[robert]

Right now I have an SMC M100 2.8 that I really like and a Super Takumar 135 3.5 which is decent also.
Any other I should have?

[reh321]

Right now I have an SMC M100 2.8 that I really like and a Super Takumar 135 3.5 which is decent also.
Any other I should have?

I suppose every true Pentaxian should have an eight-element Takumar 50mm F/1.4 ……. but those were made years ago, so the supply would limit the number of “Pentaxians”.

[Sandy Hancock]

Is that the sound of Pandora's box opening?

There are soooo many.

[Abbazz]

Right now I have an SMC M100 2.8 that I really like and a Super Takumar 135 3.5 which is decent also.
Any other I should have?

I think that it is safer to stay in the 28mm - 135mm range for vintage lenses (this doesn't apply to the Pentax-A series) if your are looking for high quality pictures on recent cameras with high density sensors. But it can also be interesting to have a few lenses outside this range if you are after a specific rendering. For example, I love the small Pentax-M 20mm f/4.0 for its wonderful colors.

My favorite manual focus lenses (on a full-frame camera):

Pentax

• Pentax-M 20mm f/4.0 - Tiny lens with superb rendering. Never really sharp in the extreme corners but that shouldn't be a problem for most pictures.
• Pentax-K 28mm f/3.5 - Sharp, high quality lens punching in the same category as the best Zeiss glass.
• S-M-C Takumar 35mm f/3.5 - Little jewel of a widish lens, Top class quality.
• Pentax-M 40mm f/2.8 - Nice pancake lens delivering beautiful pictures. 40mm is my favorite focal length.
• Pentax-M 50mm f/1.7 - Wonderful normal lens, sharp, well built and very compact.
• Pentax-A 50mm f/2.8 Macro - Great as a macro lens and also able to deliver superb results as a normal lens.
• Super-Multi-Coated Takumar 85mm f/1.8 - Superb portrait lens: beautiful bokeh, smooth rendering wide open that becomes very sharp at f/4.0-f/5.6 making it a very versatile lens.
• Pentax-M 100mm f/4.0 Macro - Longer macro lens for those shy critters. Also a great portrait lens with superb bokeh thanks to its classic Heliar/Dynar optical formula.

Other brands

• Voigtländer Color-Skopar 20mm f/3.5 - Good super-wide lens when closed down a bit. Very compact for the focal length. The 0.2m close-focus is a plus.
• Voigtländer Ultron 40mm f/2.0 - Also very compact (almost a pancake lens), Better image quality and faster than the Pentax-M 40mm. This lens pretty much resides permanently on my K1-ii.
• Voigtländer APO Lanthar 90mm f/3.5 - Super sharp short telephoto. It focuses down to 1:4 ratio without any accessory and goes to 1:2 with the provided high-quality close-up achromatic doublet, delivering results on par with the highly praised 125mm f/2.5 Apo-Lanthar. Works excellently with teleconverters.
• Voigtländer APO Lanthar 180mm f/4.0 - One of the best 180mm lens available. Delivers superb results at infinity but also shines for close-up photography.

These Voigtländer SL and SLII lenses are really exceptional but also very hard to find nowadays in Pentax mount. They can fetch high prices but are totally worth it IMHO. The 20mm, 40mm and 90mm fit into a very small bag and deliver top-notch images, while being very versatile thanks to their very short minimum focus. Add a teleconverter and the Voigtländer close-up lens and you will have the ideal compact travel kit going from superwide to long tele and allowing to shoot at 1:2 reproduction ratio (and even 1:1 macro with the 90mm + close-up + 2x teleconverter).

Cheers!

Abbazz

[Sandy Hancock]

There are soooo many.

To expand:

At the spendy end, the K 28/2.0, the K or A 50/1.2 and the A*135/1.8 all have fabled rendering.

And at the other end, I reckon everyone should try one of the Helios 58/2.0 variants at some point. They are dirt cheap and loaded with character.

[pschlute]

The M 50mm 1.7 is cheap and is an excellent lens.

To add to Sandy's "spendy" list :

K 18mm 3.5
K 28mm 3.5
M* 300mm 4.0

[kypfer]

Right now I have an SMC M100 2.8 that I really like and a Super Takumar 135 3.5 which is decent also.
Any other I should have?

I think another factor to consider is whether we're considering use on a full-frame or APS-C camera.
As the Helios-44 has already been mentioned … (especially good on a full frame) … I'll chime in with the Meyer Optik 30mm f/3.5 Lydith, (the original, not the over-priced re-release), for it's "painterly" properties, but the list really does go on and on
Good luck and get a bigger bag, you'll need it

---------- Post added 08-25-22 at 11:27 PM ----------

I suppose every true Pentaxian should have an eight-element Takumar 50mm F/1.4 ……. but those were made years ago, so the supply would limit the number of “Pentaxians”.

That counts me in then

[Fogel70]

I prefer old m42 Takumars because of their beautiful build quality.
And also those old ones from late 1950s to early 1960s offer some unique characteristics that you will not find in more modern lenses.
I like having old lenses that deliver something special that modern lenses can not deliver. It does not necessarily mean they are better in every way, just different.

[Henrico]

On APS-C most M-lenses work fine, those with miniaturized optical formulas compared with the K-series suffer some border and for sure corner performance. M-lenses with similar formulas as the K-lenses perform equally good (f.i. K1.4 vs M1.4).

On FF I prefer K-lenses, for most lenses there is more glass in the K-series what results in better performance all over the frame.

I got about 30 K and M-lenses.

On APS-C I really like the M20, M28/2.8, M50/1.4, M85, M100/2.8 and M200

On FF I like the K28/3.5, K35/2.0, K50/1.2, M85, M100/4.0, K135/2.5, K200/4.0 and A400

The bigger K-lenses also are more balanced on a K1.

[JensE]

To address the original question: You should have those manual lenses, which you'd actually use to take pictures, which you otherwise would not. It's a 'would' not 'could'. That is highly dependent on your photographic interest and approach - even though cases have been documented where interesting lenses have extended those considerably.

The manual lenses that I would not want to part with, because they have something special that I enjoy are the Irix 150mm and Laowa 100mm macros, the Voigtländer 20mm/3.5 ultra-compact super wide and the outstanding 12mm Samyang fisheye. I do own quite some others and while I e.g. sometimes cherish the rendering of my two adapted Carl Zeiss Jena lenses, I rarely use them and there are no Pentax lenses in the list. Both because Pentax managed to produce a range of AF lenses, that have an equally interesting or special appeal to me as some potential MF lenses, like the FA Ltd. series, and I simply enjoy the relative ease of use.

So what makes you like your M100/2.8? Is it the specific look, the process of taking pictures with it or the extension of photographic options on a tight budget? The answers may help to come up with good recommendations.

[ZombieArmy]

The Auto-Takumar 35mm f2.3 is one of the wildest lenses Pentax ever made. To me it's a must have especially given they're still reasonable in price despite the low production numbers.

Artistic wide open and sharp closed down is a perfect combo to me.

[AfterPentax Mark II]

Pentax A 35-105mm F3.5 as no one has mentioned a zoom yet. And the A 50mm F1.4, build quality superb, when using them, both feel with zooming and focusing like the day I bought them and that was 40 years ago, they outlived my Super A, (which is standing lonely and unused in a corner) cannot be repaired anymore....

[HanSch]

The Pentax K 1.8/55mm is an excellent portrait lens on APS-C, and the lens I like best is the SMC K 1.8/85mm (that was my portrait lens in the film era). The 85mm has great image quality, and the smoothest focussing you can imagine.

[Oldbayrunner]

A "must have lens" is strictly dependent on ones needs/wants. What may be a must have for someone can be different then another.

[Fogel70]

The Auto-Takumar 35mm f2.3 is one of the wildest lenses Pentax ever made. To me it's a must have especially given they're still reasonable in price despite the low production numbers.

Artistic wide open and sharp closed down is a perfect combo to me.

That is probably my most wanted lens right now. Unfortunately it seems to be very difficult to get hold of a copy in nice condition where I live.
One of these unique 1950s design lenses.