What is a Mirrorless Camera?

The minute I start telling people about mirrorless cameras, they give me a funny look. I have to pause mid-sentence as I realize that they have no idea what I'm talking about.

Here's the high-level definition: a mirrorless camera is what you get when you blend a compact camera with a digital SLR.

That's pretty simple, but it doesn't completely answer the question, especially if you're not familiar with digital SLRs.

So, to answer the question "what is a mirrorless camera", we actually have to begin with a different question: "what is a digital SLR?"

Once you know the answer to that, the "mirrorless" part makes a WHOLE lot more sense.

What is a Digital SLR?

Digital SLRs are the larger, heavier cameras you often see professional photographers toting around.

Pros use these cameras instead of compacts for a variety of reasons:

  • There's no delay when you press the button to take a picture
  • Autofocus is very fast
  • They offer a greater level of manual control
  • You can change the lens depending on what you want to photograph

When you put your eye up to the viewfinder of a digital SLR camera, you see exactly what the lens sees. An arrangement of mirrors inside the camera reflect the image passing through the lens and bounce it up to the viewfinder.

The benefit of this optical system is speed: you zoom the lens, and you instantly see the image change in the viewfinder. Out-of-focus subjects immediately become clear when the autofocus engages.

This type of speed and visual feedback is essential for those who make a living taking pictures. If pros had to deal with the delayed reaction time of most compact digital cameras, they would never capture spontanouse moments. Sports photography as an entire category would not exist.

The mirrors are a good thing. This much is clear.

So why would a camera manufacturer in their right mind choose to eliminate this optical system?

Mirrors Add Bulk

The unfortunate drawback to a system of mirrors is that they greatly increase the size and weight of the camera.

If you compare the smallest digital SLR camera made today and a large compact, the difference in size is still substantial. The compact will fit into a large pocket - unless you have extremely baggy jeans, there's no way you're going to do that with a DSLR.

Manufacturers were looking for a way to create a camera with the superior image quality of a digital SLR and the small form factor of a compact camera.

The answer, in the end, was quite simple: take out the mirrors.

By eliminating the cluster of mirrors, manufacturers are able to dramatically reduce the size of their cameras, especially the depth.

While the mirrors are gone - either permanently or replaced with electronic alternates - the rest of the features of a DSLR are still there: speedy performance, fast autofocus, manual controls and the ability to change lenses.

It's All About Sensor Size

One main advantage that mirrorless cameras have over their compact cousins is that the sensors inside them are physically larger.

Without going into great detail here (I do that on another page about sensor size) I can summarize it like this: larger sensors capture higher-quality images.

This is especially true when you're taking pictures in low light.

In dim light, any digital camera can leverage a feature called ISO. ISO is a measurement of the sensor's ability to absorb light. The higher the ISO, the faster the sensor absorbs light.

High ISO numbers give photographers the ability to shoot pictures hand-held in very dim available light, but they also come with a drawback: reduced image quality.

The smaller the sensor size, the worse the image quality at high ISO values.

Bottom line: low-light images taken with a compact camera will be of a lesser quality than those taken with a mirrorless camera.

Transition Cameras

Mirrorless cameras are aimed at a population of people who are unsatisfied with the performance of their compact cameras, but are intimidated by the size, heft and feature set of digital SLRs.

In addition to being smaller and lighter, many of these cameras include "intelligent" automatic modes.

Intelligent automatic modes are designed to help photographers working with an SLR-like camera to get better results. For example, let's say you want a portrait image with a nice blurry background, but aren't sure what camera settings will achieve that look.

In intelligent auto mode, just select "blur background" and let the camera do the rest.

Since many mirrorless cameras don't have viewfinders, you often take photos using the LCD, just like you do with a compact. This shooting style is often easier for compact camera users to get used to - with regular DSLRs, taking pictues using the viewfinder is much more common.


So now you know what a mirrorless digital camera is:

  • It's like a digital SLR, only without the mirror(s)
  • It's much smaller and lighter than a normal DSLR
  • It shares many features with a DSLR
  • Its controls and operation are more like a compact
  • Its larger sensor helps to improve image quality

Hopefully this page has helped you to determine if a mirrorless camera is right for you.

Really, the reason to choose a mirrorless camera over a regular digital SLR is if you want a camera that's fast and responsive with exceptional image quality but can still (almost) fit into your jacket pocket.

Mirrorless cameras are designed as go-everywhere types of cameras, to be carried with you at all times so you never miss a great photo opportunity.

If you don't see yourself carrying around a camera all the time, then maybe a true digital SLR is a better option for you.