Manual Focus Lens Choices for Pentax

That old glass is amazing!

By K David in Articles and Tips on Jul 19, 2015
Manual Focus Lens Choices for Pentax

Pentax users have at their disposal a large variety of Pentax legacy glass, much of it manual focus. We also have brand-new manual focus lenses from makers like Samyang, Zhongyi Optical, and Venus Optics. This article looks at contemporary options, legacy K-mount lenses, M42 mount lenses, and even the uncommon M37 mount lenses. Each type of lens has uses, drawbacks, and advantages that make them good options for different scenarios.

This two-part series discusses manual focuses lenses on Pentax DSLR bodies. This article provides a description of the different manual focus mounts made by Pentax and third-party makers who produce K-mount lenses. The second article in this series will discuss specific manual focus lens uses and techniques.

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Manual Focus Lenses

You may never have realized that manual focus lenses have a lot of uses, some are even more useful for certain types of photography than autofocus lenses. In reverse-chronological order, we'll talk about different types of manual focus lens mounts and how they can be used on your Pentax DSLR body.  More information about the Pentax K Mount's evolution can be found in this article

Using a manual focus lens on your Pentax DSLR requires that you make sure you have some settings in your camera adjusted properly. Chiefly, you need to make sure that you camera will allow the use of the lens's aperture ring.  If you're unfamiliar with the required procedure, we recommend that you see our brief video detailing Pentax DSLR settings for manual lens use. If you're still unclear on what to do, see our in-depth guide on how to set your Pentax DSLR to accept legacy lenses. In this article, we won't be getting quit as technical as the aformentioned guide, instead focusing on artistic and practical considerations.

You might wonder if manual focus lenses can provide suitable quality. And that's a fair question. We're talking about lenses that will typically be about 30 to 50 years old. This article provides sample photos taken with various manual focus lens types. But to answer the immediate question, can manual-focus lenses take photos of suitable quality? You can judge that right now.

"Sunset Moorage, Sausalito, California" | Pentax K-7, Vivitar 135mm f/2.5
"The XO Sends a Text" | Pentax K-7, Vivitar 135mm f/2.5
"Star Trails over Mono Lake, Lee Vining, California" | Pentax K-3, Fish-eye Takumar 17mm f/4

Types of Manual Focus Lenses for Pentax DSLRS

Manual focus lenses, especially older prime lenses, are every bit as sharp, contrasty, and colorful as modern lenses. As an added bonus, a high-quality Vivitar 135mm f/2.5 can be as little as $15 in good condition. There's an amazing amount of lens quality and value to be had for relatively little money in the manual focus lens market.

Take a look at our Pentax Lens Database and Third-Party Lens Database to see what's out there!

KA Mount Lenses (Mounts with Contacts)

These lenses, such as the Pentax A series, can be used on any Pentax K-mount DSLR and they will meter properly without any restrictions in terms of shooting modes. For film buffs, any of theses lenses that have an aperture ring will work on your K-mount film bodies.

Modern manual focus lenses with the contact pins works exceedingly well on Pentax bodies. These include lenses like the Samyang prime lenses. Because the lenses come with contact pins, all the Pentax user needs to do is set the lens length (an option that your Pentax body will give you upon startup) and place the aperture ring in "A" mode. With those two tasks completed, the third-party lenses will work well on your Pentax body. It's also a good idea to set the camera's exposure mode to manual or aperture priority as the camera will function optimally with the manual-focus lens in those modes. Modern manual focus lenses with contacts are good for any photographic application, even sports photography. (Part 2 of this two-part series will detail some of the techniques you'll need to use these lenses effectively in some settings.)

Any shooting mode will work well for these lenses. Shoot with these in the manner you're comfortable with, the only difference being that you get to pick the focal point. Aperture-priority shooting is probably the easiest mode to use these lenses in. This mode allows users to set the focus, set the aperture, and take a photo as the camera meters it.

Here are some great, and perhaps unexpected, uses for modern K-mount lenses: videography, architecture, portraiture, street, studio, fashion, macro, astro, flash, landscapes, cityscapes, and night and low-light. The full explanation of each is presented at the end of this article.

Sample Photos

"Casting Practice" | Pentax K-7, Sigma 35-80mm f4
"Classical Guitar Jukebox Monkey" | Pentax K-7, Sigma 35-80mm f4
"Sunset Oak Tree" | Pentax K-3, Samyang 10mm f2.8

K and M Lenses (No contacts but with aperture linkage)

These lenses will mount on your Pentax K-mount DSLR body but will not meter properly. These will mount and meter properly on you manual-focus film bodies, though.

Believe it or not, these are the hardest lenses to use on a Pentax DSLR. K and M lenses, any Pentax K-mount lens without electronic contacts, only stop down during image taking in full manual (M), bulb (B), flash sync (X) modes, and possibly user modes depending on how you have them configured. In all other modes, your DSLR will not stop down the aperture when the image is taken. When recording video, your Pentax DSLR will stop the lenses down.

In typical shooting, these lenses have to be used in manual or flash sync modes to obtain any aperture other than wide open. This means that either users need to chimp at the exposures and correct errors in post or take a wide-open meter reading and compensate with each shot. So let's run through the process of using a K or M lens on your Pentax DSLR.  Before you get started, make sure your camera is fully configured.

  1. Mount your lens
  2. Switch to M mode
  3. Set your aperture to your selected setting
  4. Press the green button / DOF preview button to get the camera to set the shutter speed
  5. Take the photo

For instance, if you use the 50mm SMC-M f/1.4, all your meter readings will be at f/1.4 until you press the green button, which will force the camera to stop down. If your camera says the proper meter reading is 1/500th of a second at f/1.4, and you set the lens to f/8, it will compensate for the difference one the green button is pressed.  Since there's a five-stop difference, a shutter speed of 1/15th of a second should be selected.  Note that manual lenses don't always meter with perfect accuracy, so you may need to compensate for this in some scenarios. 

You can of course calculate the proper shutter speed in your head and set it manually every time, but we recommend at least using the camera's shutter speed suggestion as a starting point for the sake of convenience.

Using the contact-less K and M lenses with an aperture linkage is a trickier proposition than using any other type of manual focus lens. These lenses do have some surprising uses. Chief among them, videography is a great choice for these lens. Your Pentax DSLR will stop the aperture down in video mode. This allows these near-silent-focusing lenses to be used in videography. The results are fantastic and this is probably the best use of the K and M Pentax lenses for most users.

Controlled situations are also very good for K and M lenses. In general, if you are going to take time to compose a shot, meter it precisely, and wait for the proper lighting, these lenses work well. If you need a rapidly responsive lens, for instance for sports or pet photography, these lenses are not your best choice.

Recommended uses: videography, architecture, portraiture, studio, macro, astro, flash, landscapes, cityscapes, and night and low-light

Sample Photo

Sample Photo, SMC-M 50mm 1.4"Thirty Minutes of Sunset" | Pentax SMC-M 50mm 1.4, Pentax K-3

Legacy M42, 6X7, and Aperture Linkage-less K Mount Lenses

M42 lenses mount on Pentax DSLR bodies with an adapter. No-aperture-linkage K mount lenses will mount without an adapter. These lenses, if not set to automatic aperture, will meter properly in any shooting mode on your Pentax DSLR, but will tend to underexpose at f/22 (maybe also f/16 and f/11, depending on the lens, though the underexposure is less noticeable than at f/22.) Your M42 bodies will be able to work with the M42 lenses as designed. However, some of your K mount film cameras may have issues metering properly with the M42 lenses. Also, with an adapter, Pentax's 6X7 medium format lenses can be used in a manner nearly identical to M42 lenses.

Some modern lens makers such as Zhongyi Optical, Venus Optics, Zenit, and potentially others make lenses in Pentax mount with neither contacts nor aperture linkages. However, no-contact and no-aperture-linkage modern and legacy K lenses can be used in any shooting mode, just like M42 and 6X7 lenses. You just need to make sure that the apertures are stopped down. So, believe it or not, these lenses are more useful on a Pentax DSLR than are the K and M lenses.

M42 lenses will require an infinity-focus adapter to work in your DSLR; aftermarket versions are also available. Here is an eBay search for other options. With these lenses, make sure you keep the removing key or remove the spring on the adapter's side (I prefer the latter). The latter results in the lenses mounting in a different alignment than they do on an M42 camera, but the adapter is easier to put on and take off the camera and won't risk jamming. I even removed the spring from my Pentax-made adapter for the same reason. If you leave the spring on, the lenses will typically align properly but you will need the key that comes with the adapter to remove it from the DSLR (or film camera) body.

Pentax 6X7 adapters for K mount bodies are also available. I have both a Pentax-made and a third-party 6X7 to K adapter. There exist two differences between them: 1- The Pentax-made adapter has the external flanges. 2- The third-party adapter fell apart on the first use and almost dropped my 105mm f/2.4 on the ground.

The third-party option was repairable with proper screws (the wrong size had been used at the factory) and rubber cement over the screw caps. That said, we cannot in good faith recommend using a third-party product in this case.

If you want to use either the long 6X7 telephoto lenses or, and this is more likely, the very-large 6X7 system macro bellows, you will need a Pentax-made adapter. The 6X7 bellows is significantly larger than the K bellows and, with a 6X7 to K adapter and a Pentax DSLR, will allow significantly greater magnification.

These lenses are easier to use on Pentax DSLR bodies than are the K and M manual focus lenses because your camera will properly meter when the lens is stopped down. Here's the best way to use one of these lenses on your Pentax DSLR.

  1. Mount the adapter (typically these need to be mounted first) with an M42 or 6X7 lens
  2. Mount the lens
  3. Switch to your preferred mode (e.g., AV, M, or TAV)
  4. Set the lens diaphragm clutch to manual (if any)
  5. Take a photo (your DSLR will meter properly for you in AV mode, select the best shutter speed in TAV, and so forth)

That's all that's required to take a photo with an M42, 6X7, or basic K lens with no aperture linkage arm.  Interestingly, it's actually easier than with manual K-mount lenses since stop-down metering is not necessary.  If you're interested in using legacy lenses, M42 options are the least expensive and typically best bet for Pentax DSLR users. 

M42 lenses offer a number of good uses. Videography is not necessarily one of them. With age some M42 lenses are a bit stiffer to focus. And because there's an adapter, there's a risk that focusing the lens will cause it to rock on the mount or even unseat the adapter. I have used select M42 lenses for videography and the results are stunning. I've also used M42 lenses and had the results be unusable.

If you intend to use an M42 lens for videography, the lenses need to be in good repair, seated firmly in the adapter (which in turn needs to be seated firmly in the camera), and able to focus smoothly, quietly, and without much effort to avoid the image rocking around as you shift focus. These lenses are ten to thirty years older than the K and M lenses discussed above, so often the lubricants have gotten thick and focusing is commensurately stiff. In manual aperture mode, M42 lenses provide a stable focus point, controlled depth of field, and the M42 lenses tend to render well for video.

Here's a sample video taken with the 17mm f4 Fish-eye Takumar, the pre-SMC version. As you can see, the video quality is surprisingly good for such an old lens.

M42 lenses can be a good option for sports and action photography. If your lens focuses easily, having the aperture at a fixed setting will help ensure consistent depth of field, tonality, color, and shutter speeds in burst mode. This can also help preserve balanced lighting across an entire shoot or event.

Some M42 lenses truly shine for portraiture, too. The 50mm f/1.4 and 55mm f/1.8 both, to varying degrees, suffer from element oranging. Suffering isn't really a good word, though, because the tinting adds warmth to an image without interfering with image quality like filters do. This can give a nice tone or glow to skin tones in portraiture. In fashion photography, however, this can throw off the color of clothes and a lens with oranging is not a good idea for a fashion shoot.

If you shoot in black and white, a lens with an oranging element will increase contrast, darken blue and green tones, and give a nice kick to your image's gamma. Landscapes and cityscapes benefit nicely from this effect.

Recommended uses: Street, studio, portraiture, flash, landscapes, and cityscapes

Sample Photos

"You Got Some Nuts, Pal" | Takumar 6X7 105mm f2.4, Pentax K-3

"Sublime Squirrel" | Auto Takumar 135mm f3.5, Pentax K-3

"Black Tail Deer and Fawn" | Tokina 400mm TX Mount with M42 Ring, Pentax K-3

"Free Climbing" | Takumar 6X7 200mm f4, Pentax K-3

Legacy M37 Mount Lenses

Before Pentax released M42 lenses in 1957 with the original Asahi Pentax, they made M37 lenses for their Asahiflex series from 1953 to 1956. These lenses are rare and, by today's standards, not up to snuff. M37 lenses were the last lenses that Pentax calculated manually — my understanding is that in or around 1955 Pentax procured a surplus military computer left over from WWII and used it to compute lens formulae. This led to the lenses released in M42 mount, all of which were computer-designed.

The M37 lenses have a certain charm and elegance about them. Know that if you are fortunate enough to ever use an M37 lens that you're using the end-product of thousands of hours of engineers and other nerds using slide rules, protractors, and calculation tables to figure out how light would move through glass lens configurations. The engineers at Pentax in the early 1950s accomplished amazing work on the M37 lenses. Fun fact, 58mm lenses were easier to calculate manually than 50mm and 55mm lenses, so that was the standard lens. That's why all Pentax bodies up through at least the Spotmatic series had 100% viewfinder magnification at infinity with 58mm lenses, not 50mm or 55mm.

The M37 lenses pose a significant problem for users. They require an M37 to M42 adapter (a ring threaded on the inside and out) and then an M42 to K adapter. (These adapters aren't expensive, about $7 in early 2015.) There exist M37 to K adapters, too, but they are rarer than hens' teeth.

An added problem with the adapter setup, the M42 to K infinity adapters have two large holes for the unlocking key. These channel light right past the lens and into the shutter box because the barrel diameter of M37 lenses is significantly smaller than the barrel diameter of M42 lenses. This creates orange flares on images and video. Using an M37 lens on a Pentax DSLR requires thick tape or another means of covering the K mount adapter holes. In practice, though, the flare isn't noticeable as flare all the time. In shade, it typically appears around f/8 and until then simply robs images of contrast (manifesting as flat, soft images.) In full sun, the flare is always noticeable.

I have one M37 lens, the 58mm f/2.4. It's optimized for f/16, and it is a reasonable assumption that all the M37 lenses are optimized for that aperture. It stands to reason that M37 lenses would be f/16 optimized: most people used the Sunny 16 rule for shooting since light meters were still pocket-sized accessories.

Two advantages that M37 lenses have over M42 and K and M lenses are the stepless aperture and aperture stop ring. This allows easy stopping down for focusing then metering (AV mode works well), fade-in and fade-out effects in videography, and easy DoF selection.

The M37 lenses have a great use in portrait photography. They are slightly softer than modern lenses, have stunning and accurate color transmission, and nice contrast. They all have round apertures created by blades that number up to 22 (depending on the lens model) and for that they deliver fantastic and smooth bokeh.

These lenses are not as technically perfect as newer lenses, nor are there any wider than 50mm. Landscapes, cityscapes, street, and architecture would not be good options for these lenses.

Recommended uses: Videography, experimental, and portraiture

Sample Photo

58mm f2.4 Takumar M37 Sample Image"Pentax MX with FA Limited" | Asahi Kogaku Takumar 58mm f2.4 at f/16, Pentax K-3

Sample Video

"Pentax MX with 77mm FA Limited" | Asahi Kogaku Takumar 58mm f/2.4, M37 Mount, at f/2.4 during the focus changes, stopping down from f/2.4 to f/22 to create the fade-to-black.

Use Explanations

Why videography? These lenses lack motors and autofocus gearing, so focusing them does not make noise like an autofocus lens does (even in manual focus mode.) No internal gears whir around creating friction, vibration, and noise as the lens moves. For tracking movement in video with a manual focus lens, simply set the focus points for your subject, put stoppers on the lens if you can, and track the subject as they move.

Why architecture? Often architectural photography is performed at dusk and requires long exposures. Manual focus lenses allow you to focus precisely (optically or with live view) and then retain that focus. No motor weight pulls on the lens' focusing helical to shift focus during long-duration exposures.

Why portraiture? Auto focus will get you close to on-spot with portrait photography, but manual focus allows you to obtain more precise focus than autofocus. You also have more creative control over specific focal points with manual focus than with auto focus lenses. Manual focus yields more creative options and more control for portrait photography. Beyond that, manual focus lenses are typically prime lenses with fast apertures. This allows for better subject isolation and more options for ambient light portraiture.

Why street? Article 2 in this series will look at hyperfocal and zone focusing. Manual focus lenses, especially wide-angle lenses, are well suited for hyperfocal distance and zone focusing. Unlike modern autofocus lenses, new manual-focus lenses tend to still have distance scales engraved on the bodies. With no autofocus motor to shift focus around, hyperfocal and zone focusing tend to remain constant with manual focus lenses, and the focus won't shift when you're walking around your city.

Why studio? Manual focus lenses allow more precise control and more creative control. Also, working in a studio often places subjects near their background and autofocus lenses can focus on a background element instead of a subject.

Why fashion? For many of the reasons outlined in portraiture, creative control, especially. Beyond that, manual focus lenses are typically prime lenses with fast maximum apertures. This allows for ambient light outdoor fashion work, in-studio work with fewer lights, and better subject isolation for more viewer attention on the fashion subject.

Why macro? Much macro photography requires extension tubes, bellows, and reversing rings to obtain the desired magnification. In those cases, aperture and contact linkages are typically useless and a lens with an aperture that can be controlled by the ring works the best. Macro photography with a mount like a non-aperture-linked K-mount lens can be just as good as with an equivalent FA Limited lens, but at a lower cost and with no greater difficulty.

Why astrophotography? For astrophotography, you will typically only focus at infinity anyway, so autofocus is wasted. Also, with manual focus lenses, once you set the focus it will hold with no risk of the autofocus kicking on and re-focusing your lens at the wrong location.

Why landscapes? Landscapes are typically deep-focal-area images that capture the subject clearly from the front of the frame to the back. This benefits from knowing your hyperfocal distance, a technique discussed the second part of this two-part series. Using manual focus also allows you to set your camera's focus to the precise point required to capture the entire scene in crisp focus.

Why cityscapes? Like astrophotography, cityscapes are typically an infinity-focus proposition. If you're focusing on just the skyline's shape, then a larger aperture can be used. If you want to compose your cityscape like a landscape with a close object in focus as well as the distant skyline, manual focus lenses allow you to set a precise focal point and aperture that allow you to have a maximally deep image field. Autofocus is wasted in these conditions. Manual focus also allows you to fine-tune your focus. Autofocus, on some lenses, can have trouble focusing at infinity.

Why night and low-light photography? Ever dealt with an autofocus lens at night? Want to scare off your subject? Use an autofocus lens with its focus hunting and the camera's bright focus assist light. Human eyes, when adjusted to lighting conditions, see remarkably well at night and we can manually focus a lens with only modestly more difficulty than we can during the day. Manual lens focusing is typically faster and more accurate in poor lighting conditions.

Why experimental photography? The old M37 lenses require two adapters to mount on a K body. This introduces a high level of imperfection, light leaks (often), and other compatibility issues. Also, the old M37 lenses were, exclusively, developed by engineers using hand calculations. They produce softer images than Pentax users are used to, but the color transmission and image character are surprising.

Bonus Tip

Here's a bonus tip. You can use other lenses than legacy lenses on your Pentax DSLRs. Here are some sample photos that may surprise you.

"Twenty" | Pentax K-3; "Sixteen" | Pentax K-3
"Seven" | Pentax K-3; 
"Two" | Pentax MG

These images were all taken with home-made lenses — either a meniscus or biconvex lens mounted on a Pentax macro bellows. I mounted the lenses themselves in housings made of step-up and step-down rings and then attached them to the macro bellows. The first three images were taken with a lens that has an aperture iris mounted in the assembly, allowing me to control the aberration, pictorialist effect, and depth of field. Using a step-down ring with a 42mm thread on the rear allows the lenses to mount into either a K adapter or directly to an M42 body or M42 bellows.

The last image was made with a meniscus lens with a particularly deep cup. The lens height is significant as is the inner radius. The more of a cup-like shape the single-element has, the more softness the edges will contain and the faster the edges will become soft. Flatter lenses, like a biconvex with the flat side facing the image medium, will have significantly less distortion and softening.

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