The Remarkable Persistence of 24x36
&gt; Cameras that used 24x36mm sensors returned photographers&#x27; favorite lenses to the FOVs they were already long comfortable with. And, of course, the second was prestige. Status is a very strong motivator in the photography hobby. &quot;Full-frame&quot; sensor cameras were bigger and more expensive, their &quot;image quality&quot; at least detectably ahead of that of smaller sensors.<p>Some of us have also been patiently waiting for &quot;full frame&quot; DSLR bodies are doing it because a fast normal lens (so-called because it has (much handwaving) roughly the same field of view as your eyes) is so cheap as to be basically free compared to a nice DSLR body. A similarly fast and sharp 28mm or 35mm (roughly a normal lens on an APS-C-sized sensor) is vastly more expensive, if it&#x27;s available at all.<p>Pentax[0], to my (limited) knowledge never made a 35mm or 28mm lens that came close to matching the speed and sharpness of the SMC Pentax-M 50mm f&#x2F;1.7, which can be had &lt;$50 US on ebay. The first 28mm f&#x2F;2 I see listed is $430, the much commoner f&#x2F;2.8 and f&#x2F;3.5 are much cheaper, but give up a lot in low light performance.<p>The 50mm f&#x2F;1.7 is a mighty fine lens; the arguably better 50mm f&#x2F;1.4 goes for &lt;$100. It&#x27;s not until you&#x27;re looking at the rare, super fast, and arguably yet better still (I have no personal experience) 50mm f&#x2F;1.2 that you hit the price range of the 28mm f&#x2F;2.<p>So whether you&#x27;re buying at the peanuts end of the price range or the high end, you&#x27;re giving up a stop and a half of low light performance going with APS-C over 24x36.<p>It could be argued that with ever improving digital sensors, low light performance in a lens is less important now than ever. There&#x27;s probably merit to that.<p>Still, as mentioned in TFA the faster lenses let you make different choices with regards to depth of field than you have with a slower lens. I&#x27;d rather have that choice, historical preferences of f&#x2F;64 notwithstanding.<p>[0] I&#x27;m not going into lens generations here. As an extremely casual user, I buy what&#x27;s good, used, and cheap. I&#x27;m strictly an M42 and SMC-M guy, and can&#x27;t compare with anything newer; my overall impression from reading reviews is that the SMC-K, -M, and -A generations are largely comparable for the same focal length and aperture. The M42 generations are adequately comparable, at least for folks like me.