Choosing your first mirrorless camera: sensor size, lenses and the true cost of the system

Think in systems, not bodies

The most useful advice a first-time buyer can hear is that the camera body is the part you are most likely to replace. Lenses tend to stay. Each manufacturer uses its own lens mount, such as Canon RF, Nikon Z, Sony E or Fujifilm X, and lenses for one mount do not fit another without adapters and compromises. Picking a body therefore means picking the family of lenses you will build around.

That theme comes up repeatedly in DPReview's beginners' forums. In a 2022 thread from a new photographer with a budget of around 800 to 1,000 dollars, euros or pounds, one experienced member asked whether the buyer was prepared to spend about the same again on lenses over a few years. If not, the member suggested choosing a cheaper body and setting the difference aside, because lenses will shape the photographs far more than the camera will. The same reply advised starting with the standard kit and working out what else you need only after some practice, rather than buying every lens up front.

Sensor size, crop factor and what it really changes

Mirrorless cameras for beginners mostly use one of three sensor sizes: Micro Four Thirds, APS-C and full frame. DPReview's long-running explainer on equivalence sets out how to compare them. A smaller sensor captures a narrower view from the same lens, which is where the crop factor comes from. DPReview's example is Four Thirds, whose diagonal is about half that of full frame, so a 50 mm lens frames like a 100 mm lens on a full-frame camera. APS-C crop factors sit around 1.5 to 1.6.

The less obvious part is light. DPReview explains that the f-number describes light intensity per square millimetre of sensor, so it does not change with sensor size, but a larger sensor collects more total light at the same settings. Unless the larger sensor is much worse, that generally means cleaner images in dim conditions and the option of shallower depth of field. The trade-off, as the article notes, is that larger-sensor cameras and their lenses tend to be bigger, heavier and more expensive.

For most beginners, APS-C is a sensible middle ground: noticeably better than a phone in low light, compact enough to carry, and supported by affordable lenses. Full frame is worth considering if you already know you will shoot indoor events, night scenes or portraits with very blurred backgrounds, and you accept the cost of matching lenses. Micro Four Thirds trades some low-light headroom for smaller telephoto lenses, which suits travel and wildlife on a budget.

Start with what and how you will shoot

Replies in the same DPReview thread pushed the buyer to answer a few questions before looking at models at all. Do you actually want interchangeable lenses? How much do size and weight matter? Have you tried both an electronic and an optical viewfinder? One member who travels often explained choosing a small APS-C Sony with an 18-55 mm kit zoom precisely because it was light and affordable, and pointed out that almost any current camera will serve a beginner who is willing to learn the basics.

That is a useful reality check. Write down the three subjects you photograph most, whether that is children indoors, hiking trips, sport or street scenes, and where the camera will live when you are not using it. A camera that is pleasant to carry gets used; one that stays home because it is too heavy does not. If you can, handle your shortlisted bodies in a store, or rent one for a weekend, to judge the grip, the menus and the viewfinder before you commit. If full frame is on your list, our research review of the Sony A7 IV (Sony Alpha 7 IV review) shows how much of its premium depends on video features that many stills shooters will never need.

Check the lens roadmap before you buy

Before committing to a mount, list the lenses you are likely to want in the next two or three years: perhaps a bright prime for portraits and low light, a wide zoom for landscapes, or a long telephoto for birds and sport. Then check whether affordable versions exist for the smaller-sensor bodies in that system, not only for its full-frame cameras.

Third-party support can change this picture, so look beyond the camera maker's own catalogue. In April 2024, for example, Sigma announced six lenses designed for Canon's APS-C RF cameras, such as the EOS R7 and R10, including an 18-50 mm F2.8 zoom and several F1.4 primes. As trade coverage of that launch pointed out, the shared RF mount means those lenses also fit full-frame EOS R bodies, but with a cropped field of view. If you think you may move up to full frame later, check how each system handles its smaller-format lenses on its larger bodies before you invest heavily in them.

Features that matter more than the spec sheet suggests

Stabilisation is a good example. Some entry bodies have no in-body image stabilisation and rely on stabilised lenses instead, which matters if you plan to use older or bright prime lenses without it. Our research reviews note that the Sony A6400 (Sony Alpha 6400 review) has no in-body stabilisation, and the original Nikon Z 50 (Nikon Z 50 review) also leaves stabilising to the lens, while the Canon EOS R7 (Canon EOS R7 review) includes five-axis in-body stabilisation.

Screen design, card slots and battery life also shape daily use. If you plan to film yourself, check which way the screen flips and whether a microphone on the hot shoe will block it. If you shoot events, two card slots provide a backup copy. Look at the battery model too, because it decides how much spare batteries will cost. The Canon EOS R10 (Canon EOS R10 review), for instance, uses the small LP-E17 battery and has a single UHS-II SD slot, which our review explains in context.

The true cost of getting started

A realistic starter budget includes the body and kit lens, at least one spare battery, a fast and reliable memory card, a protective bag, and editing software if you plan to shoot raw files. Within a year, many people add a second lens. Pricing these extras before choosing a body often changes which camera looks like the better deal.

Used equipment can stretch a budget further. Several members in the same DPReview thread recommended buying used or choosing a body a generation or two old, so that more money goes toward lenses while you discover which kind of photography you enjoy. Others suggested that a one-lens superzoom bridge camera might suit a beginner who mainly wants range and is not yet sure about interchangeable lenses.

Canadian buyers should also check warranty status. The Canadian price-comparison site PhotoPrice.ca explains that manufacturers' Canadian subsidiaries generally honour warranties on products they imported, and that grey-market stock, meaning items not imported by the local subsidiary, usually comes with a retailer or third-party warranty instead. The hardware is the same, but service and support may not be, so confirm what coverage you are getting before choosing the lower price.

From a tech standpoint

Choose the lens system first and the body second, because the glass will outlast the camera. For most beginners, an APS-C kit with a clear path to one or two affordable lenses is the best balance of quality, size and cost. Budget for batteries, cards and a second lens from the start, and check whether the warranty is Canadian before you buy.