The same lens, a different next stop for light
How do we see the picture before taking it? Follow the yellow light path: one camera uses a mirror to send light toward the eye; another reads a sensor and shows the result on a tiny screen. The mirror and shutter do different jobs.
Try two small comparisons
- Follow the yellow light path in the two camera types.
- Pause during a photo and watch the mirror move out of the way.
No reflex mirror does not mean no mechanical shutter
Look closer: observations and controls
The “reflex” in single-lens reflex names the mirror inside the body. During conventional optical viewing, that tilted mirror sends incoming lens light upward to a focusing screen. Viewfinder optics then carry the image to your eye. The main sensor remains covered by the shutter: your view does not first pass through that sensor and a display.
To take a photograph, the mirror lifts out of the sensor’s path. The first curtain starts exposure and the second ends it. The optical finder briefly goes dark because its light path has been interrupted. When the mirror returns, optical viewing resumes. Mirror movement and shutter movement are separate, coordinated operations.
A mirrorless camera has no reflex mirror switching between these paths. During live viewing, lens light reaches the sensor. Its readout passes through processing and becomes an image on an electronic finder or rear display. An electronic finder emits new light from a small screen; it does not deliver the original lens beam directly to your eye.
- Seek to “The mirror clears the path” and pause after the mirror rises but before the first curtain opens. Viewing is already interrupted, yet this exposure has not started.
- In exploration, select the optical DSLR and drag “Slow one capture.” Track the same hinge and connected metal links, then watch both curtains cross the sensor from top to bottom.
- Select DSLR live view. The mirror stays up and the shutter stays open so the main sensor can supply a rear-screen image. The optical finder can no longer provide its original view.
- Select mirrorless and adjust preview compensation. The electronic preview responds to the readout and display state. Switch back to optical viewing: that number does not alter the direct optical route to the eye.
The compensation input demonstrates a brightness relationship. It does not reproduce a particular camera’s menu or automatic exposure algorithm.
How do two curtains define exposure?
This sequence uses a slow exposure. The first curtain opens downward; its crossing time starts exposure for each row. The second curtain follows in the same direction and ends that row’s exposure. Every row receives the same time window, even though its start time depends on its position. At faster speeds, a traveling slit may cross the sensor without uncovering the whole sensor at once.
Mirrorless cameras may use mechanical shutters, electronic first curtains, or fully electronic shutters. To separate the definitions, this film shows one mechanical sequence: the shutter is open for live viewing, closes before the capture, and then starts a fresh exposure. Finder blackout, freezing, delay, and continuous-view capability depend on the sensor, shutter mode, and camera. “Mirrorless” does not guarantee an uninterrupted finder.
What does this section model, and what does it omit?
The mirror rotates about a fixed hinge. Its side linkage closes throughout the motion. This is a geometrically connected representative mechanism, not a reconstruction of a particular camera. The light path follows the same mirror angle and reflection law. The yellow marker slows down a central ray’s direction; it neither represents the speed of light nor traces every ray forming an image.
The pentaprism’s sagittal section uses two physical reflecting facets to turn upward light toward the back. Actual reflex finders also correct image orientation with roof geometry or other viewfinder optics. This film omits the transverse roof reflections, focusing-screen scattering, eyepiece adjustment, lens aberrations, and dedicated autofocus assemblies. The glass forms identify the internal lens assembly; they are not a real optical prescription.
DSLR live view uses the rear display. The model’s blue signal line reaches that display while the optical eyepiece remains dark. A separate enlarged viewing image below the section supports comparison. Preview compensation uses a brightness factor of two raised to the compensation value. ISO, noise, dynamic range, and final image quality are outside this model, so it cannot rank camera types.
Primary mechanism references: Canon DSLR technology, Canon mirrorless technology, Nikon’s DSLR and mirrorless anatomy, and Sony’s electronic front curtain and mechanical shutter explanation.