Re: Why are lenses unsharp wide open?
 

Alfred Molon <alfred_molon@yahoo.com> wrote:
>
>Just wondering - does it come from physics or is it pure economics, i.e.
>too expensive to make a lens with corner to corner sharpness at F1.4?


Economics has a big part to play. Many Leica lenses M lenses are
superbly sharp wide open, but they cost a lot more than more prosaic
Canon and Nikon glass that performs best when stopped down.

My current favourite lens is the Leica 24mm f/2.8 Elmarit-M. It is
sharpest in the centre at f/2.8, and across the whole frame at f/4.
There is no benefit to sharpness from stopping down any further.

Re: Why are lenses unsharp wide open?
 

Rich <none@nowhere.com> wrote:
>Bruce <docnews2011@gmail.com> wrote in
>news:neqa37pe07u4gj5p3bj0afvvutlvgfuumb@4ax.com :
>> Alfred Molon <alfred_molon@yahoo.com> wrote:
>>>
>>>Just wondering - does it come from physics or is it pure economics,
>i.e.
>>>too expensive to make a lens with corner to corner sharpness at F1.4?
>>
>>
>> Economics has a big part to play. Many Leica lenses M lenses are
>> superbly sharp wide open, but they cost a lot more than more prosaic
>> Canon and Nikon glass that performs best when stopped down.
>>
>> My current favourite lens is the Leica 24mm f/2.8 Elmarit-M. It is
>> sharpest in the centre at f/2.8, and across the whole frame at f/4.
>> There is no benefit to sharpness from stopping down any further.
>>
>>
>
>That's enviable performance.


Enviable indeed. I bought my Leica 24mm f/2.8 Elmarit-M ASPH (I left
out the ASPH in my previous posting) at a time when Leica prices were
much lower than they are now. I probably couldn't justify paying
today's prices.

At around the same time I bought a Leica 35mm f/1.4 Summilux-M ASPH,
another outstanding performer. Both lenses are now worth, in Sterling
terms, somewhere between three and four times what I paid for them. Of
course Sterling has dropped in value during that time thanks to the
UK's indebtedness. Even so, these lenses have been a remarkable
investment. I'm tempted to cash in and buy a Leica M9 body with the
proceeds, but then I would need some lenses ...


>One of the shocks you get going from 4/3 to
>APS or FF is the terrible edge performance of all but the best lenses,
>wide open anyhow. Using a Zeiss 35mm f2.0 against Nikon's very good but
>inexpensive 35mm f1.8 was a shock, with the Zeiss being much sharper wide
>open, and I wouldn't have described the Nikon as bad wide open by any
>means.


The Carl Zeiss Distagon 35mm f/2 is a beautiful lens. As long as you
don't mind focusing manually, it is a far better choice than any 35mm
lens Nikon has ever made. And if you really need f/1.4, there is the
outstanding Samyang which is optically marginally superior to the
spectacularly expensive AF-S Nikkor.

Of course all these superb lenses are completely wasted on the vast
majority of buyers who want zoom lenses = preferably with a large zoom
range so they don't ever have to take them off their cameras - and are
prepared to accept lousy optical performance in return.

Pearls before swine ...

Re: Why are lenses unsharp wide open?
 

On Wed, 03 Aug 2011 11:54:20 +0100, Bruce <docnews2011@gmail.com> wrote:
: Rich <none@nowhere.com> wrote:
: >Bruce <docnews2011@gmail.com> wrote in
: >news:neqa37pe07u4gj5p3bj0afvvutlvgfuumb@4ax.com :
: >> Alfred Molon <alfred_molon@yahoo.com> wrote:
: >>>
: >>>Just wondering - does it come from physics or is it pure economics,
: >i.e.
: >>>too expensive to make a lens with corner to corner sharpness at F1.4?
: >>
: >>
: >> Economics has a big part to play. Many Leica lenses M lenses are
: >> superbly sharp wide open, but they cost a lot more than more prosaic
: >> Canon and Nikon glass that performs best when stopped down.
: >>
: >> My current favourite lens is the Leica 24mm f/2.8 Elmarit-M. It is
: >> sharpest in the centre at f/2.8, and across the whole frame at f/4.
: >> There is no benefit to sharpness from stopping down any further.
: >>
: >>
: >
: >That's enviable performance.
:
:
: Enviable indeed. I bought my Leica 24mm f/2.8 Elmarit-M ASPH (I left
: out the ASPH in my previous posting) at a time when Leica prices were
: much lower than they are now. I probably couldn't justify paying
: today's prices.
:
: At around the same time I bought a Leica 35mm f/1.4 Summilux-M ASPH,
: another outstanding performer. Both lenses are now worth, in Sterling
: terms, somewhere between three and four times what I paid for them. Of
: course Sterling has dropped in value during that time thanks to the
: UK's indebtedness. Even so, these lenses have been a remarkable
: investment. I'm tempted to cash in and buy a Leica M9 body with the
: proceeds, but then I would need some lenses ...
:
:
: >One of the shocks you get going from 4/3 to
: >APS or FF is the terrible edge performance of all but the best lenses,
: >wide open anyhow. Using a Zeiss 35mm f2.0 against Nikon's very good but
: >inexpensive 35mm f1.8 was a shock, with the Zeiss being much sharper wide
: >open, and I wouldn't have described the Nikon as bad wide open by any
: >means.
:
:
: The Carl Zeiss Distagon 35mm f/2 is a beautiful lens. As long as you
: don't mind focusing manually, it is a far better choice than any 35mm
: lens Nikon has ever made. And if you really need f/1.4, there is the
: outstanding Samyang which is optically marginally superior to the
: spectacularly expensive AF-S Nikkor.
:
: Of course all these superb lenses are completely wasted on the vast
: majority of buyers who want zoom lenses = preferably with a large zoom
: range so they don't ever have to take them off their cameras - and are
: prepared to accept lousy optical performance in return.
:
: Pearls before swine ...

But aren't the optical advantages of even a fine prime lens largely wasted if
you end up having to crop the image to a quarter of its original size because
you couldn't zoom?

Of course the standard reply to that question is, "Well, you should zoom with
your feet." But if there's a river, or a busy highway, or two or three
referees, or 100 meters of vertical separation in your way, ...

Bob

Re: Why are lenses unsharp wide open?
 

Robert Coe <bob@1776.COM> wrote:
>But aren't the optical advantages of even a fine prime lens largely wasted if
>you end up having to crop the image to a quarter of its original size because
>you couldn't zoom?
>
>Of course the standard reply to that question is, "Well, you should zoom with
>your feet." But if there's a river, or a busy highway, or two or three
>referees, or 100 meters of vertical separation in your way, ...


So that's why so very few good pictures were taken before the
introduction of zoom lenses. ;-)

Re: Why are lenses unsharp wide open?
 

Robert Coe <bob@1776.COM> wrote:

> But aren't the optical advantages of even a fine prime lens largely wasted if
> you end up having to crop the image to a quarter of its original size because
> you couldn't zoom?

Well, that sort of depends on the lenses in question. A 50mm prime
cropped to 100mm equivalent is worse than a usable zoom at 100mm,
but a 300mm f/2.8 is vastly better than a 70-300mm f/4-5.6 zoom.
It's even better than a 70-*2*00mm f/2.8 cropped to 300mm.

AFAIK tests have shown that a teleconverter + a lens gives a
better result than just upsampling without the teleconverter ---
this fits with my own observations.

How much better a 300mm f/2.8 (or f/4) is than a 70-300mm zoom
depends a lot on the zoom --- there are cheap consumer zooms and
even a Canon L zoom in that range, and I bet the L zoom is very
noticably better than the consumer zoom.


As to the 50mm lens --- you could try a 2x TC on it and compare
that against your zoom. Depending on the zoom, the 50mm could
well come out ahead. (I cannot test that, I don't have bad zooms.)


> Of course the standard reply to that question is, "Well, you should zoom with
> your feet." But if there's a river, or a busy highway, or two or three
> referees, or 100 meters of vertical separation in your way, ...

Then you'd better pack a more fitting lens the next time.

OK, you says, I use my 18-270mm. OK, but a 200mm f/2 + 1.4x TC
beats it. And is better in low light. And if you need more,
a 200mm f/2 can carry a 2x TC --- and for the mad ones, even a
1.4x + a 2x works. And should focus. (how good it works depends
which TC you put closest to the lens.) :-)

-Wolfgang