[Just1MoreDave]

I haven't seen anyone compare these two less-common lenses before. They are different optical formulas but pretty close in specs - 6 aperture blades, 1.8m minimum focus distance. So far it feels like they are nearly identical in performance. I see two differences. The color rendering of the M vs. Super-Multi-Coating, slightly cooler for the M. And the M is softer wide open in the extreme corners. It is difficult to compare the two at f4 because I think the M aperture ring stops at f4.5. The center is a draw. Anyway, it's the kind of splitting hairs difference you see in tests. In the real world, at f5.6 they are the same sharpness, and very usable wide open. Worry more about the minimum focus distance, which is great for social distancing. Unfortunately I was limited to subjects I could get to under lockdown.

Since I was testing, I added in my DA 50-200 WR and HD 55-300 WR (not the PLM, the older one) to the sharpness test. In the center, the zooms areas good as the old primes. In the extreme corners, they aren't. This is a 100% crop of the M150 at f3.5:



Here is the DA at a similar sharpness but at f11:



Here is the HD at f4.5:



The DA has a lot of vignetting wide open and only opens to f5.6. The HD has a lot of pincushion distortion at this focal length, much less vignetting than the DA, opens to f4.5 and colors/contrast seem nicer.

[.a.t.]

Thanks for the comparison! Just knowing Asahi / Pentax actually made 150mm lenses makes me smile. Glory days!

For years I've been curious about them simply because 150mm is an uncommon length. But the long, 1.8m MFD has kept me from actively pursuing one.

And seeing this thread has reminded me of a question I've wondered about :
What was the rationale for a 150mm lens when 135s were plentiful?

So I looked in my S-M-C era "Takumar Lenses" booklet and found this:

[Just1MoreDave]

I forgot another difference, the M150 stops down to f32!

Maybe if you had a 50mm and an 85mm, you could get the 120/2.8 and a 150. It also might have been a good price.

[pres589]

What's surprised me is how lackluster the DA 50-200 is. My copy seems to be acting about as well as anyone else's. The 55-300's have all been very good performers for their price, in my estimation, but the 50-200 was just not up there.

[monochrome]

What's surprised me is how lackluster the DA 50-200 is. My copy seems to be acting about as well as anyone else's. The 55-300's have all been very good performers for their price, in my estimation, but the 50-200 was just not up there.

I had the original 50~200 for a few months but replaced it when the 55~300 was first released. The 50~200 was just plain dull. In good light the original 55~300 is bright, colorful and pretty sharp but it can fall off at the longer end due to the low max aperture.

[pentaxus]

The 150mm was made because it was the longest you could make an f/4 lens that uses a 49mm filter. The 120 was the longest 2.8 that could use a 49mm filter. For people wanting to save money on filters for their system. The 200mm 5.6 also used 49mm. So you could go from 28mm to 200mm and only need one set of filters.

[Just1MoreDave]

What's surprised me is how lackluster the DA 50-200 is. My copy seems to be acting about as well as anyone else's. The 55-300's have all been very good performers for their price, in my estimation, but the 50-200 was just not up there.

I like the DA 50-200 for size and weight - 285 grams, two-thirds what the 55-300s are. I was perfectly happy in my dream world, never owning a 55-300. The 50-200 was just fine, all I ever needed, other people were just wrong. I'll keep it but the niche it was filling just got smaller.

[gofour3]

There was also the K150/4, which is on the rare side. Same optical setup as the SMC Takumar version, except it had a minimum aperture of f32 and a 52mm filter thread.

Phil.

[pres589]

I like the DA 50-200 for size and weight - 285 grams, two-thirds what the 55-300s are. I was perfectly happy in my dream world, never owning a 55-300. The 50-200 was just fine, all I ever needed, other people were just wrong. I'll keep it but the niche it was filling just got smaller.

If you are happy with the DA 50-200 and you get the images you want out of it then by all means keep using it. I just don't find mine to be all that great. It's not one of those lenses that sells for much less than it ought to based on IQ. I kind of feel like this was the last "bad" zoom that Pentax sold.

[monochrome]

I haven't seen anyone compare these two less-common lenses before. They are different optical formulas but pretty close in specs - 6 aperture blades, 1.8m minimum focus distance. So far it feels like they are nearly identical in performance. I see two differences. The color rendering of the M vs. Super-Multi-Coating, slightly cooler for the M. And the M is softer wide open in the extreme corners. It is difficult to compare the two at f4 because I think the M aperture ring stops at f4.5. The center is a draw. Anyway, it's the kind of splitting hairs difference you see in tests. In the real world, at f5.6 they are the same sharpness, and very usable wide open. Worry more about the minimum focus distance, which is great for social distancing. Unfortunately I was limited to subjects I could get to under lockdown.

The DA has a lot of vignetting wide open and only opens to f5.6. The HD has a lot of pincushion distortion at this focal length, much less vignetting than the DA, opens to f4.5 and colors/contrast seem nicer.

There was also the K150/4, which is on the rare side. Same optical setup as the SMC Takumar version, except it had a minimum aperture of f32 and a 52mm filter thread.

Phil.

I have both the M150 (the only M lens I own) and the K150. I pretty much concur with the OP on all points given the K and Tak differ only slightly as to coatings. IMO the M150/3.5 is a sleeper lens that I’ve kept because mine is a bit sharper than the K150/4.

Over the years I have noticed M (and A) coatings are often noticeably cooler than their K counterparts. IME this is especially true of the comparable 50’s.

[StarTroop]

I wonder how the M 75-150/4 compares to the primes. I suppose back when zooms were much worse, the need to fill out the focal range with primes was more necessary, but the 75-150 is considered to be quite a good zoom for the time.

[gofour3]

I wonder how the M 75-150/4 compares to the primes. I suppose back when zooms were much worse, the need to fill out the focal range with primes was more necessary, but the 75-150 is considered to be quite a good zoom for the time.

I have the K150/4 and the M75-150/4.

At 150mm the M Series zoom is not as good as the K Series prime. An old zoom that is closer would be the A70-210.

Phil.

[Jonathan Mac]

What's surprised me is how lackluster the DA 50-200 is. My copy seems to be acting about as well as anyone else's. The 55-300's have all been very good performers for their price, in my estimation, but the 50-200 was just not up there.

I got the WR version of the 50-200mm a few years back to use for travelling because the 55-300mm was just too big and heavy and so I never took it. I found that I got much nicer results from the M 135mm f/3.5 than from the 50-200mm so I later bought the M 120mm f/2.8 which I think is the best small, K-mount lens around that focal length.

[johnha]

I used to use a M135/3.5 as my three lens kit tele due mainly to its small size. I have since tried M200/4, M75-150 & M80-200 - all three are good but they're very similar in size and too big to fit in my small bag insert.

I've acquired an M150/3.5, which mostly gives the extra reach with only a minimum increase in size. Although, in the current situation I haven't had a chance to use it.

I know 135 was a classic focal length from the rangefinder era, but it has not been long enough for me (or too long as say a portrait option).