Will adapting a lens crop my image?
Not inherently. Cropping occurs based on the sensor size of your camera body versus the image circle the lens was designed to project. A full-frame vintage lens adapted to an APS-C sensor will be cropped, but adapting to a full-frame sensor will retain the original field of view.
Do I lose autofocus when adapting?
If you are adapting vintage manual-focus lenses, yes, you must focus manually. However, modern "smart adapters" can translate autofocus signals between different modern electronic mounts (e.g., Canon EF to Sony E), retaining AF functionality.
Why does my adapted lens not focus to infinity?
This is usually due to poor manufacturing tolerances on cheap adapters. If the adapter is machined even a fraction of a millimeter too thick, the lens sits too far from the sensor, shifting the focal plane closer and destroying infinity focus.
What is a focal reducer or 'Speed Booster'?
It is a specialized adapter containing a condensing optical element. It takes the image circle designed for full-frame and shrinks it down to fit a smaller sensor (like APS-C or Micro Four Thirds). This restores the original field of view and concentrates the light, effectively making the lens a stop faster.
Can I adapt rangefinder lenses (Leica M) to a DSLR?
No. Rangefinder lenses sit very close to the film plane (short flange distance). DSLRs have deep mirror boxes. A rangefinder lens would physically hit the mirror before it ever achieved focus.
Is it safe to mount heavy vintage lenses on modern bodies?
Generally yes, but use caution. Very heavy brass lenses can place undue stress on the thin metal mounts of modern lightweight cameras. For large telephoto lenses, always support the lens with your hand or use a tripod collar attached to the lens/adapter, not the camera body.
How do I control the aperture on adapted lenses?
Most vintage lenses have manual aperture rings right on the lens barrel. You control the iris manually. For modern electronic lenses adapted to different systems, you must use a smart adapter with electronic contacts, otherwise, the lens will be stuck wide open (or fully closed).
What is 'focus peaking'?
It is a software feature on mirrorless cameras that highlights edges of maximum contrast in the viewfinder, usually in red or yellow. It makes manually focusing vintage adapted glass incredibly fast and accurate compared to old optical split-prisms.