[acoufap]

I go by what I see on the lens charts. If I ever see a lens for sale on ePhotozine or Optical limits or somewhere I'll be happy to add a disclaimer, how ever in the absence of any commercial lenses for commercially available cameras with no aberrations, I'll just stick with their aren't any. I always like to point to things people can buy for their cameras, when discussing lenses. So we are as far as I can tell taking about different things. I'm happy to believe it might be worth it to produce cameras for satellites that are ridiculously corrected, but until they are commercially available at Henry's or Canada Camera, they aren't what I'm talking about.

Theoretically, yes a lens can be produced to not produce CA to any notable degree.
Practically no, you can't buy one for your camera.


Some reading...
https://en.wikipedia.org/wiki/Chromatic_aberration

They discuss many ways to reduce CA, not to eliminate it.

Some points fo interest.




Note the use Pentax makes of CA used to produce smooth out of focus areas is not discussed. I'd be interested in seeing how a true super-achromat lens handles out of focus areas. Until I know that, I haven't even taken step one, which would be deciding if eliminating CA is even desirable.

This seems to be such an APO design lens …

https://www.venuslens.net/product/laowa-100mm-f-2-8-2x-macro-apo/

[normhead]

This seems to be such an APO design lens …

https://www.venuslens.net/product/laowa-100mm-f-2-8-2x-macro-apo/

Is there a chart for it? All lenses are designed with some Achromatic reduction of CA. As I said, my Rokinon 14 2.5 is rated for .26 pixel and under, a very high level of correction. There's difference between APO and completely corrected. Given that this lens is recommended as the best for Astro photography by some sites not owned by Rokinon.

It would be interesting to ask those who look at such things... what is the best corrected lens you own?

As for the Loawa referred to, after a short investigation.


There is visible CA, even for this size image, which is reduced in size to what it would be pixel peeping.
What I'm reading is finer tolerances for reducing CA, I've not seen any reference to complete elimination.

[Serkevan]

I am ever in despair at the thought that finances absolutely don't allow for this purchase I absolutely don't require. Such lovely shots.

Sorry, couldn't resist....

You, good sir, are the bane of my LBA.

[acoufap]

Is there a chart for it? All lenses are designed with some Achromatic reduction of CA. As I said, my Rokinon 14 2.5 is rated for .26 pixel and under, a very high level of correction. There's difference between APO and completely corrected. Given that this lens is recommended as the best for Astro photography by some sites not owned by Rokinon.

It would be interesting to ask those who look at such things... what is the best corrected lens you own?

As for the Loawa referred to, after a short investigation.


There is visible CA, even for this size image, which is reduced in size to what it would be pixel peeping.
What I'm reading is finer tolerances for reducing CA, I've not seen any reference to complete elimination.

My guess would be that an APO design theoretically should deliver zero CA but in reality might mostly support tighter tolerances. As I discovered Sigma also designates some of their lenses as APO.

[normhead]

I am ever in despair at the thought that finances absolutely don't allow for this purchase I absolutely don't require. Such lovely shots.

I could say that about the whole ltd. series. Unlike others who find fault with them, I think of them as lenses with character. I would put them ahead of better MTF images who's images I find for the most part to be sterile. One person's negative is another's positive. My only issue with them has always been price.

But that's a pretty big issue.

---------- Post added 11-07-21 at 09:42 AM ----------

My guess would be that an APO design theoretically should deliver zero CA but in reality might mostly support tighter tolerances. As I discovered Sigma also designates some of their lenses as APO.

My Sigma 70-300 was designated APO, and it had CA and purple fringing coming out the wazoo.
A lens being designated APO means they have taken some corrective action, but there is no standard that a lens has to achieve before it's called APO. They just have to make an attempt and achieve a slight reduction. Like the term macro. For most lenses, although there are few exceptions a lens has to go to 1:1 to be designated as macro by Pentax. With Sigma it's 1:2. A company calling a lens APO means nothing, unless they've defined the standard by which it receives that designation.

[acoufap]

I could say that about the whole ltd. series. Unlike others who find fault with them, I think of them as lenses with character. I would put them ahead of better MTF images who's images I find for the most part to be sterile. One person's negative is another's positive. My only issue with them has always been price.

But that's a pretty big issue.

---------- Post added 11-07-21 at 09:42 AM ----------



My Sigma 70-300 was designated APO, and it had CA and purple fringing coming out the wazoo.
A lens begin designated APO means they have taken some corrective action, but there is no standard that a lens has to achieve before it's called APO. They just have to make an attempt and achieve a slight reduction. Like the term macro. For most lenses, although there are few exceptions a les has to go to 1:1 to be designated as macro by Pentax. With Sigma it's 1:2. A company calling a lens APO means nothing, unless they've defined the standard by which it receives that designation.

So an APO designation more sounds like a marketing issue like Macro on my Vivitar Series 1 2.8-4.0/70-210. With its 1:3.5 it‘s better than most zooms but far from a real macro. Thanks for clarification!

[Serkevan]

I could say that about the whole ltd. series. Unlike others who find fault with them, I think of them as lenses with character. I would put them ahead of better MTF images who's images I find for the most part to be sterile. One person's negative is another's positive. My only issue with them has always been price.

But that's a pretty big issue.

Yeah, I have the 43 and 77 (I got them for 350€, which probably has exhausted my luck on deals for a good while). They are absolutely fantastic lenses... to the point they are the main reason I like shooting primes in the first place. And their aberrations aren't bothersome except in some specific circumstances.

[normhead]

Yeah, I have the 43 and 77 (I got them for 350€, which probably has exhausted my luck on deals for a good while). They are absolutely fantastic lenses... to the point they are the main reason I like shooting primes in the first place. And their aberrations aren't bothersome except in some specific circumstances.

No one's ever offered one in my world for under $650 USD, or $800 CAD. 350€ is 500 CAD. Lucky you.
Mind you, the first one I'd buy would be the 31.

[Serkevan]

No one's ever offered one in my world for under $650 USD, or $800 CAD. 350€ is 500 CAD. Lucky you.
Mind you, the first one I'd buy would be the 31.

I definitely am! I'd love to round it up with the 31 (and/or the 21, now...), however... cheapest I've seen a 31 was about 700€. So a sharp 1000 CAD, which is too steep for me, at least nowadays.

[LennyBloke]

A little more time with the new Silver Shiny today.....

















,,, all in the Flickr Album

[Lev]

I go by what I see on the lens charts. If I ever see a lens for sale on ePhotozine or Optical limits or somewhere I'll be happy to add a disclaimer, how ever in the absence of any commercial lenses for commercially available cameras with no aberrations, I'll just stick with their aren't any. I always like to point to things people can buy for their cameras, when discussing lenses. So we are as far as I can tell taking about different things. I'm happy to believe it might be worth it to produce cameras for satellites that are ridiculously corrected, but until they are commercially available at Henry's or Canada Camera, they aren't what I'm talking about.

Theoretically, yes a lens can be produced to not produce CA to any notable degree.
Practically no, you can't buy one for your camera.


Some reading...
https://en.wikipedia.org/wiki/Chromatic_aberration

They discuss many ways to reduce CA, not to eliminate it.

Some points fo interest.




Note the use Pentax makes of CA used to produce smooth out of focus areas is not discussed. I'd be interested in seeing how a true super-achromat lens handles out of focus areas. Until I know that, I haven't even taken step one, which would be deciding if eliminating CA is even desirable.

Maybe that's why an older lenses have more character, pleasing and interesting look in bokeh?

[texandrews]

A little more time with the new Silver Shiny today.....

















,,, all in the Flickr Album

I continue to like what I am seeing from this lens.

[mlt]

I continue to like what I am seeing from this lens.

True. I’m waiting for the US release date and a phone call saying my pre-order is ready to ship.

[normhead]

The third one looks like something from a fairy tale. Top notch.

[Ex Finn.]

Would look good on my KP.
A good thing that I am a zoom guy and it is not available except for a pre-order or B&H would have my money.
LBA kicking in...