What is resolution
Higher resolution basically means higher quality. This is because with higher resolution there is more information in the image file. A digital image file consist of little dots called pixels (picture elements). These little dots store color information. The more pixels an image has the smaller the dots are, which in turn means they can create more details.
Visual example of pixels
To give you a visual example of this, here you have a picture of the letter A in various resolutions.
This first square has a resolution of 1×1 px. Since there is only one dot – one single pixel, you can’t even see the A.
By increasing the resolution to 10×10 pixels, you can kind of see the A.
Now, there is no doubt that this is an A, but you can still see the pixels in the image. The size of this is 50×50 px.
With a resolution of 100×100 px it is starting to look pretty good.
Is it making sense yet?
Higher resolution means more details
It is the same with the image files in your camera. Higher resolution equals more detail – making the image clearer and sharper. The quality increases along with the resolution.
Image resolution on screen
Your iphone, laptop screen and camera are all set to a certain resolution. The resolution on my iPhone is 750 x 1334 px, and my Canon camera has a maximum resolution of 5760 × 3840 px. You can check what resolution your camera is set to if you look in the menu (and maybe you need to refer to the manual as well). You see, when you are just going to use your image digitally you don’t need more than 72 ppi, as most displays have this resolution. Ppi = Pixels pr inch.
You can make an image seem smoother than it otherwise would by using a technique known as anti-aliasing. This technique smooths out jagged edges in text, or angled lines in images. Below you will see an example of anti aliasing turned on to the left, and off to the right.
Some screens can manipulate the sub-pixels to give the illusion of having a higher resolution than they actually do. That results in a better image.
Image resolution and printing
For print use you should aim for a higher resolution than if you are just using the images digitally. I always set my images to 300 ppi when I deliver them to my clients, which is a good resolution for printing. However, this will depend on the size of the print. You look at large prints from a further distance than a small print, so you can get away with a lower ppi and still have the image look fine.
When you print your image it should not be necessary to specify the ppi. You just send your full resolution image to the printer, specify what size you want the print to be, and the printer software will take care of the sizing and the ppi.
If you want an image enlarged to fit a poster for example, you will lose resolution, and the printer software should alert you of that, and it should still look OK when viewed from a suitable distance.
Choose the best quality your camera will allow
I recommend you choose the largest image size your camera lets you have, unless you KNOW there is no way you are going to print it later.