What is a CSC: compact system camera technology explained

What is a CSC? A compact system camera is similar to a DSLR, but with these notable exceptions…

They go by a number of different names: Hybrid, MILC (mirrorless interchangeable-lens camera) – even EVIL (electronic viewfinder interchangeable-lens) – but however you prefer to refer to them, CSCs (compact system cameras) all do the same thing: they offer the advantages of a digital SLR in a smaller, lighter format.

Those advantages include larger sensors than compacts (for the most part – see below), interchangeable lenses, the ability to use hotshoe flashguns and other accessories, and advanced controls. It’s the latter that helps to differentiate a CSC from a small SLR.

Many camera manufacturers have compact DSLRs in their range, but these are invariably targeted at beginners.

Compact system cameras, on the other hand, tend to offer more manual control over camera settings, and high-end features such as faster continuous shooting, 4K video recording and weather-sealed bodies.

SEE MORE: 5 things photographers will learn switching from DSLR to mirrorless

There’s a lot to be said for shaving weight from a camera kit. You’re more likely to take it with you, for a start, meaning that you’ll be able to make the most of potential photo opportunities.

Being more unobtrusive than a full-size DSLR – when they’re twinned with a suitably stubby lens, at least – CSCs make excellent cameras for street photography, reportage and documentary work.

Panasonic kicked off the current CSC boom with the release of the Lumix G1 mirrorless camera in 2008, followed by Olympus with its Pen E-P1 in 2009.

Both cameras were based around the Micro Four Thirds system, a standard developed by the two companies that enables lenses from one manufacturer to be used on cameras from another.

Since then, the likes of Sony, Samsung, Fujifilm and Nikon have released mirrorless cameras – although none conform to the Micro Four Thirds format, relying on their own lens mounts instead.

Because CSCs have fewer moving parts inside, they don’t have to follow the traditional SLR design. A number of CSC manufacturers have opted to keep DSLR styling, albeit miniaturised, but there are also plenty of retro-looking and rangefinder-like cameras, including those in the Olympus Pen and Fujfilm X ranges, which offer an alternative choice for the style-conscious.

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Panasonic cameras – the full and complete range explained
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Pentax cameras – the full and complete range explained

What is a CSC?

1 Interchangeable lenses
Like an SLR, a compact system camera doesn’t feature a fixed lens. Instead, you can swap between lenses depending on the subject you’re photographing or the effect you want to achieve. The lens mounts on CSCs are different to those on SLRs, which means that you can’t use SLR lenses on a compact system camera, unless you use an adapter.

2 Look, no mirror!
The most significant difference between an SLR and a compact system camera is the lack of a mirror assembly in the latter.

Not only does this allow CSCs to be much smaller and lighter, it also means they’re much quieter in operation.

Having no mirror means that you have to use the Live View monitor or an electronic viewfinder to compose your shots.

3 Pocketability
As the name suggests, compact system cameras are small – smaller than the majority of SLRs. (Obviously you lose the size advantage the second you add a filthy great telephoto lens!)

Rangefinder-style CSCs are more pocketable than those styled like diminutive SLRs, but the grip and handling afforded by the latter can be an advantage.

4 Viewfinder – or not
The lack of a mirror means that a CSC can’t be fitted with an optical TTL (through the lens) viewfinder.

Many SLR-styled CSCs include a built-in EVF (electronic viewfinder) – a small screen showing the Live View feed generated by the imaging sensor – while others can be fitted with a small viewfinder accessory on the camera’s hotshoe.

SEE MORE: DSLR vs Mirrorless – understanding the key differences

Compact system camera sizes

Some compact system cameras may look just like miniature DSLRs, but they don’t work in the same way. The key difference is the CSC’s lack of a mirror assembly. Removing the mirror and pentaprism – the ‘reflex’ bit of single-lens reflex (SLR) – means that CSCs can be made slimmer.

This has an impact on the design of lenses, as the Flange Focal Distance (FFD) – the measurement from the point where the lens is mounted to the imaging sensor – is shorter in a CSC than it is in a DSLR.

The FFD is an important consideration, as a lens is calibrated to be sharply focused at this distance. This is why you can’t use a DSLR lens on a CSC – the point at which an object would appear sharply focused isn’t the same.

As you’ll see below, adapters allow you to use compatible DSLR lenses on a CSC. These allow you to mount the lens further from the sensor, giving the ‘correct’ FFD for the lens as a result.

Light path
In a digital SLR, some light passes through the mirror to the AF sensor, but the majority is reflected up to the pentaprism, exposure meter and viewfinder assembly. This system takes up a lot of space!

FFD
The Flange Focal Distance is comparatively large in a D-SLR. It remains constant across a manufacturer’s D-SLR range, ensuring that lenses will deliver a sharp image no matter which body they’re on.

Shorter distance
The FFD in a CSC is significantly shorter. For example, Canon’s EF and EF-S D-SLR mounts have an FFD of 44mm, whereas the Q mount used in Pentax’s CSC range uses a distance of just 9.2mm.

Electronic display
In a CSC, the light strikes the sensor, and an image is generated on the rear screen and electronic viewfinder, if present. This means that the body can be much slimmer and shorter in height.

SEE MORE: Best compact system camera – 6 top CSCs go head to head

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Compact system camera sensor sizes

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Don’t be too swayed by the megapixel count when you go shopping for a compact system camera – you need to take the size of the sensor into account, too.

Larger sensors typically produce cleaner images at high ISOs and make it easier to achieve shallow depth-of-field effects, while smaller sensors enable the design of smaller and lighter cameras and lenses.

Unlike D-SLRs, which are broadly separated into two camps – those with sensors that share similar proportions to a frame of 35mm film (‘full-frame’) and those with sensors closer in size to a frame of Advanced Photo System ‘Classic’ film (‘APS-C’) – CSCs offer a much wider range of sensor sizes.

SEE MORE: What camera should I buy: pros and cons of each type (and what they’re best at)

Compact system camera lenses

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EACH manufacturer complements its range of compact system cameras with a set of equally compact lenses. These are built to fit the specific mount that has been adopted in the mirrorless design, which means that you can’t attach lenses designed for a DSLR unless you use an adapter.

As with DSLRs, the lenses are designed to be used only within each manufacturer’s ecosystem, although models that conform to the Micro Four Thirds standard are an exception; you can use Panasonic lenses on Olympus mirrorless camera and vice versa. Third-party lenses from the likes of Sigma and Tamron are also available.

Using legacy lenses
You can’t attach a DSLR lens directly to a CSC. For instance, you can’t use a Sony A-mount lens on an E-mount CSC body, and you can’t attach a Canon EF or EF-S lens to a Canon EOS M3. That is, unless you use an adapter.

Here, you can see Canon’s EF-EOS M mount adapter, which fits between the camera and the lens, enabling a wide range of SLR lenses to be attached.

Other manufacturers and third-party accessory developers also offer similar adapters.

SEE MORE: 6 reasons why a compact system camera (CSC) is better than a DSLR

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