[Emacs]

If you want long-focus sharpness, buy the FA 43 or DA 40. Both are crazy sharp stopped down (the FA 43 is sharper).

FA 43 isn't excellent infinity performer. It only reaches good figures at f8 for the infinity.

[paperbag846]

At the first, the 77 is universal telephoto (unlike FA* 85, which is actually is poor infinity performer, it's even worse in this area than both 15Ltd and 21Ltd). I don't know, may be you used it only wide open, but stopped down (4-5.6 and more tight) it's razor sharp at infinity.

I would stop a lens down to f5.6 - f8 for infinity. That is just what you do. The FA 77 *is* razor sharp at infinity, but so is the DA 15, and DA 70, for that matter, when you stop each lens down.

I'm sure there are lenses that are marginally sharper at infinty than the DA 15, but not to the extent that you claim. Lenses suffer from diffraction past f8, you know this, and it is often the sensor that determines sharpness after you stop down past f8.

Infinity performance... are you actually talking about extremely stopped down performance (i.e., f22?) That it pretty different than "infinity performance".

31 LTD is very sharp but in my experience not any sharper than other fast lenses stopped down to f5.6 - f8, or much sharper than the DA ltds.

You make it sound like its a black and white difference, but have a look...

FA 77: Pentax SMC-FA 77mm f/1.8 Limited - Review / Test Report - Analysis

FA 43: Pentax SMC-FA 43mm f/1.9 Limited - Review / Test Report - Analysis

DA 15: Pentax SMC-DA 15mm f/4 AL ED Limited - Review / Test Report - Analysis

In other words... I'll put the onus on YOU to show us that infinity performance of these other lenses are significantly better at a fair aperture... say, f5.6 or f8.

[ManuH]

FA 43 isn't excellent infinity performer. It only reaches good figures at f8 for the infinity.

I'm curious about these kind of claims. It would be so much better to have pictures samples to illustrate this. Otherwise people can argue ad infinitum.

Personally I have not noticed any issue on my DA 15mm, 21mm and 35mm Ltd at infinity, they look as sharp as can be possible on K-5 IMHO.

[Spotmatic]

I'm curious about these kind of claims. It would be so much better to have pictures samples to illustrate this. Otherwise people can argue ad infinitum.

Personally I have not noticed any issue on my DA 15mm, 21mm and 35mm Ltd at infinity, they look as sharp as can be possible on K-5 IMHO.

+1 Parallels my results too.

[Hello_Photo]

I can't speak to the 15mm, but here is a shot that I think illustrates what the DA35 Macro is capable of at a distance (albeit not technically at infinity, per se):



Disclosure: I've played with the curves a little and applied my standard sharpening in Lightroom (radius 0.5, amount 95). K10D (10 MP) with the DA 35 at F2.8, 1/320s, ISO 100. Focus was on the green tree in the middle.

Centre crop (including intended focus point):



In terms of outright resolution in the centre, I couldn't reasonably ask for more from a lens at F2.8 at a distance (with or without a "macro" label engraved on it). Granted, this shot isn't at infinity, but I think the difference is academic - the focus point in this shot is in the neighbourhood of 70 feet away and the house behind it is also very sharp at about 100 feet.

Extreme left edge (the tree is slightly in front of the plane of best focus; the roof shingles appear to be sharper):



Here, I see a fall-off in resolution at the extreme edge of the frame, compared to the centre. What do you expect? It's wide-open!

Between the centre and left edge (but behind the plane of best focus):



This crop simply shows the usual depth of field effects of a large aperture lens focused closer than it's hyperfocal distance (for pixel peeping purposes).

Overall, with more than 2 years and thousands of frames under my belt with this lens, I really haven't seen any degradation in optical performance at different distances. It's uncanny how this lens (or at least, my copy of it) can perform so well in so many different scenarios.