Easy Guide to Understanding Camera Resolution

By Karthika Gupta

Related course: Photography for Beginners

The latest trend among most camera manufacturers is to increase camera resolution. Some full-frame cameras on the market have already reached 61 megapixels. Medium format cameras are even pushing beyond 80 MP.
But gear lust aside, how much resolution do you really need from a camera? Do you need the Sony 7R IV at 61MP or the Pentax 645Z at 51.4MP? Or will you be happy with the Canon Rebel, a very popular entry-level camera, at 6.3MP?
Here’s our easy guide to understanding camera resolution so you can answer these questions and more yourself.

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What Is Camera Resolution?

In general, digital camera resolution is measured in megapixels (MP). One megapixel is actually made of one million pixels or dots. These pixels are what store data about the image.
If your camera is slated to capture 6.3-megapixel images, that is around 6,300,000 pixels per image (6.3 x 1,000,000).
But this pixel information tells you nothing about the actual pixel dimensions of your image. It only tells you the total number of pixels that comprise the image.
The general rule is that the higher the megapixels number, the higher the camera resolution. This can mean better quality of the photograph.
When you are buying a digital camera, resolution can be one of the most important things to take into account, second to your budget.

How Does Camera Resolution Affect Image Print Size?

In short, yes. The higher the camera resolution, the larger the potential print size. When printing digital images, most photographers and print professionals will look for a certain number of dots per inch (DPI).
A high-quality print with good details should be anywhere between 150DPI to about 300 DPI. The actual size of the print is calculated by taking image width and height and dividing it by the DPI number.
The math might seem a bit complicated but bear with me. Most digital cameras across the board are set to capture images with an aspect ratio of 1:5 by default. In my Canon 5D MK III, I can change the aspect ratio using the menu settings in-camera. But 1.5, or 3:2, is the default.
Medium format cameras and large format cameras or even film cameras will have different aspect ratios as default.
This means that the ratio of the number of pixels along the longer edge of the image to the shorter edge is 3:2. Each full-size raw image that the camera generates is 4672 x 3104 pixels in dimension.
Multiply those two dimensions and you get the actual number of pixels in an image, approx. 14.6 MP.
You can use photo editing software to check the image height and width for your specific camera. If you are using Lightroom, you can find image dimensions in the Library module. Check under the Metadata section.
If you want to print a 4×6 image at 300 DPI, then you need a file an image that is at least 1200×1800 pixels in size. To get this number, multiply 4×300 (pixels along the short side) and 6×300 (pixels along the long side).
For an 8×10 image at 300 PPI, the result is 2,400×3,000 pixels.
What all this math does is affect your choice in new cameras. You should base this on the most common image size you’re going to print.
If you never or rarely print your images, you might not need a camera with a very high resolution.

How Does Resolution Impact Image Cropping?

In general, the higher the camera resolution, the more room there is to crop your image. Most of us try to avoid cropping images in post-production.
Sometimes, this is necessary to give focus to the desired subject. It can be the case if your subject is far away and you don’t have enough zoom on your lens.
This is also true for wildlife and sports photography. You might not be able to get close enough to the subject to isolate it.
Cropping is a good way to get rid of all the surrounding distractions and isolate the subject.

An image taken with my iPhone 7 but cropped down to focus on the people in the image 

shows how grainy and unclear the image is.

An image taken with my Canon 5D MKIII – cropped down to focus on me, is not as bad as 

the cell phone image cropped but is still not very clear.

Cropping reduces the resolution. This is why wildlife and/or sports photographers tend to want as much resolution as possible.
More often than not, they opt for high-end cameras with high resolutions.

Higher Resolution Doesn’t Always Mean Better Images

It is important to note that a camera’s sensor size is not the same as the camera’s image resolution. Without getting too technical, a camera’s sensor captures light through small pixels and turns them into a digital signal.
The Canon Powershot is a point and shoot camera from Canon that has an image output of 20.1MP. Whereas the entry-level Canon Rebel T6 DSLR is at 18.6MP. A point and shoot can have a higher megapixel than a DSLR but completely different sensor size.
The sensor size controls the actual size of the pixels themselves. That’s the important part. Most point and shoot cameras have smaller sensors and that means smaller pixel sizes.
This is why higher resolution doesn’t always mean a better camera. A more advanced camera with a larger sensor and lower megapixels will be better than a point-and-shoot with higher resolution.
A smaller sensor cannot capture as much light. The images it produces will have less dynamic range and more noise at higher ISOs.

Poor Quality Lenses Perform Worse on High-Resolution Cameras

There is a reason why photographers covet glass more than the latest and greatest cameras. A camera is just a box without the right type of lens.
You cannot have a camera with a high megapixel count attached to a lens with poor quality. The quality of the lens provides data for each pixel on the sensor.
You cannot compare a small sensor camera with a bad quality lens to a full-frame DSLR and a high-end lens.
Another issue that some cameras have is with diffraction. This is amplified with smaller sensors that have diffractions at larger apertures. Diffraction will reduce sharpness and affect resolution.
Poor quality lenses do worse on cameras with higher resolutions.
A lens might do quite well on an entry-level Canon Rebel of 6.3 MP. But it might fail to perform optimally on a Canon 5D MKIII 22.3MP camera. You’d be losing most of the benefits of a high-resolution camera in the first place.
In such cases, you might be better off not upgrading to a higher resolution camera at all.

Professional quality glass – an L series lens will always produce sharper results compared 

to a standard/kit lens. It just depends on the output that fits your needs.

Stick With a Lower Resolution Camera If You’re Just Starting Out With Photography

Another important factor to consider when deciding to upgrade your camera is your skill level.
Are you at a point where a higher resolution camera is going to make a world of difference? Is gear the only thing holding you back? I don’t mean this in a derogatory way but in a very practical sense.
You might have the best of the best gear in terms of cameras and lenses. And you can still end up with poorly executed images that lack details or use bad lighting.
High-resolution cameras amplify everything. This can be camera shake because of poor camera holding stance or shutter vibrations at really low light. It can be bad focusing techniques, or even using poor quality tripods.

This image is from a client shoot in 2013. I had the best glass and camera I could afford at that time – Canon 5D MKII and 24-70MM f/2.8 which I still use today.
But at 1/15th of a second handheld and at 2.8 wide open, the image is blurry when zoomed in and not the best.

Can You Take Print-Worthy Images With Your High-Resolution Smartphone?

These days everyone wants a smartphone that can take amazing looking photos.
I had an inquiry the other day where a mom was shopping for a photographer for her child’s 16th birthday party. When I told her my rate, she texted back saying it was outside her budget.
She said she would rely on her cell phone to take print-worthy photos.
I have to admit there was a part of me that cringed when I heard that. Cell phone photos, no matter how great, cannot always produce print-worth images.
This happens because of some of the very reasons we have already discussed, like print size and sensor size.

These two images are of the same area – one on a cell phone and the other via DSLR. Can 

you tell which is which? Left is iPhone 10 and right is Canon 5d MKIII

Not all cell phones have poor photo-taking abilities. In fact, the latest version of iPhones improved upon the 2018 version of iPhone XS and XS Max. It adds an ultra-wide lens and front and back cameras for selfies.
The new iPhone 11 is supposed to have two high quality back cameras as well as features like slow-mo selfies! But good photos aren’t always about the hardware or the gear.
On the Android side, Pixel 3 is still a strong contender.
With cellphone images, the quality is also affected depending on what type of editing you do on the image. If you add a lot of filters and effects, any grain due to low resolution will be more pronounced.
In general, try and keep editing simple for both mobile photos as well as DSLR images. Also, zoom the cell phone image after you have taken the picture. Don’t use the digital zoom when you are clicking a photo.
A cell phone image several hundred yards away will look grainy and blurry. It doesn’t matter how good of a photographer you are.
Here is a quick rundown of popular cell phones and their megapixel capabilities:

• Nokia Lumia 1020 at 41MP
• OnePlus 5 offers a dual-camera set up with 16MP and 20MP sensors
• Sony Xperia XZ Premium at 19MP
• Google Pixel 3 at 12.2MP
• iPhone X at 12MP

While 12MP is standard in most cell phones, these go above and beyond. They provide higher megapixels for customers who want to do more with their images.
Doing more might not always mean printing cell phone images on huge billboards. If you have seen the iPhone pro shots across the country, you might be tempted to print your own cell phones images to a large size.
In general, keep in mind things like light, colors, processing, and subjects when printing cell phone images.

If you do decide to upgrade to a camera with a much higher resolution, make sure it is for the right reasons and for the right outcomes. Perfect your craft, learn the limits of your existing gear, optimize your lens by understanding that lens sweet spot.
If you don’t, you might be wasting the potential of your existing camera gear. And upgrading to a higher camera resolution might be a very expensive mistake in the long run.

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