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Sony A7S vs Pentax K20D Comparison

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Sony A7S

12 MP | Full frame (35.8 x 23.9 mm) CMOS Sensor

Sony A7S
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Pentax K20D

15 MP | APS-C (23.4 x 15.6 mm) CMOS Sensor

Pentax K20D
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Sony A7S vs Pentax K20D Comparison Overview

Here we are comparing two cameras with different body types: Sony A7S, which was introduced in April 2014 is a Pro Mirrorless camera with a 12.0MP Full frame sensor whereas Pentax K20D, which was introduced in June 2008 is a Advanced DSLR camera with a 15.0MP APS-C sensor. As you can see, K20D is 6 years older than A7S. Let's see if this age difference between two cameras makes a big difference.

Despite some fundamental differences of these two body types, Mirrorless cameras are becoming serious alternatives to DSLR cameras thanks to their size/weight advantages and recent improvements in their focus speeds , which makes this comparison even more interesting.

Here is a brief look at the main features of Sony A7S and Pentax K20D before getting into our more detailed comparison.

Sony A7S Key Specs

  • Announcement Date: 2014-04-06
  • 12MP - Full frame CMOS Sensor
  • ISO 100 - 409600
  • Sony E Mount
  • 3 Tilting Screen
  • 2359k dot Electronic viewfinder
  • 5 fps continuous shooting
  • 4K (UHD) - 3840 x 2160 video resolution
  • 120 fps High-Speed Video
  • Built-in Wireless
  • 489g. 127 x 94 x 48 mm
  • Weather Sealed Body

Pentax K20D Key Specs

  • Announcement Date: 2008-06-25
  • 15MP - APS-C CMOS Sensor
  • ISO 100 - 3200 ( expands to 6400)
  • Pentax KAF2 Mount
  • Sensor-shift Image Stabilization
  • 2.7" Fixed Type Screen
  • Optical (pentaprism) viewfinder
  • 3 fps continuous shooting
  • No Video Mode
  • 800g. 142 x 101 x 70 mm
  • Weather Sealed Body
  • Replaced Pentax K10D Compare

Sony A7S was replaced by Sony Alpha 7S II. You may also be interested in these comparisons:
Sony Alpha 7S II vs Sony Alpha A7S
Sony Alpha 7S II vs Pentax K20D

Let's read on the following sections in order to better understand in detail how Sony A7S and Pentax K20D compares and hopefully end up with enough arguments to decide which one is better for you.

Reasons to choose Sony Alpha A7S over Pentax K20D
Wireless Connection
Built-In vs None Better connectivity
LCD Screen
Tilting vs Fixed Type Flexible shooting positions
Viewfinder Magnification
0.71x vs 0.64x Larger Viewfinder
Face Detection Focus
Yes vs No very handy for portraits
Max ISO
409.600 vs 3.200 12700% higher Max ISO
Number of Focus Points
25 vs 11 14 more focus points
LCD Screen Size
3 vs 2.7" 0.3 inches larger display
LCD Screen Resolution
1.230k dots vs 230k dots 434% higher resolution screen
Viewfinder Coverage
100% vs 95% More accurate viewfinder
Max Mech. Shutter
1/8000s vs 1/4000s faster mechanical shutter
Continuous Shooting
5.0fps vs 3.0fps 2 fps faster
Weight
489 g vs 800 g 311 g lighter
Microphone Port
Yes vs No High quality audio recording option
Headphone Port
Yes vs No better video control
Color Depth
23.9 vs 22.9 higher color depth
Dynamic Range
13.2 vs 11.1 higher dynamic range
Low Light ISO
3702 vs 639 better High ISO performance
Sensor Pixel Area
71.24µm2 vs 25.18µm2 182% larger pixel area
Max Video Resolution
3840 x 2160 vs None Higher Resolution Video
AE Bracketing Range
±5 EV vs ±3 EV Wide Bracketing range is useful for HDR
NFC Connection
Yes vs No Easy wireless connectivity with compatible devices
Smartphone Remote
Yes vs No Remote control your camera with a smartphone


Reasons to choose Pentax K20D over Sony Alpha A7S
Image Stabilization
Sensor-shift vs None Sharper images at longer focal lengths and long exposures
Built-in Flash
Yes vs No Useful in low-light
Max Sensor Resolution
15 MP vs 12 MP 25% more pixels
Timelapse Recording
Yes vs With optional app creative shooting
Top LCD
Yes vs No Help viewing and changing settings easily
Flash Sync Port
Yes vs No Connect off-camera flash

Common Strengths of Sony Alpha A7S and Pentax K20D
External Flash Shoe
Yes vs Yes Better for flash photography
Viewfinder
Yes (Electronic) vs Yes (Optical) Better framing and control
RAW Support
Yes vs Yes Better image quality
Environmental Sealing
Yes vs Yes shoot at tough conditions
AE Bracketing
Yes vs Yes Useful for tough lighting conditions and HDR
Common Weaknesses of Sony Alpha A7S and Pentax K20D
LCD Screen Size
3 vs 2.7" Small display
Sony A7S vs Pentax K20D: Physical Specs and Body features Comparison

Size and weight is a big decision factor when you are trying to find the ideal camera for your needs. In this section, We are going to illustrate Sony A7S and Pentax K20D side-by-side from the front, back and top in their relative dimensions. Sony A7S has external dimensions of 127 x 94 x 48 mm (5 x 3.7 x 1.89″) and weighs 489 g (1.08 lb / 17.25 oz) (including batteries). Pentax K20D has external dimensions of 142 x 101 x 70 mm (5.59 x 3.98 x 2.76″) and weighs 800 g (1.76 lb / 28.22 oz) (including batteries).

Below you can see the front view size comparison of Sony A7S and Pentax K20D. Sony A7S is clearly the smaller of the two cameras. Its body is 15mm narrower, 7mm shorter and 22mm thinner than Pentax K20D.

Sony A7S vs Pentax K20D Camera Size Comparison - Front View
Comparison image of Sony A7S and Pentax K20D Size, Weight and External Dimensions - Front View

Here is the back view size comparison of Sony A7S and Pentax K20D.

Sony A7S vs Pentax K20D Camera Size Comparison - Back View
Comparison image of Sony A7S and Pentax K20D Size and Weight - Back View

Now lets look at the top view comparison of Sony A7S and Pentax K20D.
Sony A7S vs Pentax K20D Camera Size Comparison - Top View
Top View Comparison image of Sony A7S and Pentax K20D Size

Weight is another important factor especially when deciding on a camera that you want to carry with you all day. Sony A7S is significantly lighter (311g ) than the Pentax K20D which may become a big advantage especially on long walking trips.

Also keep in mind that body weight is not the only deciding factor when comparing two interchangeable camera bodies, you have to also take into account the lenses that you will be using with these bodies. Since Sony A7S has a Full frame sensor and Pentax K20D has a smaller APS-C sensor, Pentax K20D's lenses for a similar focal length and aperture will generally be lighter and smaller than the Sony A7S lenses.

Weight Comparison

DSLR Cameras

A7S
K20D
Min
Average
Max
Thickness Comparison

DSLR Cameras

A7S
K20D
Min
Average
Max

Weather Sealing

Both A7S and K20D have weather sealings in their body, making them resistant to water and dust.

LCD Screen Size and Features

Sony A7S's 3 LCD screen is slightly larger than Pentax K20D's 2.7" screen.

In addition to the size advantage, Sony A7S LCD screen also has a Tilting feature where you can change the angle of the screen to make it easier to shoot from waist or over the head levels. On the other hand, Pentax K20D has a fixed type screen which provides less flexibility in shooting positions compared to A7S.
Sony A7S vs Pentax K20D: Sensor Comparison

Sony A7S has a 12.0MP Full frame (35.8 x 23.9 mm ) sized CMOS sensor and features Bionz X processor. On the other hand, Pentax K20D has a 15.0MP APS-C (23.4 x 15.6 mm ) sized CMOS sensor .

Below you can see the A7S and K20D sensor size comparison.

Sony A7S vs Pentax K20D Sensor Size Comparison
Sensor Size and Resolution Comparison image of Sony A7S and Pentax K20D Cameras


As seen above, Sony A7S has a 2.3x Larger sensor area than Pentax K20D. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.

DxOMark Sensor Scores

Both Sony A7S and Pentax K20D sensors have been tested by DxoMark. DxoMark scores camera sensors for color depth (DXO Portrait), dynamic range (DXO Landscape) and low-light sensitivity (DXO Sports), and also gives them an overall score. Of the two cameras that we are comparing, A7S has scored 87, 22 points higher than K20D.

Model Overall Color Depth Dynamic Range Low-light ISO
Sony A7S 87 23.9 bits 13.2 Evs 3702 ISO
Pentax K20D 65 22.9 bits 11.1 Evs 639 ISO
Sony A7S vs Pentax K20D Comparison of Available Lenses
Which camera has more lenses?

Number of available lenses is a big decision factor while choosing your interchangeable lens camera. When we look at the available lenses for these two cameras, we see that Pentax K20D has an advantage over Sony A7S There are 151 lenses for Pentax K20D's Pentax KAF2 mount, on the other hand there are only 128 lenses for Sony A7S's Sony E lens mount.

Another important factor is the availability of image stabilization. Pentax K20D has a big advantage in this regard because it has a sensor based image stabilization which means that all the lenses mounted to this body will be stabilized. On the other hand, Sony A7S doesn't have this feature so you have to buy a lens with optical stabilization feature. Currently there are 31 lenses for Sony E mount with Optical Image Stabilization features.

Lens Type # of Sony A7S Lenses # of Pentax K20D Lenses
Standard Zoom 12 (9 Full Frame) 22
Standard Prime 18 (9 Full Frame) 20
Wideangle Zoom 7 (6 Full Frame) 12
Wideangle Prime 42 (26 Full Frame) 24
Telephoto Zoom 9 (7 Full Frame) 21
Telephoto Prime 18 (14 Full Frame) 12
SuperZoom 8 (1 Full Frame) 15
Wideangle Fisheye Prime 2 (0 Full Frame) 3
Macro Prime 8 (7 Full Frame) 14
Perspective Control Prime 2 (2 Full Frame) 8
Telephoto Mirror Prime n/a n/a
TOTAL 128 (81 Full Frame) 151


Now let's compare some sample lenses from each mount with typical Focal ranges for Sony A7S and Pentax K20D to see how these lenses compares:

Fast Standard Zoom Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 24-70mm F2.8 GM Lens Sony FE 24-70mm F2.8 GM
24 - 70mm 886gr 1375gr 136mm Amazon B&H Photo
Pentax DA 16-50mm F2.8 ED Lens Pentax DA 16-50mm F2.8 ED
24 - 75mm 565gr 1365gr 99mm Amazon B&H Photo
Fast Tele Zoom Equivalent Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 70-200mm F2.8 GM OSS Lens Sony FE 70-200mm F2.8 GM OSS
70 - 200mm 1480gr 1969gr 200mm Amazon B&H Photo
Pentax DA 50-135mm F2.8 ED Lens Pentax DA 50-135mm F2.8 ED
75 - 202.5mm 685gr 1485gr 136mm Amazon B&H Photo
Fast Normal Prime Equivalent Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 50mm F1.4 Lens Sony FE 50mm F1.4
50mm 778gr 1267gr 108mm Amazon B&H Photo
Pentax FA 31mm F1.8 L Lens Pentax FA 31mm F1.8 L
31mm 345gr 1145gr 69mm Amazon B&H Photo
Fast Wideangle Zoom Equivalent Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 16-35mm F2.8 GM Lens Sony FE 16-35mm F2.8 GM
16 - 35mm 680gr 1169gr 122mm Amazon B&H Photo
Pentax 12-24mm F4.0 ED AL Lens Pentax 12-24mm F4.0 ED AL
18 - 36mm 430gr 1230gr 84mm Amazon B&H Photo
24-105mm f4 Equivalent Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 24-105mm F4 G OSS Lens Sony FE 24-105mm F4 G OSS
24 - 105mm 663gr 1152gr 113mm Amazon B&H Photo
Pentax 17-70mm F4.0 AL SDM Lens Pentax 17-70mm F4.0 AL SDM
25.5 - 105mm 485gr 1285gr 94mm Amazon B&H Photo
Super-Tele Zoom Equivalent Lenses
Model FF Equiv. Weight Weight w/ Cam Length Street Price
Sony FE 100-400mm F4.5-5.6 GM OSS Lens Sony FE 100-400mm F4.5-5.6 GM OSS
100 - 400mm 1395gr 1884gr 205mm Amazon B&H Photo
Sigma 120-400mm F4.5-5.6 DG HSM Lens Sigma 120-400mm F4.5-5.6 DG HSM
120 - 400mm 1640gr 2440gr 203mm Amazon B&H Photo
What types of Photography are Sony A7S and Pentax K20D Good for?
In this section, we rank and compare Sony A7S and Pentax K20D for five different photography types in order to make your decision process easier in case you are specifically interested in one or more of these areas.

Sony A7S for Portrait Photography

GOOD

Pentax K20D for Portrait Photography

GOOD
Large Full frame (35.8 x 23.9 mm) sensor
Electronic Built-in Viewfinder
Good Ergonomics&Handling
Average Resolution Sensor: 12.0MP
No Image Stabilization
Read the details
Large APS-C (23.4 x 15.6 mm) sensor
Image Stabilization
Optical Built-in Viewfinder
Good Ergonomics&Handling
Average Resolution Sensor: 15.0MP
Read the details

Sony A7S for Street Photography

GOOD

Pentax K20D for Street Photography

GOOD
Large Full frame (35.8 x 23.9 mm) sensor
Electronic Built-in Viewfinder
Live-view
Face-Detection Focusing
Tilting LCD Screen
Medium sized Body
No Image Stabilization
Read the details
Large APS-C (23.4 x 15.6 mm) sensor
Image Stabilization
Optical Built-in Viewfinder
Live-view
Large Body
Read the details

Sony A7S for Sports Photography

GOOD

Pentax K20D for Sports Photography

GOOD
Electronic Built-in Viewfinder
Good Ergonomics&Handling
Environmental Sealings
Fast Max shutter speed: 1/8000s
25 Focus Points
Good Low Light ISO
Wireless Connection
Average Continuous Shooting: 5.0fps
No Image Stabilization
Read the details
Image Stabilization
Optical Built-in Viewfinder
Good Ergonomics&Handling
Environmental Sealings
Fast Max shutter speed: 1/4000s
11 Focus Points
Slow Continuous Shooting: 3.0fps
Read the details

Sony A7S for Daily Photography

EXCELLENT

Pentax K20D for Daily Photography

GOOD
Large Full frame (35.8 x 23.9 mm) sensor
Environmental Sealings
Medium size Body
489g
Body Thickness 48mm
Read the details
Large APS-C (23.4 x 15.6 mm) sensor
Environmental Sealings
Large Body
800g
Body Thickness 70mm
Read the details

Sony A7S for Landscape Photography

AVERAGE

Pentax K20D for Landscape Photography

AVERAGE
Large Full frame (35.8 x 23.9 mm) sensor
Environmental Sealings
Live-view
Average Resolution Sensor: 12.0MP
Read the details
Large APS-C (23.4 x 15.6 mm) sensor
Environmental Sealings
Live-view
Average Resolution Sensor: 15.0MP
Read the details

Sony A7S vs Pentax K20D: OUR DECISION

You may have already made your decision about which camera suits better for your needs and your budget so far but in case you wonder how we rated Sony A7S and Pentax K20D, below you can find their scores in five different aspects. Our Decision Algorithm dynamically scores cameras using 63 different specs, current price and DxO Mark scores (where possible) in order to make a more objective and consistent comparison.

Here is a summary of how Sony A7S and Pentax K20D scores compare:

Sony A7S
Imaging
Features
Value
Portability
Overall
Ranked #39 out of 88 in SLR-style mirrorless cameras
Ranked #71 out of 1223 in all Cameras
Pentax K20D
Imaging
Features
Value
Portability
Overall
Ranked #58 out of 94 in Mid-size SLR cameras
Ranked #394 out of 1223 in all Cameras

Sony A7S is the clear winner of this comparison. It has a higher Overall Score and beats Pentax K20D in all criteria. It has better general image quality, more features, more compact body and offers more value for the money

Sony A7S
Sony A7S
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Pentax K20D
Pentax K20D
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Pentax K20D vs Sony A7S Specs Table
Detailed comparison of specifications
General Sony Alpha A7S Pentax K20D
Brand Sony Pentax
Announced 2014-04-06 2008-06-25
Body Type SLR-style mirrorless Mid-size SLR
Sensor
Type CMOS CMOS
Size Full frame APS-C
Dimensions 35.8 x 23.9 mm 23.4 x 15.6 mm
Area 855.62mm2 365.04mm2
Megapixels 12 megapixels 15 megapixels
Max Resolution 4240 x 2832 4672 x 3104
Max Native Light sensitivity 409,600 ISO 3,200 ISO
Max Boosted Light Sensitivity - 6400 ISO
Min Native Light sensitivity 100 ISO 100 ISO
RAW Support
Autofocus
AF Touch
AF Continuous
AF Single
AF Tracking
AF Selective
AF Center
AF Multi Area
AF Live View
AF Face Detection
AF Contrast Detection
AF Phase Detection
Number of Focus Points 25 11
Lens
Manual Focus
Lens Mount Sony E Pentax KAF2
Number of Available Lenses 128 151
Screen
Type Tilting Fixed type
Size 3 2.7"
Resolution 1,230k dots 230k dots
Touch Screen
Viewfinder
Viewfinder Electronic Optical (pentaprism)
Viewfinder Resolution 2,359k dots no electronic viewfinder
Viewfinder Coverage 100% 95%
Viewfinder Magnification 0.71x 0.64x
Photography Features
Max Mechanical Shutter 1/8000s 1/4000s
Shutter Priority
Aperture Priority
Manual Exposure Mode
Custom White Balance
Image Stabilization No Sensor-shift
Built-in Flash
Flash Range no built-in flash 13.00 m (at ISO 100)
Max Flash Sync n/a 1/180s
External Flash
Continuous Shooting 5.0 fps 3.0 fps
Multi-Segment
Average
Spot
Partial
AF-Area
Center Weighted
AE Bracketing
WB Bracketing
Video Features
Max Video Resolution 3840 x 2160 None
Video Formats MPEG-4, AVCHD, XAVC n/a
Microphone Port
Headphone Port
Connectivity
Wireless Connectivity Built-In None
HDMI
Physical
Environmental Sealing
Weight 489g 800g
Dimensions 127 x 94 x 48mm 142 x 101 x 70mm
Battery Life 360 shots n/a
Other Features
Timelapse Recording With Downloadable App
GPS None None
DxO Sensor Scores
DxO Overall Score 87 65
DxO Color Depth 23.9 22.9
DxO Dynamic Range 13.2 11.1
DxO Low Light ISO 3702 639
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