Sigma fp vs. Sony a7S III

Comparison

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fp image
vs
a7S III image
Sigma fp Sony a7S III
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Megapixels
24.60
12.10
Max. image resolution
6000 x 4000
4240 x 2832

Sensor

Sensor type
CMOS
CMOS
Sensor size
35.9 x 23.9 mm
35.6 x 23.8 mm
Sensor resolution
6075 x 4050
4260 x 2840
Diagonal
43.13 mm
42.82 mm
Sensor size comparison
Sensor size is generally a good indicator of the quality of the camera. Sensors can vary greatly in size. As a general rule, the bigger the sensor, the better the image quality.

Bigger sensors are more effective because they have more surface area to capture light. An important factor when comparing digital cameras is also camera generation. Generally, newer sensors will outperform the older.

Learn more about sensor sizes »

Actual sensor size

Note: Actual size is set to screen → change »
vs
1.01 : 1
(ratio)
Sigma fp Sony a7S III
Surface area:
858.01 mm² vs 847.28 mm²
Difference: 10.73 mm² (1%)
fp sensor is slightly bigger than a7S III sensor (only 1% difference).
Pixel pitch
5.91 µm
8.36 µm
Pixel pitch tells you the distance from the center of one pixel (photosite) to the center of the next. It tells you how close the pixels are to each other.

The bigger the pixel pitch, the further apart they are and the bigger each pixel is. Bigger pixels tend to have better signal to noise ratio and greater dynamic range.
Difference: 2.45 µm (41%)
Pixel pitch of a7S III is approx. 41% higher than pixel pitch of fp.
Pixel area
34.93 µm²
69.89 µm²
Pixel or photosite area affects how much light per pixel can be gathered. The larger it is the more light can be collected by a single pixel.

Larger pixels have the potential to collect more photons, resulting in greater dynamic range, while smaller pixels provide higher resolutions (more detail) for a given sensor size.
Relative pixel sizes:
vs
Pixel area difference: 34.96 µm² (100%)
A pixel on Sony a7S III sensor is approx. 100% bigger than a pixel on Sigma fp.
Pixel density
2.86 MP/cm²
1.43 MP/cm²
Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor.

Higher pixel density means smaller pixels and lower pixel density means larger pixels.
Difference: 1.43 µm (100%)
Sigma fp has approx. 100% higher pixel density than Sony a7S III.
To learn about the accuracy of these numbers, click here.



Specs

Sigma fp
Sony a7S III
Crop factor
1
1.01
Total megapixels
25.30
12.90
Effective megapixels
24.60
12.10
Optical zoom
 
 
Digital zoom
Yes
ISO sensitivity
Auto, 100-25600 (expandable to 6-102400)
Auto, 80-102400 (extends to 40-409600)
RAW
Manual focus
Normal focus range
Macro focus range
Focal length (35mm equiv.)
Aperture priority
Yes
Yes
Max. aperture
Max. aperture (35mm equiv.)
n/a
n/a
Metering
Multi, Center-weighted, Spot
Multi, Center-weighted, Spot
Exposure compensation
±5 EV (in 1/3 EV steps)
±5 EV (in 1/3 EV, 1/2 EV steps)
Shutter priority
Yes
Yes
Min. shutter speed
30 sec
30 sec
Max. shutter speed
1/8000 sec
1/8000 sec
Built-in flash
External flash
Viewfinder
None
Electronic
White balance presets
6
10
Screen size
3.2"
3"
Screen resolution
2,100,000 dots
1,440,000 dots
Video capture
Max. video resolution
3840x2160 (30p/​25p/​24p)
4264x2408 (60p)
Storage types
SD/SDHC/SDXC
SD/SDHC/SDXC/MS Pro Duo/CFexpress
USB
USB 3.0 (5 GBit/sec)
USB 3.0 (5 GBit/sec)
HDMI
Wireless
GPS
Battery
BP-51 lithium-ion battery
NP-FZ100 lithium-ion battery
Weight
422 g
614 g
Dimensions
112.6 x 69.9 x 45.3 mm
128.9 x 96.9 x 69.7 mm
Year
2019
2020




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vs

Diagonal

Diagonal is calculated by the use of Pythagorean theorem:
Diagonal =  w² + h²
where w = sensor width and h = sensor height

Sigma fp diagonal

w = 35.90 mm
h = 23.90 mm
Diagonal =  35.90² + 23.90²   = 43.13 mm

Sony a7S III diagonal

w = 35.60 mm
h = 23.80 mm
Diagonal =  35.60² + 23.80²   = 42.82 mm


Surface area

Surface area is calculated by multiplying the width and the height of a sensor.

fp sensor area

Width = 35.90 mm
Height = 23.90 mm

Surface area = 35.90 × 23.90 = 858.01 mm²

a7S III sensor area

Width = 35.60 mm
Height = 23.80 mm

Surface area = 35.60 × 23.80 = 847.28 mm²


Pixel pitch

Pixel pitch is the distance from the center of one pixel to the center of the next measured in micrometers (µm). It can be calculated with the following formula:
Pixel pitch =   sensor width in mm  × 1000
sensor resolution width in pixels

fp pixel pitch

Sensor width = 35.90 mm
Sensor resolution width = 6075 pixels
Pixel pitch =   35.90  × 1000  = 5.91 µm
6075

a7S III pixel pitch

Sensor width = 35.60 mm
Sensor resolution width = 4260 pixels
Pixel pitch =   35.60  × 1000  = 8.36 µm
4260


Pixel area

The area of one pixel can be calculated by simply squaring the pixel pitch:
Pixel area = pixel pitch²

You could also divide sensor surface area with effective megapixels:
Pixel area =   sensor surface area in mm²
effective megapixels

fp pixel area

Pixel pitch = 5.91 µm

Pixel area = 5.91² = 34.93 µm²

a7S III pixel area

Pixel pitch = 8.36 µm

Pixel area = 8.36² = 69.89 µm²


Pixel density

Pixel density can be calculated with the following formula:
Pixel density =  ( sensor resolution width in pixels )² / 1000000
sensor width in cm

One could also use this formula:
Pixel density =   effective megapixels × 1000000  / 10000
sensor surface area in mm²

fp pixel density

Sensor resolution width = 6075 pixels
Sensor width = 3.59 cm

Pixel density = (6075 / 3.59)² / 1000000 = 2.86 MP/cm²

a7S III pixel density

Sensor resolution width = 4260 pixels
Sensor width = 3.56 cm

Pixel density = (4260 / 3.56)² / 1000000 = 1.43 MP/cm²


Sensor resolution

Sensor resolution is calculated from sensor size and effective megapixels. It's slightly higher than maximum (not interpolated) image resolution which is usually stated on camera specifications. Sensor resolution is used in pixel pitch, pixel area, and pixel density formula. For sake of simplicity, we're going to calculate it in 3 stages.

1. First we need to find the ratio between horizontal and vertical length by dividing the former with the latter (aspect ratio). It's usually 1.33 (4:3) or 1.5 (3:2), but not always.

2. With the ratio (r) known we can calculate the X from the formula below, where X is a vertical number of pixels:
(X × r) × X = effective megapixels × 1000000    →   
X =  effective megapixels × 1000000
r
3. To get sensor resolution we then multiply X with the corresponding ratio:

Resolution horizontal: X × r
Resolution vertical: X

fp sensor resolution

Sensor width = 35.90 mm
Sensor height = 23.90 mm
Effective megapixels = 24.60
r = 35.90/23.90 = 1.5
X =  24.60 × 1000000  = 4050
1.5
Resolution horizontal: X × r = 4050 × 1.5 = 6075
Resolution vertical: X = 4050

Sensor resolution = 6075 x 4050

a7S III sensor resolution

Sensor width = 35.60 mm
Sensor height = 23.80 mm
Effective megapixels = 12.10
r = 35.60/23.80 = 1.5
X =  12.10 × 1000000  = 2840
1.5
Resolution horizontal: X × r = 2840 × 1.5 = 4260
Resolution vertical: X = 2840

Sensor resolution = 4260 x 2840


Crop factor

Crop factor or focal length multiplier is calculated by dividing the diagonal of 35 mm film (43.27 mm) with the diagonal of the sensor.
Crop factor =   43.27 mm
sensor diagonal in mm


fp crop factor

Sensor diagonal in mm = 43.13 mm
Crop factor =   43.27  = 1
43.13

a7S III crop factor

Sensor diagonal in mm = 42.82 mm
Crop factor =   43.27  = 1.01
42.82

35 mm equivalent aperture

Equivalent aperture (in 135 film terms) is calculated by multiplying lens aperture with crop factor (a.k.a. focal length multiplier).

fp equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Sigma fp, take the aperture of the lens you're using and multiply it with crop factor.

Since crop factor for Sigma fp is 1, the equivalent aperture is aperture.

a7S III equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Sony a7S III, take the aperture of the lens you're using and multiply it with crop factor.

Crop factor for Sony a7S III is 1.01

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