The Truth about 50mm Lenses

I have been reading a lot of articles and blog posts lately about the benefits of the venerable 50mm lens.  There is no doubt in my mind that 50mm lenses are great and useful lenses. There is however, some confusion in my mind as to exactly what lenses these writers are talking about.

When we talk about a 50mm lens we generally refer to the focal length of the lens. In the days of film cameras when the overwhelming majority of interchangeable lens cameras were 35mm SLR’s (Single Lens Reflex) or rangefinders there was no issue. Everyone knew exactly what a 50mm lens was.  These were the lenses that came with cameras and were sometimes called “normal lenses.” The 50mm focal length actually provided just a slight bit of magnification so it was good for portraits but still had a sufficiently wide enough angle to allow for snap shots or street photography. These lenses were also some of the fastest lenses available, meaning they had a large (fast) aperture that was suitable for taking pictures with available light rather than requiring a flash, even indoors or in low light situations.

In the digital age when the vast majority of folks are using a DSLR (Digital Single Lens Reflex) or MILC (Mirrorless Interchangeable Lens Camera) camera with an APS-C type sensor things are a bit more complicated.  In these cameras the 35mm negative has been replaced by the APS-C sensor which is only about 22mm rather than 35mm. Therefore the “normal lens” or what is sometimes referred to a 50mm equivalent lens for a camera with an APS-C sensor would actually be a 35mm lens. Likewise an actual 50mm lens would be a short telephoto lens offering the 35mm camera equivalent of a 75mm lens. This is based on the generally accepted crop factor of 1.5 for these cameras.

Are you sufficiently confused yet?

The bottom line is that there are definite advantages to any of the possible 50mm lenses available for use on either kind of camera. I just wish these writers would be more specific about which one they are talking about.

In the case of the new “DX” (or cropped frame) lenses which are 50mm equivalent (actually 35mm) lenses designed specifically for the APS-C DSLR’s and MILC’s we have fast and great general purpose lenses with all the advantages of the old 50mm lenses that were provided with most 35mm film cameras. If there is a down side to these lenses it is that they are usually a little pricy, costing more than the zooms generally provided as “kit lenses” with the DSLR’s and MILC’s, whereas the original 50mm lenses provided with the old film cameras were comparatively inexpensive, probably due to the huge quantities manufactured at the time.

In the case of “FX” (or full frame) lenses which are 50mm lenses designed specifically for today’s full frame (35mm sensor) digital cameras, everything I said above holds true except they are even more expensive, but then so are the cameras. These are generally professional level cameras and lenses costing thousands of dollars. I suppose if you are willing to spend that much on a camera then you can certainly justify buying lenses to go with it.

There is of course third possibility which is the most exciting for me. Full frame (35mm) legacy lenses designed originally for use on 35mm cameras offer an inexpensive alternative for modern DSLR’s and MILC’s. A few of these lenses are still sold new for DSLR’s but most are available on the used market. It is common to find 50mm, f1.8 lenses in most mountings for $100 or less. There are a couple things to certain of before you rush out and buy one of these great lenses though.

First, will your camera accept and work with these older legacy lenses which are usually manual lenses. This means that the camera and lens must have the same mounting flange type or an adapter must be used. The camera will also have to have a manual setting and function properly with such a lens. Most modern DSLR’s will allow you to manually focus a lens but not all of them will a work correctly with a lens that requires the aperture to be set manually too.

Second, you must decide whether you are up to shooting in manual mode and manually focusing the lens. It’s not difficult. Many photographers prefer to shoot on manual and some of us are old enough to have grown up without the option but if your camera is always set on Auto and you have never tried to focus manually before you should try it first (shooting with everything on manual) before deciding to invest in a manual lens.

Finally, you should realize that if you do decide to buy one of these high quality 50mm legacy lens for your DSLR or MILC camera what you will have bought is an extremely fast, short telephoto lens which is great for portraits and any similar kind of photo best taken at short distances.