The Rodney Dangerfield of Apertures: f/3.5

    I don't know if Rodney Dangerfield was into photography, but if he was he must have used f/3.5 lenses, judging by the way he was always bugging his eyes out. Which would be understandable, because any half-baked photographer knows that f/3.5 is a raging vortex where photons go to die, leaving your eyes straining for the faintest trace of light. Not to mention the utter impossibility of achieving anything remotely resembling shallow depth of field (DOF) with such an infinitesimal iris. No proper lens jockey would be caught dead with such a miserable excuse for a photographic tool. So if you have any remaining shred of photographic self-respect, let me save you the trouble now of reading any further ;-).  

  Whither Goest Thou, O Dim One?

​    What a difference seven decades dost maketh! From being cutting-edge in wide angles and telephotos in the early 1950's to an afterthought in our enlightened age, the lowly f/3.5 slogs along today in consumer zooms that are optically better than they have any right to be for all of their pitiful plastickiness. How has it managed to survive, and even thrive, in a sales context, despite the widespread antipathy (from photographers in the know ;-)) towards its humble qualifications? In a word: affordability. F/3.5 hits about the perfect balance between cost, size, and sufficient performance for the so-called "average" photographer. But how much of a performance hit do you really take with f/3.5 versus, oh say...f/2.8, particularly when it comes to lenses from the mid-1970's when the 3.5 primes began to be displaced by 2.8s as the standard offerings from the manufacturers? 

  A Bit of Background (Not too blurry; this is f/3.5 after all)

    The original 35mm still camera, the Leica A (1924), sported a 50mm f/3.5 Elmar lens. From the 1930s onward, the Zeiss Tessar (and its imitators) became the dominant common lens on all sorts of cameras due to the blend of performance vs. price. Although the design was pushed to f/2.8 early on, the Tessar is happiest (you guessed it) at f/3.5. More light-gathering capability = larger elements = more correction required, thus increasing complexity, size, weight, and ultimately, cost. Fewer elements also made a larger difference in the period from the 1930s to 1950s, when lens coatings were more primitive (or non-existent). Every air-to-glass surface (two for each lens element or cemented group) robs light and contrast, so using the least amount of elements (and/or groups) possible during that period was critical. So we find that wide angle (at that time, 35mm) and telephoto (90 - 135mm) lenses for 35mm cameras tended to bottom out at f/3.5 - f/4 for the best balance of cost vs. performance for enthusiasts and even professionals in that period. They were not budget optics by any means.  

    Fast forward to the 1953 and the introduction of the first 28mm retrofocus (reverse telephoto) wide angle lens by Angenieux. And the chosen aperture? Good ol' f/3.5 :-). They followed that up with a 24mm f/3.5 in 1957. The retrofocus design was essential to achieving proper wide angle lenses for SLRs due to the greater back focus length that the mirror box prescribed. And it was 28/3.5s that led the early Japanese wide angle charge: Nippon Kogaku (later Nikon) introduced their entrant in 1959, Asahi Optical (later Pentax) followed in 1962, Minolta in 1963, and Canon in 1966. Of these, the Nikkor would prove to be the most influential in subsequent wide angle development, particularly with regard to the arrangement of its rear elements. Optical principles discovered in its creation are still used in designs to this day. Minolta, Nikon, Olympus, and Pentax would all offer a 28/3.5 into the mid-1980s, while Canon dropped theirs in 1975 with the introduction of their first 28/2.8. You could say that 1974-77 basically marked the turning point for wide angle 3.5s. They were either eliminated completely from lens lineups or moved to the lowest budget position, as f/2.8 became the standard prime aperture, with f/2s, f/1.8s, and f/1.4s becoming more widely available in the mid-to-upper echelons of lens hierarchies. Minolta didn't even offer an f/3.5 wide angle prime in North America post-1975.   

    When it came to longer lenses the story followed the same script, but just a bit faster. At the dawn of the SLR revolution (say 1957-1960) most of the medium telephotos (135s & 200s) topped out at f/3.5 (with most 200s settling around f/4, even less palatable to any self-respecting photog ;-)). With the exceptions of Minolta and Canon (who had a 135/2.8 or 2.5 available from 1960 onward), this held true until the mid-'60s with the 135s, after which the 3.5s had assumed the menial mantle of budget telephoto.

     As far as the 180/200s went, the timeline fairly mirrored that of the wide angles. Nikon brought out their first 180/2.8 in 1970, Canon a 200/2.8 in 1975, Pentax their 200/2.5 in 1977, and Minolta (finally) their  200/2.8 in 1979. But these premium optics were still quite rare in enthusiast's bags. The moderate-aperture 200s still ruled the medium telephoto market. As a matter of fact, your average 200/4 cost as much as a 24/2.8 at that time. Rather than the fast 2.5-2.8s being the cause of the slide of the 200/3.5-4 to the cellar, it was the convenience of similar-aperture zooms that spelled the end of the moderate prime telephoto as a popular option. 

  Dost Thou Darest Defile Your Camera?

    Okay, so obviously f/3.5 is not the be-all and end-all. Otherwise, everybody would still be using the same lenses we had 40 or 50 years ago. But let's try to take a semi-rational (I know that's a stretch ;-)) look at the situation by starting with the real and perceived drawbacks of moderate apertures.

• Too much Depth of Field. In today's bokeh-obsessed, anything-less-than-f/1.4-sucks atmosphere, you would expect f/3.5 to render everything pin-sharp from right in front of your nose to infinity. But what is the real story? Let's take a look at the DOF tables for 28mm and 135mm lenses at minimum, intermediate, and infinity distances. First up, 28mm at apertures of f/2, 2.8, and 3.5 and distances of 0.3m, 1.5m, 5m, and infinity: ​

              Distance          0.3m                      1.5m                        5m                       20m 
​      
  F/stop            

      2

    2.8

    3.5

0.29-0.31

"

"

1.35-1.69

1.29-1.78

​1.25-1.88

3.62-8.07

3.25-10.8

​2.98-15.5

7.91-Infinity

6.33-Infinity

​5.37-Infinity
​

  Next up 135mm, at distances of 1.5m, 5m, 20m, and infinity:​

                Distance        1.5m                        5m                          20m                      295m 
​        
   F/stop                      

       2

      2.8

​      3.5

1.49-1.51

"

"

4.92-5.08

4.89-5.12

​4.86-5.15

18.8-21.4

18.3-22

​17.9-22.6

149.7-infinity

124.3-infinity

108.1-infinity

    Ooookaaay...so what does all of this add up to? Clearly, as subject distance increases, the disparity between large and moderate apertures becomes more apparent. But what does this translate to in the real world? Well first, let's think of what we commonly use these focal lengths for. 

    28mm is generally regarded nowadays as the bare minimum for a wide angle when we are talking the 35mm format. But it has increasingly become the standard perspective that the smartphone generation has become familiar with. So it has become a catchall focal length and thus gets used for everything from landscapes & street (traditional) to portraits (definitely a newer application, and one that requires some skill to manage the inherent distortion when used in that way). So the first thing to decide is whether you are going to be using such a lens for more traditional applications or in a more modern fashion. If portraits (or other shallow DOF or very low light situations) are going to be a big deal for you, f/3.5 is not going to cut it. However, if you are more of a landscape or hyperfocal street shooter, you will likely be living from f/5.6 and up, and that is where a 3.5 can shine. Let's just take a quick look at the 1.5m data for the 28mms. Comparing the f/2 and the f/3.5 we see that the acceptably sharp range on the 3.5 is about 10cm (4") more in front of the subject and about 19cm (8") further behind than the f/2. So all in all, 29cm (11.5") total more DOF.  When compared to the f/2.8, that figure is cut in half (4cm in front and 10cm behind = 14cm overall). Is that enough of a difference to notice? For some people and applications, definitely. But in general shooting, most people would very likely never notice. Increase the subject distance much more than that, and no 28 is going to blur out your background into bokehlisciousness. There are better tools for that job, and focal length and subject distance are going to be far greater factors than 2/3 - 1 2/3 stops in aperture.

    Let's move to the 135mm end of the scale now. Traditionally, 135mm was at the long end for portraits, being used in that 1.5m - 5m range, mostly. At 1.5m we are talking literally mere millimeters of difference between the f/2 and the f/3.5. Most DOF calculators simply round the overall DOF to 2cm (3/4") for all three apertures. Really. Even at 5m, f/3.5 expands the zone of acceptable sharpness 6cm (2 5/16") in front of and 7cm (2 3/4") behind the subject as opposed to f/2. In other words, less than 15cm (6") total. Again, how noticeable will that be to you? And there really are not that many 135/2s running around out there; f/2.8s were much more common as competitors to the lowly 3.5s. That cuts those figures in half. Splitting of hairs, no? 

• Ease (or lack thereof) of focusing.​​ This is probably the biggest actual deficiency  for f/3.5 lenses, particularly the wide angles. There are two factors at play here: 

1. A darker viewfinder - No matter how you slice it, there is less light making its way through the optical chain to your eye. This impacts the effectiveness of such focusing aids as microprism patches and split-image rangefinders. The split image is still in pretty good shape at f/3.5, but some people have difficulty with a microprism (especially with many pre-1975 viewfinders with their less efficient prism coatings and focusing screens) at that aperture. This is very subjective, however, as each individual's eyesight capabilities are really the critical point here. Using the matte field surrounding whatever other focus aids your SLR has for focusing is the best technique to overcome this. Practice does indeed make a difference.​
2. Larger DOF makes critical focusing more of a challenge - People love fast 50s for focusing not only because of the bright viewfinder, but also for the fact that they can easily see where their exact point of focus is wide open due to the skinny DOF available at f/1.4 or wider apertures. With f/3.5 wide angles, it is undoubtedly more difficult to discern this, as a result of the smaller magnification in the viewfinder. Again, with a bit of practice, this can be overcome to a degree. 

• Slower shutter speeds in low light. As with the previous point, your physical makeup is a major factor in how much of an impact this will have. Some people are just steadier and able to handhold a camera more effectively. But that doesn't mean that with some work on technique and practice (oooh, there's that word again!), that you can handle shutter speeds in the 1/30 sec. and even slower range with 28 & 35mm lenses. Using faster film, or a tripod if practical, are other solutions. Of course, if you live for low light handheld photography, a larger-aperture lens may be the most practical solution of all. F/3.5 is no panacea ;-)

  Dare to be Different

    It's not that f/3.5 lenses will necessarily give you more than an f/2 or f/2.8 in any given situation, rather it's really about how much performance they give you outright for their smaller size, lesser weight, and much lower cost. Their simpler optical constructions often give them equal or even slightly better contrast than their wider-eyed siblings, particularly if quality multi coatings were used. The larger-aperture lenses (particularly the 35 - 70 year old optics we are talking about here) often need to be closed at least a full stop (and sometimes two) to match the wide-open 3.5 as far as flare and contrast are concerned. And by the time you get to f/5.6 with either lens, there will be virtually no difference. And that brings us to the most important aspect of whether you should look at f/3.5 lenses. Do you really need more aperture in the first place? (Only you can answer that.)

    For example: the Minolta MC/MD 28/2 (1975-85) is a gorgeous lens that regularly sells for $250 - $300 USD, and weighs from 265 (last version) to 340 (first version) grams. The corresponding 5-element 28/3.5 (1975-85) sells regularly for $60 - $75 (which is also about $20 USD less than the 7-element 28/2.8), and weighs 160 (2nd last version) to 220 (first version) grams. If you are primarily a daylight landscape shooter, for instance, does it make sense to spend 4 times the money and carry over 50% percent more weight to have a lens that you are going to be setting at f/5.6 to f/11 for 90% or more of the time? That's your call :-). Now, obviously, there are more things to consider than just the maximum aperture and weight of your lenses. The "look" that they give you is more important. But the objective of this little exercise is to emphasize that f/3.5 alone should not dismiss a lens from your consideration, especially if you do not need the extra light-gathering capability.

    R...E...S...P...E...C...T -  A Few Good Lenses

     The following list traces the evolution of the Big 5's f/3.5 prime lenses. The amount of choices may seem overwhelming initially, but don't panic, it is a fairly simple process to pare them down based upon your personal priorities :-). My personal picks are highlighted in green. I should add that the same basic trends apply to the smaller manufacturers such as: Contax/Yashica, Chinon, Fuji, Konica, Topcon, as well as the aftermarket.

  Canon

• FD 28/3.5 (1971) - (6 elements in 6 groups); 6 aperture blades; 0.4m (16") min. focus; 55mm filters; 290 grams; chrome nose
• FD 28/3.5 S.C. (1973) - 250 grams; black nose; Spectra Coating
• FD 35/3.5 (1971) - (6e/6g); 0.4m (16") min. focus; 55mm filters; 325 grams; chrome nose; 6 aperture blades f/16 min.; 8 rows on waffle focus grip
• FD 35/3.5 S.C.(I) (1973) - 295 grams; black nose; 6 aperture blades f/16 min.; 7 rows waffle grip 
• FD 35/3.5 S.C.(II) (1975) - 236 grams; 5 aperture blades f/22 min.; 6 rows waffle grip
• FD 35/3.5 S.C.(III) (1977) - 5 rows waffle grip; otherwise identical to S.C.(II)
• FD 135/3.5 (1970) - (4e/3g); 8 aperture blades; 1.5m (60') min. focus; f/22 min. aperture; 55mm filters; 480 grams; chrome nose; 11 rows waffle grip
• FD 135/3.5 S.C.(I) (1973) - 465 grams; black nose; Spectra Coating; otherwise identical to 1970 version
• FD 135/3.5 S.C.(II) (1976) - (4e/4g) new optical design; 385 grams; 6 aperture blades; 19 rows waffle grip
• New FD 135/3.5 (1979) - (4e/4g) 325 grams; 1.3m (52") min. focus; 6 aperture blades & f/32 min. aperture; 52mm filters; 13 rows waffle grip

   Minolta

• Auto W.Rokkor-SG 28/3.5 (AR II; 1963) - (7e/7g); 6 aperture blades; f/16 min.; 0.6m (24") min. focus; flat knurled metal focusing grip; black, fine-ribbed aperture ring; chrome knurled DOF stop-down lever; chrome nose; 67mm filters; 345 grams
• MC W.Rokkor-SG 28/3.5 (MC I; 1966) - re-styled; open-aperture metering; chrome aperture ring; 350 grams; re-styled DOF stop-down lever; no other changes from Auto Rokkor
• MC W.Rokkor-SG 28/3.5 (MC I; 1968) - downsized; 55mm filters; 245 grams; no other changes
• MC W.Rokkor-SG 28/3.5 (MC II; 1970) - re-styled; "hill and valley" scalloped metal focusing grip; no other changes
• MC W.Rokkor-SG 28/3.5 (MC(-X); 1973) - re-styled; rubber focusing grip w/ 3 waffle rows; black, coarse-knurled aperture ring; no other changes
• MC W.Rokkor 28/3.5 (1975) - new, improved optical design (5e/5g); 6 aperture blades f/16 min.; 0.3m (12") min. focus; 55mm filters; aluminum-on-brass focusing helicoid; 220 grams
• MD W.Rokkor 28/3.5 (MD I; 1977) - MD aperture assembly w/ minimum aperture f/22; aluminum-on-aluminum focusing helicoid; 55mm filters; 195 grams; same optics as previous MC Rokkor
• MD W.Rokkor 28/3.5 (MD II; 1978) - smallest version; 160 grams; 49mm filters; same optics as previous MC & MD Rokkors
• New MD 28/3.5 (MD III; 1981) - MD lock added; New MD styling; 170 grams; same optics as previous versions
• MC Tele Rokkor-QD 135/3.5 (MC I; 1966) - (4e/4g); 6 aperture blades f/22 min.; 1.5m (60") min. focus; 55mm filters; flat knurled metal grip; chrome aperture ring; 370 grams; push-button DOF preview button on aperture ring
• MC Tele Rokkor-QD (MC II; 1969) - "hill and valley" scalloped metal grip; simplified DOF scale; DOF preview button moved to lens barrel; chrome nose; no other changes
• MC Tele Rokkor(-X) QD 135/3.5 (MC(-X); 1973) - re-styled; rubber focusing grip w/ 10 waffle rows; black, coarse-knurled aperture ring; DOF button eliminated late in production (around serial # 165xxxx); 415 grams
• MC Tele Rokkor(-X) 135/3.5 (MC(-X); 1976) - QD-code dropped late in production; built-in sliding lens hood; 7 rows waffle grip; 420 grams
• MD Tele Rokkor(-X) 135/3.5 (MD I; 1977) - identical to last MC-X Rokkor except for MD aperture assembly and aperture ring with MD tab for Shutter-Priority function with XD bodies; 6 waffle rows grip
• MD Tele Rokkor 135/3.5 (MD II; 1978) - identical to MD I except for 55mm filter size now imprinted on front trim ring
• MD Tele Rokkor 135/3.5 (MD II; 1979) - (5e/5g new design); 6 aperture blades; f/22 min.; 1.5m (60") min. focus; 49mm filters; built-in sliding lens hood; sloped DOF scale; 265 grams
• New MD 135/3.5 (MD III; 1981) - added MD lock and New MD styling; otherwise identical to previous version; 285 grams
• Auto Tele Rokkor-QF 200/3.5 (AR I; 1960) - (6e/4e);  8 aperture blades; f/22 min.; 2m (78") min. focus; flat knurled metal focusing grip; black mid-barrel aperture ring w/ chrome DOF stop-down lever; 67mm filters; 755 grams
• Auto Tele Rokkor-QF 200/3.5 (AR II; 1963) - re-designed aperture assembly; black DOF stop-down lever; 765 grams
• MC Tele Rokkor-QF 200/3.5 (MC I; 1966) - (6e/4g); 6 aperture blades; f/32 min.; 2.5m (98") min. focus; flat knurled metal focusing grip; chrome mid-barrel aperture ring; 62mm filters 740 grams
• MC Tele Rokkor-QF 200/3.5 (MC II; 1970) - re-styled; "hill and valley" scalloped focusing grip; aperture ring now rear-mounted; improved optical performance over previous version, although layout was unchanged; chrome nose; 775 grams
• MC Tele Rokkor(-X) QF 200/3.5 (MC(-X); 1974) - re-styled; rubber focusing grip w/ 8 waffle rows; black, coarse-knurled aperture ring; improved optical performance over previous version although layout was unchanged; no other changes

  Nikon

• Nikkor-H Auto 2.8cm/3.5 (1960) - (6e/6g); 5 aperture blades; f/16 min.; 0.6m (24") min. focus; 52mm filters; 220 grams; chrome nose; fine-ribbed aperture ring; focus throw 190 degrees
• Nikkor-H Auto 28/3.5 (1968) - re-styled with black nose, scalloped aperture ring, slightly larger diameter; 215 grams; otherwise identical to previous version; very late-production changed to cross-point screws
• Nikkor-H.C. Auto 28/3.5 (1973) - multi coated; otherwise identical to previous version
• New Nikkor (K) 28/3.5 (1975) - rubber focusing grip; waffle pattern aperture grip; 0.3m (12") min focus; 7 aperture blades; f/22 min.; 230 grams
• AI Nikkor 28/3.5 (1977) - new optical design (still 6e/6g, though) and styling (slightly coarser rubber grip); AI (Automatic Aperture Indexing) tab on aperture ring; 4.5mm longer than previous version; focus throw 200 degrees; 235 grams; other specifications identical to previous version
• AI-s Nikkor 28/3.5 (1981) - AI-s allows for Program and Shutter-Priority on Nikon FG, FA, N2000 (F-301), and N2020 (F-501) bodies; re-styled from AI version (DOF scale moved to chrome grip ring); focus throw reduced to 90 degrees; 220 grams; otherwise identical to previous version
• Nikkor-Q Auto 13.5cm/3.5 (1959) - (4e/3g); 6 aperture blades; f/22 min; 1.5m (5') min. focus; 52mm filters; chrome nose; fine-ribbed aperture ring; focus throw 230 degrees; 370 grams
• Nikkor-Q Auto 135/3.5 (1969) - re-styled; same optics; 7 curved aperture blades; f/32 min.; scalloped aperture ring; focus throw 190 degrees; 460 grams
• Nikkor-Q.C. Auto 135/3.5 (1973) - multi coated; black nose; otherwise identical to previous version
• New Nikkor 135/3.5 (1975) - re-styled w/ rubber focusing grip and waffle pattern aperture grip; 455 grams; otherwise identical to previous version
• AI Nikkor 135/3.5 (1977) - (4e/4g); completely new design; AI tab on aperture ring; 7 aperture blades; 1.3m (52") min. focus; built-in sliding lens hood; focus throw 220 degrees; 400 grams
• AI-s Nikkor 135/3.5 (1981) - AI-s functionality & styling; focus throw 180 degrees; 420 grams; otherwise identical to AI version

  Olympus

• G.Zuiko AUTO-W 28/3.5 (1972) - (7e/7g); 6 aperture blades; f/16 min.; 0.3m (12") min. focus; 49mm filters; silver (early) & black nose (1979 & up) versions; single coated; 180 grams
• E.Zuiko AUTO-T 135mm f/3.5 (1972) - (5e/4g); 6 aperture blades; f/22 min.; 1.5m (58") min. focus; 49mm filters; silver (early) & black nose (1979 & up) versions; single coated; built-in sliding lens hood; 280 grams; at some point, several internal mechanical improvements were made according to parts lists, but no date or serial # indications were given
• Zuiko AUTO-T 135mm f/3.5 (1982) - (5e/4g) new mechanical design with same dimensions and 10 grams more weight; late version of the 135/3.5, dropping the "E." designation before Zuiko and adding "Japan" on the front trim ring 

  Pentax

• Super Takumar 24/3.5 (1967) - (9e/8g); 5 aperture blades; f/16 min.; 0.25m (10") min. focus; 58mm filters; 247 grams 
• Super-Multi-Coated Takumar 24/3.5 (1972) - multicoated; lug for open-aperture metering with Spotmatic F and ES (II) models; 243 grams; no other changes from previous version
• Super Takumar 28/3.5 (1962) - (7e/6g); 5 aperture blades; f/22 min.; 0.4m (16") min. focus; 58mm filters; fine-ribbed aperture ring; 260 grams
• Super Takumar 28/3.5 (1965) - f/16 min.; scalloped aperture ring; otherwise identical to previous version
• Super Takumar 28/3.5 (1966) - (new design 7e/7g); 49mm filters; 208 grams; other specifications identical to previous version
• Super-Multi-Coated Takumar 28/3.5 (1971) - multi coatings; lug for open-aperture metering with Spotmatic F and ES (II) models; 212 grams; otherwise identical to previous version
• SMC Pentax 28/3.5 (K-mount; 1976) - (new design 8e/7g); rubber focusing grip w/ 6 rows of lugs; 5 aperture blades; f/22 min.; 0.3m (12") min. focus; 52mm filters; 261 grams
• SMC Pentax-M 28/3.5 (1977) -  (new design 6e/6g); rubber focusing grip w/ 3 rows of lugs; 5 aperture blades; f/22 min.; 0.3m (12") min. focus; 49mm filters; 180 grams
• Auto Takumar 35/3.5 (1959) - (5e/4g); 5 aperture blades; semi-automatic aperture; f/22 min.; 0.45m min. focus; 46mm filters; 147 grams
• Super Takumar 35/3.5 (1962) -   fully automatic aperture actuation, fine-ribbed aperture ring; 49mm filters: 152 grams; otherwise identical specifications to previous version
• Super Takumar 35/3.5 (1964) - f/16 min.; scalloped aperture ring; no other changes from previous version
• Super Takumar 35/3.5 (1966) - distance scale now shows through a cut-out ("window") in the lens barrel; no other changes
• Super-Multi-Coated Takumar (1971) - multi coatings; lug for open-aperture metering with Spotmatic F and ES (II) models; 149 grams; no other changes
• SMC Pentax 35/3.5 (K-mount; 1975) - same optical formula as M42 lenses; f/22 min.; 0.3m (12") min. focus; rubber focusing grip w/ 3 rows of lugs; 161 grams
• Takumar 135/3.5 (1957) - (5e/4g); chrome forward-mounted aperture ring; 8 aperture blades; preset (manual) aperture; f/22 min.; 2m (78") min. focus; chrome DOF scale; 46mm filters; 300 grams
• Auto Takumar 135/3.5 (1959) - re-styled; black rear-mounted aperture ring with chrome stop-down lever; semi-automatic aperture; fine-ribbed aperture ring; 1.8m (72") min. focus; black DOF scale; 49mm filters; 317 grams
• Takumar 135/3.5 (1961) - re-styled black version of original Takumar 135/3.5; 1.5m (60") min. focus; 49mm filters; 315 grams
• Super Takumar 135/3.5 (1963) - final version with 5e/4g optical formula; 6 aperture blades; fully automatic aperture; fine-ribbed aperture ring; 350 grams
• Super Takumar 135/3.5 (1965) - (new design 4e/4g); 6 aperture blades; f/22 min.; 1.5m (60") min. focus; 49mm filters; scalloped aperture ring; 343 grams
• Super-Multi-Coated Takumar (1971) - multi coatings; lug for open-aperture metering with Spotmatic F and ES (II) models; 331 grams; otherwise identical to previous version
• SMC Pentax 135/3.5 (K-mount; 1975) - same optics as late-M42 135/3.5; f/32 min.; 52mm filters; rubber focusing grip w/ 16 rows of lugs; 365 grams
• SMC Pentax-M 135/3.5 (K-mount; 1977) - (new design 5e/5g); 8 aperture blades; f/32 min.; 1.5m (60") min. focus; rubber focusing grip w/ 10 rows of lugs; built-in sliding lens hood; 270 grams

  How to Choose??

​   So what are my reasons for choosing certain lenses over others in the above list? It comes down to my personal priorities (which may be far different from yours, and that's OK :-)). Please note that these factors are not independent of one another, they often converge and have to be considered in light of the others. These are listed in order of importance (for me) and are far from hard and fast, but you will notice some definite trends:

1. Overall Optical Performance - Most of the time, a newer optical design will offer some improvement over a previous version whether it be contrast, resolution, aberration corrections, or coatings (at least up to the late-'70s or so in the case of f/3.5s). Comparing performance (in real pictures first, then test charts if available) is my first step in this process. Sometimes an older version just "looks" better to me and that will trump "improved" optical design :-). Bear in mind that any particular copy of a lens could be de-centered or have some other problem that is not indicative of the general performance of that model. It may take a few tries to get a good one.
2. Minimum Focusing Distance - I usually opt for a version with the shortest MFD. This adds versatility and allows me to minimize the small DOF penalty (when I want to) of f/3.5 in many cases by letting me shorten the distance to my subject. 0.3m - 0.4m beats 0.6m for a wide angle in my books any day.
3. Weight vs. Build Quality & Compatibility - This one is almost always a compromise :-). 20 or 30 grams either way is not going to bother me much, so, all else being equal, I will opt for more BQ in such a case. But when we start talking 100 grams +, then I am often willing to pass up a bit of quality for the weight savings, which often is accompanied by improved optical performance (that newer design thing :-)). When there have been modifications to a lens mount, for whatever reason, sometimes that will impact your choices. (For instance, with S-M-C Pentax M42 lenses, the open-aperture metering lug will often physically prevent you from mounting the lens on other brands of M42 SLRs or adapters. If you only use Pentax M42 bodies this will be of no consequence and you can enjoy the benefits of their top-notch multi coatings. But if you use other M42 SLRs or adapters, you will be limited to the older Super Takumars from Pentax.) Also, while filter sizes aren't super-critical (there are always step-up rings), it is nice when you can keep a common filter size among your lens arsenal.
4. Lens Coatings - The heyday of the 3.5s coincided with the largest gains in lens coating technology. The jump from single (or double) to multi coatings was in full swing by the early- to mid-1970s and that is when the largest gains were made. Improvements in multi coatings (MCs) from that time forward were definite, but more incremental. About the only thing that will make me turn down better MCs is a big difference in Overall Optical Performance or Build Quality & Compatibility, which is pretty rare. Some f/3.5s never did receive multi coatings (such as the Canon 28 & 35/3.5s and the Olympus 28 & 135/3.5s), and thus make this a moot point. Using lens hoods is always a good idea, but is a necessity when using lenses with more basic coatings. 

    Let me give you a practical example of this decision-making process using the Minolta 28/3.5, of which there were 9 iterations. 

1. Overall Optical Performance - The 5-element version (1975 +) is optically superior to the previous 7-element, especially from f/3.5 - f/8. Two fewer elements reduced the number of air-to-glass surfaces by four, which, when coupled with improved multi coatings, increased contrast and improved flare & ghosting performance. Coma correction was also improved. Right there, I have eliminated 5 possible choices (the 7-element lenses). The 5-element lens would receive no further optical changes aside from coating improvements.
2. Minimum Focusing Distance - 7-element = 0.6m; 5-element = 0.3m. 'Nuff said :-).
3. Weight vs. Build Quality - Here comes the swing vote in this case. Of the four 5-element iterations, the first (MC Rokkor; 1975; 220 grams; 55mm filters) was the only one with an aluminum-on-brass focusing mechanism (smoother focusing and longer cycles between re-lubings). All succeeding versions went to aluminum-on-aluminum to save weight and cost along with thinner lens barrels. The MD-I (1977) dropped 25 grams while maintaining the same dimensions; the MD-II  (1978) slimmed down a further 35 grams and dropped to 49mm filters; the MD-III (1981) jumped back up 10 grams from the MD-II and added the MD lock. If you are an S-mode (XD) or P-mode (X-700) shooter, the MD lenses will be more suitable, due to their slightly faster-acting aperture mechanisms. For an Aperture-Priority or Manual shooter like myself, this isn't a big deal. My other Minolta lenses use 55mm filters so that knocks out the two latter MD versions, just for the sake of continuity. So that leaves me with the 25 gram difference and the focusing mechanisms of the MC and MD-I. I am a sucker for smoootthhh focusing ;-), so the MC wins by a nose. Topping it off is the MD-I's higher price in general (usually $10 or $15 more than the MC).
4. Lens Coatings - With Minolta, changes in lens coatings were not clearly delineated by iteration cycles. Improvements were introduced during production as they were discovered. In the case of the 28/3.5, to the best of my knowledge, there was no change in coatings from the MC (1975) to the MD-I (1977). And even if there were, the improvements generally from the last-gen MCs to the first and second gen-MDs were not earth-shattering. So there is not enough difference, in this case, to swing my vote back to the MD-I. But I would be plenty happy with one, just the same :-). 

  Wrap-Up

​    What you want (Baby it's got it)
    What you need (Do you know it's got it?)
    Ain't gonna cost you much money...
    All I'm askin' is for you is to give it a little respect (just a little bit)

    Take care, TCB ;-)  

  References:

    Canon FD Lenses @ https://global.canon/en/c-museum/
    Minolta Manual Lenses Index @ http://minolta.eazypix.de/lenses/index.html
    Nikon Lenses @ http://www.photosynthesis.co.nz/nikon/lenses.html
    Nikkor - The 1001 Nights #12 @ https://imaging.nikon.com/history/story/0012/
    Olympus Zuiko Lenses @ http://www.mir.com.my/rb/photography/hardwares/
    Pentax Lenses @ https://www.pentaxforums.com/lensreviews/