We live in a golden age of photography, with a lot of different options available, from very small sensors in phones to large ones in medium format cameras. We still have the classical mirror design, but now also modern options with pure electronic viewfinders, eliminating the chance of mistuned autofocus thanks to using the sensor for it.
Also thanks to better computers we now can get much better designed lenses and which are also purer with corresponding higher optical quality. This has made zooms with astonishing sharpness possible, as now all the elements can be positioned exactly, and so the penalty for having many more elements in a zoom has been greatly reduced.
But with all this choice comes the question how to choose from all these options, to know what you need. I always look at the following characteristics when deciding on a camera.
Weight
Never underestimate it. You can only take a picture if you have a camera with you, and you will only have it with you if it is light enough to just be there. The lightest camera by far is the phone, as you carry it anyways. Above it are four classes of carry-ability:
- fits into a shirt or trouser pocket, e.g., the Sony RX100
- fits into a jacket pocket, or hand bag, e.g., the Fujifilm X100, or a 4/3rd with a pancake lens, maybe even a Leica M9
- camera on shoulder or neck strap still light enough to hand hold shots
- so heavy that a tripod is required, e.g., the fast long tele-lenses like the 400 f/4, or large format cameras
The first two classes are realistically the only candidates for a camera that you will always carry. For me, the X100 just fits a jacket pocket, and is just that tiny bit too large to always be there.
The other advantage of a small package is that it is not perceived as professional, and makes it a lot easier to get good spontaneous shots of other people.
Low Light and Flash
To get good shots in low light, you have four options: increase the exposure, use a wider aperture, crank up the ISO and provide your own light. Increasing the exposure is the best option, but it only works with a tripod and requires a static scene.
A wider aperture comes with a shallower depth of field, which is often helpful for composition, but requires more discipline to focus correctly. It is often the best option, and you should first try f/2.0 or faster before thinking that you need to change cameras.
Cranking up the ISO’s will reduce the quality of your image. For indoor images, you will typically have ISO 3200 at f/2 with 1/40 s shutter. From my experience, the Nikon D90 was too grainy at these settings, and the D7000 just about acceptable.
You can reduce the ISO by adding your own light to a scene, which typically happens in the form of flash. You will want a standard xenon flash, as the light from the LED flash on a phone still has a unnatural feel to it. You will not want to use too much flash, so that the lightning does not look too artificial. This limits the gain to about 2 exposure steps, aka ISO 800 must look good. If you use a big camera, it its advisable to use a separate flash unit for the ability to bounce the light from a wall, as well as the longer battery life.
Nikon and especially the Fuji X100 have a good reputation for automatically getting the fill flash right.
Size and Resolution
To get high resolution images, you need high resolution optics. Digital cameras have now come so far that sensor resolution is no longer the limiting factor, it is again down to optics. And because a larger sensor can use larger pixels to get the same resolution, they can reach higher resolutions before they reach the optical limits of the lens.
But this only matters when you want to print huge sizes, wider than a meter. The largest size you will have on a desk is a two page spread, roughly A3. At 264 dpi this is 13 MPixel, so practically even 8 MPixel are enough for almost all normal uses. Beware that noise reduction at higher ISO settings will also reduce the effective resolution, this is a problem for most compacts for photos not taken in bright light outdoors.
Mirrors or Electronic Viewfinders?
Mirrors are a leftover from the analog days. They are loud, and cause unwanted vibrations for longer exposures. They are inaccurate in showing how the final image will look like as the eye has a higher dynamic range than the sensor. They limit the speed with which you can take consecutive photos, and interfere with autofocus. They cost space that makes lenses larger. They need autofocus fine tuning. They will die out in a few years.
But at the moment mirrors are still just a bit better. The main problem with the electronic finders is their higher energy consumption, in resolution and color accuracy they will soon be good enough, and they are much better at providing context info then the optical finders with the tiny LCD line at the bottom.
Also the cost for sensors have now come down so far that again the lenses will dominate your budget. Get the right lens for what you want to shoot, and get the corresponding body.
Ergonomics
This is a tricky one. The best interface I know is the iPhone. Just tap where you want your focus and exposure, and the rest is done automatically. Compared to this, almost all cameras are overloaded with options, and can be difficult to learn. To deal with this complexity, two features are very useful, first a custom menu where you can place the settings you actually need, and second the ability to quickly recall settings, to optimize the camera for differrent situations quickly.
Recommendations
If you want a good camera to upgrade from your phone, the Sony RX100 is a very good choice, light and with very good quality for everything apart from low light shoots.
As a separate camera for people, the Fujifilm X100 is excellent.
If you do not need telephoto reach ( or can wait for the lenses to come out), the light weight Fujifilm X-E1 is probably the best camera to buy when it comes out in November.
For the budget conscious, the half format cameras from Nikon, Canon and Sony are a good choice. Sony stands out with very fast frame rates, and continuous autofocus even during video. Nikon has the 18-200, which is the highest quality all in one zoom currently on the market for half format. You might want to check out used bodies and lenses, the mirrors on these bodies are rated for at least 100 000 activations, and you can often find bodies with less than 10 000.
You should not need to go full format. They are better in low light, and have a large selection of lenses available because it is the professional de facto standard, but they are overshooting in quality for most people. You should only consider them or even larger formats only when you find a problem with your photos that it would resolve; often you will be better rewarded by investing in your photographic skills.