Pentax 300mm M42 lens opinions?

Apparently Pentax made both an f/4 and f/6.3 version of their 300mm lens in M42 mount; one being a preset lens (which I don't mind).

I'm thinking of getting one or the other, but reviews and opinions of these lenses on the web are few.

So, anyone have one or used one of these? If so, what do you like or not like?

Is there one in K mount as well?

I'm thinking of using it for birds and animals - or a UFO if I see one.

Thanks in advance.

I've had the f/4 300mm screw mount model 1 lens since about 1960 and used it with a pistol grip with cable release for sports photography. https://www.pentaxforums.com/lensreviews/Takumar-300mm-F4-1958.html

Pentax made 5 300mm in M42, 3 F4s, one 5.6 and 1 6.3 in M 42 and 1 4.0 in K. The 6.3 is a preset. In m42 I have a F4 and a 6.3, don't know which version of the F4, at F8 no difference, the F 4 is easier to work with as you don't have open up to focus and stop to shot. The other difference is speed. Other option is a Vivitar 300 5.6 in M 42, also sold by Sears, make by Toknia, as good as Pentax, the coating on the K might be better, not sure, I don't have a K mount. Odd as it seem my sharpest 300 is a Petri, too bad the cameras are crap.

I had the last version M42 (S-M-C Takumar) 300mm f/4.0, it did well on film as long as shutter speeds were high enough. On digital it did not hold up as well as more modern designs like a Tamron 60B 300/2.8 which is my main tele now. Minimum focus is rather long so if you're chasing birds it can be a pain to pull the lens off, add a ring, re-focus, etc. The focus is conventional type so you're moving quite a bit of glass. Later designs went to internal focus so it's easier and faster to follow subjects.

That being said, I find accurate focus and shutter speeds eliminating camera shake the two biggest issues for my 200mm+ adventures, not so much lens quality. I have made some nice prints from a cheap 500mm mirror because they were shot correctly (held steady, shutter speed high enough).

I have the M42 Asahi 300mm f/6.3 preset Tele Takumar (58mm filter). For the price, it is a real bargain.

I have one of the Takumar 300 f/4 lenses and I had one of the K Mount 300s. Both are good lenses on film but I rarely used either on digital.

As mentioned already, and as expected I guess, good technique is critical if you want a usable photo. Use the hood and be aware that purple fringing around edges WILL happen if the light is right.

I sold the K-mount 300 and bought the SMC A 400 5.6 because it has a tripod mount on the lens. You may not believe it but unless I had the 300 bolted down to my big Gitzo with the Majestic gear head even the tiniest bit of breeze would cause vibration. The 400 is WAY easier to control though I still use a heavy tripod anyway. Because it is an A lens it is easier to work with on digital and the image performance holds up on digital a bit better than either of the 300s I used.

If you are going to get one of the 300s find a tripod mount for the lens. They are out there and it will make a difference. I also strongly recommend a gimbal mount. For anything 300mm or longer it makes life far easier.

EDIT - BTW, the K mount 300 f4 has a different optical formula than the M42 SMC/Super Takumars have. The SMC Takumar is 5 elements in 5 groups while the later K mount is 7 elements in 5 groups.

I have the M42 Super-Multi-Coated Takumar 300mm f/4, it's one of the best built lenses I've seen. It's all metal, has a very smooth focus action, a tripod socket and built-in telescopic hood. I've only used it on APS-C digital (Pentax K-5) where it gives slightly muted (almost pastel) colours under some lighting conditions.

There are several K mount 300mm f/4 lenses, but once you get to the 'M' series they're the * (star) lenses, as such they're the premium lens line with premium prices - pushed up further by their compatibility with all of the Pentax DSLRs. They were expensive (read 'rare') when they were new, so are rarer (read 'more expensive') today.

One other option if you wanted to stick to Pentax is the 67 version with an factory adapter to go from 67 to M42 or PK, depending on your needs/what you can find to purchase. The adapters can sometimes be found for pretty cheap, and I got better results from the 67 version than my M42 mount lens. Neither had a tripod ring so these tests were handheld. Just another idea.

Thanks everyone - I have a lead on a SMC Takumar 300/4, but I found someone who can show me the old f/6.3 as well. Decision to come in a few weeks.

My decision was to get the SMC 300/4, although it doesn't have the collar. I suspect I'll have to prop the lens up with a folded hand towel for stability, as I don't think the collars are easy to find.