Good thought experiment there Cynog Ap Brychan - ergonomics is also a distinct consideration to be taken into account when considering whether one lens is " better" than another*. I recall many old school photographers settling for lenses like the K55 f/1.8 - In opposition to all those photographers who spent what they called "wasted money" on 50mm f/1.2 and f/1.0 lenses.
In a nutshell: The FA35mm f/2 is a decent lens, though 6 aperture blades compared to the FA31 which has 9 blades, tips bokeh factor significantly in favour of the FA31. Resolution between the two lenses is similar, In terms of physical construction the FA31 beats the FA35 hands down.
I work professionally with a number of
very sharp lenses - The Schneider 240mm f/5.6 APO Symmar, Voigtlander 125mm f/2.5, Zeiss 21mm f/2.8, the Pentax FA*200mm f/4 ED MACRO,Noct Nikkor 58mm f/1.2, Leica APO-Summicron-M 50mm f/2. And IMO Pentax the FA31mm f/1.8 Is one of the most upsettingly sharp wide angle lenses you can buy for the Pentax K mount, I certainly look forward to the New Pentax full frame camera where its full potential will be realised.
Would this image have been sharper if I had stopped the lens down? probably, would there have been less CA? - yes, though the FA31 manages it better than the FA35.
Sharpened 100% crop from lower left corner of an image.
Even at f/1.8 with contrasty lighting the FA31 still puts in an extremely impressive performance, especially on the Pentax K5IIs. There is only one 35mm lens that can do better under those kind of conditions, it is worth 3X the price of the FA31 and it has a red dot on it.
Originally posted by Allison The aberrations are an issue on the 31 and it does not use the most current coatings since this was a design originally made for film.
The Takumar 50mm f/1.4 doesn't have digital specific coatings on it and it performs just as well and in some cases, better than some modern 50mm f/1.4 lenses do. The coatings on a lens have practically no effect on the aberrations exhibited by a lens, only optical design and the use of exotic glass types can eliminate them - the primary function of optical coatings is to reduce internal reflections at the air/glass barrier and reduce the impact of flare. Incidentally I know that the sigma 35mm f/1.4 isn't any better than the FA31 Limited in terms of CA and PF - From RAW images sent to me by colleagues from this lens: as far as I can see it looks worse than the FA31.
*Though if you want my take on ergonomics: the FA31 manually focuses better than any sigma lens I have ever used, also the aperture ring on it is really handy when you want to use extension tubes that do not have lens contacts. Also in an optical note the FA31 doesn't have the strong "onion ring" bokeh which is a result of poorly polished aspheric lenses that are used in many of sigma's f/1.4 lenses. Also Pentax lenses have focus rings that move in the same direction as all other pentax lenses, the focus rings on sigma lenses work the other way around - even though I do work with camera systems that have focus rings that rotate in the opposite direction from pentax lenses - this thing is more problematic for photographers who have greater familiarity with pentax lenses who throw in a few sigma lenses into their kit.
Last edited by Digitalis; 02-19-2013 at 03:47 AM.