[swanlefitte]

Glad you learned. That's what the forum is for.
In case you didn't know about calibrating lenses for proper focus, and for anyone else who may read this thread I will link these.
AF fine tuning of lens - PentaxForums.com
Fixing Front and Back Focus - Introduction - In-Depth Articles

[englishphotographer]

The Samyang 135mm is the sharpest lens I own although the Pentax 70-200mm f2.8 is pretty much identical but with a cooler rendering. The Sigma 35mm f1.4 is also incredibly sharp, better than the Pentax 31mm. A friend's Sigma 70mm macro was sharper than the Pentax 77mm. If sharpness is what you're looking for, those lenses will deliver it. The Pentax 31mm is smaller and lighter than the Sigma though, and flares less. The Pentax 70-200mm is a lot more versatile than the Samyang too. I'd like the 77mm and it looks like the new 50mm f1.4 is a contender for sharpness king too; has anyone compared it with the 50mm macro? Fenwoodian also converted several Zeiss and Leica lenses to Pentax mount that may be sharper still but I've not seen a direct comparison.

[zapp]

DFA 100macro is sharp all the way, DFA*50 feels sharper, but you get the 50 for rendering not sharpness for repro work. Samyang 135 is also extremely sharp, but hard to focus.
I am still wondering what you are really looking for in the lens. If you have the 100 macro, go take photos.The 43 will not be sharper, but it can produce very sharp images.

[RobA_Oz]

DFA 100macro is sharp all the way, DFA*50 feels sharper, but you get the 50 for rendering not sharpness for repro work. Samyang 135 is also extremely sharp, but hard to focus.
I am still wondering what you are really looking for in the lens. If you have the 100 macro, go take photos.The 43 will not be sharper, but it can produce very sharp images.

I don’t think the OP was simply looking for the sharpest lens available, regardless of FL. From what I gather, he was looking for lenses that were as sharp as his 100 Macro, and the 43 caught his attention. On APS-C, the FoV of the 100 at 13.5° is less than half that of the 43, so unless a user has a strong and abiding particular interest, the 100 is going to be very limiting.

[builttospill]

I am not interested in macro or any zoom lens that is not at least the equal in IQ to a prime.

A zoom lens equal to IQ of a prime lens doesn't exist. There are some incredible zooms out there, but a prime always wins when it comes to IQ.

There have been some great suggestions here. The FA 43 is a magic lens capable of meeting your requirements. The DA 35 Macro is a great option.

I'm on my cell phone right now, or I'd share some images from the FA* 80-200. This is my favorite zoom lens due to it's rendering, sharpness, and colors.

[swanlefitte]

A zoom lens equal to IQ of a prime lens doesn't exist. There are some incredible zooms out there, but a prime always wins when it comes to IQ..

Have you seen the sigma 18-35 f1.8?

Sigma 18-35mm f/1.8 DC HSM A Lens Review

[builttospill]

Have you seen the sigma 18-35 f1.8?

Sigma 18-35mm f/1.8 DC HSM A Lens Review

I have used this lens. Keep in mind, as discussed in this thread, there are different optical properties of lenses appealing to different photographers. Sigma certainly has made some very fine lenses during the last several years, but would I trade my FA 43 for a Sigma 50 1.4 Art lens? Would I trade my FA 77 for the Sigma 85 1.4 Art? Canon doesn't have anything like the FA Limited lenses, so I've used Sigma's 35, 50, and 85 Art lenses on a 5D mk iii and mk iv a lot during the last couple years.