Crop Factor

Crop factor is a number used to compare the size of a camera sensor with a 35mm full-frame sensor.

It helps creators understand how a lens's field of view will differ between cameras.

Common examples include:

  • Full frame: 1.0×
  • Many APS-C cameras: about 1.5×
  • Many Canon APS-C cameras: about 1.6×
  • Micro Four Thirds: about 2.0×

Crop factor does not change the actual focal length of a lens.

Crop-factor formula

A simplified field-of-view comparison is:

Full-frame-equivalent focal length = actual focal length × crop factor

Example:

A 20mm lens on a 1.5× APS-C camera provides a field of view similar to approximately:

20mm × 1.5 = 30mm

The lens remains a 20mm lens. The framing resembles what a 30mm lens would show on full frame.

Why smaller sensors create a crop

A lens projects a circular image toward the sensor.

A full-frame sensor captures a larger portion of that image.

A smaller sensor captures a smaller central portion.

This produces:

  • Narrower angle of view
  • Tighter framing
  • Fewer pixels around the outside of the projected scene

It does not optically zoom the lens.

Crop factor vs. focal length

Focal length Crop factor
Optical property of the lens Comparison based on sensor size
Printed on the lens Associated with the camera format
Does not change between bodies Changes when the same lens is used on different formats
Helps determine angle of view Converts angle of view to full-frame equivalent

See focal length.

Common APS-C examples

Actual focal length 1.5× equivalent 1.6× equivalent
10mm 15mm 16mm
16mm 24mm 25.6mm
24mm 36mm 38.4mm
35mm 52.5mm 56mm
50mm 75mm 80mm
85mm 127.5mm 136mm

These figures compare field of view, not every visual property of the systems.

Why crop factor matters to YouTubers

Small-room filming

A lens that looks moderately wide on full frame may look too tight on APS-C.

For example:

  • 24mm on full frame is wide.
  • 24mm on 1.5× APS-C resembles about 36mm.
  • The APS-C setup may require the camera to be farther away.

Vlogging

Arm's-length creators need a sufficiently wide equivalent view.

A 16mm APS-C lens provides approximately a 24mm equivalent field of view on a 1.5× system.

Electronic stabilization can crop the frame further.

Telephoto reach

A smaller sensor can frame distant subjects more tightly with the same lens.

This is useful for:

  • Sports
  • Wildlife
  • Stage events
  • Conferences

It is not free optical magnification. The result depends on sensor resolution, lens quality, and comparison method.

Lens shopping

A creator should compare equivalent fields of view rather than assuming that a focal length recommendation applies equally to every camera.

Does crop factor change aperture?

The physical f-number printed on the lens does not change.

A 35mm f/1.8 lens remains an f/1.8 lens for exposure.

When comparing depth of field and total-light behavior of different formats at equivalent framing, creators may use equivalent-aperture calculations. That is a separate comparison and does not mean the lens stops transmitting light as f/2.7.

For beginners:

  • Use the actual f-number for exposure.
  • Use crop factor to compare field of view.
  • Treat depth-of-field equivalence as a more advanced comparison.

Crop factor and depth of field

At the same camera position, focal length, aperture, and focus distance, the smaller sensor simply crops the image.

To create equivalent framing, the APS-C creator may:

  • Use a shorter focal length
  • Move the camera farther away

Those changes can produce deeper depth of field than a full-frame setup with equivalent framing and the same f-number.

Crop factor and image quality

Crop factor alone does not determine:

  • Sharpness
  • Dynamic range
  • Noise
  • Color
  • Resolution
  • Autofocus quality
  • Video quality

Those depend on the specific sensor, processor, lens, settings, and recording mode.

APS-C lenses on full-frame cameras

Some full-frame cameras can use lenses designed for APS-C.

The camera may:

  • Enter crop mode automatically
  • Record a smaller image area
  • Reduce still-image resolution
  • Limit certain video modes
  • Show dark corners if crop mode is not used

Compatibility varies by mount and manufacturer.

Full-frame lenses on APS-C cameras

A compatible full-frame lens can often be used on an APS-C body.

The APS-C sensor captures the central portion of the image circle.

The creator should still check:

  • Lens mount
  • Autofocus support
  • Stabilization
  • Size
  • Weight
  • Equivalent field of view

Additional crops in video

Sensor crop factor is not the only crop a creator may encounter.

A camera can crop because of:

  • Electronic stabilization
  • High-frame-rate mode
  • 4K or 8K recording mode
  • Digital zoom
  • Active stabilization
  • APS-C or Super 35 mode
  • Aspect-ratio changes

These crops can stack.

Common crop-factor mistakes

  • Saying the lens becomes a longer focal length
  • Using equivalent focal length as if it changes exposure
  • Ignoring additional video crops
  • Comparing lenses without stating sensor size
  • Assuming tighter framing always means more image detail
  • Treating all APS-C cameras as exactly the same size
  • Confusing crop factor with digital zoom
  • Ignoring lens-mount compatibility

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Frequently asked questions

Does crop factor make a lens zoom in?

No. It narrows the recorded field of view because the smaller sensor captures less of the lens's projected image.

What is the crop factor of APS-C?

It is commonly about 1.5×, while many Canon APS-C cameras use approximately 1.6×. Check the specific camera.

Do I multiply aperture by crop factor?

Not for exposure settings. The actual f-number remains the actual f-number. Equivalent aperture is used only for certain cross-format comparisons.

Why is crop factor important for vlogging?

A lens may be too tight at arm's length after sensor and stabilization crops are considered.