Sony's on a bit of a roll at the moment. It seems like just yesterday it was launching the A7V (it was actually late last year – how time flies), and it’s now followed that up with the sixth generation of A7R. The A7R has long been the go-to full-frame camera for anyone who prioritizes outright resolution, but by going north of 60 megapixels, recent A7Rs have been compromised in other areas. There's the obvious issue of huge image and video file sizes, but the drawbacks of such a high resolution come in other, more subtle forms.
Squeezing more and more pixels (they're actually photodiodes, but I'll use the word pixels for simplicity) onto a sensor of a fixed size - in this case, 35mm full-frame - means each individual pixel must be reduced in size. Shrinking a pixel means it captures less incoming light during a set shutter speed than a larger pixel. This in turn makes the pixel, and by extension, the sensor, more susceptible to generating image noise, and it can also reduce the amount of dynamic range that can be captured.
Sony knew all this when the A7R was in its formative generations, as in addition to the standard A7 lineage, it also produced the A7S line: cameras which intentionally sacrificed resolution in order to improve light sensitivity (hence the 'S' suffix), thereby reducing image noise and boosting low light image quality.
These days Sony seems to have abandoned the A7S line, but the regular A7, now in its fifth incarnation, still exists as an option for photographers who'd rather have the benefits of a more modest pixel count. But while there are image quality drawbacks from increasing resolution (assuming sensor size remains the same), are they still pronounced enough to make a camera like the A7R VI unsuitable of low light or high contrast environments?
I've lab tested every A7R generation (along with all the A7R VI's main rivals), testing resolving power, image noise levels, and dynamic range. As you'd expect, the A7R VI excels in our resolution benchmark, and it’s less impressive in our noise and dynamic range tests. However, the image quality drawbacks of its high pixel count really aren't as significant as you might expect.
Dynamic range (EV):
At lower sensitivities resolution doesn't really affect outright dynamic range. Both the 33MP A7V and the 66.8MP A7R VI perform pretty much identically, capturing 12.5 stops of dynamic range. You need to push past ISO800 for the A7R VI's resolution to start to restrict its dynamic range, whereupon the A7V pulls out a 1-stop advantage. Would you notice this in real-world shooting? Maybe, but remember that these results are obtained by disabling Sony's DRO dynamic range enhancement, so this is a worst-case scenario for the A7R VI. What's more, despite it having a significantly higher resolution than rival cameras such as the ~45MP Canon EOS R5 Mark II and Nikon Z8, the A7R VI outperforms them for dynamic range at all sensitivities.
Signal to noise ratio (decibels):
When it comes to image noise, both the A7R VI and V produce more noise than the A7V, but we'd expect that – the A7V has to have something to show for having half the A7R VI’s effective megapixel count. Where the A7R VI does impress is its ability to match (and at some sensitivities, slightly beat) the Nikon Z8's noise levels, despite the Sony having 32% more pixels. Granted, the Z8 is now a three-year-old camera, but even the far more modern EOS R5 Mark II barely produces less noise than the A7R VI at higher ISOs.
Resolution (line widths/picture height):
Obviously the A7R VI aces our resolution test, resolving far more fine detail than the A7V. It's here that you're most likely to see an image quality difference between the two cameras, assuming you're viewing photos at 100% image size.
With the A7R VI, Sony has demonstrated that you can have incredible resolving power without having to make noticeable image quality compromises elsewhere. Inevitably such an accomplished performance comes at a hefty financial cost, but if you’ve got the cash to splash, image quality from Sony’s latest A7R doesn’t disappoint.
