What is resolution? If you want the maximum detail in your images, it’s not just about pixels. We explain why, first by answering some of the common questions people have about camera resolution, and then we’ll show you step-by-step how to change image resolution.
What is resolution: common questions answered
So what is resolution exactly?
In photography, resolution is all about the ability of the camera to capture as much detail as possible. For many, resolution is the Holy Grail. Camera manufacturers strive to create cameras that can capture more detail by adding more pixels.
Lens designers tweak optics so that their glassware can resolve more detail. And photographers chase the optical settings to maximise the amount of detail that their gear can produce.
Why is resolution important?
The more detail you capture, the more accurate a record you have of the thing you are photographing. If you’re shooting architecture, the more resolution you have, the greater your ability to see every brick and layer of mortar in a building. If you’re shooting wildlife, the more chance you have of seeing every hair on an animal’s back.
Is this really necessary?
That’s a good question. The resolution of digital imaging has improved an incredible amount in the last decade – and the race to add more pixels and improve image quality shows little sign of slowing down.
But it is just progress for the sake of progress? It would be great to be able to crop into the smallest part of a picture and still be able to create a big blow-up. But in many instances, fine detail is redundant.
It only shows in the areas of images that are in focus, for instance – and we often want to blur large parts of the frame anyway. Similarly, we rarely want to show every pore and whisker on a person’s face.
So too much detail can be bad?
It’s true that the amount of detail in a photo isn’t always necessary. The amount of resolution you need really boils down to how you’re going to use it. If you’re creating an A1 print you’ll need as much resolution as possible.
If the image is going to be shown as a thumbnail on a Facebook page, resolution is redundant.
However, you rarely know how a shot will be used when you take it (or how much it will need to be cropped), so it’s usually best to capture it with the most detail possible in the key areas, then adjust the resolution afterwards.
So you can reduce the amount of detail later?
Yes, you can use blur tools to cover up pimples that you later decide you don’t want to be shown in fine detail.
A drawback of highly detailed pictures is that they create very large digital files – which make them unsuitable, say, for emailing people or posting on the web.
However, editing programs enable you to reduce the pixels and file size to more manageable proportions.
Can you increase the resolution?
Well, you can increase the size of the image. Enlargement is a useful editing trick when making big blow-up prints, for instance. A seemingly capable 18Mp camera produces an uncropped image measuring 5,184×3,456 pixels.
To create a high-quality print at 300 dots per inch means that the maximum size we can print at is just over 17×11 inches. But what if we want a 30×20-inch print – or something to cover an entire wall? If we print an 18Mp image this big, the individual pixels will show up as recognisable squares.
However, if we upscale the image using standard editing software we can effectively add more pixels (using a trick known as interpolation), and we can get the giant blow-up we want.
So you shoot with the highest number of pixels your camera allows, then adjust to the actual number you need later, depending on how you’re planning to use the picture?
Yes, that’s right. But it’s important to realise that setting your camera to use all of the available pixels is only the start to maximising resolution.
What else do I need to remember?
The two other essential things you should know about resolution have to do with the lens. First, the optical quality of lenses varies significantly from model to model – and also across its own field of vision and through its focal range.
It might seem obvious, but lenses with similar focal length ranges improve in quality the more you pay for them.
Pay four times more for your telephoto zoom, and optical quality should improve significantly. Even so, don’t expect a four-fold increase or even a doubling in resolution.
In many cases, the difference in quality may not be immediately noticeable. But whatever you pay for your lens, expect resolution in the centre of the image area to be greater than at the edges (this is simply the way lenses work).
So what’s the other lens feature that affects resolution?
The aperture setting used is also crucial for ultimate image resolution. What’s more, it’s the one thing that we can often change to maximise detail.
The important thing to remember is that lenses don’t give their best at either end of their aperture ranges. Used wide open, you not only get less depth of field, but less detail is resolved.
To get the best results you normally need to stop down a couple of f/stops (say, from a maximum aperture of f/4 to f/8); but any setting in between also shows an improvement.
Paradoxically, however, the image resolution doesn’t get better if you stop down further – in fact the resolution actually reduces because of diffraction.
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