I'll make this really easy. Whichever camera you can afford, is the right one.
But regardless of how much one can afford to spend, one should also ask which type of camera does one really need? Well, it depends on what one wants to do with the images; print them, display them on the web, use them for emails, share with friends & family or put an image on a business card for example.
How you or indeed your viewers see your images can make a huge difference to your budget. So if you never print images, read on to discover how you can acquire second hand, professional grade gear for peanuts that will still meet your needs.
Right now, you are probably reading this from a laptop/desktop or a mobile device such as a smart phone. On every one of them,
Samsung17 inch laptop
the screen resolution compared to even budget priced cameras is rubbish. Seriously. But it doesn't matter because our eyes can't tell.
This web site was created using a now obsolete Samsung laptop with a 17 inch, 16:9 ratio screen with a visible window that measures about 15 inches wide by 8.5 inches high. Pixel count is 1,600 on the long side & 900 on the short side. The total pixel count is calculated as 1,600 x 900 = 1,440,000 pixels or 1.4 MP. It produces a resolution of about 107 dpi horizontal & 106 dpi vertical. (dpi = dots per inch). Today, if someone tried to sell you a new digital camera which had a sensor with only 1.4 MP on it, you would rightly laugh.
But to my eyes & indeed to anyone else's, my laptop screen looks perfectly sharp. That's because someone with 20/20 vision is only able to resolve about 100 dpi at the typical viewing distance, which for a laptop, is about 30 inches. And since the resolution of this laptop is marginally higher than what my eyes can resolve, text & images looks sharp. Explanation here.
Bigger is best. Right?
But you may have a higher resolution screen than this, such as one made by Apple called Retina. Last time I checked, their 13 inch MacBook Pro had a pixel count of 2,560 x 1,600 = 4,096,000 (4.1 MP) with a resolution of 227 dpi.
Apple's 15.4 inch MacBook Pro had a pixel
count of 2,880 x 1,800 = 5,184,000 (5.2 MP) with a resolution of 220 dpi.
Regrettably, unless you move your head unnaturally close to either Retina screen, your eyes are simply incapable of resolving these resolutions due to the limitation of human acuity.
Look at the chart (Click to enlarge). To "benefit" from Apple's Retina display resolution, one needs to sit with one's head about 15 inches (40 cm) from the screen (A). That's rather uncomfortable.
Toshiba were the first to offer a 4K laptop, the Satellite P50t 4K Ultra HD which at the time, they claimed it offered four times the resolution of standard HD (1080p) laptops. Its 15.6" model had a 16:9 ratio screen measuring 13.6 inch x 7.6 inch (3,840 pixels x 2,160). And thus the resolution on the long side is 282 dpi & on the short side, 284 dpi. It's just a shame if not a waste of money that even with 20/20 vision, our eyes can't resolve these resolutions.
So, at normal viewing distances (about 30 inches), my feeble 1,600 x 900 pixel, 1.4 MP laptop screen (B) looks just as sharp as Apple's 5.2 MP screen or even Toshiba's 8.3 MP 4K screen. Sure, their screens have a broader colour gamut, display more saturated colours, make blacks look punchier, blah, blah, but to me, they still don't look any sharper. But hey, if you really like the look, go & spend the extra money. Just know that to get any resolution benefit from these high definition screens, you'll have to sit with your chin resting on the edge of the keyboard.
Just as high definition laptop screens are somewhat pointless, there's also no point in posting full size JPEGs on-line either. Your display can't replicate the camera's resolution even with a 4K screen & if it did, the human eye is limited by its visual acuity anyway.
Furthermore, the web browsing experience is going to be very slow indeed if the server is stuffed with huge image data files.
There may be an argument for uploading a full size file so that viewers can zoom in to pixel revealing levels to compare say, differences between the performance of manufacturers' products. That's fine but most of the time, viewers just want to see regular sized images that look sharp, display correctly & load quickly.
Price of Progress
So if one only ever displays images on a computer or on the internet & rarely if ever prints them, it's easy get away with a camera that has a sensor no bigger than 2 megapixels because eyes simply cant resolve more than this on a 13, 15 or even a 17 inch laptop at 30 inches. But it is not possible to buy a new camera in 2017 with just 2 MP.
Commonly, the lowest is around 10 MP & the highest from Hasselblad, is 200 MP. In between, there are lots of camera sensors with pixel counts in the 15 MP to 36 MP range & a few almost affordable ones from Canon, Fuji & Pentax in the 50 MP range. Huge prints are possible but few users ever take full advantage, despite spending thousands on these cameras.
Second Hand Bargains
But you can find lots of second hand examples of ideally suited, small sensors for really cheap money. Here's one; a Canon EOS-1D. It was released in 2001 & cost about £4,700 ($7,100) new, body only. That's over £6,900 ($10,300) in today's money. Ouch!
It was Canon's flagship pro camera & purchased by press photographers (actually, more likely by their employers) because of its metal construction, weatherproofing & Teutonic build quality. It can shoot at 1/16,000 second at up to 8 frames per second. That's fantastic even now.
But by today's pixel war standards it has a tiny APS-H (x1.3 cropped), 4.15 MP, (2,495 x 1,662) CCD sensor. And because of that sensor, I picked up one of these bullet proof machines in mint condition, with barely 7,000 shutter actuations, for £130 ($195). That's a 98% discount, adjusted for inflation. Not bad, eh?
For action, sports & wildlife images that will only ever live on the web, in an email or in a brochure, it's perfect. Yes, I also print landscape & built heritage images in dimensions measured in feet rather than inches.
And for that, I have a much slower 50MP monster with a bunch of manual focus lenses. It's hopeless as a sports/action camera but it is ideal for the job I use it for. So, decide what you really want to do with your images & choose your next camera & indeed laptop, wisely. And if you are willing to wait a few years, & let others iron out the bugs, you'll be amazed at some of the bargains to be had.
Got a few minutes? Drop me a line firstname.lastname@example.org & let me know what bargains you've found for yourself.