Crop factor and sensor equivalence: how APS-C, Micro Four Thirds, full frame and medium format compare

How to use crop factor when buying a lens: 3 everyday rules

Whether you shoot Micro Four Thirds, APS-C, full frame or medium format, three rules tell you how a lens will look on your camera.

• Want the classic 85mm full-frame portrait on APS-C or Micro Four Thirds?

  Divide 85 mm by the crop factor. A 56 mm f/1.2 or f/1.4 on APS-C (1.53×) and a 42.5 mm f/1.2 on Micro Four Thirds (2.00×) frame and blur like that 85 mm portrait.

  Compare 56mm APS-C and 85mm full frame
• Want a 50mm everyday prime on a crop sensor?

  A 50 mm lens on APS-C is a tight 76 mm portrait. For a true 50 mm view, use about 33 mm on APS-C or 25 mm on Micro Four Thirds.

  Open 33mm APS-C beside 50mm full frame
• Stepping up to 44×33 mm digital medium format?

  Multiply by 0.79×. An 80 mm f/1.7 frames and blurs like 63.2 mm f/1.3 on full frame, and a 110 mm f/2 is a short portrait, not an 85 mm.

  Compare 80mm medium format and 85mm full frame

Do you multiply the f-stop by the crop factor? Yes for blur, no for exposure

An f-number does two jobs, which is why the argument never ends.

Exposure brightness per square millimeter does not change with sensor size. At f/1.4, each square millimeter of a 1-inch, APS-C or full-frame sensor gets the same light. If the full-frame camera meters 1/250 s at f/1.4 and ISO 100, the APS-C camera at f/1.4 and ISO 100 uses the same 1/250 s.

Depth of field and background blur do scale. To match an 85 mm view from the same spot, APS-C uses 56 mm. At f/1.4 that lens has a 40.0 mm entrance pupil, the same opening as 85.5 mm f/2.1 on full frame. At f/1.2 the pupil is 46.7 mm, which matches 85.5 mm f/1.8.

1. Exposure: keep the printed f-stop

f/1.4 on APS-C is f/1.4 brightness

Same shutter speed at the same ISO

2. Blur: multiply the f-number too

56 mm f/1.4 on APS-C matches 85.5 mm f/2.1

Same entrance pupil and the same blur

What happens when you put a 50mm or 85mm lens on APS-C?

Mount the same 50 mm f/1.8 and stay at 2.00 m. The APS-C sensor crops the middle of the image circle. The horizontal view narrows from 39.6° to 26.6°, and the sharp zone shrinks from 16.9 cm to 11.0 cm because the smaller sensor is enlarged more.

In real shooting the frame is too tight, so you step back to 3.05 m. The person fits again, the sharp zone widens to 26.0 cm, and the background blur gets smaller relative to the person. That is the framing and depth of field of 76.3 mm f/2.7 on full frame. On Micro Four Thirds the same lens is 100 mm f/3.6: 8.4 cm if you stay at 2.00 m, and 34.2 cm if you step back to 4.00 m.

The same 50 mm f/1.8 on full frame, APS-C and Micro Four Thirds.

Camera sensor	Full-frame equivalent look	Depth of field at 2.00 m	Distance for the same subject size	Depth of field there
Full frame	50 mm f/1.8	16.9 cm	2.00 m	16.9 cm
APS-C Sony / Nikon / Fuji	76.3 mm f/2.7	11.0 cm	3.05 m	26.0 cm
Micro Four Thirds	100 mm f/3.6	8.4 cm	4.00 m	34.2 cm

Popular APS-C, Micro Four Thirds and medium-format equivalents

These primes are focused at 2.00 m. Exposure uses the printed f-number. Field of view and depth of field match the full-frame column.

Full-frame equivalent focal length and f-number at 2.00 m.

Format	Lens on the camera	Full-frame equivalent	Entrance pupil	Depth of field at 2.00 m	Exposure brightness
APS-C Sony / Nikon / Fuji	16 mm f/1.4	24.4 mm f/2.1	Ø 11.4 mm	89.2 cm	f/1.4
APS-C Sony / Nikon / Fuji	23 mm f/1.4	35.1 mm f/2.1	Ø 16.4 mm	41.5 cm	f/1.4
APS-C Sony / Nikon / Fuji	33 mm f/1.4	50.4 mm f/2.1	Ø 23.6 mm	19.9 cm	f/1.4
APS-C Sony / Nikon / Fuji	35 mm f/1.8	53.4 mm f/2.7	Ø 19.4 mm	22.7 cm	f/1.8
APS-C Sony / Nikon / Fuji	50 mm f/1.8	76.3 mm f/2.7	Ø 27.8 mm	11.0 cm	f/1.8
APS-C Sony / Nikon / Fuji	56 mm f/1.2	85.5 mm f/1.8	Ø 46.7 mm	5.8 cm	f/1.2
APS-C Sony / Nikon / Fuji	56 mm f/1.4, Viltrox	85.5 mm f/2.1	Ø 40.0 mm	6.8 cm	f/1.4
APS-C Sony / Nikon / Fuji	85 mm f/1.8	129.7 mm f/2.7	Ø 47.2 mm	3.7 cm	f/1.8
Micro Four Thirds	12 mm f/1.4	24 mm f/2.8	Ø 8.6 mm	126.4 cm	f/1.4
Micro Four Thirds	17 mm f/1.2	34 mm f/2.4	Ø 14.2 mm	50.1 cm	f/1.2
Micro Four Thirds	25 mm f/1.2	50 mm f/2.4	Ø 20.8 mm	22.8 cm	f/1.2
Micro Four Thirds	42.5 mm f/1.2	85 mm f/2.4	Ø 35.4 mm	7.8 cm	f/1.2
Digital medium format 44×33	63 mm f/2.8	49.8 mm f/2.2	Ø 22.5 mm	20.8 cm	f/2.8
Digital medium format 44×33	80 mm f/1.7	63.2 mm f/1.3	Ø 47.1 mm	7.7 cm	f/1.7
Digital medium format 44×33	110 mm f/2	86.9 mm f/1.6	Ø 55.0 mm	4.7 cm	f/2

• 56mm APS-C vs 85mm full frameThe portrait match
• 63mm medium format vs 50mm full frameA standard view on 44×33 mm
• 80mm medium format vs 85mm full frameA medium-format portrait
• 23mm APS-C vs 35mm full frameA wide view on APS-C
• 33mm APS-C vs 50mm full frameA standard view on APS-C
• 35mm APS-C vs 50mm full frameA slightly tighter standard
• 75mm APS-C vs 110mm full frameA short portrait on APS-C
• 90mm APS-C vs 135mm full frameA long portrait on APS-C
• 45mm medium format vs 35mm full frameA wide view on 44×33 mm
• 110mm medium format vs 85mm full frameA medium-format portrait
• 135mm medium format vs 105mm full frameA longer medium-format portrait

Sensor size and crop factor chart, from 1-inch to 8×10

Crop factor is 43.3 mm divided by the sensor diagonal. Formats smaller than full frame are above 1.00×. Medium and large format are below 1.00×. Sony, Nikon and Fujifilm APS-C is 1.53×, about 1.5×. Canon APS-C is 1.61×, about 1.6×. The stop column is how much deeper or shallower the depth of field is at the same marked f-stop and the same framing.

Dimensions, area, crop factor and circle of confusion against 35mm full frame.

Sensor format	Dimensions	Diagonal	Area	Crop factor	Circle of confusion	Depth of field vs full frame
1-inch	13.2 × 8.8 mm	15.9 mm	116 mm² (13%)	2.73×	0.011 mm	+2.9 stops deeper
Micro Four Thirds	17.3 × 13.0 mm	21.6 mm	225 mm² (26%)	2.00×	0.015 mm	+2.0 stops deeper
APS-C Canon	22.3 × 14.9 mm	26.8 mm	332 mm² (38%)	1.61×	0.019 mm	+1.4 stops deeper
APS-C Sony / Nikon / Fuji	23.6 × 15.7 mm	28.3 mm	371 mm² (43%)	1.53×	0.020 mm	+1.2 stops deeper
Full frame	36.0 × 24.0 mm	43.3 mm	864 mm² (100%)	1.00×	0.030 mm	Reference (0 stops)
Digital medium format 44×33	43.8 × 32.9 mm	54.8 mm	1,441 mm² (167%)	0.79×	0.038 mm	−0.7 stops shallower
Medium format 645	56.0 × 41.5 mm	69.7 mm	2,324 mm² (269%)	0.62×	0.048 mm	−1.4 stops shallower
Medium format 6×7	70.0 × 56.0 mm	89.6 mm	3,920 mm² (454%)	0.48×	0.062 mm	−2.1 stops shallower
Large format 4×5	121.0 × 96.0 mm	154.5 mm	11,616 mm² (13×)	0.28×	0.107 mm	−3.7 stops shallower
Large format 8×10	240.0 × 190.0 mm	306.1 mm	45,600 mm² (53×)	0.14×	0.212 mm	−5.6 stops shallower

See also Depth of field, Bokeh, Lens compression and How it works.

Questions

Do you multiply aperture (f-stop) by the crop factor too?

For exposure, no. An f/1.4 lens is f/1.4 brightness per square millimeter on every sensor. For depth of field and background blur at the same field of view, yes: multiply focal length and f-number. A 56 mm f/1.2 on APS-C (1.53×) matches 85.5 mm f/1.8, with a 46.7 mm entrance pupil and 5.8 cm of depth of field at 2.00 m.

What is a 50mm lens equivalent to on APS-C?

On a 1.53× APS-C sensor, a 50 mm f/1.8 frames like 76.3 mm f/2.7 on full frame. Stay at 2.00 m and the sharp zone is 11.0 cm. Step back to 3.05 m for the same subject size and it becomes 26.0 cm, the look of that slower full-frame lens. Canon APS-C is 1.61×, a little tighter.

What is a 56mm APS-C lens equivalent to on full frame?

A 56 mm lens on APS-C (1.53×) sees the same angle as 85.5 mm f/1.8. At f/1.2 the entrance pupil is 46.7 mm and the sharp zone at 2.00 m is 5.8 cm. At f/1.4 it matches 85.5 mm f/2.1.

What is the crop factor of Micro Four Thirds and 1-inch sensors?

Micro Four Thirds is 2.00× against a 43.3 mm full-frame diagonal. A 1-inch sensor (13.2 × 8.8 mm) is 2.73×.

What is the crop factor of digital medium format (44×33 mm)?

A 44×33 mm sensor is 0.79× relative to full frame. An 80 mm f/1.7 on that sensor frames and blurs like 63.2 mm f/1.3 on full frame.

What is equivalent aperture?

Equivalent aperture is the full-frame f-number with the same depth of field and background blur. Multiply the marked f-number by the crop factor. Exposure stays at the printed f-number: f/1.4 is f/1.4 brightness on every sensor.