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03-09-2016, 05:44 PM   #1
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50mm vs 55mm, why have both?

Looking at both the Takumar and K series primes, I'm struck by curiosity over why a lens maker would have two series of lenses so close in focal length. Obviously the 50mm was the Asahi choice for the fastest glass (the 1.4s, and the K 1.2), but let's face it, those lenses didn't get used at maximum aperture ALL the time - there must have been many an occasion when even the fastest lenses found themselves operating at f/8 or even higher.

So, restricting our discussion to the film era in which these lenses were developed, what was so magical about the 55mm focal length that led Asahi to continue it when there was a perfectly good 50mm lens right next door, so to speak? Or alternatively, what led to them bringing the 50 in in the first place? I know they likely resurrected 55 for the DA*55 because on crop that has the equivalent FOV close to an 85, but let's stick to full frame for now.

03-09-2016, 05:47 PM   #2
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I'm not seeing a 55mm F1.4, which would suggest that it may have been kept in the lineup as a cheaper alternative.

www.pentaxforums.com/lenssearch/?minfl=50&maxfl=55&mount[]=M42&inproduction=0

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03-09-2016, 05:57 PM   #3
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They certainly went out of their way to rationalise it out of the lineup in the M series.

OTOH my personal f/1.2 lens is a 55mm by Ricoh, and an auto-aperture P version at that, which begs the question of why they didn't make it a fifty. I almost bought myself a 55mm K lens a week ago to see what the fuss was about (and to compare it directly to my 55mm SMC Takumar), but somebody beat me to it by inches!
03-09-2016, 06:06 PM   #4
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50mm vs 55mm vs 58mm
Let us not discard the Voigtlander Nokton 58 mm f1.4. A great lens, outstanding IQ, metallic, full-frame. It is a special lens....

03-09-2016, 06:15 PM   #5
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Um, I remember reading that actually 55mm was the standard before the 50mm, but lens brands kept making the lenses wider because it was fashionable. 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..
I think you can still see this with Pentax. DA*55mm is for portraiture, while the DA 50mm f1.8 is the nifty fifty and the FA 50mm f1.4 as the "higher end" 50mm. And then there is the DFA 50mm f2.8 macro.

There are small differences between f1.4, f1.8, f2.8. There is a little difference between 50mm, 55mm, and 58mm. Then there are differences between the lens designs - even some different 50mm f1.4 lenses might render images quite differently. So choices are not bad imo. Study the differences, see what fits your needs
03-09-2016, 06:22 PM   #6
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If the 50/55 offerings seem an embarrassment of riches, consider the K-series 28/2; 28/3.5, and 30/2.8--each and every one flirting with legendary status. Once I can justify having all three to my wife, I know satori is within my grasp.
03-09-2016, 06:31 PM   #7
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Often, the actual focal lengths are rounded off anyway for convenience or marketing purposes.

In use, personally, I tend to find that the 55/58mm is a bit more 'portrait orientated' especially wrt framing and working distance.

The 50mm on the other hand seems to fall in better as an all rounder 'normal'.

03-09-2016, 06:35 PM - 2 Likes   #8
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I got into photography in the mid-70's. At the time, 58mm was the holy grail because it was thought of as the exact equivalent to human vision. My perception is that 55mm became a popular alternative more for marketing purposes as did 50mm, a nice round number that was approximately a normal or standard prime. Realistically, the 55mm and 50mm were progressively less expensive to manufacture and smaller than the 58mm and with a slightly wider angle of view, more practical. Anyone considering a portrait lens was considering 85mm and a 50mm is better spaced from the usual trifecta of the 24/28mm and 85/90mm primes.

Also, back in the day, the standard kit lens was the 50/55/58mm prime, so unlike today with choices between Nikon's three 18-55mm zooms (non-VR, VR, and VR II) or Canon's two 18-55mm zooms (IS STM or IS II), sometimes the manufacturer would tweak the standard prime for better or cheaper. (Thinking Nikon Series E lenses).

The reality may have been behind the scenes patent conflicts or parts availability or something trendy like odd number aperture blades vs. even. But it's mostly marketing. f/1.8 or f/2 was the bargain. f/1.2 if you wanted the elite pricey option. So f/1.4 for the rest of us in the middle.

Why 55mm for APS-C? It's a lot closer to the 85mm FF equivalent as a short telephoto, but also closer to the magic FF 58mm of yesteryear.
03-09-2016, 06:35 PM   #9
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Na Horuk, It wasn't so much as fitting MY needs as a historical question of why the same company would carry both focal lengths. I have 55mm SMC Takumar (2.0) and Rikenon (the latter a special case; f1.2); 50mm DA 1.8, FA 1.4, A 2.0 (I inherited that one rather than buying it) and Super Tak 1.4, and each has its own strengths and purposes (and the FA1.4 will certainly find new purpose the day I buy the K-1).

Nevertheless you've given me enough of a perspective to have sort of answered my question. Thank you.
03-09-2016, 06:38 PM   #10
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QuoteOriginally posted by Na Horuk Quote
Um, I remember reading that actually 55mm was the standard before the 50mm
And for the Sonnar type on an SLR, 58mm was the best they could do.
03-09-2016, 06:38 PM   #11
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QuoteOriginally posted by pathdoc Quote
Looking at both the Takumar and K series primes, I'm struck by curiosity over why a lens maker would have two series of lenses so close in focal length.
In the M42 and SMC K series lenses (essentially the same lenses with different coatings and substitution of the bayonet mount) my 50's have softer edges and a pleasing isolation of the sharper center subject area at wide apertures, while the 55's are somewhat flatter. In a 1975 Lenses and Accessories brochure I have the K55/1.8 is described as suitable for work on a copy stand or copipod (IOW, for 'flat work'). That distinction carried over to the M and A 50/1.4's vs. 50/1.7's.

Then there is product segmentation.

The 50/2.0 lenses were supposedly identical to the 50/1.7 lenses but for the addition of a baffle at the rear element to prevent stopping down further than f/2. I've read the economic theory was, they were still profitable at the lower price, the distinction allowed charging even more for the 50/1.7 and 50/1.4 and they made an affordable kit lens with budget bodies such as the SP500 and the K1000 (which were also virtually identical internally to the more feature-rich bodies, with some features disabled).

For instance by removing the lever for self-timer and DoF preview from the K1000, and covering the battery test button with a hump on the top plate, they turned a KX/KM into a budget camera; or by simply not marking the 1/1000 shutter speed on the SP500 (it is there, the dial will go to 1/1000, but it isn't marked) they made a budget Spottie vs. the SPII.

Last edited by monochrome; 03-09-2016 at 06:57 PM.
03-09-2016, 06:39 PM   #12
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From various makers, I have one 50/1.4, a 55/1.4, a 58/1.4, three 50/1.7, three 55/1.8, one 55/1.8, a 58/2, one 53/1.8 (chew on that one a bit), and multiple 50/2. Half the above were made within five years of each other.

There is absolutely no rhyme or reason or pattern by age, performance, or sophistication.


Steve

Last edited by stevebrot; 03-09-2016 at 07:15 PM.
03-09-2016, 06:40 PM   #13
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Interesting question. I don't have any of these lenses, but just looking at the info. in the lens database. They used 50mm for the 1.4s and macros and 55mm for the f/1.8/1.9/2. Is it possible they used the same optical design for all of the 55s up through the K series? Would have saved some R & D cost over almost 20 years.

Another curiosity I picked up from Adam's search. They seem to have settled on a 49mm filter size in the takumars (a few of the older ones are 46, but most are 49). Then they went to 52mm for the K series, then back to 49mm for the M series. ??

---------- Post added 03-09-16 at 07:45 PM ----------

QuoteOriginally posted by stevebrot Quote
From various makers, I have two 55/1.4, a 58/1.4, three 50/1.7, three 55/1.8, one 55/1.8, a 58/2, one 53/1.8 (chew on that one a bit), and multiple 50/2.
So doing the math you have at least 13 50ish lenses. I counted and I only have 8 right now. But I am not done yet...
03-09-2016, 07:14 PM   #14
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QuoteOriginally posted by pathdoc Quote
It wasn't so much as fitting MY needs as a historical question of why the same company would carry both focal lengths.
I have two Minolta Rokkors, a 50/1.4 and 58/1.4 with manufacture dates about a year apart in the early 1970s. Both are MC series and both take the same size filters. The 50mm is somewhat longer and heavier than the 58mm and has an additional element (5-7 vs. 5-6), but both are Planar design. I have not done any comparisons between the two lenses and have not read consensus indicating that one performs significantly better than the other. Why did Minolta change design and focal length? I suspect that it is because the 58mm focal length is just a little long for walk-around use. FWIW, there was a 55/1.8 during the same period.

Oh...BTW...I no longer own a Super Tak 50/1.4, but IMHO, the ST 55/1.8 is the better of the two lenses. The difference in focal length may simply be a matter of design constraints, but I like to think that once you get it right (the Auto Tak 55/1.8), why mess with success?


Steve

Last edited by stevebrot; 03-09-2016 at 07:23 PM.
03-09-2016, 07:17 PM   #15
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QuoteOriginally posted by KC0PET Quote
They seem to have settled on a 49mm filter size in the takumars (a few of the older ones are 46, but most are 49). Then they went to 52mm for the K series, then back to 49mm for the M series. ??
Yep, that is true. The strange thing is that optically the K-series has more in common with the SMC Takumars than with the M series that followed.


Steve
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