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Canon EF 11-24mm f/4 USM L announced
#11
Ahem... did I miss something here?

Price will be 3000,- Euro?

 

Sorry, but ... ok, no comment...

#12
The lens does not contain 2 CaF2 elements. It is a faux pas on the American Canon website website. Most probably someone mistook the fluorine coatings on the two front and back element front and back surfaces respectively to mean that the lens contains 2 CaF2 elements. It does contain one UD and one S-UD element. 

 

The Japanese website correctly does not show a CaF2 "icon" but does mention the fluorine anti smudge coating:

https://translate.google.com/translate?s...edit-text=
#13
Quote: 

The retrofocus construction is an inverted telephoto.  I wonder what the equivalent (size) f/4 telephoto lens would be for an 11mm retrofocus?
front element ~5mm rear element ~10mm sensor clearance 3-4mm, length ~20mm including image clearance.  This is only for one design that I quickly scaled down.

 

The performance quickly deteriorates into oblivion away from the central 10 or so degrees of half field of view.  The telephoto formation is not very compatible with very wide fields of view.

 

Basic symmetry theory here;

 

Elements have two radii of curvature.  If R2=-R1, the petzval sum of the element is 0 (that is, no field curvature). 

 

Unfortunately this contributes to strong astigmatism and spherical aberration.  A retrofocus needs to have net negative power in the front.  Meniscus elements do not contribute strongly to the petzval sum since R1 and R2 are in some range near each other.  By making R2 slightly smaller (=stronger curvature) than R1 the element has net negative power and contributes a positive-signed petzval sum (=forward bending field).  These elements unfortunately focus light, which is contrary to what is desirable.  What is widely agreed to be the best basic retrofocus form is to use a pseudo-relay system like this; http://i.gyazo.com/5ccfe17ce4bcea9fa3f86783a44be89a.png

 

To correct it is an easy thing to just keep splitting the front two elements into many many elements so you gain many degrees of freedom to correct with as the rear portion (which in this case is a cooke triplet with a split rear element) is decently corected itself.  The split split split split split split split method results in the stacked/nested meniscus front formation of most retrofocus lenses we see today.  Large bulbous front elements are created by pushing the lens into a design space where the radius of curvature is very small.  This practice will create strong field curvature used to balance the tendency of the design form.

#14
The lens looks badass, a real technological tour de force. Unfortunately the price is a little prohibitive - if I had sold ALL of my other lenses I would've been JUST able to afford this new toy. So the 16-35 and 14mm will have to soldier on for awhile longer. Smile

#15
    Hmm...

           The tests shots posted here show when fully open a certain amount of edge and corner softness at @ 11mm,  ephotozine's "hands on" shows that it's not disappeared by F5.6!

 

 Guess we'll have to wait for the expensive version!  :unsure:

#16
Quote:    Hmm...

           The tests shots posted here show when fully open a certain amount of edge and corner softness at @ 11mm,  ephotozine's "hands on" shows that it's not disappeared by F5.6!

 

 Guess we'll have to wait for the expensive version!  :unsure:
I don't know any UWA that gets borders this sharp, let alone at 11mm...

http://www.magezinepublishing.com/equipm...148989.jpg

http://www.magezinepublishing.com/equipm...140105.jpg

#17
Quote:I don't know any UWA that gets borders this sharp, let alone at 11mm...

http://www.magezinepublishing.com/equipm...148989.jpg

http://www.magezinepublishing.com/equipm...140105.jpg
  I don't know many that are sharp at the edges at 11mm either!

 

     Dont get me wrong it's good but I just wonder if it's three grand good, maybe it is!

#18
In the f/11 sample with the pointy looking building the railing is out of focus, not soft, in the lower right corner because of the backwards curving field. 

 

In Dave's f/5.6 sample at 11mm you can see strong astigmatism at the left and right edges of the frame.  Looks like the meridional plane is weaker than the sagittal plane which is very good itself.  These samples are reduced in size from the native 50mp so it will look worse at full res.  Whether this has to do with the centering quality of the used sample or not I do not know, but such a short focal length will be extremely sensitive to centering.

  


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