[Klaus]

Quite impressive MTFs:

http://www.usa.canon.com/cusa/consumer/p...m_f_4l_usm

 

[Brightcolours]

The icons show 2 fluorite elements to be in this lens on the USA site, that seems to be an error (CaF2 usually is used in tele lenses).



In the japanese site they messed up the colours of the UD and S-UD elements (in the diagram both have the same colour, in the legend one is light blue but all elements for the rest are light blue).

Impressive lens.

 

** Someone at Canon.jp noticed the error, and got rid of the light blue dot with S-UD legend. Now both the UD and the S-UD element are still "UD" green. The image is hyperlinked.

[Brightcolours]

Some high res.-ish sample images:

http://www.cameraegg.org/wp-content/uplo...images.jpg

http://www.cameraegg.org/wp-content/uplo...ages-1.jpg

http://www.cameraegg.org/wp-content/uplo...ages-2.jpg

http://www.cameraegg.org/wp-content/uplo...ages-3.jpg

http://www.cameraegg.org/wp-content/uplo...ages-4.jpg

http://www.cameraegg.org/wp-content/uplo...ages-5.jpg

[netrex]

I see Canon people will still be using the Nikon 14-24mm for astro and aurora photography as this is not f/2.8. It is wider, I wonder how big it would have been with an f/2.8 aperture.

[Brightcolours]

I see Canon people will still be using the Nikon 14-24mm for astro and aurora photography as this is not f/2.8. It is wider, I wonder how big it would have been with an f/2.8 aperture.

A lot bigger, this f4 lens is already considerably bigger than the 14-24mm f2.8 Nikkor:

http://www.dpreview.com/articles/2310593...-l?slide=8

[davidmanze]

   This lens has a monstrous front element, it nearly dwarfs the camera, I never realized how huge and exposed it is!

 

http://www.dpreview.com/articles/2310593...-24mm-f4-l

[dave9t5]

I see Canon people will still be using the Nikon 14-24mm for astro and aurora photography as this is not f/2.8. It is wider, I wonder how big it would have been with an f/2.8 aperture.

I'm no BC or Scythels, but roughly: 

 

Area is the aperture, but elements are roughly proportional to the aperture.  

+1 stop => 2x the area => 1.414x the diameter

 

So roughly expect for every stop increase: the diameter of the lens increases 41% and the weight doubles.

[JJ_SO]

Basically you're right, dave9t5. I'm just not sure if that rule is valid for those FLs, because they have to do tricks to get that "impossible" FL - distance between sensor and rear element on a FF DSLR never is less than 40 mm. So each lens with an FL below those 40 mm needs some extra elements. 11 mm / 4 is a diameter of 2.75 mm and that is "aperture wide open". I'm sure, Scythels could elaborate on this and I'm also sure I wouldn't understand and mumble something like "pretty amazing".

[Scythels]

This lens contains CAF2, the patents preceding it contain CAF2 and the decision to use a material with anomalous partial(=order of 1000x price of normal material) occurs long before final tweaks are done to the design.  The anomalous partial was probably necessary to attain the telephoto ratio they hit and CAF2 would be a natural choice because they already produce it thus the cost is lower. 

 

Regarding making it f/2.8 this would not be "impossible" but rather impractical.  The front portion of the lens would not grow by a factor of sqrt(2) since the chief ray (=FoV) already defines the front diameter vs the marginal ray essentially doing the leg work in e.g telephoto design.  Coma grows by x^3 as the FoV grows so controlling it for such a massive field is already very difficult.  Coma also grows by rho (= element diameter) but not too strongly; the reason stopping down some lenses doesn't "kill" coma too well is because the rays which contribute to the coma are being un-vignetted by stopping down just as fast as the worst offenders are being clipped by stopping down.

 

Astigmatism will be the greater problem and in modern designs is often the biggest challenge.  It grows exponentially with element diameter. 

 

In general we may examine the etendue of the systems to compare their design complexity, momentarily ignoring the difficulty dealing with the BFL >>> EFL problem.

 

Nikon 14-24: DFOV  = 114.2deg | PUPIL AREA = 78.5mm

 

Canon 11-24: DFOV = 126.1deg | PUPIL AREA = 23.7mm

 

a rough lagrange invariant for the 14-24 is then 8965.  For the 11-24 it is 2989.    This definition doesn't truly work for wide angles (too much round off error) but gives a very rough estimate.  The net meaning is that the 14-24 is the "better" or "harder" design, but then one must deal with the telephoto ratio which drives the 11-24 complexity as well as the radial projection problem.  Note the shape of the following two curves, 11mm is further into the process of 'blowing up' as compared to 14mm.

 

http://i.imgur.com/Nnyz8C3.png

 

Plot focal length * tan(theta) in radians to see this for yourself.  This is the source of so-called rectilinear distortion.  The returned value is radial distance i.e "sensor height" for that AoE.  To fit wider AoVs onto the same size sensor one adds barrel distortion - reduced magnification at the edge of the image.  This counter-balances f*tan(theta) distortion.

 

More later, work soon.

[dave9t5]

Basically you're right, dave9t5. I'm just not sure if that rule is valid for those FLs, because they have to do tricks to get that "impossible" FL - distance between sensor and rear element on a FF DSLR never is less than 40 mm. So each lens with an FL below those 40 mm needs some extra elements. 11 mm / 4 is a diameter of 2.75 mm and that is "aperture wide open". I'm sure, Scythels could elaborate on this and I'm also sure I wouldn't understand and mumble something like "pretty amazing".

 

Yep, that's why I mentioned that I'm not Scythels, ha ha.

 

It's a rule of thumb that I used and probably breaks down on extreme lenses like this one.  

 

On the other hand, this is a huge lens for f/4 so I can't imagine an f/2.8 construction would be anything less than unmanageable huge.

 

The retrofocus construction is an inverted telephoto.  I wonder what the equivalent (size) f/4 telephoto lens would be for an 11mm retrofocus?