Originally posted by lytrytyr While the FA Limited primes are all f/1.8 or f/1.9,
one interesting feature of the DA Limited primes is how the maximum aperture steadily decreases as they get wider.
The short tele, DA 70, is f/2.4, the normal DA 40 and DA 35 Macro are f/2.8, the wide DA 21 is f/3.2, and the more extreme wide DA 15 is f/4.
This makes very good photographic sense in terms of the slowest shutter speed to avoid camera shake.
If you fix that at 1/f seconds for the focal length f in mm, all the lenses are right for around EV 8 wide open.
A bit obscure (?) but interesting observation which highlights a parameter that might be acting in the design of the lineup.
For those discussing the size and build quality. These are obviously limited trademarks which are well known. It's the other things and which I find more interesting.
My point with the description of the 21mm was that as far as I'm concerned the relatively slow speed of the lens is a non issue for the type of photography I use it for (and it's designed for?) The two use cases of 1) landscape/street/group shots which require large DOF 2) and wide angle closeups of objects are well catered for.
The f2.4 of the 70mm is in my usage also fast enough for head/torso portraits. Faster and the DOF tends to become to shallow? Often even f2.4 is to fast and bits of the face become to blurry. For full body portraits a faster lens might be useful for better subject separation though.
As far as i know the 70mm is quite sharp across the frame which it might actually not have to be. Perhaps there is a second use case with the 70mm where this becomes important. Anyone has a favourite type of photo with the 70 that requires across the frame sharpness?
I dont' own the 40mm as I have the 35mm plastic fantastic and I don't want to give in to LBA (for philosophical rather than financial reasons.) This one has a less clear raison d'être to me as it would be useful to have this one fast? Obviously it's absolutetly tiny instead. Anyone got ideas for the usecase and design parameters of this one?
Looking at the tiny size and visual design of the lenses you could guess that Pentax has been going after mobile and discreet photographers. Perhaps with a bit of nostalgia for old street/rangefinder photography considering the visual design and build of the lens. The custom hoods are a real sign of this emphasis imho. The decision to allow distortion of the 21mm would be explained by this. As it's only really for architectural photography the pincusion distortion is a problem, and us architecture nerds should be using large format anyway
Perhaps someone can argue against my claim that super fast lenses are a bit redundant for the above scenarios? I'd also like to hear more about how people see the limitations of the limiteds and how (if) it affects their photography negatively.