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Sony RX100 III versus Sony A9

The Sony Cyber-shot DSC-RX100 III and the Sony Alpha A9 are two digital cameras that were officially introduced, respectively, in May 2014 and April 2017. The RX100 III is a fixed lens compact, while the A9 is a mirrorless interchangeable lens camera. The cameras are based on an one-inch (RX100 III) and a full frame (A9) sensor. The RX100 III has a resolution of 20 megapixel, whereas the A9 provides 24 MP. Read on to find out how these two cameras compare with respect to their size, their sensors, their features, and their reception by expert reviewers.

Body comparison: Sony RX100 III vs Sony A9

The physical size and weight of the Sony RX100 III and the Sony A9 are illustrated in the side-by-side display below. Three consecutive views from the front, the top, and the rear side are shown. All width, height and depth dimensions are rounded to the nearest millimeter. If you prefer, you can also use the toggle button to switch to a comparison in percentage terms (in this case, the camera on the left – the RX100 III – represents the basis or 100 percent across all the size and weight measures).

Snapsort Sony RX100 III vs Sony A9
Compare RX100 III versus A9 top
Compare RX100 III and A9 rear

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A9 is considerably larger (106 percent) than the Sony RX100 III. It is noteworthy in this context that the A9 is splash and dust-proof, while the RX100 III does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete and possibly misleading, as the RX100 III has a lens build in, whereas the A9 is an interchangeable lens camera that requires a separate lens. Attaching the latter will add extra weight and bulk to the setup. You can find an overview of optics for the A9 and their specifications in the Sony FE Lens Catalog.

Concerning battery life, the RX100 III gets 320 shots out of its NP-BX1 battery, while the A9 can take 650 images on a single charge of its NP-FZ100 power pack.

The table below summarizes the key physical specs of the two cameras alongside a broader set of comparators. If you want to switch the focus of the display and review another camera pair, just select a new right or left comparator from among the camera models in the table. Alternatively, you can also move across to the CAM-parator tool and choose from the broad selection of possible camera comparisons there.

Camera Body Specifications
  Camera
Model
Camera
Width
Camera
Height
Camera
Depth
Camera
Weight
Battery
Life
(CIPA)
Weather
Sealing
(yes/no)
Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Sony RX100 III» 4.0 in 2.3 in 1.6 in 10.2 oz 320 n May 2014 799- i Sony RX100 III
Sony A9« 5.0 in 3.8 in 2.5 in 23.7 oz 650 Y Apr 2017 4,499 i i Sony A9
Canon G5 X« » 4.4 in 3.0 in 1.7 in 12.5 oz 210 n Oct 2015 799 i i Canon G5 X
Canon G7 X« » 4.1 in 2.4 in 1.6 in 10.7 oz 210 n Sep 2014 699- i Canon G7 X
Panasonic FZ1000« » 5.4 in 3.9 in 5.2 in 29.3 oz 360 n Jun 2014 899- i Panasonic FZ1000
Ricoh GR II« » 4.6 in 2.5 in 1.4 in 8.9 oz 320 n Jun 2015 699- i Ricoh GR II
Ricoh GR« » 4.6 in 2.4 in 1.4 in 8.6 oz 290 n Apr 2013 799- i Ricoh GR
Sony A7 III« » 5.0 in 3.8 in 2.9 in 22.9 oz 610 Y Feb 2018 1,999 i i Sony A7 III
Sony A7R III« » 5.0 in 3.8 in 2.9 in 22.9 oz 650 Y Oct 2017 3,199 i i Sony A7R III
Sony RX100 V« » 4.0 in 2.3 in 1.6 in 10.5 oz 220 n Oct 2016 999 i i Sony RX100 V
Sony A7R II« » 5.0 in 3.8 in 2.4 in 22.0 oz 290 Y Jun 2015 3,199- i Sony A7R II
Sony A7S II« » 5.0 in 3.8 in 2.4 in 22.1 oz 370 Y Sep 2015 2,999 i i Sony A7S II
Sony RX100 IV« » 4.0 in 2.3 in 1.6 in 10.5 oz 280 n Jun 2015 999- i Sony RX100 IV
Sony A7 II« » 5.0 in 3.8 in 2.4 in 21.1 oz 350 Y Nov 2014 1,999- i Sony A7 II
Sony A5100« » 4.3 in 2.5 in 1.4 in 10.0 oz 400 n Aug 2014 549 i i Sony A5100
Sony RX100 II« » 4.0 in 2.3 in 1.5 in 9.9 oz 350 n Jun 2013 749- i Sony RX100 II
Sony RX100« » 4.0 in 2.3 in 1.4 in 8.5 oz 330 n Jun 2012 649- i Sony RX100

The price is, of course, an important factor in any camera decision. The listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The RX100 III was launched at a lower price than the A9, despite having a lens build in. Usually, retail prices stay at first close to the launch price, but after several months, discounts become available. Later in the product cycle and, in particular, when the replacement model is about to appear, further discounting and stock clearance sales often push the camera price considerably down. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

 

Sensor comparison: Sony RX100 III vs Sony A9

The imaging sensor is at the core of digital cameras and its size is one of the main determining factors of image quality. A large sensor will tend to have larger individual pixels that provide better low-light sensitivity, wider dynamic range, and richer color depth than smaller pixel-units in a sensor of the same technological generation. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its background. On the downside, larger sensors tend to be associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Sony RX100 III features an one-inch sensor and the Sony A9 a full frame sensor. The sensor area in the A9 is 630 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 2.7 and 1.0. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

Sony RX100 III and Sony A9 sensor measures

With 24MP, the A9 offers a higher resolution than the RX100 III (20MP), but the A9 nevertheless has larger individual pixels (pixel pitch of 5.94μm versus 2.41μm for the RX100 III) due to its larger sensor. Moreover, the A9 is a much more recent model (by 2 years and 11 months) than the RX100 III, and its sensor will have benefitted from technological advances during this time that further enhance the light gathering capacity of its pixel-units.

RX100 III versus A9 MP

Consistent information on actual sensor performance is available from DXO Mark for many cameras. This service assesses and scores the color depth ("DXO Portrait"), dynamic range ("DXO Landscape"), and low-light sensitivity ("DXO Sports") of camera sensors, and also publishes an overall camera score. Of the two cameras under consideration, the A9 offers substantially better image quality than the RX100 III (overall score 25 points higher). The advantage is based on 2.5 bits higher color depth, 1 EV in additional dynamic range, and 2.8 stops in additional low light sensitivity. The adjacent table reports on the physical sensor characteristics and the outcomes of the DXO sensor quality tests for a sample of comparator-cameras.

Sensor Characteristics
  Camera
Model
Sensor
Class
Resolution
(MP)
Horiz.
Pixels
Vert.
Pixels
Video
Format
DXO
Portrait
DXO
Landscape
DXO
Sports
DXO
Overall
Camera
Model
Sony RX100 III» 1-inch 20.0 5472 36481080/60p22.412.349567Sony RX100 III
Sony A9« Full Frame 24.0 6000 40004K/30p24.913.3351792Sony A9
Canon G5 X« » 1-inch 20.0 5472 36481080/60p----Canon G5 X
Canon G7 X« » 1-inch 20.0 5472 36481080/60p23.012.755671Canon G7 X
Panasonic FZ1000« » 1-inch 20.0 5472 36484K/30p22.111.751764Panasonic FZ1000
Ricoh GR II« » APS-C 16.1 4928 32641080/30p23.613.7107880Ricoh GR II
Ricoh GR« » APS-C 16.1 4928 32641080/30p23.613.597278Ricoh GR
Sony A7 III« » Full Frame 24.0 6000 40004K/30p25.014.7373096Sony A7 III
Sony A7R III« » Full Frame 42.2 7952 53044K/30p26.014.73523100Sony A7R III
Sony RX100 V« » 1-inch 20.0 5472 36484K/30p22.812.458670Sony RX100 V
Sony A7R II« » Full Frame 42.2 7952 53044K/30p26.013.9343498Sony A7R II
Sony A7S II« » Full Frame 12.0 4240 28324K/30p23.613.3299385Sony A7S II
Sony RX100 IV« » 1-inch 20.0 5472 36484K/30p22.812.659170Sony RX100 IV
Sony A7 II« » Full Frame 24.0 6000 40001080/60p24.913.6244990Sony A7 II
Sony A5100« » APS-C 24.0 6000 40001080/60p23.812.7134780Sony A5100
Sony RX100 II« » 1-inch 20.0 5472 36481080/60p22.512.448367Sony RX100 II
Sony RX100« » 1-inch 20.0 5472 36481080/60p22.612.439066Sony RX100

Many modern cameras are not only capable of taking still images, but can also record movies. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the A9 provides a better video resolution than the RX100 III. It can shoot movie footage at 4K/30p, while the RX100 III is limited to 1080/60p.

 

Feature comparison: Sony RX100 III vs Sony A9

Beyond body and sensor, cameras can and do differ across a range of features. The two cameras under review are similar with respect to both having an electronic viewfinder. However, the one in the A9 offers a substantially higher resolution than the one in the RX100 III (3686k vs 1440k dots). The adjacent table lists some of the other core features of the Sony RX100 III and Sony A9 along with similar information for a selection of comparators. If you need more detail on the specs, you can find comprehensive listings, for example, in the dpreview camera hub.

Core Features
  Camera
Model
Viewfinder
(Type or
'000 dots)
Control
Panel
(yes/no)
LCD
Size
(inch)
LCD
Resolution
('000 dots)
LCD
Attach-
ment
Touch
Screen
(yes/no)
Shutter
speed
(1/sec)
Shutter
flaps
(1/sec))
Build-in
Flash
(yes/no)
Build-in
Image
Stab
Camera
Model
Sony RX100 III»1440 n 3.0 1229 tilting n 2000 10.0 Y Y Sony RX100 III
Sony A9«3686 n 3.0 1440 tilting Y 8000 20.0 n Y Sony A9
Canon G5 X« »2360 n 3.0 1040 swivel Y 2000 5.9 Y Y Canon G5 X
Canon G7 X« »- n 3.0 1040 tilting Y 2000 6.5 Y Y Canon G7 X
Panasonic FZ1000« »2359 n 3.0 921 swivel n 4000 12.0 Y Y Panasonic FZ1000
Ricoh GR II« »- n 3.0 1230 fixed n 4000 4.0 Y n Ricoh GR II
Ricoh GR« »- n 3.0 1230 fixed n 4000 4.0 Y n Ricoh GR
Sony A7 III« »2359 n 3.0 922 tilting Y 8000 10.0 n Y Sony A7 III
Sony A7R III« »3686 n 3.0 1440 tilting Y 8000 10.0 n Y Sony A7R III
Sony RX100 V« »2359 n 3.0 1229 tilting n 2000 24.0 Y Y Sony RX100 V
Sony A7R II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7R II
Sony A7S II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7S II
Sony RX100 IV« »2359 n 3.0 1228 tilting n 2000 16.0 Y Y Sony RX100 IV
Sony A7 II« »2400 n 3.0 1230 tilting n 8000 5.0 n Y Sony A7 II
Sony A5100« »- n 3.0 922 tilting Y 4000 6.0 Y n Sony A5100
Sony RX100 II« »- n 3.0 1229 tilting n 2000 10.0 Y Y Sony RX100 II
Sony RX100« »- n 3.0 1229 fixed n 2000 10.0 Y Y Sony RX100

The A9 is a current model that online retailers, such as amazon, will have in stock. In contrast, the RX100 III has been discontinued (but it can be found pre-owned on eBay). As a replacement in the same line of cameras, the RX100 III was succeeded by the Sony RX100 IV.

Review summary: Sony RX100 III vs Sony A9

So how do things add up? Which of the two cameras – the Sony RX100 III or the Sony A9 – has the upper hand? The listing below highlights the relative strengths of the two models.


Arguments in favor of the Sony Cyber-shot DSC-RX100 III:

  • Ready to shoot: Has a lens build-in, whereas the A9 requires a separate lens.
  • More compact: Is smaller (102x58mm vs 127x96mm) and thus needs less room in the bag.
  • Less heavy: Is lighter even though it comes with a build-in lens (unlike the A9).
  • Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
  • More affordable: Was introduced at a lower price, despite coming with a build-in lens.
  • More heavily discounted: Has been available for much longer (launched in May 2014).


Advantages of the Sony Alpha A9:

  • More detail: Has more megapixels (24 vs 20MP), which boosts linear resolution by 10%.
  • Better image quality: Scores substantially higher (25 points) in the DXO overall evaluation.
  • Richer colors: Generates noticeably more natural colors (2.5 bits more color depth).
  • More dynamic range: Captures a broader range of light and dark details (1 EV of extra DR).
  • Better low-light sensitivity: Can shoot in dim conditions (2.8 stops ISO advantage).
  • Better video: Provides higher definition movie capture (4K/30p vs 1080/60p).
  • More detailed viewfinder: Has higher resolution electronic viewfinder (3686k vs 1440k dots).
  • More detailed LCD: Has a higher resolution rear screen (1440k vs 1229k dots).
  • Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
  • Faster shutter: Has higher mechanical shutter speed (8000/sec vs 2000/sec) to freeze action.
  • Faster burst: Shoots at higher frequency (20 vs 10 flaps/sec) to capture the decisive moment.
  • More flexible: Takes interchangeable lenses and can thus be used with specialty optics.
  • Longer lasting: Gets more shots (650 versus 320) out of a single battery charge.
  • Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
  • More modern: Reflects 2 years and 11 months of technical progress since the RX100 III launch.

If the number of relative strengths (bullet points above) is taken as a guide, the A9 is the clear winner of the contest (15 : 6 points). However, the relevance of individual strengths will vary across photographers, so that you might want to apply your own weighing scheme to the summary points when reflecting and deciding on a new camera.

RX100 III 06:15 A9

In any case, while the comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it remains partial and cannot reveal, for example, the handling experience and imaging performance when actually working with the RX100 III or the A9. At times, user reviews, such as those published at amazon, address these issues in a useful manner, but such feedback is on many occasions incomplete, inconsistent, and unreliable. This is why expert reviews are important. The adjacent table relays the overall verdicts of several of the most popular camera review sites (cameralabs, dpreview, ephotozine, imaging-resource, photographyblog). The detailed reviews can be accessed by clicking on the site logo in the table header.

Review Scores
  Camera
Model
cameralabs dpreview ephotozine imaging-resource photographyblog Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Sony RX100 III»HiRec82/1004.5/54.5/55/5 May 2014 799- i Sony RX100 III
Sony A9«HiRec89/1005/55/55/5 Apr 2017 4,499 i i Sony A9
Canon G5 X« »HiRec78/1004.5/54/54.5/5 Oct 2015 799 i i Canon G5 X
Canon G7 X« »HiRec77/1004.5/53.5/54.5/5 Sep 2014 699- i Canon G7 X
Panasonic FZ1000« »HiRec82/1004.5/54.5/54.5/5 Jun 2014 899- i Panasonic FZ1000
Ricoh GR II« »--4.5/54.5/54.5/5 Jun 2015 699- i Ricoh GR II
Ricoh GR« »-79/1004.5/54.5/54.5/5 Apr 2013 799- i Ricoh GR
Sony A7 III« »HiRec89/1005/5-5/5 Feb 2018 1,999 i i Sony A7 III
Sony A7R III« »HiRec90/1004.5/55/55/5 Oct 2017 3,199 i i Sony A7R III
Sony RX100 V« »HiRec83/1004/55/54.5/5 Oct 2016 999 i i Sony RX100 V
Sony A7R II« »HiRec90/1005/54.5/55/5 Jun 2015 3,199- i Sony A7R II
Sony A7S II« »Rec-4.5/55/55/5 Sep 2015 2,999 i i Sony A7S II
Sony RX100 IV« »HiRec85/1004/54.5/54.5/5 Jun 2015 999- i Sony RX100 IV
Sony A7 II« »Rec82/1004.5/55/55/5 Nov 2014 1,999- i Sony A7 II
Sony A5100« »Rec-4.5/54.5/55/5 Aug 2014 549 i i Sony A5100
Sony RX100 II« »HiRec79/1004.5/55/54.5/5 Jun 2013 749- i Sony RX100 II
Sony RX100« »HiRec78/1004/55/55/5 Jun 2012 649- i Sony RX100

The review scores listed above should be treated with care, though. The ratings are only valid when refering to cameras in the same category and of the same age. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and comparisons of ratings among very different cameras or across long time periods have little meaning. Also, please note that some of the review sites have changed their methodology and reporting over time.

 

Other camera comparisons

Did this review help to inform your camera decision process? In case you would like to check on the differences and similarities of other camera models, just use the search menu below. Alternatively, you can follow any of the listed hyperlinks for comparisons that others found interesting. If you do not see the camera that you are looking for, please send me an email, and I will try to add information on that model to the database.

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