Sony A7R III vs A9

Sony A7R III vs A9

High-ISO resolution comparison of the Sony Alpha 9 and Alpha 7R III: comparison of high and low resolution in full format at high ISO

The lower the resolution of a camera, the larger the pixels and the lower the noise. Thus, if one wants to photograph at high ISO sensitivities, one should not only take a camera with the largest possible image sensor, but also one with the lowest possible resolution. But is that really the case? We compared the two full-frame cameras Sony Alpha 9 (24 megapixels) and Sony Alpha 7R III (42 megapixels) once at high ISO sensitivities.

The Sony Alpha 9 is primarily designed for speed, with its full-frame sensor resolving “only” 24 megapixels. [Photo: Sony]

The comparison of the two mirrorless system cameras resulted from an internal discussion in the comments in this blog, and was therefore not made 1:1 against each other with the identical lens, as each of our readers where using different lens.

In our laboratory tests, we have been photographing a test image for quite some time, and we proceed as follows: The focal length and aperture combination with the highest resolution in the center of the image, determined in the test laboratory with the standard lens, is the basic setting of the camera, in which an ISO series is photographed in raw and JPEG in automatic aperture mode. With the Sony Alpha 9 and the Alpha 7R III these were different lenses. While the Alpha 9 used the Sony FE 24-70 mm F2.8 GM (SEL2470GM) at 41 millimetres with F4 as the upper class lens, the Alpha 7R III used the Sony FE 24-105 mm F4 G OSS (SEL24105G) at 24 millimetres with F8 as the middle class lens. That the Sony Alpha 7R III would be advantaged by the lens can’t be said to be so.

A first hint that the Sony Alpha 9, despite the lower sensor resolution at higher ISO sensitivities than expected, isn’t better than the Alpha 7R III is provided by our “classic” laboratory test. There we measure the texture sharpness, whereby the DxO Analyzer does not determine a comparable absolute value here, because it does not depend on the sensor resolution, but calculates how many details are visible on a 60 x 40 centimeter photo at a viewing distance of 60 centimeters. This is of course a very theoretical value, but it works quite well if you know how to interpret the numbers. A value of 1 means that all expected details are visible. Values above 1 mean that sharpening has created artificial details that do not belong there, such as double contours. If the value falls below 1, details are missing, where about 0.9 is the threshold at which the images are felt to be sufficiently detailed. If the value falls below 0.8, details are visibly missing. You always have to compare the pictures from practice, because it happens that with identical values one camera subjectively performs a bit better than another. This is one of the reasons why we record an ISO series of test images as described in the first paragraph and evaluate them accordingly in our camera test reports.

The Sony Alpha 7R III, on the other hand, with its 42 megapixels resolution on the full-format sensor, is the current resolution record holder in the Sony E system. [Photo: Sony]

If you now compare the laboratory readings of the Sony Alpha 9 and 7R III (see diagrams below), then both cameras are up to ISO 6,400 at a value of over 1 and at ISO 12,800 still just over 0.9. But then it becomes exciting: The value drops steeply at the Alpha 9 above ISO 6,400, while the Alpha 7R III already catches itself again at ISO 12,800. Even at ISO 51.200, the Alpha 7R III is only slightly below 0.9, while the Alpha 9 drops significantly below 0.8. However, in the brightness noise in the laboratory test, the Alpha 9 has a clear advantage here, and this is quite exactly an ISO sensitivity level. This means that the brightness noise of the Alpha 7R III at ISO 25.600 is as strong as that of the Alpha 9 at ISO 51.200.

But what use are all the theoretical values, what does it look like in practice? Here we have chosen a picture at ISO 51.200, where according to the laboratory clear differences should be visible. Does the Alpha 7R III really show more details and in return is more noisy than the Alpha 9? What is practically relevant for the image impression? To compare the cameras, you can choose different approaches. Do you scale the Alpha 7R III image down or the Alpha 9 image up? We tried both, but the result was the same: purely subjectively, the Alpha 7R III wins quite clearly. It shows more detail and the noise is finer and less annoying. The image of the Alpha 9 looks much more detailed. Even if the images are reduced to six megapixels, so that the loss of detail of the Alpha 9 shouldn’t play a role anymore, the Alpha 7R III still shows the slightly better image, even if there are hardly any differences visible.

Comparison of the Alpha 9 (left) and Alpha 7R III (right) at ISO 51.200. The image of the Alpha 9 was scaled up to the resolution of the Alpha 7R III.

When comparing an specific image section in the image above, the Alpha 7R III shows much more structure in the hair of the doll, the eyelashes are still visible compared to the Alpha 9 and the dress also shows more structure. The 7R III shows a somewhat more aggressive noise, but that doesn’t really matter, because the picture simply looks much sharper overall. The fact that the images are exposed slightly differently is a peculiarity of the cameras, because both were operated in the automatic timer, as already mentioned above. The light source was the same. By the way, so that everyone can get their own picture, we have linked the original JPEG images from the cameras at ISO 6.400 and 51.200 in full resolution below. But beware: the ZIP file generated is about 75 megabytes in size.

By the way, the result does not look any different compared to an Alpha 7S, for example. At ISO 51.200, the noise is already clearly visible, but even less detailed than with the Alpha 9 or 7R III. Physically or optically, there is certainly a maximum somewhere in the current sensor technology where an increase in the sensor resolution no longer brings anything. For example, the APS-C camera has been stuck with a maximum sensor resolution of 24 megapixels for years, apart from the Samsung NX1, which is no longer available and which achieved 28 megapixels. With the Micro-Four-Thirds sensor, the maximum resolution is currently 20 megapixels, with the cameras showing hardly more resolution than with 16 megapixels, but also no more noise.

Who might be wondering what’s going on with Canon: Unlike Sony and Nikon, they use sensors from their own production instead of Sony’s, some of which lag significantly behind in performance at high ISO sensitivities. Thus, the Canon EOS 5DS R with its 50 megapixel sensor only reaches a maximum of ISO 12,800 and at ISO 6,400 shows about the same level of detail as the Sony Alpha 9 at ISO 51,200, despite its significantly higher resolution, which the 5DS R can only play at low sensitivities and then even surpasses a Sony Alpha 7R III. However, the EOS 5DS R is also over two years older than a Sony Alpha 7R III and so it remains to be hoped that Canon will perhaps bring models with improved sensor technology onto the market this year and thus be able to catch up to the competition even with higher ISO sensitivities.

Bottom line

If you have the choice, you should choose the higher sensor resolution, especially in full format. The prerequisites are the latest sensor technology and the latest image processing processors. A lower resolution only plays out its advantages when it comes to fast serial images and storage times, because the data volumes are smaller. But here, too, Sony and Nikon’s high-resolution cameras are now entering speed ranges that are “fast enough” for most applications. You should never forget the lens, because the sensor can’t image what it can’t resolve.

Which is newer Sony A9 or Sony A7R III

Sony A7R III is newer than the Sony A9. Sony A7R III was released in 2018 whereas Sony A9 was released in 2017.

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