Pixels and Resolution Explained
There's an old saying among photographers, "the best camera is the one you have with you." Although it means what you are probably thinking it means, it has another more apt meaning for avid photographers. And that is to not struggle too much with deciding what kind of gear to bring along.
Serious shooters usually have seriously bulky and heavy camera gear that gets tiresome to lug around, especially on a vacation where you're gone for two or three weeks visiting many places. International travel just makes it that much worse.
Sometimes we have to just "let go" and bring along something light and easy to carry so we aren't too weighed-down by our professional-grade gear. But that creates a quandary in every shooters mind: "I own all this high-end gear and now I'm not going to bring it with me?!? Seriously?!?"
The best camera is the one you have with you.
Pretty much everyone these days is carrying around a high-quality digital camera that happens to double as a phone. Today's smart phones have camera chips that seriously rival the dedicated, purpose-built digital cameras of just a few short years ago. They're so good, in fact, that the market for point and shoot cameras has pretty much dried-up, leaving only the market for higher-end gear.
So from an equipment perspective, you've already got what you need for some pretty good pics. A lot of people are aware (somewhat) of the importance of subject, composition, lighting -- all the usual things we remember from the days of film (if you're old enough to have ever shot on film, lol). But to really get the most from your digital pics, especially if you share them via email, social media, photo websites like SmugMug, and if you print them, then you'll get better results if you understand how pixels, resolution, compression, and color depth works -- and when, where, and why to adjust those settings.
You (very likely) already know that pixels are the tiny dots that make up our images. But do you know what DPI and PPI means and when that's important to know? How about compression?
Each pixel, in and of itself, is pretty meaningless. What matters is resolution, compression, and color depth which depends on how you plan to use the images.
When printing, you want your images to be at least 300 DPI*. Less than that, you're more likely to see jagged lines, especially on diagonals, mushy edges, and loss of detail. Imagine a square inch: That square is 300 pixels wide and 300 pixels tall. Multiply 300 x 300 and you get 90,000 -- the number of pixels in a square inch. Look at the sample pics up top.
8x10 Example: Assume you are printing an 8x10 inch photo. Multiply 8 inches x 300 DPI (=2400), then 10 x 300 (=3000), then multiply those answers 2400 x 3000 which gives a total of 7,200,000 pixels
4x6 Example: Assume you are printing a 4x6 inch photo. Multiply 4 x 300 (=1200), then 6 x 300 (=1800), then multiply those answers 1200 x 1800 which gives a total of 2,160,000 pixels
* DPI (Dots Per Inch) and PPI (Pixels Per Inch) are expressions of resolution. DPI and PPI technically mean slightly different things, but for our purposes here, they are equivalent.
Your printed photos can be greater than 300 DPI but you probably won't notice the difference.
But if your plan is to display the images on a screen then DPI becomes less important. Why? Couple of reasons:
1) On paper, you control the resolution (DPI) based on your printing parameters. But on a screen, you cannot. The resolution (DPI) of the screen is fixed by the manufacturer. A 23 inch Full HD screen (1920x1080 pixels) has about 96 DPI. But on a 13.3 inch laptop with a Full HD screen, the DPI is 166. That's because the same number of pixels (1920x1080) is crammed into a smaller space.
2) Screens can do tricks that printers cannot, These tricks can make an image with a given DPI look sharper than that same image printed on paper.
Screens with higher resolutions, such as 4K, have correspondingly higher DPI as well. But, again, you have no control over that. Some web sites are able to detect a higher resolution screen and can display a higher resolution picture if you uploaded such.
I know the foregoing might be confusing, so I'