Sony a7R IIIA vs Sony a900

This is a full comparison between the cameras Sony a7R IIIA and Sony a900. We compare them by looking at the categories you see below.

Manufacturing

These cameras are both manufactured by Sony.

Sony a7R IIIA were released 2021 and Sony a900 was released 2008. That is a 13 years difference. In tech, this period can be of interest since technology is always improving, etc.

Camera Released
Sony a7R IIIA 2021
Sony a900 2008

Type of camera

Sony a7R IIIA is a Mirrorless camera while Sony a900 is a DSLR camera. More information about their differences will come soon.

Sensors / crop factor

Both these cameras have the same sorts of sensor (called "Sony Full Frame") which means that if you compare these cameras side by side the lenses will also have the same experienced focal length. Since both cameras have a Full frame sensor there will be no crop factor.

Camera Focal length, 50mm f/1.8 **
Sony a7R IIIA 50 mm
Full-frame sensor
No crop factor/focal length multiplier
Sony a900 50 mm
Full-frame sensor
No crop factor/focal length multiplier

** Experienced focal length when using a lens such as a common "50mm f/1.8"

Learn more about crop factor and focal length multiplier here:
Camera selection can affect the focal length (Sony)

Resolution

Sony a7R IIIA has a 42 MP (Megapixels) resolution while Sony a900 has 25 MP. If we break down this in more detail this is the data behind the numbers:

Camera Megapixels
Sony a7R IIIA 42 MP
42177408 pixels
7952 x 5304
Sony a900 25 MP
24385536 pixels
6048 x 4032

Sony a7R IIIA has a 73 % larger resolution than Sony a900. This could give you more details in the picture but also a possibility to crop more in the pictures, afterward while editing the pictures, if needed that is.

ISO range

Sony a7R IIIA has a larger ISO-range than Sony a900. Sony a7R IIIA has an ISO range that stretches from 100 to 32000 while Sony a900 has 100 to 1600.

Camera ISO Range
Sony a7R IIIA 100-32000
Sony a900 100-1600

Autofocus and lens compatibility

Both of these cameras have a built-in autofocus motor. Some lenses, that support autofocus, do not have an autofocus motor of their own but this won't cause any problems with these two cameras.

Here is a complete overview of which lenses work with each camera:
Lens compatibility chart for Sony a7R IIIA
Lens compatibility chart for Sony a900

Pictures per second

Depending on what you are shooting the FPS, or frames/pictures per second, can definitely be of interest. Sony a7R IIIA can shoot up to 10 pictures per seconds and Sony a900 can shoot up to 5 pictures per seconds.

Camera FPS (Frames per second)
Sony a7R IIIA 10
Sony a900 5

Ability to record movies

It is becoming more and more popular to record movies with digital cameras.

When comparing these two cameras there is only one of them that can shoot movies and that is Sony a7R IIIA. Unfortunately Sony a900 does not support recording movies and movie clips.

Weight

The weight of the camera can be an extremely important factor, especially if the camera is about to be used, or carried around, for several hours at a time.

Sony a900 weighs 895 gr (equal to 1.97 lb) which is 36% heavier than Sony a7R IIIA and its 657 gr (or 1.45 lb).

Camera Weight
Sony a7R IIIA 657 gr
1.45 lb
Sony a900 895 gr
1.97 lb

Sony a7R IIIA vs Sony a900 Specs

Below you will find the complete and detailed technical specs for both Sony a7R IIIA and Sony a900, next to each other. Each category of data is a link to an article covering the subject, giving you a deeper understanding so you can better understand the strengths and weaknesses of the two camera models.

Product
Sony a7R IIIA
Sony a900
Name Sony a7R IIIA Sony a900
Manufacturer Sony Sony
Release Date and Price
Sony a7R IIIA
Sony a900
Release Year 2021 2008
Release Date 2021-04-07 2008-09-09
MSRP 3199 USD 2999 USD
Buy it today
Camera Type
Sony a7R IIIA
Sony a900
Camera Type Mirrorless DSLR
Sensor
Sony a7R IIIA
Sony a900
Sensor Size Full Frame (approx 36 x 24 mm) Full Frame (approx 36 x 24 mm)
Sensor Type BSI-CMOS CMOS
Resolution 7952 x 5304 pixels 6048 x 4032 pixels
Megapixels 42 MP 25 MP
Image Processor BIONZ X Bionz
Image
Sony a7R IIIA
Sony a900
ISO Range 100 - 32000 100 - 1600
White Balance Presets 10 7
Custom White Balance Yes Yes
Image Stabilization Yes
(Sensor-Shift (5-axis))
Yes
(Sensor-Shift)
Image Stabilization CIPA Rating 5.5 stops 0 stops
Uncompressed format RAW RAW
Optics & Focus
Sony a7R IIIA
Sony a900
Autofocus Motor Yes Yes
Autofocus Contract Detect (sensor)
Phase Detect
Multi Area
Center
Selective Single Point
Tracking
Single
Continuous
Touch
Face Detection
LiveView
Phase Detect
Multi Area
Center
Selective Single Point
Single
Continuous
Focus Points 399 9
Lens Mount Sony E

See Compatible Lenses
Sony A

See Compatible Lenses
Focal Length Multiplier Full frame
No multiplier
Example:
24 mm remains 24 mm
50 mm remains 50 mm
100 mm remains 100 mm
200 mm remains 200 mm
Full frame
No multiplier
Example:
24 mm remains 24 mm
50 mm remains 50 mm
100 mm remains 100 mm
200 mm remains 200 mm
Screen & Viewfinder
Sony a7R IIIA
Sony a900
Articulated LCD Tilting Fixed
Screen size 3” 3”
Screen dots 2360000 921600
Touch screen Yes No
Screen type TFT LCD TFT Xtra Fine color LCD
Live view Yes No
Viewfinder Type Electronic Optical (pentaprism)
Viewfinder Coverage 100% 100%
Viewfinder Magnification 0.78x 0.74x
Viewfinder Resolution 3686400 N/A
Photography features
Sony a7R IIIA
Sony a900
Frames per second 10 fps 5 fps
Minimum Shutter Speed 30 seconds 30 seconds
Maximum Shutter Speed 1/8000 seconds 1/8000 seconds
Built-in Flash No No
Built-in Flash Range N/A N/A
External Flash Yes Yes
Self-Timer Yes Yes
Time-lapse No No
Metering modes Multi
Center Weighted
Spot
Multi
Center Weighted
Spot
Exposure Compensation +/- 5 (at 1/3 EV, 1/2 EV steps) +/- 3 (at 1/3 EV steps)
Videography features
Sony a7R IIIA
Sony a900
Video recording Yes No
Video format MPEG4
XAVC-S
AVCHD
N/A
Video resolution 1920 x 1080
3840 x 2160
N/A
Built-in Microphone Yes No
Built-in Speakers Yes No
Storage
Sony a7R IIIA
Sony a900
Memory Card SD/SDHC
Compact Flash
Memory Stick Pro Duo
Connectivity
Sony a7R IIIA
Sony a900
HDMI Output Yes Yes
Microphone Port Yes No
Headphone Port Yes No
Wireless Yes
Built-in (802.11b/g/n + NFC + Bluetooth)
No
Remote Control Yes (wired, wireless, smartphone) Yes (Wired or Wireless (Optional))
GPS No No
Body & Dimensions
Sony a7R IIIA
Sony a900
Enviromentally sealed Yes Yes
Battery Battery Pack Battery Pack
Battery Details NP-FZ100 lithium-ion battery and charger
Lithium-Ion NP-FM500H rechargeable battery & charger
Battery Life (CIPA) 650 shots 880 shots
Width 127 mm 156 mm
Height 96 mm 117 mm
Depth 74 mm 82 mm
Weight 657 gram 895 gram