The SMC Pentax-M 1:1.4 50mm

Pentax 50mm f/1.4

This is one of the many fabulous fifties out on the used market waiting to be gobbled up for around $100 (as of  June 2012) if it's in excellent condition.  I've seen them ranging from $60 for a junker with oily blades and dents to $199 for minty fresh versions straight out of the box.  I have to tell you,  this lens is a wonder, has a beautifully smooth bokeh wide open, and mine is as sharp as a tack.  Let me give you my list of pros and cons for this little 50.  Mind you, I'm using this lens on an APS-C sensored DSLR.

Focus and aperture ring (f1.4-22)

PROS:


+It's Fast.  Yes it is.  It is a full stop faster than the Pentax M 50 f/2, a lens I'll review later, and only a half step slower than the f/1.2
+It's sharp:  Mine is pretty good from f/1.2 through f/2.8, and just silly sharp from there to f/16. At f/22 I think you can see how diffusion properties impair this lens
+Bokeh:  I has it and it is awesome - at F/1.4 only.  In VERY specific situations, other apertures have a strange little pinwheel effect from the blade ends.  See the odd blade end shape below at f/2.

Pinwheel aperture at f/2

+Great Indoors:  You can shoot in all but the darkest interior situations.
+Wamth:  This is a warm lens, everything I shoot has just little bit warmer tonal curve than the norm.
+Focus Throw:  The length of throw required during focusing is a plus, especially at small apertures.

CONS:

 -Metering is inconsistent:  This takes a bit more in the way of explaining.  All that awesome glass catches a lot of light, sometimes it bounces around a little too much in and tells your camera that there is more light available than is really there, and images will sometimes be underexposed (depending on overall and directional lighting)  if you rely on the camera's metering.  There are really only a couple of fixes, 1. check your images on the fly and adjust, or 2. get or fabricate a hod that limits the area of front glass exposed to only what you need for an APS-C sensor.  Remember - your only shooting through the center of the glass on a standard APC-S DSLR.

MISCONCEPTIONS:

So I'm sure that if you've gotten here, then you've probably read all about this lens elsewhere.  I think there are some common misconceptions about this lens.

1.  It's so heavy:  This lens is a little heavier than the kit 18-55mm that comes with most Pentax DSLRs these days.  Definitely not enough to ruin your day shooting.  If you want a plastic 50, buy a brand new lens.

2.  It's not sharp at f/1.2:  I challenge you to find any zoom lens as sharp as this prime for the price.  You won't, and if you just stop down a little tiny bit, it'll rock your socks.

3.  This lens is so hard to focus at f/1.2.  I actually think the f/2 manual version of the 50 is substantially harder to focus, due to less apparent light making it up to the viewfinder.  Yes there will be a finer depth of field at low aperture numbers, but the brightness more than makes up for it in my opinion.  Further, if you still have issues, I'd check your diopter settings - that might fix a lot more than you planned on.

SHARPNESS:

I've placed a few test images at 10 x magnification at a full marked f-stop range (I skipped unmarked intermediates).  If I had a few more megapixels handy I think you would notice that this lens sharpens nicely by f/2.8, peaks between f/4 and f/8 or maybe f/11, and falls off from f/16 to f/22.  Please note that these were shot on a tripod with a delay and a trigger, so camera shake wasn't at play here.  I find that the lens is about as good wide open as it is stopped down.  This may not be the most scientific way to measure sharpness, but I think our eyes are trained to pick out the differences we see in imagery.

f/1.4  -  10X magnification

f/2  -  10X magnification

f/2.8  -  10X magnification

f/4  -  10X magnification

f/5.6  -  10X magnification

f/8  -  10X magnification

f/11  -  10X magnification

f/16  -  10X magnification

f/22  -  10X magnification

My Take:

I love this lens.  It's a keeper.  If you find one cheap that hasn't been run over or grown some fungus, GET IT!  Once you're used to it, you'll certainly appreciate it's quality of construction, optics, and fun level!