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The RX1R III is Sony's latest full-frame, prime lens compact. It's a 61MP update of a series that dates back to the original RX1 in 2012 and that hasn't seen a refresh since 2015's RX1R II.
But a lot has changed in that time. The original RX1 arrived a year before Sony introduced its first full-frame photo-focused mirrorless camera, the a7. Since then we've seen four generations of a7, five of the high resolution a7R series and, more recently the introduction of the more compact a7C models. It's these, and the high-resolution a7CR in particular, that draw the RX1R III's specs into sharp relief.
Especially given the a7CR was launched for $3200/€3700/£3200, whereas the RX1R III has a list price of $5100/€4200/£4200.
Does the cheaper, more flexible camera obviate the need for an updated RX1, or is there more to the story? We dig a little deeper.
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Commonality
It's entirely fair that people would look at the RX1R III and wonder whether Sony's budget high-res a7CR model can't do more, for (a lot) less, mainly because of the high degree of commonality between the two cameras' spec sheets.
Both cameras have the same 61MP full-frame BSI sensor at their heart, and combine this with Sony's latest Bionz XR processors and "AI processing unit," meaning the two cameras should provide comparable image quality, speed and AF capabilities. The co-processor is dedicated to running the complex algorithms developed by machine learning to recognize and track a range of subjects.
They also share the same viewfinder: a 2.36M dot unit with optics that deliver 0.7x magnification. That resolution is relatively low by modern standards, but is one of the highest available in the 0.39 Type (∼8 x 6mm display) panel format. Most higher resolution displays are 0.5 Type (10.1 x 7.6mm), which take up more space with a larger panel, surrounding case and optics. In both these models, the EVF panels have been chosen to minimize the amount of camera taken up by the viewfinder.
Size
The key difference between the two cameras is probably size. The a7CR is very small for a full-frame ILC, but that's quite a significant qualifier. The RX1R III's body is significantly smaller, in practice, than the a7CR's.
Add in a lens and the difference becomes even greater. The RX1R III's lens pushes back almost to the point of touching the sensor, whereas the a7CR has to leave room for a mechanical shutter and lens mount between the sensor and the rear element.
For some users, the difference isn't going to be meaningful: once a camera isn't pocketable, the degree to which it's not pocketable isn't as important. But as a carry-everywhere camera or a camera you want to be relatively unobtrusive, the difference may well be critical to some.
In terms of weight, at 498g, the RX1R III is 3% lighter than the a7CR even before you add a lens. Attach the Sigma 35mm F2.0 we used in the graphic above and the ILC comes out as 70% heavier.
Stabilization
Other than the ability to switch lenses, perhaps the most obvious difference between the a7CR and the RX1R III is that the CR has image stabilization.
There's certainly an argument to be made that a bright 35mm lens doesn't need stabilization (hence so few primes historically having the feature), and that the a7CR's stabilization is more valuable when you mount longer lenses on it.
But, even though, in principle, more moving elements risk denting absolute image quality, in practice the extra stability a good IS system brings means more shots that deliver the full capability of the 61MP sensor.
The RX1R III uses the same Zeiss-branded lens as the 2012 version and, in the name of size, illuminates the sensor and very little beyond it: it would need to project a larger image circle to allow sensor-shift IS (making both the lens and body bigger), or would need a complete redesign to have optical stabilization incorporated into the lens itself.
Shutters
As alluded to in the previous slide, the a7CR has a physical shutter in front of its sensor. In this case it only has a series of shutter blades to end the exposure: an electronic first curtain shutter approach. In most respects this works as well as a full mechanical exposure plane shutter with the only risk being misshapen bokeh when used with wide apertures and very short exposures. The a7CR's flash sync is limited to 1/160 sec.
By contrast, the RX1R III has an in-lens, 'leaf' shutter, which closes in from several directions, rapidly creating an ever smaller aperture as it does so. This affects the light level to the entire sensor as it closes and opens, meaning it has a whole-sensor, 'global' shutter action. This allows the RX1R III to sync with flashes up to its maximum shutter speed.
However, it's worth noting that the camera's maximum shutter speed varies with aperture, because the shutter has more distance to cover when the aperture diameter is large. Like the previous model, the RX1R III can shoot at up to 1/2000 sec when wide open, 1/3200 sec at F4 and narrower, and 1/4000 sec when stopped down to F5.6 or beyond.
Batteries
The larger body of the a7CR has enough room for Sony's largest NP-FZ100 battery, a honking-great 16.4Wh unit that powers the a7CR to a CIPA battery rating of 530 shots per charge using the rear screen and 470 through the viewfinder.
The RX1R III makes do with the smaller NP-FW50 battery, which has a capacity of 7.3Wh. This helps give the smaller camera ratings of 300 and 270 shots per charge, respectively. Which aren't as impressive but also aren't terrible. This is big improvement over the 4.5Wh BX1 battery used in the previous RX1 models which, despite ratings of 220/200 shots per charge, were limiting enough that the RX1R II invited jokes about giving such a film-like experience that it felt like you were limited to 36 shots at a time.
Screens
The knock-on effect of the move to the larger battery - the NP-FW50 is twice as deep as the one used in the previous model: taking up 18.5mm of a body that's only around 31mm, front to back - is that Sony has decided a moving rear monitor would add too much additional depth. It features a 2.36M dot (1024 x 768px) panel, but one that can't be moved away from the camera for waist-level shooting.
By comparison, the a7CR has a 1.04M dot (720 x 480px) display but one that's mounted on a fully-articulating hinge, making it more useful for waist-level work, video, selfies and tripod-based photos. On which note, the a7CR also has a multi-shot high res mode (arguably best suited to landscape work), which the RX1R III lacks.
It should, perhaps, be noted that the first four generations of X100 sold quite happily with a fixed rear screen, as did the first two generations of Leica Q and all Ricoh GRs to date. However, there is certainly a part of the audience for fixed-lens compacts that finds it useful as both Fujifilm and Leica have adopted tilting screens in their more recent models.
Summary
Perhaps ironically, several of the decisions that have been most criticized: the small, hence low-resolution, EVF and the fixed rear screen of the RX1R II, were made to keep the body as small as possible, and maximize the size difference between the RX1R III and the a7CR. And yet its these same compromises that will, to many photographers, make the a7CR look more attractive.
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We believe a fixed-lens camera is thing unto itself: it isn't just an interchangeable lens camera with restrictions. And, much as we love them, we recognize that the greater flexibility of an ILC will often win out over the size and focus of a fixed-lens camera for the majority of people.
We suspect the respective pricing of the RX1R III and the a7CR will reduce the compact camera's appeal still further. But until we've shot with it more, we're not going to just assume that the more flexible camera is inherently better.
