There's a lot to like about brand new lenses that exist within a brand's overall system. They interface well with cameras, provide full exposure automation and are the most effective companion to the cameras when it comes to autofocus. In fact, if you demand AF and don't want to become a photographer who is okay with manually setting stuff then you can just ignore any further advice and get back to taking photographs. Especially so if you have an older camera that depends on image stabilization in the lens to offset your jittering hands.
As a group photographers have a tendency to think that newer lenses are so powerfully blessed by cutting edge computer design of optics that there is no contest between their imaging power and that of older lenses and, especially better than lenses that were designed before digital. But there is a flip side to just about everything and that includes lenses.
First off, you can find a wide range of lenses from a deep pool of lens makers in the used lens market which may deliver the same basic imaging performance as the newest lenses. You can pick up a decent condition 50mm f1.4 that was designed for a Contax Y/C camera for around $300 or a 50mm f1.4 Canon FD lens that was designed for their F-1 system for around $190. Current AF 50mm f1.4 lenses designed for various camera systems can range from $600 up to a nosebleedy $6,000 if you want a brand new lens that matches the camera body from your favorite maker. If you are a "found object" or "street photographer" you may actually find one of the older, manual focus, lenses almost as easy to use as one of the "cutting edge" lenses; especially when mated to a mirrorless camera that allows you to "punch in" or magnify your image in the finder or back screen to assist you in really homing in on the sharpest point of focus.
There's no question that if you are looking for the highest possible optical performance you're probably going to find it in the premium lines of current lenses. But at the same time there will also be a certain sameness to those lenses as makers pursue the same kinds of complex optical designs to achieve both high sharpness and a flatness of field across the frame. While objective measurements may indicate that a high end, new lens "outperforms" an older lens the evaluations rarely take into account the "personality" of a lens. And most reviews don't take into account how an artist might want the final image to look. Not everyone prizes absolute sharpness and high resolution over all other characteristics.
Here is something else to consider... many lens makers and, by extension, camera makers have discovered that they can aim to correct various parameters of a lens but can't correct everything. There are tradeoffs in every direction, including price, field curvature (a bane of fast wide angle lenses) and vignetting. As the designers struggle to get sharpness all the way to the corners of a new lens they sacrifice when it comes to the amount of vignetting which occurs as a result. There are other issues with incredibly complex designs that might also include zones of lower sharpness occurring in areas of a frame. Think in concentric circles from the center to the edges. A design might attempt to maximize center and corner sharpness but that design might have consequences for sharpness in one of the intermediate "circles."
Contemporary lens makers assume that certain negative properties can be mitigated by writing some code that "corrects" for a lens fault that would be harder or more expensive to correct via pure optics. Vignetting is a good example. The current crush of reviewers is the "new" Sigma 35mm f1.4 DG DN Art lens. Without any in-camera correction it has monstrous vignetting. According to most folks pulling up over two stops of underexposure in the corners of the frame is nearly invisible but.....it's not. Especially with cameras that are using older sensors. I'm not talking about super old sensors but even just the sensors from a couple of years ago. An exposure increase of two stops brings with it increased noise and the possibility of banding interfaces which gets worse as the ISO performance of the sensor is worse.
Another interesting difference between current lenses and much older legacy lenses is in the complexity of construction. A simple, manually focused lens basically has a stop down function for the aperture and a helicoid for focusing. That's it unless it also moves an element independantly as the lens is focused (floating element or, in Nikon-Speak: CRC). That's it. Not a lot to go wrong.
Not so with newer lenses with AF motors and linkages, I.S. actuators and circuitry, and more complex lens designs which are sometimes held in place with....tape.
But for me, the reasons to adapt older, manual focus lenses to newer, mirrorless cameras are: The older lenses are usually more compact which makes them more discreet and physically manageable. The older lenses are much, much easier to zone focus for quick work. The cost to performance ratio, optically, is tilted more toward the older lenses as most of them are very, very good when used where we use them the most: at middle distance and at middle apertures.
I posted an image above that was taken with a 28mm f2.8 Contax Y/C lens made in the late 1980's or early 1990s. I was able to magnify the image by 8X or 12X in the finder of a Leica SL to ensure crisp focusing. The frame was shot at f8.0 which, on a sunny day, is a normal exposure setting for a wide angle lens like this. When the frame is enlarged to 100% it's obvious that it is critically sharp even into the corners and, unlike a new lens, doesn't require camera profiles to make it whole.
Sure, there are arguments to be made to the contrary if you use your fast lenses mostly at their widest apertures or, if you need to work with wider angle lenses that may need more consideration for the telecentric requirements of modern sensors. Many older super wide lenses, designed solely for film cameras, have issues with coloration deviances across the frames. But, if you are looking for lenses in the normal focal length ranges and, especially, in the short telephoto range, these issues rarely intrude.
The biggest argument though is one that is also made by many film and video makers who understand that every generation and line of lenses has its own "look" and having a differentiated approach to making photographs or movies is part of our core selection of choices as artists.
My 90mm Leica Elmarit f2.8 lens has a completely different overall look than my much, much newer Sigma 85mm f1.4 Art lens. Not better or worse (unless all your measurements are scientifically objective) but different. It's all about having the look that resonates with a particular user. Using an older lens with good "faults" goes a long way to prevent a cookie cutter approach to being a photographer.
Here's an image of the 28mm lens adapted to a Leica camera with a $20 adapter. It's my favorite wide angle set up.
It's good to see different. It's good to shoot different. Otherwise? Robots....
