Lens adapters have transformed modern mirrorless cameras from systems with limited lens choices into universal optical platforms capable of accepting virtually every camera lens ever manufactured. For photographers and filmmakers who want to explore vintage glass, use legacy lenses from previous systems, or access optical designs no longer in production, the used adapter market on eBay offers extraordinary value.
This guide covers every major adapter combination, what to look for when buying adapters on eBay, active versus passive adapters, speed boosters, and the pitfalls to avoid.
How Lens Adapters Work
A lens adapter works by filling the space between a lens designed for one camera mount and a camera with a different mount. The critical measurement is the flange focal distance — the distance from the lens mount to the film or sensor plane. If a lens has a longer flange distance than the camera body, an adapter can fill the gap mechanically, allowing the lens to focus correctly including at infinity.
This is why mirrorless cameras are so much better for adapting lenses than DSLRs. Mirrorless cameras have very short flange distances — Sony E-mount is 18mm, Fujifilm X is 17.7mm, Canon RF is 20mm, Nikon Z is 16mm, Micro Four Thirds is 19.25mm. Almost every legacy lens has a longer flange distance than these, meaning adapters are purely mechanical with no optics required.
DSLRs, by contrast, have longer flange distances (Canon EF is 44mm, Nikon F is 46.5mm). Adapting lenses to DSLRs requires either accepting the loss of infinity focus or adding an optical corrector element — which degrades image quality.
Passive vs Active Adapters
A passive adapter is purely mechanical — it holds the lens at the correct distance from the sensor with no electronic communication between lens and camera. You lose autofocus (for AF lenses), image stabilisation control, EXIF data recording, and aperture control (for electronically controlled lenses). You gain: compatibility with any lens from the correct mount, low cost ($8-$25), and zero risk of electronic incompatibilities.
An active adapter adds electronic contacts that allow communication between lens and camera. Active adapters enable autofocus (on compatible lenses), EXIF data recording, aperture control from the camera body, and sometimes image stabilisation. They cost more ($80-$300) and vary significantly in quality and compatibility.
M42 Screwmount Adapters — The Most Versatile Option
M42 (42mm diameter screwmount) is the most prolific vintage lens mount in the world. Manufactured from the 1940s through the 1990s by Pentax, Carl Zeiss, Asahi Optical, Meyer-Optik, Cosina, and dozens of Soviet and Eastern European manufacturers, M42 lenses include some of the finest vintage glass available.
M42 adapters are available for every mirrorless mount:
- M42 to Sony E: $8-$15. The most popular combination — works with Helios, Super Takumar, Carl Zeiss Jena, and hundreds more.
- M42 to Fujifilm X: $10-$15. Equally popular among Fujifilm users.
- M42 to Canon RF: $12-$18. Works perfectly on Canon R system bodies.
- M42 to Nikon Z: $12-$18. Compatible with all Nikon Z bodies.
- M42 to Micro Four Thirds: $8-$14. Excellent for BMPCC 4K and Olympus/Panasonic bodies.
When buying M42 adapters on eBay, stick to brands with verified feedback: K&F Concept, Fotodiox, Kipon, Urth. Avoid unbranded adapters under $4 — poor tolerances can prevent infinity focus.
Canon EF to Sony E — The Most Popular Active Adapter
Adapting Canon EF lenses to Sony E-mount is the most popular active adapter combination in photography, driven by the millions of Canon EF lenses in circulation and the popularity of Sony's A7 series. Two options dominate the used eBay market:
Sigma MC-11: The most reliable active EF-to-E adapter. Supports autofocus, EXIF data, and image stabilisation on compatible Canon and Sigma EF lenses. Works best with Sigma Art, Sports, and Contemporary lenses. Limited compatibility with some Canon L-series lenses. Used price on eBay: $120-$180.
Metabones EF-to-E Smart Adapter: Better Canon EF lens compatibility than the MC-11, particularly with Canon L-series lenses. Supports phase-detect autofocus on compatible combinations. Used price: $180-$280 depending on version (IV or V).
For vintage Canon FD lenses (not EF — FD is the breech-lock mount used before 1987), you need a passive FD-to-E adapter ($12-$18). Canon FD lenses do not communicate electronically and require manual aperture setting.
Nikon F to Sony E Adapters
Nikon F has one of the finest lens heritages in photography — from the original Nikkor AI lenses of the 1970s to the current AF-S generation. Adapting F-mount lenses to Sony E opens up decades of excellent glass.
Passive Nikon F to Sony E: $10-$22. Aperture is set by the ring on the lens itself. Works perfectly for manual focus Nikkor AI/AIS lenses. No AF or EXIF data.
Fotodiox Pro Nikon G to Sony E: $25-$40. Adds an aperture control ring for use with modern Nikon G lenses (which have no aperture ring). Manual focus only but allows aperture control for G-mount lenses.
Commlite Nikon F to Sony E AF adapter: $80-$130. Enables autofocus with compatible Nikon AF-S lenses on Sony bodies. AF performance is acceptable but not fast enough for moving subjects.
Speed Boosters — Using Full-Frame Glass on Crop Cameras
A Speed Booster (also called a focal reducer) is an active adapter with an optical element that reduces the focal length by a factor of 0.64x or 0.71x while increasing the maximum aperture by approximately one stop. A 50mm f/1.4 lens becomes a 32mm f/1.0 on a 0.64x Speed Booster. A 85mm f/1.8 becomes a 54mm f/1.2.
For BMPCC 4K users (MFT sensor, 1.9x crop factor), a Metabones Speed Booster Ultra 0.64x (Canon EF to MFT) effectively gives near-full-frame field of view from EF glass. A 24mm f/1.4 lens becomes equivalent to approximately 29mm f/0.9 — genuinely outstanding performance.
Used Metabones Speed Boosters on eBay: $250-$400 for the Ultra version. Viltrox Speed Boosters are a more affordable alternative at $100-$180 used, with slightly less autofocus reliability.
What to Look for When Buying Adapters on eBay
Electrical contacts on active adapters should be clean and undamaged. Even slight corrosion or physical damage to contacts can cause intermittent communication failures. Ask the seller for a close-up image of the contacts.
Mount tolerances matter more than most buyers realise. A poorly machined adapter can cause a lens to sit slightly off-axis, resulting in one corner of the frame being sharper than the other. This is very difficult to detect from listing photos — buy from sellers with strong feedback and good return policies.
For passive adapters: confirm the adapter allows infinity focus with the lens you intend to use. Some cheaper adapters are slightly too thick, preventing infinity focus. Most reputable adapters include a small adjustment ring to calibrate infinity focus.