This article has everything you need to know about megapixels and image resolution. From what they are to how to use them for professional photos. Image resolution is not only a number. You have to consider different things related to printing, editing, or exporting.
Most of us know our camera’s resolution to the decimal place. But nowadays, we tend to concentrate only on the megapixels, although image quality relies on many different factors. For example, you could have a camera body with a 50-megapixel sensor, but what if your lens can’t keep up with that?
Let’s look at what you need to know about image resolution and image quality.
What is a Megapixel?
A digital camera captures images through what we know as pixels. Pixels are the smallest components of a digital camera sensor. This means that they are the smallest parts of a sensor or a display that you can control.
Digital images come from thousands of tiny tiles capturing light and colour.
A megapixel (MP) is one million ( or 1,048,576 to be precise) of these pixels. So a 30-megapixel camera has 30 million pixels on its sensor.
What is Image Resolution?
The number of pixels of an image determines the image resolution. The more pixels, the more detailed the image is and the higher its resolution. Image resolution is measured in pixels and megapixels.
To calculate the resolution of the image, simply multiply the width by the height of an image. For example, an image that’s 2048 pixels wide and 1152 pixels tall has a resolution of 2.36 megapixels.
Image resolution is often given in PPI (pixels per inch). It means how many pixels are displayed per inch in the image.
Photo resolution is a factor that determines image quality. However, the camera sensor, processor, and even the quality of the lens you are using also play a part.
Image resolution relates to the images’ print size. It also refers to the amount of detail the photograph or image has when viewed at 100% on a computer monitor.
Do More Megapixels Mean a Better Image?
You might think the more pixels mean better images. But then smartphones could outrank some semi-pro DSLRs. Yes, they might have a higher MP number written on them, but it’s not what determines image quality.
Higher-resolution photography can mean higher image quality, but only if you have the right lens for it. The sharpness, definition, and detail go up alongside the image resolution. A good quality image also comes from many other factors like good lighting, correct exposure, and composition.
But yes, more megapixels can mean better quality. You also need a higher resolution for printing and editing.
A clear, well-focused image at the best resolution is key.
Why is it Important to Have the Right Lens?
You could have a 40-megapixel camera and still won’t be able to take advantage of it without the right lens. Usually, your lens is not able to resolve as much information as your camera is capable of providing. The quality of the lens determines how much detail it can manage.
Also, when your lens tends to produce errors, a high-resolution sensor will draw them more sharply. For example, the lines of the chromatic aberration will be more visible on your images.
Diffraction is something that also limits the resolution of a lens. This means that above a certain aperture value (usually f/16), you will encounter loss in image quality and decreasing sharpness because of the optical interference of light. However, it is a general phenomenon in optical physics, so every kind of lens has this disadvantage.
The best way to compare optics and see your lens capabilities is to double-check its ranking on this chart by DxOMark. This is one of the most reliable databases online.
Sometimes it’s better to buy an expensive lens for a not-so-expensive body. This way, you can maximise the image resolution.
Why is it Important to Have High Image Resolution for Post-Processing?
By cropping the image during post-processing, a composition can look much better. This is a technique that is used in analogue photography too. Having a higher photo resolution gives you a little more playroom and helps avoid a serious drop in quality.
Also, your image might need perspective correction or to be adjusted to standard aspect ratios (i.e. for printing purposes). Both can result in losing some details.
An image with more pixels holds more information, so it’s less of a problem if you lose some.
How Can You Find Out the Resolution of Your Images?
You may want to find out the pixel size of your camera or the resolution of your images. For this, you can look at the information from one of your images. For example, a camera can give an image of 6016 x 4016 pixels. This means the max resolution of the camera is 24.2 megapixels.
This information is easily accessible. Simply right-click on your image and then click “Properties” on Windows or “Get Info” on Mac to see the EXIF data of your shot. Sometimes it’s also written in your camera’s manual.
Best Resolutions for Editing, Exporting, and Printing
For photo editing, you will need as high resolution as possible. You should use your camera on the maximum resolution (image size) it can achieve. Most of the time, it’s the best to shoot in RAW. RAW files are better for editing than JPEGs. They contain a lot of information, and you can bring more details out of them during post-processing. They are also better for cropping.
When exporting, you may find that your 20-megapixel (or higher) image becomes redundant. If your image is for a website, or sharing platform such as Flickr, don’t use the highest image resolution. You’re shooting yourself in the foot. Sure, it makes your image look great, but if it takes too long to load (due to the file size), viewers will scroll past.
Facebook and Instagram automatically resize any images over a certain resolution. It compresses them to a lower resolution to be able to store millions added each week. This has the potential to turn a great image into one with poor resolution. You can resize your images before uploading them to Facebook. Setting the longer edge of an image to 2048 pixels while exporting is just enough. It will also take less time to upload them.
But, there is a difference between screen resolution and photo resolution for printing.
Your image may look great on the computer screen. But when it comes to printing or print quality, it’s a whole different ballgame.
We’ve talked about PPI, which means the number of pixels per inch on a screen or a sensor. Now we should talk about DPI which means dots per inch. This refers to the number of ink dots on a print. The higher the number, the higher the quality. You can set the DPI value on your computer, but it really matters when it comes to printing.
The standard is 300 DPI. You might want a higher resolution, but usually, it’s enough. Under this, your images quickly lose their quality.
If you have limited knowledge about printing, it may be best to leave this to the professionals until you get up to speed. Printing your images at a high resolution on the wrong paper will cause inks to bleed. This will result in a blurry effect.
You need to make sure the ink and materials you use are for digital photography printing. You can find great art print labs and services to print your images. You’ll also be able to learn information about the materials and techniques they use.
Optimise your image into a canvas that fits the desired scale of your print. You should also pay attention to the RGB/CMYK colour spaces.
You should never print your images at the same resolution as your screen. These are typically 72 dpi (dots per inch), so you want to aim for anything between 300 and 1,800 dpi when printing.
Also, we should mention file formats. It’s preferable to use TIFF or TIFF compression (LZW) for printing. Printing an image in JPEG can cause a huge loss in image quality. It decreases pixel density by compressing and merging pixels to optimise the file size.
For images at 300 DPI, follow this table to print your photographs at the ideal size.
It’s a megapixel myth that you need more megapixels for your images to look great. This is a great way to sell cameras. Remember that there’s more to photography than image resolution.
Some photographers do need more megapixels for advertising, fashion, or editorial purposes. But everyday photographers aren’t taking images for multi-million dollar campaigns. Nor are they printing their high-quality images to the size of small buildings.
New cameras these days are never below 10 megapixels, which will be enough for 99% of your photographic work!