The 5 Best Pentax KX Camera Lenses

By Nathaniel Stephan
Last Updated: April 9, 2020
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The Pentax KX is a fantastic 35mm film single lens reflex (SLR) camera. This page is going to talk about the 5 best lenses for the Pentax KX, as well as a selection of substitute options.

In a rush? The following is the list of the best lenses for the KX:

  1. Kit Lens - SMC Pentax-M 50mm f/1.7
  2. Wide Angle Lens - SMC Pentax-M 28mm f/2.8
  3. Portrait Lens - SMC Pentax 135mm f/2.5
  4. Zoom Lens - Vivitar Series 1 28-90mm f/2.8-3.5
  5. Macro Lens - SMC Pentax 100mm f/4 Macro

The best Pentax K mount lenses are categorized by price and type of photography. There are a number of proposed choices to choose from that have a wide range of prices ideal for the cost of the camera.

Standard Lenses

This is a few 50mm focal lengths that you can use with the KX. At the time when the camera was being sold as new, there was generally an offer bundling a 50mm lens as kit for a reduced price.

They are referred to as standard lenses due to the fact that the angle of view for the lens is similar to what the human eye sees.

SMC Pentax-M 50mm f/1.7

  • "Kit" lens for the KX.
  • Fantastic value.
  • Light, small, and compact.
  • 49mm filter threads.

Also found at: eBay, KEH, Adorama

If you do not already own it, a capable initial lens to purchase is the SMC Pentax-M 50mm f/1.7. The 50mm f1.7 is widely available used, is light, has good image quality, is inexpensive, and portable. More photographs have been shot with this lens when compared to any other lens.

You can also purchase the next version, the SMC Pentax-A 50mm f/1.7.

SMC Pentax-M 50mm f/1.4

  • Exceptional optics.
  • Improved performance from optical multi-coatings.
  • Easy to find.
  • Comparatively economical.

Also found at: eBay, KEH, Adorama

The SMC Pentax-M 50mm f/1.4 is approximately a stop faster than the f/1.7, at the added cost of increased size and weight. Expect to pay more than you would for an f/1.7 or f/2 lens. The previous version, SMC Pentax, and later version, SMC Pentax-A, will both work with the KX.

SMC Pentax 50mm f/1.2

Just like all of the competing camera brands, Pentax released a 50mm "halo" lens. The resulting SMC Pentax 50mm f/1.2 is a very expensive, fast, and huge hunk of glass.

The lens can be hard to come across since it will work on Pentax DSLRs so the appeal extends beyond use with 35mm film cameras. If you want to get one you may have to check and see what's available for purchase through weeks or months.

Find at: eBay or KEH

More Options

Here are a few other good lenses that are comparable options. In addition to 28mm or 35mm focal lengths.

SMC Pentax 50mm f/1.2AmazoneBayKEHAdorama
SMC Pentax 50mm f/2AmazoneBayKEHAdorama
SMC Pentax-M 28mm f/2.8AmazoneBayKEHAdorama
SMC Pentax 35mm f/3.5AmazoneBayKEHAdorama

Wide Angles

SMC Pentax-M 28mm f/2.8

  • Great combination with a 50mm lens.
  • Super Multi Coating (SMC) to improve performance.
  • Many copies are available.
  • Relatively low cost.

Also found at: eBay, KEH, Adorama

The SMC Pentax-M 28mm f/2.8 isn't the best option. The truth is, plenty of people may not actually consider it a wide angle lens. Nevertheless, it is a lot cheaper than any wider option.

There are many of wider Pentax focal lengths to consider, but they are either significantly less affordable or third-party options have obvious barrel distortion. On top of that, it is easy to see optical flaws such as chromatic aberrations in third-party lenses.

More Options

The general relationship for pricing is easy to understand. As the field of view gets wider, the lens will be priced higher. Fast lenses will also be more expensive.

Be aware that vintage wide angle lenses don't incorporate corrections that modern wide angle lenses have. The issue you're most likely to see with older wide angles is going to be obvious barrel distortion.

SMC Pentax-M 20mm f/4AmazoneBayKEHAdorama
SMC Pentax-M 28mm f/2AmazoneBayKEHAdorama
SMC Pentax 18mm f/3.5AmazoneBayKEHAdorama
SMC Pentax 24mm f/2.8AmazoneBayKEHAdorama

Portrait & Telephoto Lenses

SMC Pentax 135mm f/2.5

  • 85mm substitute.
  • Excellent value.
  • Relatively inexpensive.
  • Widely available.

Also found at: eBay, KEH, Adorama

The 85mm focal length wasn't as commonly used as they are today in comparison to when the KX was initially introduced in 1975. 100mm or 135mm focal lengths were more commonly used thanks to their lower cost.

The difference in price can be seen when you view available listings online.

Alternatives

There are many telephoto lenses to select from. Focal lengths longer than 135mm and 85mm lenses are going to be expensive.

SMC Pentax 85mm f/1.8AmazoneBayKEHAdorama
SMC Pentax 85mm f/2.2 SoftAmazoneBayKEHAdorama
SMC Pentax 105mm f/2.8AmazoneBayKEHAdorama
SMC Pentax 120mm f/2.8AmazoneBayKEHAdorama

Zoom Lenses

Before the introduction of autofocus, in the early 1980s, there were a few lenses made by third-party brands that performed better than what Pentax was offering.

A good deal of the best performers were released with the Vivitar brand. Any zoom lens with the Vivitar Series 1 branding is going to have the best optics you'll see from a vintage zoom.

Sadly, obtaining one of these lenses in acceptable condition can be very challenging. Keep in mind, no vintage zooms offer noteworthy performance. If you find one on sale that is cheap enough, it could be worth buying.

Vivitar Series 1 28-90mm f/2.8-3.5

  • Covers a popular zoom range.
  • Great for portrait or wildlife photography.
  • A rare time when a third-party lens is the better choice.

Also found at: eBay and KEH

Alternatives

Here are some more alternatives that you can take a look at if you want a zoom lens for your KX. None of them are going to be incredible, and you'd likely be better off buying a couple of prime lenses instead.

SMC Pentax 85-210mm f/3.5AmazoneBayKEHAdorama
Vivitar Series 1 70-210mm f/3.5AmazoneBayKEHAdorama
SMC Pentax 45-125mm f/4AmazoneBayKEHAdorama

Pentax Macro Lenses

Macro lens options for the Pentax KX suffer from problems with availability. The supply of Pentax K mount choices is tiny, which increases prices higher than you'll pay for similar Nikon F mount or Canon FD mount lenses.

SMC Pentax 100mm f/4 Macro

  • Ideal focal length for 1x magnification.
  • Widely available.
  • Mediocre value.

Also found at: eBay, KEH, Adorama

A small number of people online have encountered problems with balsam separation of the front doublet. This is concerning because even a little separation will spread gradually and make it unusable. If you see any evidence of balsam separation, avoid that copy and keep looking.

Vivitar 55mm f/2.8 Macro

Vivitar 55mm f/2.8 Macro Lens

  • The second best vintage macro lens I've used.
  • An outstanding lens for close-up photography.
  • Can achieve life-size magnification without needing an extension tube.

Also found at: KEH and Adorama

My favorite vintage macro lens I've owned, the 90mm Vivitar, was made for a variety of mounts. Unfortunately, it will be hard to get a copy that's got a Pentax K mount.

The Vivitar 55mm is my second favorite vintage macro lens. Keep in mind that it does have a shorter working distance than the 90mm. It is an excellent choice for close-up and table top photography, but it is not the best choice if you would like to take macro images at 1x magnification.

Both Vivitar macros were built by Komine and were released under various different brand names. If you decide to look for one also check under the Panagor, Elicar, Quantaray, Spiratone, and Rokunar brand names.

There is a Vivitar 90mm Macro Review and a Vivitar 55mm Macro Review.

For capturing images at macro magnification (1x), focal lengths in the 90mm-105mm range will be the ideal choice. You will have a big enough working distance to be able to use flash, while avoiding excessive weight and excessive costs that come with longer focal lengths.

Alternatives

SMC Pentax-M 50mm f/4 MacroAmazoneBayKEHAdorama
Lester A Dine 105mm f/2.8AmazoneBayKEHAdorama

Used Pentax Lens Prices

Prices change all the time depending on supply and demand in manual focus glass. During the last several years, shooting film has grown in popularity, which has caused prices to rise.

More upwards pricing pressure comes from Pentax DSLR users collecting and buying lenses. Third party manufactures tend not to produce lenses for the K-mount, unlike the Nikon F or Canon EF lens mounts.

Marketing circumstances are continuously changing, and unexpected events can lead to big changes in prices. Even so, the price differences between choices should be similar.

Checking a few websites is a very good way to get accurate market information. If you are lucky enough to discover an excellent deal, buy it due to the fact that the best deals do not last very long.

What Lens Mount Does the Pentax KX Use?

The Pentax KX uses the Pentax K lens mount.

Introduced in 1975, the Pentax K mount is still being used in current cameras. It replaced the M42 screw mount Which was used on cameras such as the Asahi Pentax Spotmatic. Over time improvements have been done to add autofocus, CPU contacts, metering information, and electronically controlled apertures.

As long as a lens has an aperture ring, it will be compatible with Pentax film cameras. However, it is not a good idea to spend money on expensive features that can't be useable. The exception would be if you also own Pentax DSLRs.

It's also possible to use the older M42 screw mount by using an adapter. People like to do this as some of the M42 screw mount Takumar lenses are spectacular. Even so, I would not recommend doing this as finding them without a tight focus ring can be frustrating.

Lens Cap Size

The standard lens cap and filter ring thread diameter used on most older manual focus Pentax K mount lenses is 49mm. Lenses were originally sold with slip-on caps, not the more commonly used center-pinch kind today. Looking at what's available, you will see not very many lenses sold with matching lens caps.

Bear in mind large front elements will need to use larger caps and filters.

The benefit of using a standardized thread size is that you only need to have just one set of filters.

Pentax-M vs Pentax-A

SMC Pentax and Pentax-M lenses were designed to include a stop-down coupler which is built with a mechanical linkage to the camera. The stop-down coupler enables the camera to know what the aperture is set to so that the light meter will meter accurately without having to rely on stop-down metering.

The Pentax-A series introduced the capability for the aperture in the lens to be set by the camera. This means cameras that support the Pentax-A changes have the capability to do shutter priority and aperture priority modes.

However, because that capability is not compatible with the camera, it would not make financial sense to spend money on features that the camera is unable to use.

Related Posts

That's it for details on the best lenses for the KX. Here's some further info that will give you more info about the camera can be found listed below:

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