Like someone mentioned above, Nikon uses ED (extra low dispersion glass) in many of their higher end lenses. Canon also uses some fairly exotic glass. They have their UD (extra low dispersion) and they also use fluorite glass:
Anon Moss wrote:
Hi Tariq,
I was wondering whether Canon had any 'apo' named lenses too. I couldn't recall any, and your look through the catalog answers that question. Canon has many excellent lenses (mostly what I shoot along with a few alts) and I would assume that they must be going to a lot of effort to apo correct their lenses. How well corrected Canon's better lenses are relative to say Leica's designated 'apo' lenses - I don't know. I'm curious about how close Canon's better lenses are to being 'apo' (and at approx what 'f' stop), and if some of them do qualify (which I suspect they do)...it's interesting that Canon has chosen not to push that aspect in the marketing.
Scott...Show more →
Canon's photography division cut its teeth in telephotos, and still milks that legacy. Without doubt their high end telephoto primes satisfy the measure other manufacturers are using for "Apo". None of the "fast" camera lenses come close to Abbe's definition wide open, but as focal length increases it becomes easier to approach theoretically perfect performance at common aperture and format.
It's little dated, but there's an interesting shootout here, between an EF 600/4 and an upper end amateur astronomical refractor of similar aperture. Some searching will turn up reviews of this review which point out some gripes here and there, but overall it's quite informative both of the nature of "being Apo" and the compromises and advantages of camera lenses versus special purpose optics.
Yes, at least they published the definition (weak as it may be) that they're working under. It also permits explanation of the large amounts of Coma the Apo-Summicron 90/2 ASPH shows when wide open.
Are you sure you have a good copy? I just shot with mine, mostly wide open. I haven't seen any 'large amounts of Coma '.
phuang3 wrote:
Are you sure you have a good copy? I just shot with mine, mostly wide open. I haven't seen any 'large amounts of Coma '.
Try a tracked wide open shot with some bright stars toward the edge of the field to confirm/refute. Unless I really have just seen a dud I'd recommend a different lens for this type of application.
I see. Stars are the most challenging for a lens, especially a fast prime. I don't think there is any fast lens on the market can do this without seeing any abberations. I've seen night shots by famous Nikon 58/1.2 Noct, and it behaves the same. Usually, 1 or 2 stop down will reduce the abberations vastly.
olyacme wrote:
Try a tracked wide open shot with some bright stars toward the edge of the field to confirm/refute. Unless I really have just seen a dud I'd recommend a different lens for this type of application.
Yes, a photographic lens designed for terrestrial applications would not be my first choice but then I would not choose to shoot with a telescope for most everyday earth bound shots either. Seems like your choosing the wrong tool for your application and expecting it to perform outside of what it was designed for.
Tariq Gibran wrote:
Yes, a photographic lens designed for terrestrial applications would not be my first choice but then I would not choose to shoot with a telescope for most everyday earth bound shots either. Seems like your choosing the wrong tool for your application and expecting it to perform outside of what it was designed for.
Duh! I have nothing against the lens for pretty much any other use. Coma leaves most of the light concentrated within the intended point, but with a wide diffuse spread out from there. Except on very high contrast edges, or isolated points, it won't be apparent in terrestrial images. In portraiture, it may even be desired for creating "glow" without destroying detail.
For astronomical use I'd try the Z* 100/2, or OM 90/2 or 100/2, all of which have more CA, but less Coma. In this case CA is less objectionable as it's held much tighter. They all should be stopped down somewhat as every one of them has its own mix of aberrations wide open.
Anon Moss wrote:
That's it - the last straw...I'm taking it back! For the astronomical price I paid for my 2/90AA...it should darn well shoot astronomical :-(
Nono, I'll buy it from you for the price of its weight in scrap glass and metal...
:-)
Heading off now for Ecuador y Colombia for 3 weeks...adios mi amigos !!
At 8,000' maybe I'll be able to get this piece of junk metal to focus on a star or two.
I don't know - might be easier said than done...I might be in a coma myself :-)
Thanks for all the interesting information -
Scott
