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.

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.

** 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:

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.

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.

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).

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
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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