Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | OM System - OM-1 Mark II | Sony - α7 IV |
|---|---|---|
| Megapixels | 20 MP | 33 MP |
| Weight | 599 g | 658 g |
| AF points | 1053 | 759 |
| Sensor size | Four Thirds | Full Frame |
Between the OM-1 Mark II and α7 IV, the OM-1 Mark II comes out ahead in weight / af points, while the α7 IV wins on megapixels / sensor size. Overall, the OM-1 Mark II scores 67.4 and the α7 IV scores 70.4 on our Mars Score.
Which should you buy?
The α7 IV edges ahead on the Mars Score (67.4 vs 70.4), but the 3.0-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the OM-1 Mark II if you carry the device everywhere and weight or thickness has been the deciding factor before. The biggest gaps in its favor are weight, af points. The single most decisive one: Weight — 59.00 g less. 599 vs 658.
Pick the α7 IV if you care most about megapixels / sensor size. Its strongest claims are megapixels, sensor size. The single most decisive one: Megapixels — 65.00% more. 33 MP vs 20 MP.
Both ship with comparable max video, in-body stabilization, log profile, 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: OM System - OM-1 Mark II or Sony - α7 IV?
Sony - α7 IV leads the current Mars Score by 3.0 points.The more useful decision is the trade-off behind that result: compare megapixels, sensor size, weight against the way you will actually use the product.
Choose OM System - OM-1 Mark II if…
OM System - OM-1 Mark II has the measurable edge on weight g, af points.
Choose Sony - α7 IV if…
Sony - α7 IV has the measurable edge on megapixels, sensor size.
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 OM System - OM-1 Mark II wins
- ▲Weight — 59.00 g less. 599 vs 658.
- ▲AF points — 38.74% more. 1053 vs 759.
Why Sony - α7 IV wins
- ▲Megapixels — 65.00% more. 33 MP vs 20 MP.
- ▲Sensor size: Full Frame (vs Four Thirds).
Spec comparison
Sensor
| Spec | OM System - OM-1 Mark II | Sony - α7 IV |
|---|---|---|
| Sensor sizeⓘ | Four Thirds | Full Framelead |
| Megapixels | 20 MP | 33 MPlead |
| Max ISO | 102400lead | 51200 |
Video
| Spec | OM System - OM-1 Mark II | Sony - α7 IV |
|---|---|---|
| Max video | 4K60 | 4K60 |
| RAW video | false | false |
| Log profileⓘ | true | true |
Autofocus
| Spec | OM System - OM-1 Mark II | Sony - α7 IV |
|---|---|---|
| AF pointsⓘ | 1053lead | 759 |
| Eye AFⓘ | true | true |
| In-body stabilizationⓘ | true | true |
Body & Controls
| Spec | OM System - OM-1 Mark II | Sony - α7 IV |
|---|---|---|
| Weight | 599 glead | 658 g |
| Weather sealedⓘ | true | true |
| Dual card slotsⓘ | true | true |