Over the years I've acquired various lenses in the 50-60 millimeter focal length, something I find funny because 50mm has never been my favorite focal length. With a crop sensor camera, I use the 50mm focal length more then I would on a full frame camera. With the crop sensor utilizing only the central portion of a full frame sensor, the nifty fifty gives the equivalent field of view that a 75mm lens would on a full frame camera. The 50 becomes very usable for upper body shots that I previously would have used an 85mm to shoot on a full frame camera. The thing to remember is that 50 millimeters is still 50 millimeters, just because the field of view has changed by using a crop sensor camera does NOT mean that the subject isolation that occurs with an 50mm lens has changed. If you want true subject isolation and "lens compression" then a true 85mm lens (or longer) is needed.
Lens compression may provide a more pleasing perspective, but bokah is what helps provide the subject isolation from the background. Having ready access to various lenses that provide a 50mm focal length, I wanted to test them and see how they compared to each other. I was particularly interested in how older lenses would compare to more modern lenses. Modern day lenses tend to be more highly corrected for corner to corner sharpness and low chromatic aberration. Modern lenses have better coatings to reduce internal reflections and flare. Modern lenses tend to have higher element counts. If a lens designer held the diameter of the glass constant, high element count lenses would be slower (their lowest aperture would be higher then a low element count lens). This is because every piece of glass you put in front of the light reduces the amount of light that passes through. To get more light through, the designers need to increase the diameter of the glass. So if we hold the sensor size/format constant, then two things influence a lenses' physical size, the lowest aperture and the number of elements. That's why a low aperture lens (for a given format) will be bigger/fatter then a high aperture lens.
So why be interested in old lenses? Physical size is one reason, modern high element count lenses tend to be larger and heavier then their predecessors. Hauling around four or five 800 gram lenses in a camera bag all day can leave a photographer with a sore shoulder. Cost is another reason, old lenses can be purchased for pennies on the dollar compared to new lenses. Most important, with every piece of glass you put in a lens (high element count) you reduce the ability of the lens to transmit minute differences in color and shading (rendition).
On the opposite side to the scale, new lenses can have incredible sharpness, weather sealing, automatic aperture, and auto focus. Auto focus is particularly important on modern DSLRs because modern DSLRs lack the focusing aids of yesteryear. When manual focus lenses reigned supreme, all cameras had special focusing aids in the viewfinder - microprism or split prism focusing screens. Those aids enabled the image to "pop" into focus in the viewfinder, helping the user focus. There are a few companies that sell focusing screens that can replace the screen in a modern DSLR with focuing screens designed to work with manual focus lenses. If you want to easily use manual focus lenses on your DSLR, I highly recommend you replace the focusing screen. Mirrorless cameras, however, work exceptionally well with manual focus lenses. Most mirrorless cameras have various focus aids built in that make manual focusing a lens (old or new) a joy. Focus peaking, digital split image, and magnification are all typical focus aids for mirrorless users.
Why do the testing? Basically, I wanted to see how the old lenses "stacked up" against new, state of the art, lenses. How was the sharpness, the bokah, the contrast, and the color transmission. I did not test for flare, but probably will in the future. I used all the lenses I could scrounge up that covered the 50 to 60 millimeter range. And because that range on a crop sensor gives an 85mm equivalent field of view, I also tested an 85mm with a Mitakon Lens Turbo II focal reducer. Without getting too deep down the rabbit hole, a focal reducer works like a tele-converter in reverse. In this case, the Turbo II reduces the full frame image circle of the Nikkor lenses and reduces by approximately .73 down to an APS-C image circle. Additionally, while focal reduction has the effect of reducing the image circle, it also concentrates the amount of light, effectively gaining almost a stop of light. It performs this magic through the addition of four elements to the optical path.
Methodology. I used an Fujifilm XT-2 camera. At the time of writing, the XT-2 is the highest resolution (24MP) APS-C camera made by Fujifilm. In no way, shape, or form is this super accurate testing. There are no lens resolution test charts, no brick walls, nothing like that. Just my spouse (semi tolerant), some lights behind her to create bokah, and a flash in front of her. Images were imported into Lightroom for cropping and exported. No other correction was done.
The slowest lenses tested have an aperture of F/2.8, and since no lens is at it's best wide open, I also tested at F/4.0. Lenses that are faster were also tested at lower F stops so the shape of the bokah was viewed. Some tested lenses have as few as seven aperture blades, nine was common, one has 12 blades. The 12 bladed aperture provided beautiful round bokah at all settings.
|Description||Aperture Blades||No. Elements|
|Fujifilm XF16-55mm F/2.8 R LM WR at 55mm||9 (rounded)||17|
|Fujifilm XF50-140mm F/2.8 R LM OIS WR at 50mm||7 (rounded)||23|
|Fujifilm XF56mm F/1.2 R||7 (rounded)||11|
|Fujifilm XF60mm F/2.5 R Macro||9 (rounded)||10|
|Helios 44-2 58mm F/2||8 (rounded)||6|
|Nikkor 50mm F/1.4 (pre AI)||7||7|
|Nikkor 50mm F/1.4 (pre AI) Turbo II - Effective F/1.0||7||7+4|
|Nikkor 55mm F/2.8 Micro (pre AI)||7||6|
|Nikkor 85mm F/1.8D||9||6|
|Nikkor 85mm F/1.8D Turbo II - Effective F/1.3||9||6+4|
|Zeiss Jena Tessar 50mm F/2.8||12 (rounded)||4|
The first group of images are all shown at F/2.8 to make it easy to compare them directly.
Fujifilm XF16-55mm F/2.8 R LM WR 55mm at F/2.8
Fujifilm XF50-140mm F/2.8 R LM OIS WR 50mm at F/2.8
Fujifilm XF56mm F/1.2 R at f/2.8
Fujifilm XF60mm F/2.5 R Macro at f/2.8
Helios 44-2 58mm f/2 at f/2.8
Nikkor 50mm F/1.4 (pre AI) at F/2.8
Nikkor 50mm F/1.4 (pre AI) Turbo II at F/2.8 - effective F/2.0
Nikkor 55mm F/2.8 Micro (pre AI) at F/2.8
Nikkor 85mm F/1.8D at F/2.8 (FF equiv. field of view - 127mm)
Nikkor 85mm F/1.8D Turbo II at F/2.8 - effective F/2.0
Zeiss Jena Tessar 50mm F/2.8 at F/2.8
Initial conclusions: The aperture blades on the older Nikkor lenses makes for strongly shaped polygonal bokah. Additionally, the aperture blades on the Nikkor 50/1.4 don't fully engage leaving some nasty "hooks" at the corners of the polygon bokah - although that is not typically visible. The Jena appears to be a little soft at F/2.8 (wide open) although it may be reduced contrast making it look soft; for portraiture, that actually may be a good thing. Certainly, for online use, the Jena is more then good enough. The Jena also shows some oblong shaped bokah, indicating some uncorrected aberrations towards the corners; it's not bad for a lens design that goes back to 1902. Additionally, the Jena is easily the smallest 50mm I have ever seen, weighing just 115 grams.
The Helios seems to be a nice performing lens, although physically, I did not like working with its aperture ring. The ring is stepless with a separate locking ring that controls the minimum aperture - lets just say that it's inconvenient to use.
The Nikkor 50/1.4 at F/2.8 is still short on contrast compared to more modern lenses. At F/2.8, the Nikkor 50/1.4 falls behind the Micro Nikkor 55/2.8 in sharpness and contrast.