cheve wrote:
a lot info has been given for question 1 and 2, I would appreciate further comments for question 3
IMO the best approach is to avoid situations where you know a lens performs poorly. If it's got a lot of field curvature, don't use it wide open at infinity. If it's got a lot of defocus CA, don't use it for closeups with a lot of detail in them. For CA in general, try to avoid hard light. Don't shoot into bright light if it flares. A lens that has a lot of Coma is probably a bad one to use for starfields, but it might be a great portrait lens.
The Cosina-Voigtlander 180/4 APO-Lanthar has no perceivable CA at least at any aperture across the entire frame. The Leica 100mm APO-Macro-Elmarit-R is almost as well corrected.
Reviews and sample images show the same thing, and I have seen it pixel peeping at my copies.
Cheve, if you look around you can find the Sigma 180/2.8 Macro for a few hundred. It's sharp and APO corrected from wide open. Even works beautifully with the Kenko/Tamron Pro 1.4x (from wide open).
cheve wrote:
3. Before 'APO' were invented/available; what did you do to compensate and/or to minimize the issue? Was post-processing the only route?
APO lenses have been available for more than a century and were popularized at various times in the early 20th century, long before digital post processing. This question doesn't make sense as phrased.
On film, chroma aberrations are usually less offensive in a given situation than they are in digital. I suppose it simply wasn't as big an issue for most photographers.
thrice wrote:
The Cosina-Voigtlander 180/4 APO-Lanthar has no perceivable CA at least at any aperture across the entire frame. The Leica 100mm APO-Macro-Elmarit-R is almost as well corrected.
Unless a reviewer had access to a 135 sensor with no AA filter and 160MP (or more likely a smaller sensor they can move about on the focus plane), they won't have been able to tell whether it was Apochromatic at f/4.0 or not. I didn't pull that number of MP out of thin air, either, which should put the Apo at f/2.5 (try 300MP) thing into better perspective.
Even on an attainable sensor, and at a reasonable f-stop, the lack of CA does not alone make a lens Apochromatic. The lens must also be multiply corrected for Spherical Aberration, and, by most definitions, Coma. Even with all that, we're only getting started making a nice lens.
3. Before 'APO' were invented/available; what did you do to compensate and/or to minimize the issue? Was post-processing the only route?
...
APO lenses have been available for more than a century and were popularized at various times in the early 20th century, long before digital post processing. This question doesn't make sense as phrased.
On film, chroma aberrations are usually less offensive in a given situation than they are in digital. I suppose it simply wasn't as big an issue for most photographers.
I was thinking in the context of 35mm SLR. I started my life(ie. photo) with digital:-) so in the whole scheme of thing, I am very much a newbie. I welcome all comments and education.
By that account no lens is likely a "true" APO lens, but do I care? I have used plenty of lenses and I know what I see with a good APO lens. That's good enough for me.
By all means continue on with the extreme definition of APO, but it seems like your beating a dead horse?
. olyacme wrote:
Unless a reviewer had access to a 135 sensor with no AA filter and 160MP (or more likely a smaller sensor they can move about on the focus plane), they won't have been able to tell whether it was Apochromatic at f/4.0 or not. I didn't pull that number of MP out of thin air, either, which should put the Apo at f/2.5 (try 300MP) thing into better perspective.
Even on an attainable sensor, and at a reasonable f-stop, the lack of CA does not alone make a lens Apochromatic. The lens must also be multiply corrected for Spherical Aberration, and, by most definitions, Coma. Even with all that, we're only getting started making a nice lens.
pdmphoto wrote:
By that account no lens is likely a "true" APO lens, but do I care? I have used plenty of lenses and I know what I see with a good APO lens. That's good enough for me.
By all means continue on with the extreme definition of APO, but it seems like your beating a dead horse?
A precise term has been marketed into being nearly meaningless, at least among photographers. It's a judgement call whether to accept the dumbing-down-of-everything we seem to live with these days, or get out a stick. Personally, once in a while, I like to try the stick.
If I buy a lens marked APO, I expect that in its practical application using technology readily available to photographers, I will not have any ca issues whatsoever, particularly in the out of focus areas or LoCA (and that does not include 160MP sensors because I'm not sure which DSLR offers that now nor do I expect to see it anytime soon).
pdmphoto wrote:
By that account no lens is likely a "true" APO lens, but do I care? I have used plenty of lenses and I know what I see with a good APO lens. That's good enough for me.
By all means continue on with the extreme definition of APO, but it seems like your beating a dead horse?
pdmphoto wrote:
The APO lenses I own are anything but "nearly meaningless", and the term is hardly a precise one. Even you mention the a "most definitions" clause.
Most definitions include Coma; all definitions require crossings for CA and SA within the airy disk. Besides the note about SA, it's this last bit that many people seem to fail to grok. Since the lenses listed so far cannot possibly be Apochromatic wide open, and, as far as I can tell, none say exactly where they become Apochromatic, the term has been reduced to nothing more than a marketing buzzword.
pdmphoto wrote:
Cheve, if you look around you can find the Sigma 180/2.8 Macro for a few hundred. It's sharp and APO corrected from wide open. Even works beautifully with the Kenko/Tamron Pro 1.4x (from wide open).
Thanks, will keep an eye for it. By the way, is the Sigma same size/wight as the Mamiya M645 or for that matter they all(ie. all APO corrected) come in similar size and weight in that FL range.
cogitech wrote:
I know of at least one exception. The CV 125/2.5 Macro APO-Lanthar is fairly fast for its focal length, was only $600 when released (relatively cheap) and it has excellent APO-correction (I see basically no LoCA or LaCA). On top of all that, it excels in many of the other qualities that make, as you say, "a good lens".
If there is one exception, maybe there are others?
90/3.5 APO-Lanthar. Still available for under $500 in LTM mount.
pdmphoto wrote:
I've found late version of the Nikon 300/4.5 to very near APO in correction, but they are not labeled as such. Some say Nikon used ED glass in them before ED became a marketing buzzword.
There's no ED glass in the non-ED labeled 300/4.5. Nikon sold an ED version and a non-ED version for essentially the entire life of the lens. The non-ED is very good considering its age, the ED is better, but not significantly so IMHO.
I dunno. I'd rather have things properly defined to an acceptable degree. Requiring 300MP tests is overkill when we're all using 12MP cameras, but I'd rather there be some kind of industry standard. Grouping the 125/2.5 with every single cheapo Sigma uber zoom is just wrong, but they're all labeled APO.
Look at what happened to the term "HD". It's been so abused as to be practically meaningless.
StevenPA wrote:
Requiring 300MP tests is overkill when we're all using 12MP cameras, but I'd rather there be some kind of industry standard.
All manufacturers need to do is state at what f-stop the lens becomes Apochromatic. The sensor really doesn't have any play in the definition, though it sure does in the application. It'd still be a select club of lenses, and the consumer would be better informed about how future proof their purchase is or is not.
