Upload & Sell: Off
I noticed this post by AhamB suggesting that we need some alt lens "sticky" posts to answer common questions. That seems like a good idea to me, but since no one else has posted one yet, here is my attempt at a FAQ outline mainly focused on alt lens usage on DSLRs. Please post your comments/criticisms/suggestions below, and I will attempt to edit/revise this post to incorporate them. Each item in this FAQ could be (and often has been) the topic of a long and complex thread; however, for an introductory FAQ, one needs to balance the merits of brevity against encyclopedic completeness; please keep this in mind when complaining about whatever fine details and unusual exceptions I have left out. Links that I can include to other informative threads on the alt lenses board to better describe the details would probably be most useful. Apologies in advance for typos, inconsistencies, and major missing sections. Perhaps if we can collectively edit this into a sufficiently useful and informative post, it can get "stickied" by some higher power on the board and save several of us the time of re-typing these answers every few weeks.
Alt Lens DSLR FAQ
This FAQ is meant to address common questions and issues about using "alt lenses" on DSLRs.
What are "alt lenses"?
"Alt lenses" mean alternatives to the major Original Equipment Manufacturers' ("OEMs", e.g. Canon, Nikon, Sony Alpha) current lens lineups. This can range from third-party autofocus zooms to pinhole cameras. Most of the activity here on the alt lens board revolves around manual focus lenses, many from older and discontinued lens lines, but also a few new manual-focus designs (from, e.g., Zeiss, Cosina/Voigtlander, and Samyang). Even new Nikon lenses can be considered "alt" if used on Canon bodies.
Why use an alt lens?
Alt lenses greatly expand the range of photographic possibilities beyond what the OEMs offer in their own lens lineups. Alt lenses can be less expensive, offer better image quality, or produce images with a unique rendering character that OEM lenses do not. Manual focus lenses are often smaller and lighter than their OEM autofocus counterparts. Some people are also attracted to the history and fine craftsmanship embodied in classic lenses, or like the precise control and smooth handling of a manual-focus-specific lens.
How do I use an alt lens?
For third-party autofocus lenses, operation is identical to native mount lenses. You will likely find more discussion of these lenses on the appropriate Canon/Nikon gear boards.
The "alt" lenses mostly discussed here are manual focus lenses, so you will need to focus the lens by hand. See the sections below on chipped adapters and focusing issues for more discussion. Some currently produced lenses have the electronic contacts needed to allow the camera to automatically control the aperture of the lens (e.g. Zeiss ZE/ZF/ZA lenses for Canon/Nikon/Sony Alpha, or Cosina/Voigtlander SLI/II lenses), so aperture and exposure setting works just like the OEM lenses.
However, many alt lenses require manual operation of the aperture by turning the aperture ring on the lens to the appropriate aperture before hitting the shutter button. The camera metering system also doesn't know what aperture you are using, so you either need to meter once the lens is already stopped down to the intended working aperture, or correct in your head for the correct metering. An easy way to get fairly-automatic metering is to use "aperture priority" metering mode on your camera, where you choose the aperture on the lens and the camera chooses the appropriate shutter speed for the scene right before taking the picture.
What alt lenses can I use on my camera?
A few current alt-lens manufacturers, such as Zeiss, Voigtlander, and Samyang, offer lenses that can be directly attached to popular Nikon/Canon/Sony Alpha/Pentax/etc DSLRs with no additional work. However, many lenses originally designed for other camera mounts may also be usable on your DSLR with minor (or major) additions or alterations.
The most important factor in determining whether you can use a lens on your camera is the "register distance," the distance between the lens mount and the film or sensor plane for the lens' native mount. You can find a fairly comprehensive list of mount register distances here; some of the interesting ones are:
- Leica M (rangefinder): 27.95mm
- Canon FD: 42mm
- Minolta MD: 43.72mm
- Canon EF (EOS): 44mm
- Sigma SA 44mm
- Sony Alpha: 44.6mm
- M42 (Pentax Screwmount): 45.46mm
- Pentax K: 45.46mm
- Contax/Yashica (CY): 45.5mm
- Olympus OM: 46mm
- Nikon F : 46.5mm
- Leica R (SLR): 47mm
- Contax N: 48mm
- Mamiya 645: 63.3mm
This sampling explains the popularity of Canon EOS cameras (and the emerging popularity of Sony Alpha) with many alt lens users; with one of the shorter register distances, every mount after Canon EOS on the list can be easily adapted.
Actually that's only part of the reason...The Canon EF mount shares the same short and versatile registration distance as the Sigma SA mount but the EF mount is larger in diameter, allowing a greater range of lenses to be used.
For instance, most Canon EF lenses can be converted to SA mount whilst retaining their AA and AF functions (not their IS function though) but the rear element of the Canon EF 85mm f1.2L is actually larger in diameter than the bore diameter of the SA mount, making it impossible to convert it for use on the SA mount.
However, the older FD-L versions can be converted to SA mount as they have smaller rear elements.
In general though, after the Canon EF mount, the SA mount can take a greater range of lenses than Pentax mount SLR's and DSLR's and even more than the second most popular SLR/DSLR mount out there, the Nikon F mount.