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Module 1 · Know Your Camera

Changing lenses

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Start · Module 1Topic · 5 min

Changing lenses

Lesson 8 of 12

MODULE 1 ROADMAP

  1. 1How a camera works
  2. 2Tour your camera
  3. 3Types of camera
  4. 4Sensor sizes
  5. 5Screens and viewfinders
  6. 6Settings to change first
  7. 7Batteries and memory cards
  8. 8Changing lenses
  9. 9Real-life examples
  10. 10Practice
  11. 11Quiz
  12. 12Cheat sheet

The short version

If your camera’s lens comes off, the lens mount is the metal ring that locks lens and camera together and lets them talk. Changing lenses gently, quickly and out of the wind keeps it working for decades. If your lens is built in, enjoy a short lesson: just read the Finn tip and move on.

Each system has its own mount, and a lens fits only the mount it was made for unless you use an adapter. Brands make several mounts over the years, so check the mount name, not just the brand, before you buy or borrow a lens.

The front of a mirrorless camera with no lens fitted, showing the metal lens mount ring held by screws, a red dot on its upper left, the sensor inside, a curve of gold contact pins at the bottom of the opening and a small silver locking pin on the lower left of the ring12345
  1. 1
    Index mark

    Line the lens’s mark up with this one. It is a red dot on this camera; other brands use a white dot, a raised bump or a different place on the ring.

  2. 2
    Bayonet claws

    The inner lip of the mount. Tabs on the lens slide behind it when you turn the lens, locking it on.

  3. 3
    Electrical contacts

    Pins that let lens and camera talk about focus, aperture and stabilisation. On this camera they sit at the bottom; other mounts put them elsewhere.

  4. 4
    Lens locking pin

    Springs into a hole in the lens when it clicks home. Pressing the lens release button (beside the mount; position varies) pulls it back.

  5. 5
    Sensor

    With no mirror in front, the sensor is open to dust whenever the lens is off.

Figure 1. A camera mount, numbered. The colour and position of the index mark, where the contacts sit, where the release button is and which way you turn all vary by brand, so check your manual.
The rear of a lens seen end-on, showing a cream metal mount ring with screws, a red dot near the top of the ring and the rear glass element in the centre123
  1. 1
    Index mark

    This lens has a red dot. Line it up with the matching mark on the camera, push the lens in flat, then turn it.

  2. 2
    Bayonet ring

    The metal ring at the back of the lens. Its tabs slide behind the camera’s claws and lock as you turn.

  3. 3
    Rear element

    The last piece of glass. Fingerprints here show up in pictures, so fit the rear cap the moment the lens comes off.

Figure 2. The back of a lens. You line up the index marks first and then turn; the contacts on lens and body only meet once the lens has turned and locked.

Changing a lens

Putting a lens on

  1. Switch the camera off, as most makers recommend.
  2. Find shelter from wind and spray, and point the camera’s opening downwards.
  3. Take off the body cap and the lens’s rear cap, and pop the caps straight into a pocket.
  4. Line up the index mark on the lens with the one on the camera.
  5. Push the lens in flat and turn it until it clicks. Which way you turn depends on the brand, so check your manual. If it won’t turn, never force it: it is misaligned or the wrong mount.

Taking a lens off

  1. Hold the lens, press and hold the lens release button, and turn the opposite way.
  2. Lift it straight out, fit its rear cap at once, and put the next lens or the body cap on straight away.

Looking after it: keep caps on whenever a lens is off, never touch the contacts, and if a lens error appears, switch off, wipe the contacts gently with a clean dry cloth and refit (Module 117 covers cleaning).

Will it fit? A lens made for a bigger sensor works on a smaller sensor of the same mount; you just get the tighter view from Lesson 4. A lens made for a smaller sensor on a bigger one gives dark corners or a crop mode, and on some systems it will not fit at all. Adapters can join some lenses to other mounts; check how well autofocus works through them before you rely on one.

Easy traps

  • Changing lenses facing into the wind on a beach.
  • Leaving the camera open while you dig through your bag for the next lens.

Finn tip: Take the rear cap off the new lens before you remove the old one. The camera is then open for two seconds, not twenty. If your lens is built in, your version of this tip is simpler still: keep the lens cap on in your bag and wipe the front glass with a soft lens cloth.

Key takeaways

  • Camera off, opening facing down, line up the index marks, turn until it clicks.
  • Cap everything the moment it comes off; never touch the contacts.
  • Lenses fit only their own mount; check the mount name before you buy.

Try it now · 10 minutes

If your lens comes off, practise a lens change five times at home: camera off, opening down, caps into your pocket. Time the last one. Under fifteen seconds? You are faster than most beginners already.