th, 2003, 04:15 AM

because the sensor(or film) is rectangular

butch81385 · December 20th, 2003, 04:17 AM

just a wild guess, but i would think that the lense is round so that to adjust zoom/focus, the lens can be spun, otherwise, you would be stuck at one zoom/focus unless changing the lense or flipping something over. the actual inside of the lense where it takes the picture should be rectangular...

cracked · December 20th, 2003, 04:18 AM

so why not make the sensor round to get more of a picture?

drew

bailey · December 20th, 2003, 04:29 AM

who would want a round picture

XxCowOfChaosxX · December 20th, 2003, 04:43 AM

round pictures are hard to standardise, because of the whole pi dealy. "i want a picture with a circumference of *insert long number here*" but for rectangular ones, you can just say 3 by 5 or something

crystaldragon · December 20th, 2003, 04:49 AM

Quote:

Originally posted by cracked
why are pictures squared if camera lenses are round? ive just always wondered this. sorry if it sounds like a stupid question.

drew

No such thing as a stupid question!
I used to make a living in photography.

The simple answer is image degradation. In other words as you get to the edge of the image "cone" formed by the lens the image quality becomes unusable. You see the image from the lens is not only round but also slightly curved, similar to the shape of the surface of the lense itself. To capture a usable image only the sharpest section of the image is used.

The rectangular shape of an image / print is loosley based on the "golden mean" a ration that the human eye finds balanced.

The rotation of lenses to focus is purely a mechanical convenience. Look at any of the older cameras that used a bellows, focus is a function of distance between the lense and the film (or sensor) and can be done be a straight line "in and out " movement just as well.

Clear as mud?

JD

thekingofpain · December 20th, 2003, 05:02 AM

Do you find a similar squaring of images you see thru your eyes?

bailey · December 20th, 2003, 05:19 AM

big differance between a single lens and a stereoscopic lens

crystaldragon · December 20th, 2003, 05:21 AM

Quote:

Originally posted by thekingofpain
Do you find a similar squaring of images you see thru your eyes?

Nope!

The eye can do something that no camera lense can, (and I'm not referring to spherical rotation). Our ability to see with accuracy is a function of contiuous "point focus". We do not see everything in sharp focus at the same time. If you could physically "lock focus" on a single point you would see that everything else was "blurred"

As far as us actually seeing a "squared off" image we don't. The eye makes a circular image just like any other lens. The "golden mean" comes into play with objects that we look at . Houses. pictures, cars, etc. It just a ratio that the brain finds "comfortable"

BTW The eye sees in continous motion. The effect of continous motion we see in films / movies / television is an illusion. It is based on what is called "persistence of vision" If you expose an image for less than 1/30 sec and follow it with another just slightly different. the eye/brain combination / blurs them together crating the illusion of continous image. It you look at a filem strip you'll only see individual frames but if you play it at the correct speed it appers to be continuows and smooth. Television (or monitor) for example redraws the complete image 60 times or more per second. A series of "snapshots".

edited for spelling . the old "claws" get clumsy sometimes