Re: Is it freaking Canon Day or something?

In article <1124972074.228782.255290@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, BC <brianc1959@xxxxxxx> writes

Tony Polson wrote: 
>
>Ever consider this is the reality of Canon's wide lenses on a FF sensor?


It amply demonstrates the need for (near-)telecentric lens designs.

<grins, ducks and runs>

;-) 

Lack of telecentricity has nothing to do with the appearance of lateral
chromatic aberration in wide angle lenses.  What most people don't
appreciate is that many normal lenses have exit pupil distances just as
short as the least telecentric SLR wide angles.

For example, the 55mm f/2.8 Nikkor and 20mm f/2.8 Nikkor have nearly
identical exit pupil distances.  That means they have the same lack of
telecentricity.  Despite this, the 55mm has no lateral color and the
20mm has a ton, thereby proving that telecentricity has no bearing on
the appearance of lateral color.

More evidence comes from LCD and DMD wide-angle projection lenses,
which are all perfectly telecentric.  Nevertheless, most of these
lenses exhibit lateral color.

Lateral color is by far the most difficult aberration to correct in
reverse-telephoto lenses, and it requires skillful use of abnormal
partial dispersion glasses.  As far as I know the only manufacturer to
fully address this problem is Zeiss, and even they only address it with
a single lens:  the 21mm/2.8 Distagon.  Some of the recent wide angle
zooms by Nikon and others are also very good with respect to lateral
color, but typically not over the full zoom range.

Brian

I suspect we may be in danger of getting at cross-purposes here. Brian, you are describing the lens aberration. I believe the previous discussion (though this was not explicitly stated) referred to colour fringing effects caused by light interacting with digital sensors, microlenses, AA screens etc. Many people seem to have started calling this chromatic aberration, which shows they are not very technically aware, but since the phenomenon is similar in appearance this is not surprising.

BTW, interesting point; my understanding is that LCA - that is, the real, lens-created aberration - gets worse with longer focal length lenses, which is of course likely to be the exact opposite of the position for sensor-angle artefacts.

David
--
David Littlewood
.

Relevant Pages

  • Re: 5D - raises more questions
    ... Wide angle lenses near the edges of frames appear to have more CA ... > that normal/tele lenses. ... industry call it lateral color. ...
    (rec.photo.digital.slr-systems)
  • Re: description of camera design I would like to have
    ... work with telephoto lenses that have a recessed rear element? ... of wide angle lenses easier. ... rear element will end up being placed further away from the sensor. ... how well the sensor deals with greater angle of incidence. ...
    (rec.photo.digital)
  • Re: Is it freaking Canon Day or something?
    ... David Littlewood wrote: ... > you are describing the lens aberration. ... Longitudinal chromatic aberration is the one you are ... Lateral color is always zero on-axis and increases with radial symmetry ...
    (rec.photo.digital.slr-systems)
  • Re: Canon wide angle lenses
    ... Canon lenses for wide angle shooting. ... EF-S lenses in case I upgrade my camera. ... perspective distortion wrecks the "look" I like for cars, ... higher than the optical center of the picture you're taking. ...
    (rec.photo.digital)
  • Re: Nikon D40 with 300mm lens AND teleconverter (Nikkor AF-S Teleconverter TC-20E II)
    ... the relationship between lens and perspective. ... projection is the subtended angle of the field of view. ... lenses and 63-degree lenses and so on, instead of 28mm lenses, 35mm lenses etc. ... And of course it would be complicated by smaller format DSLRs which accommodate full-frame lenses as well... ...
    (rec.photo.digital.slr-systems)