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03-09-2016, 07:18 PM   #16
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Reminds me of that story that the width of the space shuttle depends on the width of the Roman Chariot two thousand years ago. Could it be that someone made that decision for now forgotten reason, and then inertia took over? Zenit currently makes two 85mm lenses. Not only that, they are f1.4 and f1.5.

03-09-2016, 07:42 PM   #17
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QuoteOriginally posted by Na Horuk Quote
Anyway, these days, 55mm still has some advantages over 50mm. One portrait photographer insisted that 55mm is the widest lens he would ever use for portraits, and that he would never use a 50mm for portraiture. Different working distance, distortion, subject separation, bokeh..
My mind instinctively translates "I don't shoot portraits with focal lengths below X"

to

"I don't understand how optics works. I don't want to learn that focal length itself plays a minor role in distortion."
03-09-2016, 07:45 PM   #18
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Certainly once you get past the aperture ring and into focus ring territory, the 55mm SMC Takumar bears a very strong resemblance to its K mount successor. (As far as I know some of the later 50mm SMC Taks do as well, but I own the 55 and have handled the 55 K, so feel secure in commenting there.)
03-09-2016, 09:02 PM   #19
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QuoteOriginally posted by MadMathMind Quote
"I don't understand how optics works. I don't want to learn that focal length itself plays a minor role in distortion."
Now, that really depends on one's perspective, entirely.

I assume the implied context was "on full frame for head and shoulder framing", with which I would more or less concur, at least if the goal is to make the subject look good. I wouldn't go below 50mm.

03-09-2016, 09:29 PM   #20
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In the non-pentax-family part of my camera collection, I have a Konica Hexanon f/1.4 57mm normal lens, for the Konica Autoreflex series SLRs using the Konica AR mount. Konica had other "normal" focal lengths, too, including a 40mm.
03-09-2016, 09:30 PM   #21
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So people can fuel their LBA?
03-09-2016, 10:53 PM - 2 Likes   #22
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There are other considerations from lens design and marketing that may further enlighten this question.
Older film camera designs often did not offer viewfinder magnifications approaching 100% as many from the late '70s and on often did. So, perspective can appear to be that of a wider lens similar to the rendering in many DSLRs now. This seems to be the reason so many DSLR users see 50mm instead of approx. 35mm as their standard even though the camera is using APS-C crop. Viewfinder magnifications of about 70% fool the perspective.
With that said, the quickest way to market for K mount lenses from a lot of the Takumar line was to adopt the best existing designs from M42 and put a K-mount on them giving more justification for keeping the heritage Pentax 45.24mm mount flange to focal plane distance. So, SMC Takumar standbys such as 35 f/3.5, 55 f/1.8, 85 f/1.8, 135 f/2.5 were optically unchanged for SMC Pentax K mount.
In film days then, more people seemed to favor the wider view as a walk around standard and the big, bright viewfinders gave it to us with fast 50mm. Zooms were nowhere close to prime image quality then so the lens packaged as standard with a camera was always the fast prime around 50mm focal length.
For Pentax, switching from M42 thread mount to K mount gave them a diameter increase from 42mm to 46mm. The larger exit pupil this change made possible resulted in abilities impossible to have with thread mount. It enabled Pentax to have the Kf/1.2 50mm and other new optical possibilities like K28 f/2, then the M line with smaller, more compact lenses like the star* line having wide maximum apertures. The compact thinking changed filter mount from 52 to 49 mm so that the M series filter size change was for an entirely different reason than the 49mm on Takumar lenses had existed.
I was able to glean quite a bit of info while working in camera and lens retail during the middle of the Asahi transition from M42 through K, M, then A series.

03-09-2016, 11:06 PM   #23
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For full frame 35mm, technically a 43mm lens is the correct "normal" lens ( as any Pentaxian will tell you) since that is the diagonal of the frame. Leitz made a 50mm lens because it was easier to do and it became standard. When companies started making fast ( wider than 2.8) lenses for SLR cameras they made 55 to 58mm lenses because it was easier, and they designed the viewfinder optical systems so that you could open your non-viewfinder eye and have the images match. When camera companies were able to, they returned to using 50mm lenses. For Pentax, the 55mm lenses were designed in the 50's-60's. Later normal lenses were all 50mm lenses. The current 55mm lens is a design made to be more like an 85mm lens for a film camera.
03-10-2016, 12:54 AM - 2 Likes   #24
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I've always believed that the sole reason the 58mm existed in the first place, was because of the type of glass that was available at that time (the 50's) and the fact that the lenses had to clear the SLR mirror. With the availability of better glass types the standard lenses could be made of a shorter focal length without interfering with the mirror.

I'm happy to own both the 58m f/2 Takumar (Sonnar type) and the 58mm f2/4 Takumar (Heliar type). There's also a reason I also have the Helios-44 58mm f/2 and the 5,8cm f/1.9 Meyer Primoplan. All those 58mm lenses are optically radically different and also more interesting than the later common Gaussian (Ultron) designs.
03-10-2016, 04:56 AM   #25
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QuoteOriginally posted by From1980 Quote
For Pentax, switching from M42 thread mount to K mount gave them a diameter increase from 42mm to 46mm. The larger exit pupil this change made possible resulted in abilities impossible to have with thread mount. It enabled Pentax to have the Kf/1.2 50mm and other new optical possibilities like K28 f/2, then the M line with smaller, more compact lenses like the star* line having wide maximum apertures. The compact thinking changed filter mount from 52 to 49 mm so that the M series filter size change was for an entirely different reason than the 49mm on Takumar lenses had existed.
This puts things in a very new perspective; thanks. IIRC I remember asking once if M42 f/1.2 lenses existed and the answer was yes, so I'm not sure what was stopping Asahi - no doubt that it's easier to do on the K mount, though.

And regardless of why they went back to 49mm for a filter thread size on the M series (and many subsequent), it must have gladdened the hearts of Takumar users who skipped the K series (e.g. because they had just bought Spotmatic F's and ES's and stood to gain very little in function from buying a K camera) when the M lenses came in and they could at least carry all their old hoods and filters over to the new system.

QuoteOriginally posted by bertwert Quote
So people can fuel their LBA?
Give the lad a prize.
03-10-2016, 04:59 AM   #26
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After having a K55 f1.8 and VL 58mm f1.4, as well as an FA50 f1.7, I found myself going for the 55/58mm even without af.
Not sure why, I just found for portraits/objects it to be a better fit for me.
The K55 f1.8 is superb value, I picked mine up for £50 a year or so back, prices may have gone up more but I could not justify keeping the VL58 over it, given the cost difference, even if the VL58 is outstanding. The K55 is also so compact, makes an excellent pair with the K85 f1.8.

For walk around, the FA43 is just my favorite, but that's another story.
03-10-2016, 06:39 AM   #27
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QuoteOriginally posted by MadMathMind Quote
My mind instinctively translates "I don't shoot portraits with focal lengths below X" to "I don't understand how optics works. I don't want to learn that focal length itself plays a minor role in distortion."
That is why the person also mentioned working distance, subject separation, and other things; many of which I listed in my post earlier. I did not just say "herp derp focawl length is be all and end all!!"

Edit: One more thing, some say that the Pentax 50mm f1.7 genus is actually closer to 53mm, just labelled as 50mm because that is the standard. I'm not sure how true this theory is, just something that might explain why people see less of a difference between the Pentax 50mm and another brand's 55mm. Apparently focal length labels are not super accurate because they follow conventions. This is why we see so many 28mm lenses, but next to no 26mm, 27mm lenses, for example.

Last edited by Na Horuk; 03-10-2016 at 07:19 AM.
03-10-2016, 06:55 AM   #28
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And now, for some odd reason, I felt compelled to stick the 55mm f/2 SMC Tak to the front of my K-5. I have discovered to my joy that the regulation metal hood takes an aftermarket 49mm pinch cap.
03-10-2016, 11:45 AM   #29
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QuoteOriginally posted by pathdoc Quote
IIRC I remember asking once if M42 f/1.2 lenses existed and the answer was yes, so I'm not sure what was stopping Asahi - no doubt that it's easier to do on the K mount, though.
Thinking...thinking...thinking...

Yes, there were several models, all made by Tomioka with at least two different designs and sold as Tominon, Yashinon, Chinon, Porst and so on. All are pretty hefty beasts, so perhaps that is a clue.


Steve
03-11-2016, 12:08 AM   #30
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QuoteOriginally posted by From1980 Quote
For Pentax, switching from M42 thread mount to K mount gave them a diameter increase from 42mm to 46mm. The larger exit pupil this change made possible resulted in abilities impossible to have with thread mount. It enabled Pentax to have the Kf/1.2 50mm and other new optical possibilities like K28 f/2,
Both of these should fit into a m42 shell, although the 50 1.2 rear element will be somewhat tight fit. I can't think of a K lens that would not fit into m42 right now but maybe there are some.
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