What a bias A7/r review using third party lens!

Started Jan 21, 2014 | Discussions thread
ProfHankD Veteran Member • Posts: 6,163
On the "best" lens choices, old and new

DT200 wrote:

ProfHankD wrote:

...there are plenty of situations where one of my old manuals is a way better answer than any autofocus lens.

Which of YOUR old manual focus lenses is "WAY BETTER" than ANY autofocus lens? Which situations are you talking about?

Your tone is pretty obnoxious, but let's ignore that and give you a serious, detailed, answer. After all, I'm a Professor, and you just invited me to teach.

Let's start with the basics. Over the past five years, I've personally collected more than 130 lenses primarily for my computational photography research. I've made a lot of technical measurements on them, especially OOF PSF (out-of-focus point spread functions), which I've been publishing on. The latest is a paper at IS&T SPIE Electronic Imaging that I'll be presenting Feb. 4, 2014. I feel pretty safe saying I know a bit about old lenses.

Let's start with some general observations about old and new lenses:

  1. Lens coatings have steadily gotten better over time. This improves microcontrast and, most importantly, allows way more elements before contrast dies. Typically, 1970s coatings with 5-6 elements can barely match the contrast of modern lenses with 10 elements. Then again, modern lenses tend to have more elements. Does higher contrast mean the lens is better? Traditionally, yes. However, film and eyes are log sensitive, but sensors in digital cameras are linear, so lower contrast actually can be fixed with little ill effect and an effective (minor) improvement in dynamic range! In short, we'll say modern lenses do better in this respect.
  2. Computer design of lenses is now common, and it certainly helps solve complex optical problems. Extreme retrofocus wides and zooms are the primary beneficiaries. Simpler optical problems, like normal and moderate telephoto lenses, have such good simple solutions that they are hard to improve upon -- and haven't changed much for a lot longer than I've been on this Earth. New lenses can solve optical problems old ones couldn't, but often get beaten by old designs on easy problems. Modern design accounts for manufacturing tolerance ranges, often yielding lenses that are easier to build at the expense of sacrificing some IQ, while older lens designs often counted on more expensive, individual, adjustments.
  3. Most modern autofocus lenses have measurable decentering while most old manual lenses don't. The need to reduce friction and moving mass for wimpy focus motors is the primary cause, and it's pretty unavoidable physics. Incidentally, this also means that old manual lenses often have much higher resolution than modern lenses, although with low contrast -- whereas autofocus lenses often don't resolve much finer as you drop the MTF contrast threshold because resolution is limited by mechanical misalignment. Overall, non-autofocus lenses tend to win big, even if they were made half a century ago.
  4. Old lenses used to employ various heavy metals to make glass that allowed simple, small, designs to be well corrected. These unfortunately trace-radioactive additives are no longer allowed to be used in making new lenses. There are other additives, but cheap (typically molded) aspherical elements appear to have become the primary tool for correcting lens aberrations. Unfortunately, aspheric elements emphasize decentering, and the molded ones also have minor surface imperfections that show up clearly in OOF PSFs. This is honestly not a big win for either old or new lenses.
  5. Old lenses cost less and hence, giving similar optical performance, win big on price/performance.

So, for example, expecting an old 17mm Vivitar ultrawide to do really well is kinda nuts. On the other hand, I've got about 20 "fast 50s" that are beaten by or beat modern versions depending on which metrics you weight most. I've also got some short telephotos that would be hard to beat with modern lenses costing more than 40X as much. 40X. That's a pretty obvious price/performance difference. It also means I can afford to have specialty lenses that I could never afford as new lenses.  

The "best in class" (by APS-C IQ) lenses I have are a mix of old and new:

  • Canon FD 24mm f/2.8 S.S.C.
  • Minolta MC W Rokkor Si 28mm f/2.5
  • Auto Mamiya/Sekor 55mm f/1.4
  • Samyang / Opteka 85mm f/1.4 Aspherical IF
  • Tamron SP 52B 90mm f/2.5
  • Spiratone 135mm f/1.8 (especially on a Lens Turbo)
  • Sigma 8-16mm f/4.5-5.6 DC HSM (my most expensive & "touchy" lens)
  • Sigma 10-20mm f/4-5.6 EX DC (I should update my list, because 8-16 easily took this crown)
  • Vivitar Series 1 Q-DOS 70-210mm f/2.8-4.0 (great, but terrible in Q-DOS mode)

Keep in mind I'm talking about my copies and "best" is an ill-defined weighted mix of various metrics (resolution, contrast, bokeh, color, aberrations, etc.) -- so don't think I'm telling you to run out and get the above lenses in particular, because your mileage will vary.

Note that only 2 of those are AF lenses, and both have AF issues -- in fact, I always use the 8-16mm in manual focus mode. AF is easily fooled because DoF makes everything almost in focus, but manually I can nail it.

With peaking for manual lenses, I find that I'm consistently able to focus on precisely what I care about faster than using AF lenses. I'll admit that it is a pain to manually focus really fast for an extended shooting period -- it also requires practice to quickly interpolate the precise focus depth within a peaked region. With eye to an EVF (or OVF), it's too darn slow to tell the AF where I want to focus. Note also that my focus choice is often about positioning DoF, which means I often prefer composing at the taking aperture with an EVF that shows DoF (and peaking helps this!) -- the natural mode for use of manual lenses, and literally not possible with PDAF.

In addition to the above stand outs, there are lots of old manual lenses that are excellent -- my S-M-C Takumar 35mm f/2, Canon FL 55mm f/1.2, Minolta MD Macro Rokkor-X 100mm f/4, etc. There are even some excellent old AF lenses like the Minolta AF 70-210mm f/4 "beercan" (although that's really better on the A7 than on an APS-C sensor).

I'm not saying old lenses are the best for everything. There are more than a few times (e.g., shooting one-handed on a family outing in a theme park) when the kit zoom is honestly darn appealing... and IQ of the kit zooms is actually decent stopped down.

 ProfHankD's gear list:ProfHankD's gear list
Canon PowerShot SX530 Olympus TG-860 Sony Alpha a7R II Canon EOS 5D Mark IV Sony a6500 +30 more
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