[rparmar]

The subject of apochromatic lenses came up on another thread, causing me to wonder what our choices are for K-mount?

A quick primer: an achromatic lens corrects two wavelengths so they focus together on the same plane. This means that the third wavelength (one of RGB) is not in focus, leading to chromatic aberration, most noticeable as purple fringing at high-contrast edges. Apochromatic lenses correct three wavelengths into focus on the same plane and have other benefits (e.g. reduced spherical aberration).

Most lens manufactures use the designation "APO" to indicate an apochromat. However these are no guarantee of quality. The inclusion of a lens on this list is therefore not a recommendation, though I have placed an asterisk beside those considered superior. None of the Voigtländer lenses are currently made for Pentax; the longer two go for crazy money.

* Pentax FA*200mm f/4 ED Macro

Sigma 70-200mm F/2.8 II EX DG MACRO APO HSM
Sigma 70-300mm f/4-5.6 DG macro APO
Sigma 100-300mm f/4 EX DG IF APO HSM
Sigma 180mm f/3.5 APO EX DG HSM
Sigma 500mm f/4.5 EX AF APO HSM

Voigtländer APO-Lanthar 90mm f/3.5 SL II Close Focus
* Voigtländer APO-Lanthar 125mm f/2.5 SL Macro
* Voigtländer APO-Lanthar 180mm f/4 SL Close Focus

So, anyone have more lenses to add to this list? Especially primes? Warnings or recommendations? (I will edit this post so it stands as an accurate summary.)

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Last edited by rparmar; 04-04-2011 at 05:54 AM.

[rparmar]

Abbazz lists some non-K-mount APO lenses here.

[Digitalis]

apochromatic lenses? in the past pentax has made things that are even more exotic..

Pentax did produce a SMC 85mm f/4.5 super-achromat lens with Fluorite and fused quartz lenses. It was designed for UV and IR forensic photography, I have seen one in it's box and held the lens in my hand. The box contains cut and pass filters for IR and UV. This lens is Extremely rare.

The Pentax SMC 85mm f/4.5 Superachromat can focus wavelengths from 980nm far-infrared to 350nm mid ultraviolet and visible light all in the same plane of focus. The resolution characteristic of this lens is said to be exceptionally high, well over 120Lp/mm


I think many manufacturers are playing fast and casual with the label Apochromatic, hence why Tamron isn't explicitly labelling their lenses as such because they know they would cop a ton of flak for doing so. A 10~24mm apochromatic zoom lens? give me a break, that lens is achromatic at best. Also don't forget about the sigma 180mm f/3.5* which is labelled as being apochromatic (I use one, and it is pretty damn good) I also use the Pentax FA*200mm f/4 ED Macro which is also apochromatic (My lens tests indicate this)

*The sigma 180mm f/3.5 Macro that I own does suffer from slight transverse chromatic aberration which is a second order aberration which typically manifests itself as blue/red fringes at high aperture values at the extremities of the imaging field. These colour fringes tend to appear at magnifications lower than 1:3 on the Sigma 180mm f/3.5 EX Macro. The sigma 100-300mm f/4 EX DG APO I own also exhibits transverse chromatic aberration at close focusing distances of less than 2.5M. Secondly, the Sigma 180mm Macro lens that I use is also very poor performer as the focus distances get longer and longer - from my observations this lens is at it's best at the 1:1~1:5 range with a gradual reduction in resolution as things go past the 2M(6ft) mark. I will have to borrow one of my colleagues 180mm f/3.5 macro lenses and determine if mine is defective. However, I consider that highly unlikely because if there were any error in the lens alignment it would be blindingly obvious if there was any fault at 1:1 magnification.

[Digitalis]

Here is an Unsharpened 100% crop of the transverse chromatic aberration exhibited by the Sigma 100-300mm f/4 APO EX DG - bear in mind this is a worst case scenario, this is a portion of the very bottom corner of the image with the lens focused at the minimum focus distance 1.8m at f/16 @ISO 400 1/500th - the lens was at 260mm

These fringes appear in spite of the lenses apochromatic design because diffraction is blurring the colour spectrum beyond the ability of the apochromatic design's ability to compensate, therefore these blue/red fringes appear. Thankfully, Adobe Lightroom's lens profiles takes this into account and provides flawless correction for this aberration. Image on the left: uncorrected, on the right: corrected in LR with the Sigma 100-300mm f/4 APO EX DG profile.

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Last edited by Digitalis; 01-28-2015 at 12:36 AM.

[dasuhu]

I think many manufacturers are playing fast and casual with the label Apochromatic, hence why Tamron isn't explicitly labelling their lenses as such because they know they would cop a ton of flak for doing so.

Is there a standard for an Apochromat? Heck achromat means "colorless" and "apo" means without. So we have "without [color] colorless". Maybe manufacturers will have a etymapochromat one day (true without [color] colorless).

[elho_cid]

I own the Sigma 180/3,5 apo macro and it is truly great lens. Also Bigma is labeled as APO but it's aberation correction is only halfway relative to HQ primes. From what I have seen apparently the OS bigma is even worse.

Do not forget about Leica lenses. Leica produced several great apochromatic lenses (like 90mm f2) and AFAIK all of them can be converted to K-mount (google leitax).

[Digitalis]

Is there a standard for an Apochromat

I would be amazed if there actually was, as far as I know there isn't. I think many manufacturers use the term apochromatic a bit optimistically. Perhaps I'm revealing myself as being an intractable absolutist, but if a lens has second order chromatic aberrations like the sigma 100-300mm f/4 does -which could be corrected by the use of floating lens elements: can the lens really be called apochromatic? when the explicit definition of an apochromatic lens defined by having the ability to focus three primary colours(R,G,B) into perfect focus on a specific two-dimensional plane.

[rparmar]

I think many manufacturers use the term apochromatic a bit optimistically.

Now that is for sure! Hopefully we can indicate those lenses that really deserve the designation.

I have updated the original post with your two suggestions. I won't add in Leica lenses or those in other mounts, even if they could be converted, since that gets rather beyond scope.

[rparmar]

I own the Sigma 180/3,5 apo macro and it is truly great lens. Also Bigma is labeled as APO but it's aberation correction is only halfway relative to HQ primes.

According to photozone the CA performance of the 180mm looks pretty poor.

[Digitalis]

According to photozone the CA performance of the 180mm looks pretty poor.

I can vouch that the Sigma 180mm f/3.5's Less-than-stellar performance numbers is a combination of sample variation and the focus distance at which the resolution and CA tests were performed. At close focus distances 1:1~1:5 range the Sigma 180mm f/3.5 APO EX performs superbly.

[Nick Siebers]

I have a Ricoh XR "Apochromat" 300mm f/4.5 lens. It has less fringing than other long lenses of its generation, but there is still plenty there. It's nice, if not as razor sharp as I had hoped, but my bad technique with telephotos doesn't help - hand-held, manual focus, eh.

[elho_cid]

According to photozone the CA performance of the 180mm looks pretty poor.

On my Sigma there are some litle lateral aberations taht are easily removed in PP. But there are no bokeh aberations to speak of. That is what matters to me.

[alan_smithee_photos]

none of the Voigtländer lenses are currently made for Pentax; the longer two go for crazy money.

They are no longer produced but the Voigtländer APO-Lanthar 90mm 3.5 is still available from Camera Quest. Looks like they have both the old SL I ($499, Voigtlander SL Lenses) and new SL II ($589, Voigtlander SL II Lenses) available.

It's a killer lens. Highly recommended.

[rparmar]

They are no longer produced but the Voigtländer APO-Lanthar 90mm 3.5 is still available from Camera Quest. Looks like they have both the old SL I ($499, Voigtlander SL Lenses) and new SL II ($589, Voigtlander SL II Lenses) available.

It's a killer lens. Highly recommended.

Problem for me is that's at least a stop too slow for that focal length. It's easy to have low CA in a slow lens!

[elho_cid]

Try getting the 90mm Summicron-R... that is a fast APO