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08-19-2014, 05:22 AM   #1
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Pentax screw mount lens on Digital cameras?

Back in the 60's I bought a Pentax SLR which I lost in Europe in the early 70's. In the late 70's I bought a Mamiya/Sekor SLR which use the same Pentax screw mount lenses. I have a bag full of lenses and adapters that use the Pentax screw mount. When my camera's shutter began to break, I took it to a camera shop to get it fixed, but they said it would cost too much, and they suggested I buy another camera body. Now I am looking at going Digital and would like to use my many lenses Etc. from my Pentax/Mamiya/Sekor SLR.

Are there any Digital cameras that use the Pentax screw mount? Are there adapters that would let me use my many lenses on new Digital cameras? Which Digital cameras will let me use my old lenses and still do things that I used to do with my old SLR? I would like to make the jump from film to digital, but I don't have a lot of money for the best digital cameras.

What are my options?

08-19-2014, 05:33 AM   #2
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All Pentax Digital cameras can use M42 mount lenses with the Adapter made for M42 lenses. Check out this thread:
08-19-2014, 05:47 AM   #3
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I have many M42 lenses (Pentax and other brands) that I use on my K-5 IIs regularly. No worries there.
B&H Photo in NY has a K-500 going for $400. If that's too much, look at the used market.
Also, you can use screw mount lenses on many different brands, with the proper adaptor.
08-19-2014, 05:57 AM   #4
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Welcome the forum, it's good news as others have already said, just one of the joys of Pentax ownership.

08-19-2014, 05:58 AM - 1 Like   #5
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Look for used, and look for the previous flagships like the K5, K7 or K20. You can also put a split-focus screen in there, like the old manual slrs had. It may make metering a bit more difficult in low light, but it really helps focus with manual lenses.

You can have a lot of fun with manual lenses, for sure. Even with decent autofocus lenses there are times when I need to switch back to MF and rely on my eyes.
08-19-2014, 06:58 AM - 1 Like   #6
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Hey, welcome! Lots of members here use vintage and legacy lenses on modern camers.
No digital cameras use a screw mount, they all use a bayonet mount now. But with adapters, you can use m42 lenses on many if not all DSLRs. The good thing with Pentax DSLRs is that the adapter for m42 is glassless, so it doesn't reduce image quality, and it also allows the full focus range (some adapters don't allow focus to infinity, for example). It is best to buy the genuine Pentax m42 adapter, because cheap knockoffs can cause problems, even though a lot of people use them all the time. Its up to you, in the end.
Oh, and I assume your screw mount lenses are m42. There are also m39 and m37 screw mounts, which requite an additional adapter to go to m42 (just a little ring to make the diameter 42mm)
Another good feature of Pentax DSLRs is that even though old lenses don't allow AF, the camera can still do Focus confirmation and has the Focus trapping function (called Catch in Focus), which triggers the shutter when the camera detects an object is in focus. This is really useful with old lenses. And in live view, the camera allows Focus peaking, which can help with manually focusing older lenses. You can also use the automatic metering with the Green button, so the camera automatically adjusts shutter to the selected aperture
You can also use any K-mount lens on Pentax DSLRs, even those from the 70s, 80s. Of course, those lenses might not allow as much automation as modern lenses, but they can still be used manually.
Oh, and there are also some high quality new primes available at low prices, like the DA 35mm f2.4, DA 40mm f2.8XS and DA 50mm f1.8. These will be fully automatic with fast AF and great image quality. Used you can get them for under $200.

Which K-mount camera? I would suggest a K-30, K-50, or (the more advanced) K-5. The K-500 is also an option, slightly more budget model, but has the same high quality 16MP image sensor, so the photos will be good. The main feature the K-500 is missing are focus point overlays in the viewfinder, but some people don't mind. If you don't need an optical viewfinder and don't mind looking at the LCD screen, get the K-01. Same quality sensor and features, but it is mirorless, so its not a true DSLR (no catch in focus, though). You can find these cameras for really great prices if you look at the used market on these forums,, or one of the other sites that deals with this, like ebay. Its usually good to buy a camera bundled with a lens, as it is cheaper than buying them separately.
Pentax K-mount DSLRs:

Last edited by Na Horuk; 08-19-2014 at 07:11 AM.
08-19-2014, 07:21 AM   #7

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QuoteOriginally posted by skipbleecker Quote
Which Digital cameras will let me use my old lenses and still do things that I used to do with my old SLR?
As @Na Horuk mentioned, the K-01 may be a good option.
Once your lens is in focus,
you can frame your picture with the dedicated live view at the working aperture.

This means that you don't need to keep switching
a Manual/Auto or Preview lever (depending on which lens you have)
between full aperture for framing and working aperture for taking.

I keep a K-01 (in yellow ) as a dedicated M42-lens camera.
08-19-2014, 07:40 AM - 1 Like   #8
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QuoteOriginally posted by Na Horuk Quote
you can use m42 lenses on many if not all DSLRs.
Ummmm...not quite, at least not without an auxiliary correction lens. The short list for dSLRs includes:
  • Pentax
  • Sony Alpha
  • Canon EOS
  • Olympus
Note that Nikon is conspicuously absent. M42 screw mount lenses may also be adapted to most mirrorless cameras with interchangeable lenses.

An important note regarding adapted M42 lenses on all modern cameras is that metering is always stop-down and support for this feature may be limited depending on camera. This is not a big problem for people who have used stop-down meter cameras in the past. The other concern is that no modern camera has a coupler for the automatic aperture operation. As such the lens must be used with the aperture in fully manual mode. This can be cumbersome.

There is also a special warning regarding M42 adapters on Pentax bodies. Quality varies widely and there is a risk with third-party adapters of the adapter becoming stuck on the body. The genuine Pentax adapter does not have this problem, but is often difficult to find and often somewhat expensive.


(...has many M42 lenses and shoots with them regularly...)

---------- Post added 08-19-14 at 08:02 AM ----------

I might suggest one other option for the OP. While repair of your Mamiya/Sekor might be prohibitively expensive, replacement with a Pentax Spotmatic might not be. Even including a full CLA by Eric Hendrickson, my very clean Spotmatic II has cost me less than $100 USD total.


08-19-2014, 08:30 AM   #9
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There are several Spotmatics available on right now. They usually don't get bid up unless they include a 50/1.4. I believe a full CLA from Eric Hendrickson is $63.00.

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08-20-2014, 06:40 AM   #10
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Megapixels needed to compare with film?

How many Megapixels are needed to compare with film? I have use many simple digital cameras since I stopped using my 35 mm SLR, and I was wondering how many Megapixels I need to consider a good comparison with film? I see a lot of cameras with 16 Megapixels or higher, but how well do they really compare with film? Most of the digital cameras I have used were pretty simple, without many options beyond point and shoot. As I look to move up to a digital SLR I need to consider many of the features I used in my Pentax Spotmatic SLR and my Mamiya/Sekor SLR, but I also need to decide how many Megapixels I really need to replace my film camera. My phone has 3 MP and a small Polarold with 9 MP, but they don't have many options that I got used to with my 35 mm and 120 and 620 film cameras.

What do I really need if I am not a professional photographer, Etc?
08-20-2014, 07:17 AM   #11
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How many pixels you need depends entirely on what you want to do with the photos. If you want to make poster sized prints you need more pixels than you would need for an 8x10. 3 megapixels will make a good 8x10 and a fair 16x20.A 20x30 needs 24 megapixels for good quality and at least 6 megapixels for fair quality. If you just want to share photos on the Internet you don't have to worry about megapixels at all...keep in mind that a 1080p television set (close to the resolution of most computer monitors) is 2 megapixels.

How Many Pixels Make A Good Print? PictureCorrect

Digital versus film photography - Wikipedia, the free encyclopedia

But having more pixels means being able to crop more. For a wildlife photographer this can be important, many of my photos are cropped to 3 megapixels or less. But for a street photographer it would be far less important.

Last edited by boriscleto; 08-20-2014 at 07:27 AM.
08-20-2014, 07:21 AM   #12
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Very hard to compare. For resolution I have seen 100ISO 35mm film estimated to equal somewhere between 4 and 16 MP, depending on the kind of film. I believe digital has less noise than film at the same sensitivity, though (at least for same sized media).
08-20-2014, 06:48 PM   #13
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QuoteOriginally posted by savoche Quote
I believe digital has less noise than film at the same sensitivity, though (at least for same sized media).
Film does not have noise. Grain yes*, but noise no. Grain is more prominent with higher ISO films, but very low at ISO 100.

As you noted, it is not easy to make a valid comparison. I have a long history with film and have been shooting digital for about 12 years. With excellent technique a 16" x 20" optical enlargement (wet print) that will stand up to close examination is nicely doable with a 35mm negative. The same print made from a digital capture at 300 dpi print resolution would require about 30 megapixels. It can be reasonably argued that 200 dpi print resolution is good enough for viewing at normal distances. In that case you would only need 13 megapixels.

FWIW, I own a decent 4 megapixel camera and I can get a usable 8x10 print at 200 dpi, but larger is not so good. With specialized software to up-size the image I might be able to do better. As with many things photographic, YMMV.


* A film picture is made from grain. No grain, no photo.

---------- Post added 08-20-14 at 07:28 PM ----------

I should emphasize again that equivalence between a film negative and a digital capture is hard to determine due to differences in how sensors work as opposed to the image captured on film. Digital images have artificially high contrast at the limits of resolution while film images suffer from the diffraction of light around the actual silver grains or dye clouds. The end results as printed are highly dependent on the skill of the artist and the printer and the technologies used.

I currently use a hybrid approach to my film photography with the negatives being scanned to create digital files that may be edited for digital printing and/or display on a computer screen. The scanner I use for 35mm film is capable of a true optical resolution of 4000 dpi. The output files at maximum resolution have pixel dimensions of about 5640x3776 pixels (~21 megapixels).

Does this mean that my digitized 35mm film captures are equivalent to a 21 megapixel digital camera? The short answer is no. Is it better? Define "better". It is possible for me to have drum scans made at up to 8000 dpi. Yes, that would be 86 megapixels. Will such a scan "beat" the best available FF digital cameras? I don't know. I don't have such a digital camera and am not willing to pay for such a scan.

I get workable digital files from my film scans and workable digital files from my Pentax K-3. Both suit my needs. Everything is good.

In practical terms, how does today's world work for the casual film photographer who has the lab make his prints and/or do his scans? Things are actually pretty good. The prints they give you (if you order them) are based on a digital scan. The default scans should be considered to be "proof" quality. Custom scanning at higher quality is available as is custom printing. In many ways this is sort of like the practice of a few decades ago of having a large laser-scanned internegative made from a slide and using that negative as the basis for a custom print.

08-20-2014, 08:08 PM - 1 Like   #14
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As others have posted, you can use your screw mounted lenses on any Pentax digital with a simple M42 adapter, which runs about $30 or so. The best one is from Pentax. The other third parties - some of which have a flange that sits out side the camera prevents the lens from focusing to infinity. Here is probably the best discussion of the topic, I know of.Camera bodies on a budget, which is a very good topic. I have a couple of screw mount lenses that I use, so here is my take.

All the Pentax dSLRs have in body image stabilization (IS or Pentax calls it SR for shake reduction) except the *ist (D, DS, etc.) and the K110D. The stabilization will stabilize any lens mounted on the body including M42 screw mounts. I like it a lot, however when on a tripod, you should turn it off.
  • K100D and K100D Super - these go for about $100 and are now about 8 years old. 6MP using a CCD sensor - which is very colorful (saturated) and good, however you really do not want to go over ISO 800. I started out with a K100D and still have it along with my old Spotmatic IIa. I do like it a lot. It tends to take very slow pictures.
  • K10D and K200D - 10MP CCD sensor, good up to about ISO 800. Weather sealed bodies. I am going to guess that these go for $150 to $250 or so.
  • K20D and K7 - 14MP sensor that is a CMOS sensor. I had a K20D for several years and the sensor is prone to noise - I really like it for a lot of things, but would avoid it because of the noise.
  • K5/K5II/K5IIs - I really like this body (the K5). I have had one for 3 years now and consider this somewhat of a watershead sensor (16MP). Good low noise, excellent image quality and dynamic range. If you look hard, I have seen this body go for as low as $350 - usually in the $450 to $500 range. The K5II and K5IIs are the updated versions that have an improved metering system to allow auto focusing in near darkness. The K5IIs has had its anti aliasing filter removed providing an additional resolution of about 8%. The K5II goes for about $500 with the K5IIs which is still available new for about $700 or about $550 to $600 used.
  • K30/K50/K500 - These use the same sensor as the K5 family. I am breaking these out because these have an added feature called focus peaking. If you use or plan to use a tripod, focus peaking would come in handy for focusing manual lenses using the rear screen. The camera highlights the area that is in focus. You can also zoom in to a particular area to focus too (which is available on the K5/II/IIs). The K50 is on sale now for $395 new body only. The K30/K50 is a more advanced camera than the K500 - more user controls on the sealed body - same sensor.
The difference in sensor technology - CCD and CMOS. CCD is limited in processing speed and ISO range. Its more expensive to produce. CMOS has a much higher ISO range, processes faster and is cheaper to produce. Here are some images taken pretty close together in time (~5 minutes). They are taken in opposite directions, so to be able to accurately compare colors, only look at the right hand side of the K100 (CCD) image to compare it with the K5 (CMOS) image. So, which camera body, if your budget allows any wiggle room. Are you going to print large (20" x 30")? If so I would go with the 16MP sensor. If you are having eyesight problems (me, manual focusing is getting hard), then focus peaking would help. Personally, I would go with the ....
  1. K50 new for $395, which has the focus peaking and the 16MP CMOS sensor. Its probably the best deal around. here
  2. The K500 is going for $399 and comes with a 18-55 lens. here Since Pentax just announced a new entry level replacement for this body, I might wait a bit and see if they reduce the price to clear the inventory.
  3. Next, I would go with the K10D/K200D followed by the K100. There are folks here that shoot these and refuse to consider a new body because of the CCD sensor and its color saturation characteristics.
KEH.COM is a good source of used gear along with the marketplace here on the forum.

Bottom line, you really can't go wrong. Even if the budget points to the K100, its is still an excellent camera - that folks still want for its sensor and features. It has some limitations - taking pictures in low light - but how often do you want to take pictures in the dark?

Last edited by interested_observer; 08-20-2014 at 08:13 PM.
12-09-2015, 07:23 AM   #15
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Which adapters for Pentax Spotmatic?

Which adapters work for Pentax Spotmatic? Is that M42 or some other type? Which adapters also work for using the Pentax Spotmatic on Pentax P3 35mm SLR Camera or Pentax K-x 12.4MP Digital SLR? Do I need one adapter for both "new" cameras or different adapters? Do I need adapters for each lens or just for each camera?

Last edited by skipbleecker; 12-09-2015 at 07:33 AM.

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