Professional portrait and landscape photographers often use medium-format cameras because of their superb performance under controlled lighting conditions. However, as these cameras are definitely not designed for so-called “action photography” scenarios, they generally do not perform well with respect to DxO Labs’ Low-Light ISO metric. Because of this inherent low-light limitation, medium-format cameras do not receive top marks on the DxOMark Sensor Overall Score, even though they may show outstanding performance with respect to Color Depth or Dynamic Range.
The DxOMark Sensor Overall Score is designed to weight equally three photographic scenarios that, taken together, cover nearly the entire photospace: Portrait, Landscape, and Action Photography. Each scenario represents use cases that stress a specific parameter of the camera—Color Depth, Dynamic Range, and Low-Light ISO, respectively. When looking at cameras with narrow or specialized uses, considering the specific ranking for the right metric or metrics is critically important.
Medium-format cameras are designed to perform best in particular use cases—specifically, they are mostly used in a studio environment where light level is not a problem, and in landscape photography, where they are most often used with tripods to facilitate long exposure times. In light of their specific uses, medium-format cameras are optimized for low ISO performance, and so do not feature a wide “analog” ISO latitude, meaning that they show some limitations at high ISO speed. Consequently, medium-format cameras end up with lower Low-Light ISO rankings compared to DSLRs, and this affects their DxOMark Sensor Overall Score.
The table below shows the ISO latitudes of the medium-formats cameras currently ranked on DxOMark, with two high-end D-SLRs included for comparison:
|Camera||ISO latitude (manufacturer specification)|
|Hasselblad H3DII 39||50 - 400|
|Phase One P45+||50 - 400|
|Leaf Aptus 75S||50 - 800|
|Mamiya ZD||50 - 400|
|Nikon D3||200 - 25600|
|Canon 5D Mark II||100 - 25600|
It is pretty clear from these data that medium-format cameras have much less ISO latitude than D-SLRs. Again they are not designed for use at high ISO sensitivity.
While few photographers would consider using them for photo-reportage or during sport events, medium-format cameras perform very well with respect to Color Depth (corresponding to a Studio/Portrait scenario), and also perform well with respect to Dynamic Range (Landscape photography), with scores surpassing most D-SLRs.
Finally, it is important to remember that the DxOMark Sensor Scores report only on sensor RAW output, and do not address other important aspects of camera performance such as effective resolution, mechanical robustness, ease of use, flexibility, shooting speed, film/digital compatibility, and so on.