Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Sony - α7 IV | Sony - α9 III |
|---|---|---|
| Weight | 658 g | 703 g |
| Megapixels | 33 MP | 24 MP |
| Max video | 4K60 | 4K120 |
Between the α7 IV and α9 III, the α7 IV comes out ahead in weight / megapixels, while the α9 III wins on max video. Overall, the α7 IV scores 70.4 and the α9 III scores 71.7 on our Mars Score.
Which should you buy?
These two are nearly even on the Mars Score (70.4 vs 71.7). The decision is not about overall quality — both clear the bar — it is about which specific trade-offs fit your use.
Pick the α7 IV if you carry the device everywhere and weight or thickness has been the deciding factor before. The biggest gaps in its favor are weight, megapixels. The single most decisive one: Weight — 45.00 g less. 658 vs 703.
Pick the α9 III if you care most about max video. Its strongest claims are max video. The single most decisive one: Max video: 4K120 (vs 4K60).
Both ship with comparable sensor size, in-body stabilization, af points, so those specs do not separate the two — focus on the differences below.
Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity says both are well-rounded; the differences are about trade-offs, not quality.
Which should you buy: Sony - α7 IV or Sony - α9 III?
Sony - α9 III leads the current Mars Score by 1.3 points.The more useful decision is the trade-off behind that result: compare megapixels, max video, weight against the way you will actually use the product.
Choose Sony - α7 IV if…
Sony - α7 IV has the measurable edge on weight g, megapixels.
Choose Sony - α9 III if…
Sony - α9 III has the measurable edge on max video.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Sony - α7 IV wins
- ▲Weight — 45.00 g less. 658 vs 703.
- ▲Megapixels — 37.50% more. 33 MP vs 24 MP.
Why Sony - α9 III wins
- ▲Max video: 4K120 (vs 4K60).
Spec comparison
Sensor
| Spec | Sony - α7 IV | Sony - α9 III |
|---|---|---|
| Sensor sizeⓘ | Full Frame | Full Frame |
| Megapixels | 33 MPlead | 24 MP |
| Max ISO | 51200 | 51200 |
Video
| Spec | Sony - α7 IV | Sony - α9 III |
|---|---|---|
| Max video | 4K60 | 4K120lead |
| RAW video | false | truelead |
| Log profileⓘ | true | true |
Autofocus
| Spec | Sony - α7 IV | Sony - α9 III |
|---|---|---|
| AF pointsⓘ | 759 | 759 |
| Eye AFⓘ | true | true |
| In-body stabilizationⓘ | true | true |
Body & Controls
| Spec | Sony - α7 IV | Sony - α9 III |
|---|---|---|
| Weight | 658 glead | 703 g |
| Weather sealedⓘ | true | true |
| Dual card slotsⓘ | true | true |