Product Description

The Pentax interchangeable lens system provides a complete line of high-quality lenses to satisfy your every creative need. Offering a wide range of focal lengths, functions and effects for different formats, Pentax lenses are designed to maximize each camera's capabilities.

Product Details

• Brand: Pentax
• Model: 20817
• Dimensions: 1.00 pounds

Features

• Only 1.5 inches and 7.8 ounces
• 47 degree angle of view
• Fixed 50mm focal length
• Fully automatic diaphragm
• Lens construction of 6 elements in 5 groups

Amazon.com Product Description
The Pentax SMCP-FA 50mm f1.4 lens has a fully automatic diaphragm. At 1.5 inches long and weighing just 7.8 ounces, you can take this 50mm fixed focal length lens with you everywhere. You can use this lens with all Pentax SLR cameras, but the AF system only works with Pentax AF cameras.

Customer Reviews

Great solid lens
With the Pentax K10D sensor the equivalent 35mm focal length is about 75mm. Coupled with the fast f1.4 aperture of this lens, this is a great low light short telephoto lens...very good for indoor personal shots. The low f also allows autofocus and metering to work well in low light conditions.

Wide open (f1.4) this lens is soft, but sharpens quickly (noticeable difference from f1.4 to 1.8).

Nice small lens. The downsides are: (1) elements are spherical, so the lens is a little heavier than it could be with aspherical elements, (2) focus ring is locked to autofocus on body...you can't turn the focus ring when the body is set to autofocus, (3) a little soft wide open.

The upsides are: (1) even with spherical elements, the lens is small, (2) feels like a good precision instrument, (3) it's nice to have a very well defined "soft" focus region.

All in all I really like this lens. It just feels good in the hand, its small, its fast, its sharp, it works well in low light, and the price is great.

Must have for all Pentaxians.
I bought this lens when I first got the K10D one year ago and I've never regretted it! First of all, the build quality feels superb for the price. The focusing ring is super smooth and has a rubbery texture. When mounted on the K10D it feels very solid and fits perfectly in your hand; not too small, not too large.

As far as image quality goes, f1.4 - f2.4 are a bit soft, but can easily be used in a pinch to get a couple extra stops of light. Once you hit 2.8 though, things really change. Images are sharp all across the frame and the bokeh at 2.8 is truly toast worthy (buttery). The sweet spot seems to kick in around f5.6, where the images are going to be packed with detail. The image distortion is virtually non-existent. If you're not careful in harsh sunlight you could easily be caught out with some fringing and aberrations, but this can be corrected in PS.

50mm is a great prime to have, especially if you may be doing some portraits. I just did a sitting of my daughter with her grandparents and the images produced are nothing less than professional looking. All in all a great lens to have and well worth the price.

Good, but has limitations opened beyond f2.8
I don't to duplicate everything that dpreview did for this lens. They have an excellent review with detailed analysis of this lens.
http://www.dpreview.com/lensreviews/pentax_50_1p4_p15/

Some quoted highlights:
Pros:
* Excellent image quality when stopped down to F2 and smaller
* Very low lateral chromatic aberration
* Almost no rectilinear distortion

Cons:

* Very soft wide open
* Extremely 'busy' rendition of out-of-focus backgrounds at wider apertures (larger than F2.8)
* Bokeh chromatic aberration, most visible at wide apertures (F1.4-F2.8)

Short is that this is a very good lens, but if you want the best pictures you will want to not use it higher then f2.8. The sigma 50mm F1.4 HSM for pentax would give you better wide aperature performance, but you will pay for that as well.