Make all lens low apature

[Nogshale]

I suppose its a silly question, thats why im posting it here.

Just wondering why cant lens makers just make all lens like f/1.0 or something, cant be that hard surely?

Screw these 3.4-4.5 lens...gimme 1.0 damnit.

[Laurie]

i think price for one?
and maybe its just not possible?
imagine how much a 105 or even 200mm 1.0 would cost to make and then buy?

[myarhidia]

size, did you ever see the canon 50mm f1.0?

[Nogshale]

Nope never saw the 50 1.0

Anyone know why it makes it so much bigger?

There smart people i bet theres a way they can make them smaller.

[MHD]

Well mainly it is a question of resolution...

Each pixel on your camera accepts a range of angles, those angle converge at the image plane which is, conveniently, where your sensor is located..

Now in an ideal imaging system, ie a perfect lens that has a perfectly flat image plane then yes, a f/1 lens, besides having a uselessly low DOF would be great...

However this is far from the case. By having a smaller apeture the range of angles in each ray is less meaning a greater DOF meaning less critical focal plane positioning...

The reason why higher minumum fstop lenses are generally more expensive is not just because they have more glass it is also more care must be taken in the design and construction and in general better materials, otherwise the use at the maximum fstop wold be limited by hopeless sharpness.

[Glen]

Justin, you cant beat physics. The front element (front glass) has to be miles bigger to get the same light to the other end of the tunnel (the lens) as if there was no tunnel there. Someone like Steffen or Gordon can probably explain the theory better.

[Gordon]

>>Just wondering why cant lens makers just make all lens like f/1.0 or something, cant be that hard surely?

cant be hard??? you must be joking!

The optical surface tolerances to make a good f/1 lens are extremely stringent, the cost of the lenses would be BIG$$$$, just look at what 2nd hand f/1.2 NoctNikkors go for. Aberrations are going to be much more obvious, keeping them down requires aspherical surfaces and various refractive index lens elements to be included, ie more manufacturing expense. Keep in mind that the lenses I'm talking about need to be physically larger as well, approximately the same size as the FL.
Apart from that it would make the lenses much larger and bulkier, which is not necessarily what everyone wants. Also, at f/1 the DOF is going to be so small it is useless in many situations.
That said, I wouldnt mind a few good f/1 lenses for astrophotography
Astronomers sometimes get around the aberration problem by building Schmidt cameras, these can be built at f/1, but you have the problem of a curved focal plane, although this can be corrected with a focal plane corrector against the film or CCD.
I started building myself a 400mm f/2 Schmidt many years ago, I have the 250mm f/1.65 mirror complete, but several attempts to grind the corrector plate failed... its something I may have another go at one day if I can get hold of a corrector from a Celestron C-8, which is not too far off the shape I need.

Gordon

[myarhidia]

size, did you ever see the canon 50mm f1.0?

2.2lbs = 916gm

http://www.shutterbug.com/equipmentrevi ... sb_canons/

[obzelite]

at f1 the aperture size has to be equal to the lens length, so its not just a money issue its also a size issue.

A 200m lens would need a 200mm aperture at f1, thats quite a big lens.
at f2.8 you will only need a 71mm aperture, and a lot less glass.

[Matt. K]

The extra cost is in the lens cap.

[Nogshale]

Thanks for the info guys, learned a bit so far.

[Gordon]

but just think how much you could save on CCD cleaning! Used at f/1 nearly all the dust bunnies would be way out of focus and invisible

Gordon

[moz]

A 200m lens would need a 200mm aperture at f1, thats quite a big lens.

It's actually much worse than that. Because of losses inside the lens and some incident angle issues you're looking at 50% bigger or so for really small apertures. Even at f/2.8 there's an appreciable margin - my 200/2.8 takes a 77mm filter rather than the 71mm one you might expect. Of course, Sigma have beaten that somehow with their 120-300/2.8 which has a 105mm front element rather than the 107mm you'd expect if you did the maths. So it is possible (most likely by lying about the actual zoom range). But the 85/1.8 I have takes a 58mm filter not the 47mm mere maths would suggest.

And the sheer heft - every zoom I have is substantially bigger and heavier than the equivalent prime at the long end, that 85/1.8 is half the length and 1/3 the weight of the 24-70/2.8 zoom. I'd expect a 24-70/1 zoom to be at least 90mm on the front element and at least the size and weight of the 200/2.8.

[obzelite]

its aperture size, not the front element size.

the front of the lens will always need to be larger than the aperture size because the lens is really a cone. You look how a lens is made up and the iris that controls the aperture is usually one of the last things in a lens. i'd guess the sigma is really a 280mm that would give a 100mm aperture size for the 105 front element, and looking at the lens its not too much of a cone.
And you can keep going, canon made a f0.7 lens.


also the reason these look the way they do

[gstark]

I suppose its a silly question, thats why im posting it here.

I've often made the statement that the only silly question is the one that isn't asked.

I think that you've help to prove this truism; thank you for asking.