Prior recommendation: For anyone buying or considering buying their first, or back-up, interchangeable lens camera – don’t go past the Sony A6000 or ILCE6000. Its features compared to other mirrorless cameras and the best DSLRs suggest it should be 3 x its actual very affordable cost.
Compact Cameras – the lens cannot be changed
1. Number of megapixels – 12 is sufficient for most family/amateur purposes, 16 minimum for birds, or selling photos. But number of megapixels is not the only consideration – the size and the density of pixels on the sensor are critical. For example I have a relatively expensive camcorder which quotes a massive 24 megapixels for still photos, but it still will not produce a decent picture beyond a 6″ x 4″ print (no better than my old 5 MPx camera). This is because camcorders have very small sensors which are adequate for video, but not for good still pictures.
2. Size of sensor (usually very small for compact cameras, camcorders and phones) – the bigger the better, but again that is not the only consideration (see below).
3. Zoom Ratio – 5 to 10 for general use, 15 to 50 for wildlife, sports fields etc (this means “optical zoom” not “digital zoom” which expands the image digitally, losing quality).
What is Zoom Ratio? There are 2 types of lenses with regard to the size of the view seen in the screen or viewfinder of a camera, called “Fixed” and “Zoom”. The amount of the view seen with a fixed lens cannot be changed (zoom ratio = 1). A lens with a Zoom Ratio of 5 for example means we can adjust the dimensions of the potential photograph by a factor of 5. We see the maximum view with the “Wide Angle” setting (eg for a landscape), and we see the least (1/5 of the width and height of the scene in this case) with the maximum zoom or “Telephoto” setting (eg for a close-up).
4. Macro capability – extreme close-up photography, usually of very small subjects like insects, in which the size of the subject in the photograph is greater than life size.
5. Physical size and weight, and comfortable in the hand.
7. Full reviews available on the internet, and advice from friends.
After all the above, choose 3 possible cameras. Then have a good look at your 3 possibles in a camera shop to decide which you like best (remembering what you are getting it for!).
Interchangeable Lens Cameras
Choose an interchangeable lens camera if you want to get higher quality images eg for big enlargements, or selling on the internet.
Characteristics to consider:
1. Number of megapixels – 12 minimum, suggest 16 plus for wildlife etc, and for selling photos.
2. Size of sensor – the bigger the better (as long as you are aware of the following):
What is the Sensor of a Digital Camera? The sensor is a small board consisting of many small photosites called pixels which convert the light from the image into electronic signals which can be translated back to the image seen in the camera screen or on a computer or TV. Note that “size” here means physical size (millimetres width and height), NOT number of pixels or Megapixels. Note of Caution: The true measure of image quality is neither the size of sensor nor the number of megapixels per se, but is a measure of the number of pixels crowded into the sensor eg density of pixels (pixels per square millimetre), or simply the size of each individual pixel. For example, If one camera has a sensor 1/4 the size of another camera, but has just a quarter the number of pixels, the density of pixels is the same, so the quality of the images will be the same. However the size of the photo obtained from the larger sensor will be larger. To make matters even more complex, the quality of image will of course also be affected by the quality of design and manufacture. The diagram shows typical sensor sizes (the bottom row may apply to camcorders and phones):
4. Cost will always be a consideration, both from a budget point of view, and the estimated “value for money” comparison.
5. Range of lenses available – both from the camera manufacturer and 3rd parties like Sigma and Tamron.
6. Full reviews available on the internet – then make a short list of your most appropriate cameras.
Have a good look at your 3 possibles in a camera shop to decide which you like best!
Comparison of Cameras with Different Size Sensors (same MPx)
eg APS-C Sony/Nikon versus Full Frame Camera
(a) Full Frame camera with 35 mm sensor: most expensive, gives large pictures (eg 6000 pixels) of great detail and clarity. Even if you don’t always want such large images, they do give excellent opportunities for cropping still excellent quality parts or close-ups from the image.
(b) Camera with sensor 2/3 full frame linear size (4/9 area): apart from smaller pictures, a perceived advantage of a smaller sensor is its so-call “crop factor” which in the case of the said APS-C sensor would be 3/2 or 1.5. This has the affect of extending the telephoto reach of any particular lens by a factor of 1.5. For example, a lens quoted as “200mm” would act like a 300mm lens in a Nikon APS-C camera.
Similarly, camcorders with very small sensors are able to achieve very high zoom ratios.
DSLR versus Mirrorless Interchangable Lens Camera
Traditional DSLR cameras incorporate a mirror to reflect the light from the lens through to an optical viewfinder. The mirror moves out of the way for exposure, allowing the light to hit the sensor. The mirror and its functional accessories take up a lot of space in the camera, while moving the mirror also takes a measurable amount of time, lengthening the possible time between shots.
In the Mirrorless Interchangablee Lens Camera the light from the lens is directed directly on to the sensor, saving the time and space required for the mirror action in the DSLR. The result is a camera that can have as big a sensor as the DSLR (for image quality) while also allowing for more rapid continuous shots.
A further interesting characteristic of the MILC Camera is that although the camera itself is much smaller and lighter than a DSLR, the lenses needed to accomplish exactly the same duties remain the same size, so this particular advantage is partly lost when using large lenses (for image quality or long telephoto work).
Choosing Lenses for an Interchangeable Lens Camera
Consider the subjects you wish to photograph: Family activities – need a versatile lens, one that has a good wide angle of view, but will also take some portraits (ie a lens that will take pictures of a group of people, but also can be “zoomed” – say 5 times closer – to take the close up of a face). Portraits (still people) – same. It is probably worthwhile to set the camera to “portrait” to get the best “still” portrait, but for moving targets like young children or animals, you may need to set a faster speed – even a “sports” setting.
Other people’s projects, eg weddings – same as family, but formal or semi-formal photos for others usually requires higher quality lenses (and camera!).
Buildings – both a good wide angle of view and an extreme close up possibility (ie a lens with a high zoom ratio for both landscape type views and say 10 times closer for detailed building features). Rooms inside buildings may need a super wide lens.
Landscapes also need a “wide angle lens”.
Sporting events and wild-life, especially birds, need long telephoto lenses (> 300mm), preferably capable of high speed shots in moderate lighting.
Types of Lenses
Fixed focal length ie a non-zoom lens, usually with a focal length between 16mm (wide angle), or 500mm or more (long distance), usually chosen:
(a) for better quality images, often at lower light conditions,
(b) for a specific type of project, or
(c) for particular distance of image eg macro photography, studio portraits, near fixed distance sports events, landscapes.
They are usually of good quality and more expensive (and heavy)!
Zoom lenses are the natural choice for non-professionals who are going to use their cameras for a variety of purposes, perhaps including most or even all the uses mentioned above !
More about Zoom Lenses: The width or size of the view covered by a lens is designated by its so called “focal length” and is measured in millimetres, and is inversely proportional to the focal length. For example the width of a landscape covered by a lens of 100mm focal length is 4x that covered by a lens of 400mm. Conversely, a photo taken of an object with the zoom set at 400mm includes just a part of the photo taken with a lower focal length (wider zoom). Yet again, to take the same size photo of a person or object you can be 4 x further away with the 400mm lens than the 100mm lens.
Typical zoom ranges available from each camera manufacturer include 18-55mm, 18-135mm, 18-200mm, 70-300mm, 100-400mm, while more may be available from Sigma and Tamron.
The bigger the zoom, the bigger the lens – zoom lenses usually cover a range of focal lengths between 16mm (wide angle) and 500mm or more (long distance or telephoto). The most versatile reasonable cost, reasonable size and weight lenses are probably those in the 18-250m range.
Explanation regarding the light receiving capability of a lens: Better low-light capability requires a bigger diameter (and hence bigger altogether) lens. The light-receiving capability of a lens is indicated by its f-numbers. A low f-number (eg f2.0) indicates a big wide open lens capable of taking pictures in relatively low light, whereas a high f-number (eg f36.0) indicates a very small aperture for receiving light, thus needing bright sun or bright lights (or time exposure) for taking pictures. On the other hand, taking a picture with a low f-number means only a small part of the image will be in focus (in front and behind the focus point), often used for portraits with a blurred background; whereas for a landscape view where you prefer the foreground and background to both be in focus, you need to take the photo with a higher f-number eg f9 or f11.
Most lenses are capable of operating at a range of apertures (eg f3.5 – f22), the critical one being the lowest achievable (typically f3.5 or more on cheaper lenses, especially zoom lenses).