If you take a look at the current digital camera market, it’s clear that DSLRs (digital single-lens reflex) cameras are on their way out. Modern sensors that allow continuous readout at high frame rates and on-sensor phase detect auto-focus have eliminated the need for the mechanically complex and large mirror assemblies of DSLRs. In their place have come what is called interchangeable lens cameras (ILCs) or mirrorless system cameras. Just like DSLRs they provide the possibility to switch lenses, but the replacement of the mirror and prism assembly with an electronic viewfinder (EVF) has enabled a reduction in size, including that of the lenses, as the flange-sensor distances could now be reduced. This also means that it is possible to use lenses designed for DSLRs by using adapters.

Camera companies have experimented with various sensor sizes and lens mounts, with some proving unsuccessful, such as Nikon’s 1 system. We now have arrived at a situation similar to the DSLR era, with the traditional camera makers leading with traditional sensor sizes. In this overview, I’ve concentrated on systems aiming at the consumer and prosumer, and hence omitted medium-format and Leica’s offerings.

Full-frame

Full-frame means a sensor size similar to the traditional 35mm image size of 24x36mm. This also means that there is no “crop factor”, so focal lengths are directly comparable. 50mm is considered normal, shorter than that wide-angle, longer telephoto. As the lower end of the market is increasingly being taken over by phone cameras, we see that many manufacturers focus on this part of the market, where more expensive products with higher margins offset the smaller numbers. The advantage of the relatively large full-frame sensor are higher resolutions or better low-light sensitivity, whereas the main disadvantages are larger size, higher weight, and higher cost.

• Canon EOS RF: Canon was relatively late to the ILC game, but sells several bodies and already a quite large variety of lenses, including exotics such as a 1200mm telephoto prime. SLR-era EF lenses can be used with an adapter. The entry-level RP model is priced quite affordably at around €1,100. An affordable 70-300mm telephoto zoom is missing from the range, so you’ll have to use the EF model with adapter. There is however a competitively priced 100-400mm f5.6-8.0 that offers a bit more range on the long end. Those who want to spend more money have most of the traditional lineup of f2.8 and f4 lenses available.
• Nikon Z: Just like Canon, Nikon was a bit late to the large-sensor ILC game, as they first made an attempt with the small-sensor 1 system to avoid cannibalizing DSLR sales. Four full-frame bodies are available, with the Z5 starting at approx. €1,550. The lens selection is still somewhat limited, especially with regard to tele lenses. F-mount lenses can be used with the FTZ adapter, so if you’re looking for an affordable tele option, you can use the existing 70-300 lens. Alternatively you could use the DX-format 50-250mm lens, albeit at a loss of resolution.
• Panasonic S: Panasonic was an ILC pioneer, using the micro four-thirds mount. They added a range of full-frame cameras in 2019, using Leica’s L mount. The cameras clearly aim at the prosumer and professional user, with the cheapest camera, the DC-S5, starting at approx. €2,000. The lens range is limited, so to me this is not a very attractive option.
• Sony Alpha FE: Sony, not being among the traditional SLR companies, jumped onto the ILC bandwagon quite early. They have earned a good reputation especially for video use. The full-frame mount is called the FE mount, not to be confused with Canon’s EF mount. Prices are relatively high, with the latest iteration of the entry-level model, the A7 Mk IV, coming in at approx. €2,800. The lens range is quite large, but expensive. Both a 24-105 and a 70-300 will cost you more than a grand.

APS

The Advanced Photo System (APS) was an attempt to modernize film photography by using a new film cartridge and new aspect ratios. Introduced a couple of years before digital photography became commonplace, it failed to become a success. It’s legacy is in its smaller APS-C image size (approx. 16x24mm), which was a common sensor size for DSLRs from the very beginning. This results in a “crop factor” of 1.5 to 1.6, meaning that you have to multiply the focal length of a lens by this factor to get the full-frame equivalent image angle. Hence a 35mm lens is a standard lens for APS-C format cameras. The advantages with regard to full-frame are smaller camera and lens sizes and lower cost. The crop factor can also be desirable for telephoto use. The disadvantages are lower resolution or smaller photosites and hence less light sensitivity. Nevertheless, APS-C remains a sweet spot for consumer camera sensor size.

• Canon EOS M: Canon’s relatively small range of APS format ILCs. The M200 and M6 are compact-style, the M50 Mk II is held in SLR style and attractively priced at approx. €620. The M mount is not compatible with the full-frame RF mount. EF lenses can be used with an adapter. The lens range is very small, with telephoto options limited to 200mm. At least there’s an affordable wide-angle zoom. Now that APS RF cameras are available, this system will probably cease to be sold.
• Canon EOS RF-S: Canon finally followed Nikon’s example of using its full-frame lens mount for APS cameras, with the announcement of the R7 and R10 in the first half of 2022. Both feature SLR-style bodies. The R10 is priced at approx. €1,000. Native RF-S lens selection is extremely limited at this time (only an 18-45 and an 18-150 are available), but you can of course use full-frame RF lenses, and EF/EF-S lenses with an adapter.
• Nikon Z: Sticking to their one-size-fits-all approach to lens mounts, Nikon uses the same mount for APS and full-frame camera’s – which does of course mean that you can use (some) F-mount lenses with the FTZ adapter. Nikon currently sells three APS sensor models: the Z50, the vintage-styled Zfc, and the smaller Z30. They are priced at approx. €1,000. €1,100, and €800, respectively. Just like with the F-mount, there are dedicated DX lenses, but this range is currently extremely limited: There’s only a 16-50, 50-250, and 18-140. You can of course use the full-frame Z lenses, but since these are designed for full-frame coverage, they are larger and more expensive than strictly necessary. Nevertheless, a Z50 with the 16-50 and 50-250 could be a nice kit that comes in at approx. €1,400.
• Fujifilm XF: Never a player in the traditional DSLR market, Fujifilm took a different approach to ILCs with their vintage-styled offerings. Both compact and SLR-style models are available. The X-T30 II is the entry-level SLR-styled model at approx. €900, available both in black and black/silver “panda” look. The lens range is Ok, aiming mostly at the consumer/prosumer market and lacking telephoto primes. Some lenses appear a bit expensive compared to the competition (70-300 €800), others less so (100-400 €1,600). If you dig the vintage styling, this system might be worth a closer look.
• Sony Alpha E: Along with its range of full-frame camera, Sony also sells APS-sensor cameras (initially dubbed NEX). The E mount is physically identical to the FE mount, but will lead to vignetting on the full-frame cameras. This means that you can use FE-mount lenses on the APS cameras, just like you can with Nikon Z mount lenses and Z DX cameras. The E-range cameras all feature compact styling with EVF, so if you want an SLR-style camera with grip, you’re out of luck. The lens range, which consists mostly of zooms, is quite complete, though an f2.8 or f4 telephoto zoom is absent. The tele range goes up to 70-350mm. It is somewhat reminiscent of Nikon’s F-mount DX range, aimed more at the consumer with several 18-xxx options. Good selection of third-party lenses.

Micro Four-Thirds

When Olympus entered the DSLR market, they decided to use a different sensor size of 17.3x13mm, with a 4:3 aspect ratio (instead of the traditional 35mm 3:2), resulting in a crop factor of 2. Olympus has a long history in using smaller formats, dating back to its half-frame range of PEN cameras. Panasonic later joined Olympus. Both companies became pioneers in the ILC market with the introduction of the Micro Four-Thirds mount, designed for mirrorless applications. The advantages are the potential for even smaller and lighter cameras and lenses, plus the 2x crop factor can be of interest for those who want long telephoto reach. Most cameras also feature in-body image stabilization. The disadvantages are reduced resolution, smaller photosites, and generally less advanced sensor designs that e.g. offer poorer auto-focus performance than the APS and full-frame offerings of competitors. Since they use the same mount, Olympus and Panasonic lenses can be used interchangeably on cameras of either brand, with some limitations regarding functionality.

• Olympus (now OM Digital Solutions): Olympus started with their PEN-branded compact-style camera, but has since moved mostly to SLR-style cameras. Just like Fujifilm (and Nikon with the Z fc), they’ve adopted a more vintage-style look, with some models being available in black and silver. Prices start at approx. €675 for the OM-D E-M10 Mk IV. Not surprisingly for a system that has been on the market for many years, the lens range is quite extensive. Most bases are covered, with the offerings being relatively small, light-weight, and affordable. As I’m someone who uses mostly telephoto zooms for animal photography, this is a range that tickles my fancy.
• Panasonic: Panasonic sells both compact-style and SLR-style camera, and has a good reputation among video users. The styling is more modern than that of Olympus. The entry level models are priced very affordably at a bit above €500, with the mid-range DC-G9 SLR-style model selling for around €1,000. The lens range does of course overlap with the Olympus offerings quite a bit, but does contain some Leica-branded examples.

Conclusions

The big three (Canon, Nikon, Sony) would like us to spend our money on full-frame models, so this is where there’s the largest choice. If you previously were a full-frame DSLR user, this is the logical place to continue, and adapters will enable you to use your legacy lenses while slowly making the move to the new mount.

If you are more on the consumer-side of things and were happy with your APS-format DSLR, things are a bit more difficult. Canon’s and Nikon’s camera and lens range is very small, though once again you can use legacy lenses to round out the range or use lenses that you already own. Even on its own, the Nikon Z50 with its two DX lens options is likely to satisfy most of your photography needs. If you’re not locked into going with Canon and Nikon, both Fujifilm and Sony offer considerably larger ranges. On the Fujifilm side this goes combined with vintage styling, on the Sony side this unfortunately means going with a compact-style body, which may be awkward with longer lenses.

Finally, there’s Micro Four-Thirds with is compact cameras and lenses and extensive lens range due to its almost 15 years of history. If light weight is your priority and auto-focus performance (for sport or similar) isn’t, this might be your thing.

Comparison

I’ve tried to compile a table of possible replacements for my current kit, which is a Nikon D90 with a Tamron 17-50 f2.8, and Nikon 70-300 f4.5-5.6 VR (1st gen). Total price for this kit back in 2010 was approx. €1,400. Hence I’ve chosen mid-range bodies, a telephoto zoom (in the 400-450mm effective range), and both slow-aperture and (where possible) faster-aperture mid-range zooms. I’ve also added, but not taken into account for the total price, a wide-angle zoom, a macro lens (about 90mm effective focal length), a 600mm-effective zoom, and other interesting (to me) lens offers. I’ve stuck to APS and m4/3 offerings, as the full-frame options (possibly with the exception of the Canon EOS RP) are considerably more expensive.

The prices of the offerings by Fujifilm, Sony, Olympus, and Panasonic are all in the same ballpark, especially considering that the prices are always fluctuating. A choice here can be dependent on camera functionality and lens selection. You can also go a body up or down in the range. There’s more lens choice than with the younger Nikon Z and Canon RF systems, which are more focused on full frame. The Sony body is in a very compact style with only a small grip, which might be an issue with larger lenses.

The new Canon RF-S mount R10 is an interesting option if you can make the lens selection work. For a mid-range zoom, you are currently limited to the 18-45 kit lens. An EF-S wide-angle zoom would have been an option, but they no longer seem to be available. RF lenses are probably your best bet. Canon has not yet released a 70-300mm tele zoom, selling an affordable and lightweight but slow 100-400mm instead, along with a more expensive 100-500mm. If you are an existing Canon user who wants to re-use EF lenses or get a second body next to a full-frame body, this system is probably the right one for you.

The Nikon option looks a bit less attractive right now. The lens range is also very small (yes, there is a 50-250mm), and the FTZ adapter is quite expensive. You do however get the option to use the (expensive) full-frame Z lenses. Currently I would consider this to be an option if you are happy with the two native lenses, or have a couple of expensive F-mount lenses that you want to continue using. Nikon does not make an affordable 100-400mm like Canon does, so if you need the longer telephoto reach, Canon is the better option for you.

Not shown in the table is the Canon EOS M50 Mk II. This is quite a bargain with the kit (15-45 and 50-200) coming in below €1,000. The caveat is that the telephoto zoom is limited to 300mm effective, and that the native lens support is extremely limited. As this system is probably to be replaced by the RF-S system, it is unlikely that new lenses will appear, so I would skip this system.