Digital SLR or Interchangeable Lens Camera: which is right for you?

If you are looking to upgrade from your compact camera but aren't sure whether to go for an interchangeable lens camera or SLR, here are some pointers to make the decision easier.

Whether you call them mirrorless, EVIL (Electronic Viewfinder, Interchangeable Lens) or compact system cameras, there's no doubt that this segment of the photographic market is here to stay.

From humble beginnings in 2008 with the Panasonic G1 and Olympus E-P1, interchangeable lens cameras are now giving digital SLRs a run for their money with the range of options available. But what are the difference between them and which should you choose?

What is the difference between an SLR and ILC?

Digital SLRs have evolved from a standard Single Lens Reflex design in use since the 19th century. A digital SLR has a mirror and pentaprism arrangement, which reflects light from the lens into the optical viewfinder so you can see the image before it is taken. When the shutter is pressed, the mirror flips up to let the light hit the image sensor.

An ILC does not have a mirror or pentaprism, making it a lot smaller than a digital SLR. Live View is permanently active on the LCD screen, just like it is on a compact digital camera. Some ILCs also have an electronic viewfinder (EVF) as well that works like a mini-LCD display, showing all the shooting options available.

As a result of their engineering, digital SLRs are often big and bulky creatures that can weigh over 500 grams on their own, without a lens. ILCs are meant to be much lighter and more compact so they are easier to carry and are ideal for travellers who want the flexibility of taking a range of lenses. Most manufacturers who make ILCs target them towards photographers looking at a step-up from their compact camera, but who aren't ready for a digital SLR.

If size is the most important thing to you, consider one of the baby ILCs on the market coupled with what's called a pancake lens. These are lenses that are a fixed focal length (no zoom) and very compact. Current models that are almost pocketable with a pancake lens attached include the Panasonic GF3, Olympus Pen Mini or Sony NEX-C3.

Not all ILCs are created equal

Almost every major photography brand has an ILC of some description, except for Canon at the time of writing. They all have different names, but do similar things.

Panasonic	Olympus	Sony	Samsung	Nikon	Pentax
G series	Pen series	NEX series	NX series	Nikon 1	Q series

Each brand uses its own lens mount with specially designed lenses. You can also buy adapters that allow you to mount many different lenses apart from the "official" branded ones on each of these ILCs. For example, the Nikon 1 system is compatible with an adapter that lets you put on any Nikon F-mount lens from the company's SLR range. Do be aware that when using one of these adapters you may not be able to control the lens through the camera, while exposure and autofocus may be manual.

Only Panasonic and Olympus can swap lenses between them because they are both designed to the same standard, Micro Four Thirds. As most photographic manufacturers have only started developing their ILC systems over the past few years, the native accessory ecosystem can be quite small. Manufacturers like Panasonic currently have 14 dedicated lenses available, but this pales in comparison to the 400-odd Nikkor lenses that are available for Nikon SLRs.

Do ILCs offer all the same features as digital SLRs?

In most cases, ILCs have very similar features to digital SLRs. For example, you get manual exposure controls just like SLRs have, as well as automatic mode should you just want to point and shoot. HD video recording is often implemented in a much better way on ILCs, as what you see on the screen is what you get because Live View is always activated.

Where ILCs struggle at the moment is in speed. Want to capture sports or action photography? You'll want to buy an SLR, as most ILCs on the market are just not that fast at capturing continuous shots — with the exception of cameras such as the Nikon 1.

Battery life is also reduced on ILCs as a general rule as resource-intensive features like the LCD screen are switched on all the time. Some ILCs have accessory ports that are used to attach anything from external microphones to macro photography lights and stand-alone electronic viewfinders.

Accurate (and quick) focusing used to be a big issue with ILCs, but this has significantly improved over the past few years. The new generation Nikon 1 and Olympus Pen cameras both claim to have incredibly fast autofocus, even quicker than their SLR counterparts.

What does sensor size have to do with it?

Not all ILCs have the same sized sensor. The chart below gives you a relative idea of how physically big the sensors are between camera brands. As you can see there's quite a bit of difference between them, and only two camera brands have the same physical-sized sensor as consumer SLRs using APS-C format, the Sony and Samsung systems.

Generally, bigger is considered better when talking about sensors. Smaller sensors, like those found in compact cameras, tend to be more susceptible to noise issues at higher ISO sensitivities and are often not as effective as larger ones in low light conditions. A smaller sensor size also limits things like shallow depth of field and ultra-wide lenses. As is always the case, though, there's a silver lining to this cloud: the smaller the sensor, the lighter and more compact the lens can be given it doesn't need to cover such a large surface area.

Crop factor is also an issue with all sensors that aren't full frame — read up more on our digital SLR basics article.

Which camera has the best image quality?

We knew you were going to ask that. Image quality has to do with a range of factors, including the combination of image sensor and image processor, as well as the lens quality. As such it's difficult to say which camera will produce the best images for your particular purposes without knowing what you want to shoot. The top-end ILCs using APS-C sensors are definitely able to produce photos that are as good as those produced by equivalent competing SLRs.

So which camera should I buy?

That bit is up to you. In short, if you want the most portable option for everyday photography or travel, choose an ILC. For the widest range of accessories and flexibility, with a view to get a bit more serious about your photography in the future, choose an SLR.

That said, ILCs and SLRs are growing closer each day. The best advice we can give to potential photographers is to do your research and experiment with both types of camera to see which feels best to you before purchasing. Finally, whether you end up buying an ILC or an SLR, make sure to enjoy your photographic journey.

For more, make sure to read our articles on Best digital SLRs for beginners and Best interchangeable lens cameras.