Re: For the cost of today's lenses, should they be diffraction-limited, wide open?
 

Rich <none@nowhere.com> wrote:
>$1800 for an 85mm f1.4 from Nikon. That's about 2x what the old one cost.
>Is the lens $1000 better or should it be as good at f/1.4 as f/4? I'm not
>sure. I know that some optics made as f/4.0 have been diffraction limited.
>Pentax had some, but they weren't camera lenses. Some have claimed certain
>telephotos in the pro bracket have been diffraction-limited at f/2.8, but
>I've never seen it demonstrated. So, the question is, is it possible to
>make say a 35mm, 85mm diffraction-limited at f/1.4 and if so, at what
>price? Likely it is, but they haven't done it.


It might be better if, instead of using the term "diffraction
limited", you described your requirement as "a lens that gives its
sharpest results when wide open". That is what you mean after all.

Only Leica makes lenses that do that, and Leica lens prices are
self-evidently very high indeed. Ridiculously high, even for Leica
users.

I'm considering replacing two of my Leica lenses in the next year
before signs of wear mean their used values begin to fall. I'm
looking hard at Carl Zeiss ZM and Voigtländer lenses, both made in
Japan by Cosina and costing a fraction of Leica prices. However, they
don't perform at their best wide open.

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 8/11/2012 1:48 p.m., Anthony Polson wrote:
> Rich <none@nowhere.com> wrote:
>> $1800 for an 85mm f1.4 from Nikon. That's about 2x what the old one cost.
>> Is the lens $1000 better or should it be as good at f/1.4 as f/4? I'm not
>> sure. I know that some optics made as f/4.0 have been diffraction limited.
>> Pentax had some, but they weren't camera lenses. Some have claimed certain
>> telephotos in the pro bracket have been diffraction-limited at f/2.8, but
>> I've never seen it demonstrated. So, the question is, is it possible to
>> make say a 35mm, 85mm diffraction-limited at f/1.4 and if so, at what
>> price? Likely it is, but they haven't done it.
>
>
> It might be better if, instead of using the term "diffraction
> limited", you described your requirement as "a lens that gives its
> sharpest results when wide open". That is what you mean after all.
>
> Only Leica makes lenses that do that, and Leica lens prices are
> self-evidently very high indeed. Ridiculously high, even for Leica
> users.
Which Leica lenses?
http://www.photozone.de/canon-eos/20...report?start=1

Summilux R 50mm f1.4 is pretty good, but peaks at f5.6 here, much the
same as any of the ( /much/ cheaper) 50mm lenses.


>
> I'm considering replacing two of my Leica lenses in the next year
> before signs of wear mean their used values begin to fall. I'm
> looking hard at Carl Zeiss ZM and Voigtländer lenses, both made in
> Japan by Cosina and costing a fraction of Leica prices. However, they
> don't perform at their best wide open.
>
>
>

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 08/11/2012 00:48, Anthony Polson wrote:

(...)
>"a lens that gives its
> sharpest results when wide open".
>
> Only Leica makes lenses that do that,

That's a ridiculous claim.

<http://www.cookeoptics.co.uk/>
and
<http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/cine_lenses.html>
would be 2 examples of lens manufacturers other than Leica that are
sharp wide open.

And I have a hunch that these qualify as well:
<http://www.canon.co.uk/For_Home/Product_Finder/Digital_Cinema/Cine_Lenses/>
<http://www.fujifilm.com/products/optical_devices/cine/>



--
audentes fortuna iuvat

Re: For the cost of today's lenses, should they be diffraction-limited, wide open?
 

Joe Kotroczo <kotroczo@mac.com> wrote:

>On 08/11/2012 00:48, Anthony Polson wrote:
>
>(...)
>>"a lens that gives its
>> sharpest results when wide open".
>>
>> Only Leica makes lenses that do that,
>
>That's a ridiculous claim.
>
><http://www.cookeoptics.co.uk/>
>and
><http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/cine_lenses.html>
>would be 2 examples of lens manufacturers other than Leica that are
>sharp wide open.
>
>And I have a hunch that these qualify as well:
><http://www.canon.co.uk/For_Home/Product_Finder/Digital_Cinema/Cine_Lenses/>
><http://www.fujifilm.com/products/optical_devices/cine/>


With respect, I believe you have missed the point here.

First, I was talking about still photography, not cine. I have no
interest in, or specialist knowledge of, the latter. Neither is it
on-topic for this newsgroup.

Second, I was not talking about lenses that are merely *sharp* wide
open but lenses that give *their sharpest results* when used wide
open. There is a difference.

Perhaps, given the confusion I appear to have caused, I should have
stayed with Rich's term "diffraction limited". ;-)

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 08/11/2012 16:53, Anthony Polson wrote:
> Joe Kotroczo <kotroczo@mac.com> wrote:
>
>> On 08/11/2012 00:48, Anthony Polson wrote:
>>
>> (...)
>>> "a lens that gives its
>>> sharpest results when wide open".
>>>
>>> Only Leica makes lenses that do that,
>>
>> That's a ridiculous claim.
>>
>> <http://www.cookeoptics.co.uk/>
>> and
>> <http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/cine_lenses.html>
>> would be 2 examples of lens manufacturers other than Leica that are
>> sharp wide open.
>>
>> And I have a hunch that these qualify as well:
>> <http://www.canon.co.uk/For_Home/Product_Finder/Digital_Cinema/Cine_Lenses/>
>> <http://www.fujifilm.com/products/optical_devices/cine/>
>
>
> With respect, I believe you have missed the point here.
>
> First, I was talking about still photography, not cine. I have no
> interest in, or specialist knowledge of, the latter. Neither is it
> on-topic for this newsgroup.

A lens is a lens. Nothing stops you from taking stills with a cine lens.

> Second, I was not talking about lenses that are merely *sharp* wide
> open but lenses that give *their sharpest results* when used wide
> open. There is a difference.

So was I. Cine lenses must be of equal sharpness along the full range of
stops, so they should be equally sharp wide open as they are stopped down.

In fact, shouldn't a lens that is less sharp stopped down than it is
fully open be considered defective?

>
> Perhaps, given the confusion I appear to have caused, I should have
> stayed with Rich's term "diffraction limited". ;-)

There is a difference between "diffraction limited" and "sharpest at
full aperture" too... A lens that is sharpest at full aperture is not
necessarily diffraction limited.


--
audentes fortuna iuvat

Re: For the cost of today's lenses, should they bediffraction-limited, wide open?
 

On Nov 8, 12:24*pm, Joe Kotroczo <kotro...@mac.com> wrote:
> On 08/11/2012 16:53, Anthony Polson wrote:
>
>
>
>
>
>
>
>
>
> > Joe Kotroczo <kotro...@mac.com> wrote:
>
> >> On 08/11/2012 00:48, Anthony Polson wrote:
>
> >> (...)
> >>> "a lens that gives its
> >>> sharpest results when wide open".
>
> >>> Only Leica makes lenses that do that,
>
> >> That's a ridiculous claim.
>
> >> <http://www.cookeoptics.co.uk/>
> >> and
> >> <http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/cine_l....>
> >> would be 2 examples of lens manufacturers other than Leica that are
> >> sharp wide open.
>
> >> And I have a hunch that these qualify as well:
> >> <http://www.canon.co.uk/For_Home/Product_Finder/Digital_Cinema/Cine_Le....>
> >> <http://www.fujifilm.com/products/optical_devices/cine/>
>
> > With respect, I believe you have missed the point here.
>
> > First, I was talking about still photography, not cine. *I have no
> > interest in, or specialist knowledge of, the latter. *Neither is it
> > on-topic for this newsgroup.
>
> A lens is a lens. Nothing stops you from taking stills with a cine lens.
>
> > Second, I was not talking about lenses that are merely *sharp* wide
> > open but lenses that give *their sharpest results* when used wide
> > open. *There is a difference.
>
> So was I. Cine lenses must be of equal sharpness along the full range of
> stops, so they should be equally sharp wide open as they are stopped down..
>
> In fact, shouldn't a lens that is less sharp stopped down than it is
> fully open be considered defective?
>
>
>
> > Perhaps, given the confusion I appear to have caused, I should have
> > stayed with Rich's term "diffraction limited". *;-)
>
> There is a difference between "diffraction limited" and "sharpest at
> full aperture" too... A lens that is sharpest at full aperture is not
> necessarily diffraction limited.

What difference? What would cause a lens wide open and diffraction
limited (across the visual spectrum) to not be sharpest when wide
open? Resolution laws would argue otherwise.

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 08/11/2012 23:32, RichA wrote:
> On Nov 8, 12:24 pm, Joe Kotroczo <kotro...@mac.com> wrote:
>> On 08/11/2012 16:53, Anthony Polson wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>> Joe Kotroczo <kotro...@mac.com> wrote:
>>
>>>> On 08/11/2012 00:48, Anthony Polson wrote:
>>
>>>> (...)
>>>>> "a lens that gives its
>>>>> sharpest results when wide open".
>>
>>>>> Only Leica makes lenses that do that,
>>
>>>> That's a ridiculous claim.
>>
>>>> <http://www.cookeoptics.co.uk/>
>>>> and
>>>> <http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/cine_l...>
>>>> would be 2 examples of lens manufacturers other than Leica that are
>>>> sharp wide open.
>>
>>>> And I have a hunch that these qualify as well:
>>>> <http://www.canon.co.uk/For_Home/Product_Finder/Digital_Cinema/Cine_Le...>
>>>> <http://www.fujifilm.com/products/optical_devices/cine/>
>>
>>> With respect, I believe you have missed the point here.
>>
>>> First, I was talking about still photography, not cine. I have no
>>> interest in, or specialist knowledge of, the latter. Neither is it
>>> on-topic for this newsgroup.
>>
>> A lens is a lens. Nothing stops you from taking stills with a cine lens.
>>
>>> Second, I was not talking about lenses that are merely *sharp* wide
>>> open but lenses that give *their sharpest results* when used wide
>>> open. There is a difference.
>>
>> So was I. Cine lenses must be of equal sharpness along the full range of
>> stops, so they should be equally sharp wide open as they are stopped down.
>>
>> In fact, shouldn't a lens that is less sharp stopped down than it is
>> fully open be considered defective?
>>
>>
>>
>>> Perhaps, given the confusion I appear to have caused, I should have
>>> stayed with Rich's term "diffraction limited". ;-)
>>
>> There is a difference between "diffraction limited" and "sharpest at
>> full aperture" too... A lens that is sharpest at full aperture is not
>> necessarily diffraction limited.
>
> What difference? What would cause a lens wide open and diffraction
> limited (across the visual spectrum) to not be sharpest when wide
> open? Resolution laws would argue otherwise.

But you can still make a lens that is at its sharpest when wide open but
whose sharpness is not significantly improved by stopping down. Such
lenses are usually designed to avoid vignetting at the corners of the
field of view. They are not diffraction limited at full aperture but
they hold their sharpness at some particular nominal diameter.

--
Regards,
Martin Brown

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 08/11/2012 23:32, RichA wrote:

(...)
>> There is a difference between "diffraction limited" and "sharpest at
>> full aperture" too... A lens that is sharpest at full aperture is not
>> necessarily diffraction limited.
>
> What difference? What would cause a lens wide open and diffraction
> limited (across the visual spectrum) to not be sharpest when wide
> open? Resolution laws would argue otherwise.

Who says that a lens has to reach it's diffraction limit wide open? Can
it not be diffraction limited at f/11 or something, and less sharp at
any other stop, smaller or larger?

And who says that a lens which is sharpest wide open has also reached
it's diffraction limit? Can it not be sharpest wide open, but still a
long way off it's diffraction limit?

After all, what "diffraction limited" really means is "reaching it's
theoretical maximum resolution".

--
audentes fortuna iuvat

Re: For the cost of today's lenses, should they be diffraction-limited, wide open?
 

Joe Kotroczo <kotroczo@mac.com> wrote:
> On 08/11/2012 23:32, RichA wrote:

>>> There is a difference between "diffraction limited" and "sharpest at
>>> full aperture" too... A lens that is sharpest at full aperture is not
>>> necessarily diffraction limited.
>>
>> What difference? What would cause a lens wide open and diffraction
>> limited (across the visual spectrum) to not be sharpest when wide
>> open? Resolution laws would argue otherwise.

> Who says that a lens has to reach it's diffraction limit wide open? Can
> it not be diffraction limited at f/11 or something, and less sharp at
> any other stop, smaller or larger?

> And who says that a lens which is sharpest wide open has also reached
> it's diffraction limit? Can it not be sharpest wide open, but still a
> long way off it's diffraction limit?

> After all, what "diffraction limited" really means is "reaching it's
> theoretical maximum resolution".

And what is meant by "sharpest"? Sharpest in the centre? Sharpest at
the edges? Those are often two different apertures.

--
Chris Malcolm

Re: For the cost of today's lenses, should they be diffraction-limited,wide open?
 

On 09/11/2012 17:58, Chris Malcolm wrote:
> Joe Kotroczo <kotroczo@mac.com> wrote:
>> On 08/11/2012 23:32, RichA wrote:
>
>>>> There is a difference between "diffraction limited" and "sharpest at
>>>> full aperture" too... A lens that is sharpest at full aperture is not
>>>> necessarily diffraction limited.
>>>
>>> What difference? What would cause a lens wide open and diffraction
>>> limited (across the visual spectrum) to not be sharpest when wide
>>> open? Resolution laws would argue otherwise.
>
>> Who says that a lens has to reach it's diffraction limit wide open? Can
>> it not be diffraction limited at f/11 or something, and less sharp at
>> any other stop, smaller or larger?
>
>> And who says that a lens which is sharpest wide open has also reached
>> it's diffraction limit? Can it not be sharpest wide open, but still a
>> long way off it's diffraction limit?
>
>> After all, what "diffraction limited" really means is "reaching it's
>> theoretical maximum resolution".
>
> And what is meant by "sharpest"? Sharpest in the centre? Sharpest at
> the edges? Those are often two different apertures.

If you want to pick nits the problem is that to be "sharpest" as a true
fully optimised glass based apochromat requires that the red image be
truly diffraction limited and the green and blue images be very slightly
geometrically degraded. I don't think anybody does this in practice. You
end up with slight purple haloes on point sources.

resolution is 1.22D/lambda

Varies by a factor of two from deep red 680nm to violet 340nm.

Astronomical instruments are optimised to diffraction limited for object
at infinity and a realisable (not not always flat) focal plane.

Camera lenses have to cope with a wider range of object distances.
Mostly the marketing dept stick APO on to fleece wannabbees like RichA.

The RichA troll just likes to **** and moan.

--
Regards,
Martin Brown