Why Not Try Out a Prime Lens?

A brief look at primes vs. kit zooms

By PF Staff in Articles and Tips on Nov 13, 2012
Why Not Try Out a Prime Lens?

Our favorite zoom is the Pentax-DA 18-135mm F3.5-5.6 ED AL [IF] DC WR - quite a mouthful of a lens name, but we don't hold that against it!

Its focal length rage is ideal for travel photography, as it is basically a lens that can satisfy most everyday shooting needs. Its aperture isn't as fast that of a comparable prime (non-zoom) lens, but given the excellent high-ISO capabilities of modern consumer DSLRs like the Pentax K-30 or K-5, this is generally not a limiting factor.

Vacation Photo w/18-135mm

Photos in this vacation album were shot exclusively with this 18-135mm on a K-5.  We were quite pleased with the results from that particular outing, but how good is this lens really?

We were using the Pentax-FA 77mm F1.8 Limited lens while shooting test photos for a review the other day, so as a little side project, we took a couple of comparative shots with the 18-135mm set to around 77mm, just to see how close this zoom could get to the performance of a prime lens. Much to our surprise given our satisfaction with the aforementioned travel shots, the 77mm did significantly better. It would appear that the 16 megapixel sensor out-resolves the zoom at F5.6, whereas the 77mm handily out-resolves the sensor at both apertures tested.

Lens technologies are ever-evolving, and it can very well be the case that there are high-end zooms out there capable of matching the performance of older prime lenses.  However, if you level the playing field and look at current prime lenses, you can still expect them to generally deliver more sharpness, less distortion, and better overall clarity compared to modern zooms.  And remember, high-magnification "super" zoom lenses will also be a notch below professional or premium zoom lenses that have fixed apertures.

Zoom lenses offer a lot of convenience, but why not challenge yourself to shooting with a prime the next time you go out to take pictures?  You may end up being surprised by the quality of the resulting photos! 

These sample images were shot at ISO 100, in RAW (DNG), with no sharpening and no post-processing. Focus was on the near corner of the building. Click on any thumbnail to download the full JPG files.

Pentax-DA 18-135mm
Pentax-FA 77mm
F5.6
z 5.6
JPG JPG
F11
zoom F11
JPG JPG
 100% crop:

 100% crop:

F5.6
   
 100% crop:  100% crop:
F11
 
100% crop: 100% crop:
 F5.6
 
100% crop: 100% crop:
 F11

We hope that these results get you to consider a prime lens!  If you're on a budget, a mere $40 will get you a very sharp lens such as the Pentax-M 50mm F1.7, as long as you're willing to settle for manual focus. 

We believe that the emphasis that camera manufacturers place on kit zoom lenses, especially in conjunction with intro-level DSLRs, is closing a lot of doors for beginners that are interested in learning more about photography.  In addition to offering better image quality, prime lenses will get you to focus more on composition rather than allowing you to document everything around you perfectly, thus they can improve your photography as a result!

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