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12-31-2011, 06:19 PM   #1
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135mm lens

I have an SMC 135 fixed length lens that will be used on a new dslr in the near future. At the time I got it, some 30+ years ago, I was told that it was a great all around lens. Alas, so it is as I have had many excellent results with it. How will it be affected by the digital format? Are there any limitations with it?

12-31-2011, 06:36 PM   #2
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In general the lens will have the same abilities on digital as it did on film. If it was manual focus for example then it is still manual focus.

You need to provide some additional information in order to get an intelligent answer though There are at least 3 and maybe 5 (depending on how you count) Pentax lenses that could be described as "SMC 135mm". What is the exact name on the plate? What mount is it, (M42 or k)? Post a picture of the lens if you can. Or check the lens database on this forum: Pentax Reviews - Pentax Lens Reviews & Lens Database
12-31-2011, 07:22 PM   #3
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If you got it 30 or so years ago the odds are its an M135, but as jatrax said its best to be certain so please post specifics. I got one as a gift from my sister as it was her father-in-law's and he gave them all his old Pentax film gear and it had gathered dust for years until they gave it to me. If yours is the M135 it is an excellent lens with fabulous build quality. I particularly like the built in hood and its incredibly small size. Just FYI, regardless of which model it turns out to be - your perspective with it on the dSLR will be like looking through a 200mm (202.5 to be precise) lens in the old 35mm SLR days.
12-31-2011, 07:25 PM   #4
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I count at least 7 SMC versions in this database search that could be 30 years old. I have the S-M-C Takumar f/2.5 and f/3.5 versions, and the SMC-M f/3.5. There's also an SMC-A f/2.8 and a SMC-A* f/1.8, as well as K-types in f/2.5 and f/3.5. The K-types have bayonet mounts and just say Pentax SMC.

How will these work on a modern dSLR with its 'crippled' mount? The Takumars must be used a presets, without stop-down metering|exposing; they'll work in Av or M modes, and need an M42-PK adapter. The K- or M-types will stop-down for metering|exposing but only in M mode with the Green button. The A-types support full stop-down metering|exposing; set the aperture ring to A, and you can use any metering mode, and pTTL flash.

Because our APS-C dSLRs have crop-sensors, the FOV of a 135mm lens looks like that of a 200mm lens of a full-frame camera. DOF thins by about 1 f-stop worth, so if I set the aperture to f/11, I read the DOF scale at f/8. If a lens tends to vignette on FF, it won't on APS-C because those flaky edges are cropped off by the sensor. Those are the basic lens behavioral differences.

12-31-2011, 07:31 PM   #5
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QuoteOriginally posted by RioRico Quote
I count at least 7 SMC versions in this database search that could be 30 years old. I have the S-M-C Takumar f/2.5 and f/3.5 versions, and the SMC-M f/3.5. There's also an SMC-A f/2.8 and a SMC-A* f/1.8, as well as K-types in f/2.5 and f/3.5. The K-types have bayonet mounts and just say Pentax SMC.

How will these work on a modern dSLR with its 'crippled' mount? The Takumars must be used a presets, without stop-down metering|exposing; they'll work in Av or M modes, and need an M42-PK adapter. The K- or M-types will stop-down for metering|exposing but only in M mode with the Green button. The A-types support full stop-down metering|exposing; set the aperture ring to A, and you can use any metering mode, and pTTL flash.

Because our APS-C dSLRs have crop-sensors, the FOV of a 135mm lens looks like that of a 200mm lens of a full-frame camera. DOF thins by about 1 f-stop worth, so if I set the aperture to f/11, I read the DOF scale at f/8. If a lens tends to vignette on FF, it won't on APS-C because those flaky edges are cropped off by the sensor. Those are the basic lens behavioral differences.
Those were all still available purchased new in 1981 or so? Really. Wow. The M models were in production 1977 ~ 1986 and the A's didn't start until 1985 ~ 1989. The K's apparently were still in production (f2.5) in the 1977 ~ 1985 time frame which is news to me as I thought they were replaced by the M's in the 1977ish timeframe. The S-M-C Takumar 135 f3.5 was also apparently in production until 1979.

Last edited by Docrwm; 12-31-2011 at 07:39 PM.
12-31-2011, 09:59 PM   #6
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QuoteOriginally posted by Docrwm Quote
Those were all still available purchased new in 1981 or so? Really. Wow. The M models were in production 1977 ~ 1986 and the A's didn't start until 1985 ~ 1989.
I used a weasel word -- they COULD have been available about 30 years ago. Regrets if I'm wrong about the A-type timeline. Lop-off the A's, and everything else remains -- all those were available new or used in the middle of Reagan's first term.
01-01-2012, 06:16 AM   #7
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It is an "M" lens that was purchased in the summer of 1977. Traveled all over the country on my motorcycle in the tank bag with my MX as well as all over Asia and the Middle East. Never had any issues with speed.

I do not understand how the 135 acts like a 200 on a dslr. What gives with that? Sounds like I will need to find an old "M" or "K" series lens at the 100mm focal length to get the same behavior as the 135 on a film camera.

Can someone provide a link to a place where I can read about the oddities of the dslr? The more I read on this forum about the dslr the more it seems they are very different than a film camera and things don't behave in the same way as film.
01-01-2012, 06:34 AM   #8
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QuoteOriginally posted by pichur Quote
It is an "M" lens that was purchased in the summer of 1977. Traveled all over the country on my motorcycle in the tank bag with my MX as well as all over Asia and the Middle East. Never had any issues with speed.

I do not understand how the 135 acts like a 200 on a dslr. What gives with that? Sounds like I will need to find an old "M" or "K" series lens at the 100mm focal length to get the same behavior as the 135 on a film camera.

Can someone provide a link to a place where I can read about the oddities of the dslr? The more I read on this forum about the dslr the more it seems they are very different than a film camera and things don't behave in the same way as film.
It acts like a 200 on a DSLR because the digital sensor is smaller than film used to be. Essentially it is taking a center crop from the lens. I have the M135 and it is excellent although it's a little awkward to use. I find it very good for concerts where I can't get close.

01-01-2012, 07:05 AM   #9
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So, a smaller sensor means more cropping? The "magnification" remains the same? Just the field of view changes?
01-01-2012, 07:30 AM   #10
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QuoteOriginally posted by pichur Quote
So, a smaller sensor means more cropping? The "magnification" remains the same? Just the field of view changes?
That's right. Cut out a photo from a magazine. Draw a 60x45mm rectangle on it. Inside that, draw a 36x24mm rectangle. Inside that, draw a 24x18mm rectangle. Those rectangles are the frame sizes of 645, 135/FF, and APS-C cameras. The picture remains the same. Smaller frames see less of the same picture -- they crop it. The lens remains the same. Different frame record different amounts of the same projection.

Back in the day, I had a half-frame 35mm SLR, the Olympus Pen-FT, built with a portrait-mode 18x24mm frame, very close to APS-C size. I got a T2 Spiratone 400mm lens and I though, OH BOY IT'S LIKE A 600MM LENS! I quickly found otherwise -- it gave a 400mm image with the sides chopped off. The smaller frame cropped the projected image, that's all.

135mm on APS-C gives close to the same FOV as 200mm on FF.
85mm on APS-C gives close to the same FOV as 135mm on FF.
55mm on APS-C gives close to the same FOV as 85mm on FF.

Et cetera. I mentioned the DOF differences in a prior post. The main trick is to forget what a lens did on old cameras, and learn how it works on new cameras. Ain't no big thang.
01-01-2012, 08:22 AM   #11
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I would suggest googling the term "crop factor". It's very easy to get the wrong idea about it and how it works, and you really need to read just more than just a paragraph or two before it sinks in. For example, saying magnification is not affected is incorrect in so much as how most people would use that term when referring to a telephoto lens. A subject that takes up two thirds of the frame in a shot with a 135mm lens on 135 format (film or digital) is going to take up the entire frame if shot with the same lens on APS-C format (film or digital). Print the two shots the same size, and the subject is physically bigger in the second - so how is that not more magnification in any real world sense? What it might not have is more resolution, but then, your average 200mm lens isn't going to provide as much as resolution as your average 135mm lens, either. So really, that shot from the 135mm on a DSLR will likely be indistinguishable from a shot taken with a comparable quality 200mm lens on your 135 format film SLR in terms of both magnification and resolution. The only visible difference will be DOF, which will be deeper for the same aperture with the 135 on the DSLR than it would have been for the 200 on the film SLR. And no, "perspective" is not different, either.

Anyhow, this forum isn't really the right place to discuss all this - like I said, google the term, or search the Beginner's forum.
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