K-Mount Comparison: SMC Pentax-M vs XR Rikenon

[PGraham3]

Howdy, APUG!
Like a Street Figher II match, each opponent has their special moves, features, and flaws, and the same goes for most camera lenses. With SMC Pentax-M and XR Rikenon lenses, it's like KEN vs RYU, that while they utilize the exact mount type, research has shown that they differ in color rendering, sharpness, optical design, and build.
I've shot a XR Rikenon 50mm f1.4 and a XR Rikenon 50mm f1.7, and while I found the colors to pop more with the 1.4, the 1.7 appears to be sharper. And I keep reading about the XR Rikenon 50mm f2 being the "japanese summicron", etc, and just curious, is this for real? Is it really that sharp and is the color rendering up to par with the f1.4?
To be honest, I've never shot a Pentax-M lens, only a Pentax-A 50mm 1.4, and I just wasn't a fan. However, I've read good reviews regarding Pentax-M lenses. One thing that really interested me is that perhaps because of its Pentax-M special lens coatings, photos often come off with warmer tones. Is this actually true in comparison to XR Rikenon lenses? Any genuine info out there and/or experienced opinions?
As I've shot with XR Rikenons for a while, I do notice somewhat cooler tones with the XR Rikenon lenses, but solid red and blue tones really pop (more than normal I think). However, I have only noticed this in comparison to Nikkor lenses, which I find to somewhat normalize color rendering. I'm no expert here, please correct me if I'm mistaken.
I've also read that the Pentax-M 50mm f1.4 is the best K-mount lens ever made, and also some individuals claiming that the XR Rikenon P 50mm f1.4 out performs the Pentax. However, the infamous "Ricoh Pin" on these program lenses have also caused me to not even try a P lens. What do you think?

I'm in the process of obtaining a PENTAX MX and I'm looking to grab a sweet lens for it. I feel I'm a little biased toward XR Rikenon lenses because of my positive experience with them, but just looking to ascertain the primary differences between both brands, mostly regarding: color rendering, sharpness, optical design, and build.

And lastly, in your experienced opinion, what lens would you prefer out of these listed below?

SMC Pentax-M 50mm f1.4
XR Rikenon 50mm f1.4
SMC Pentax-M 50mm f1.7
XR Rikenon 50mm f1.7
SMC Pentax-M 50mm f2
XR Rikenon 50mm f2

Thanks, APUG!
-Paul

 

[jim10219]

None of the above. Go with the SMC Pentax K 50/1.4. In my opinion, it blows the M out of the water. I'd avoid the SMC Pentax M 50/2. They're super common and cheap, and they're not terrible, but there's nothing special about them. I definitely wouldn't call them a Japanese Summicrom.

 

[PGraham3]

@jim10219
Thanks for responding, Jim. Yeah, I’ve heard good about the Pentax-K 50/1.4. Just curious, now I may be mistaken, but does this lens supposedly have Thorium, or is that just the Takumars? The samples I’ve seen of the Pentax-K have yellowish glass. Is that true with yours?
Any drawbacks with this lens that you can identify?

 

[jim10219]

Yeah, the K has a Thorium element. Mine also has a yellowish tint, but the colors it produces are fine. Apparently you can lessen the yellow by leaving it out, exposed to the UV light of the sun, but I’ve not had a need to try this. In my opinion, it is one of, if not the best Pentax lens ever made. It’s one of my top 5 favorite lenses that I own for any camera mount. I also have a Super Tak 85/1.8 with a thorium element in m42 mount that is on my top 5 list. I can’t think of any drawbacks other than its slightly larger and heavier than the M. But I don’t care about a few grams and centimeters.

 

[Ian Grant]

The CohinonAuto MC 50mm f1.4 lens is one of the best K mount standard lenses, I've no idea who made it for them but they are great lenses as are the f1.7's.

Ian

 

[Ces1um]

Out of all of my smc pentax-m lenses, in my humble and limited opinion the finest is my macro 1:4 100mm lens. The clarity and colours are astounding but there's a quality to this lens that goes beyond that. There's almost a "life" to the photos taken with it.
The closest lens I own to the 50mm focal length you seem to fancy is the smc pentax-m 1:1.8/55mm. Its a workhorse of a lens and I appreciate the tighter crop. It also seems to have a very minimal close focusing distance. The only one that I've been disappointed with is the 1:3.5/28mm There's a lot of peripheral distortion so subjects should be located dead centre of the frame and horizons should be level.