I have a number of questions on APO lens on 35mm SLR:
1. Are there any poor man version of 'APO' lens exist(ie. non-APO designated lens; but provide good correction)?
There sure are; by definition pinhole cameras are apochromatic.
cheve wrote:
2. Are there any bad 'APO' lens? Bad is as in proivde good correction and yet 'soft' image.
Yes. Apochromatic refers to spherical and chromatic aberration and, depending on the definition, coma. There are plenty more aberrations available to spoil your day.
cheve wrote:
3. Before 'APO' were invented/available; what did you do to compensate and/or to mininize the issue? Was post-processing the only route?
Apochromatism, as an aspiration by designers of telescopes and microscopes, dates to the 19th century at latest. It was limited to slow designs, or to designs that could employ (small) natural fluorite elements. Artificial fluorite and more lately fluoro-ED glass have made much larger and faster designs possible.
In microscopy, imaging under monochromatic light was a popular solution.
In astronomy, use of a "minus violet" filter to remove a typical achromat's most poorly corrected portion of the spectrum remains a popular solution.
BTW, precious few camera lenses marketed as "APO" are really anything close. Even if they were, there is far more to a good lens than perfect correction for spherochromatism.
There sure are; by definition pinhole cameras are apochromatic.
I was hoping for lens to go with more 'mainstream' like Canon, Nikon or etc system:-). Pinhole cameras sounds fun however.
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In microscopy, imaging under monochromatic light was a popular solution.
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I guess, it means(also by definition) that if I shoot B/W then I do not need to care.
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In astronomy, use of a "minus violet" filter to remove a typical achromat's most poorly corrected portion of the spectrum remains a popular solution.
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Is there similar 'filter' solution for non-astronomy photography?
cheve wrote:
I was hoping for lens to go with more 'mainstream' like Canon, Nikon or etc system:-). Pinhole cameras sounds fun however.
Fast, cheap, and formal APO don't ever go together.
cheve wrote:
I guess, it means(also by definition) that if I shoot B/W then I do not need to care.
Unfortunately you'll still care. You just won't easily be able to tell the difference between CA and SA anymore.
cheve wrote:
Is there similar 'filter' solution for non-astronomy photography?
Cheers
Not in colour photography, though for B&W this is absolutely a possibility. Just bear in mind that, even in B&W, only viewing a portion of the colour spectrum will still affect how the world is presented.
olyacme wrote:
Fast, cheap, and formal APO don't ever go together.
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?
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?
Yes, but current prices of the CV 125 (which are rare) are well over $1000, I've heard $1200-$1500 range, so I don't think you can call it cheap anymore.
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.
The older Sigma 180/2.8 and 180/5.6 macro lenses are APO designated lenses, and perform as such. The Canon AF no longer have aperture control on newer EOS bodies (they do work fine wide open), but you can always get a Nikon (or other) mount version and use it on a Canon EOS camera with adapter. I have the 180/2.8 in a rare Nikon manual focus version, and it performs beautifully on my Kodak SLR/c and Canon 5DII.
can't justify a >1k lens for what I do(or do not do:-))...but does it mean there is still hope to get a 'cheap' and somewhat slow(eg. f4) but decent, 'APO'-like quality lens?
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?
It may be apochromatic by f/5 or so, but that's not fast by photographic standards. Fast cheap and APO really are exclusive.
Paul Yi wrote:
CV Apo 90/3.5 can be had for less than $400....
Again, APO at f/3.5? Optimistic beyond belief. Given that the finest sensor you can commonly stick it on runs into Nyquist around f/5.6 or so it may not matter that it's only apochromatic when stopped down. But if you can't trust a manufacturer to say under exactly what terms a lens is apochromatic, how can you trust the designation at all?
Pentax mount CV 90 APO (sweet, sweet glass) maybe for that, Nikon forget it. ;> (I know, because I've been doing some price research re: selling mine... The Elinchrom bug has firmly taken hold ;> or is it ;< ?)
You can pick up a used Leica R APO 180mm f/3.4 for less than $1,000 and the Voigtlander APO 180mm f/4 can also be picked up for less than $1,000. Neither is very fast, but both are very nice lenses.
Toothwalker wrote:
How does the f-number affect the number of wavelengths that share a common focal plane?
It lowers the bar (increases the size of the airy disk). A diffraction limited white light f/2.5 lens covering 135 format for $1000? Gimme a break!
Conversely, many (good) 135 lenses are diffraction limited by f/11-16, a sweet spot to be so on film. Of course, depending on the mix of aberrations, many (some still good) lenses will not cross the bar at any stop.
olyacme wrote:
It lowers the bar (increases the size of the airy disk). A diffraction limited white light f/2.5 lens covering 135 format for $1000? Gimme a break!
I don't make claims about any lens, I just ask how the f-number affects the number of zero crossings. See http://en.wikipedia.org/wiki/Apochromat for the definition of an apochromatic lens design. Stopping down the lens should not alter the number of wavelengths that are brought together in the same focal plane, unless you invoke some complex interaction with spherical aberration. Of course, residual color errors are reduced as the lens is stopped down, but that does not make an achromatic lens (or whatever) apochromatic.
Toothwalker wrote:
I don't make claims about any lens, I just ask how the f-number affects the number of zero crossings. See http://en.wikipedia.org/wiki/Apochromat for the definition of an apochromatic lens design. Stopping down the lens should not alter the number of wavelengths that are brought together in the same focal plane, unless you invoke some complex interaction with spherical aberration. Of course, residual color errors are reduced as the lens is stopped down, but that does not make an achromatic lens (or whatever) apochromatic.
There are no zeros here. Aberrations are always present. The very best you can hope for is that they're so well corrected that they're hidden by diffraction (within the airy disk). Stopping the lens down increases the size of the airy disk, lowering the correction demanded to qualify as Apochromatic, while simultaneously reducing certain aberrations.
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