Resolution in photography is a measure of detail. In a digital image, it specifies the number of pixels. A higher resolution means a larger number of pixels, equaling more detail.
In the world of digital photography, image quality, and detail are critical. And so, in the production of quality images, a good resolution is one of the fundamentals.
In this article, we’ll define resolution as it applies to digital and print assets, why pixel information is important, and how to optimize resolution across various platforms.
How Resolution Relates to Quality
Although the term “high resolution” is frequently used interchangeably with “high quality,” we should note that other factors also influence photographic quality. A camera’s ability to capture detail in low light, its dynamic range, noise level, and lens quality all combine to determine image quality.
A high resolution image is not necessarily a high quality image. However, high resolution makes high quality images possible.
Image Resolution Definition
In digital images, we measure resolution in pixels per inch or PPI. This quantifies the actual number of pixels within a square-inch surface. As pixels per inch increase, the result is an image with greater detail and a smoother transition between tones.
A resolution of 300 PPI is capable of rendering images that are sharp and crisp.
PPI also tells us the resolution of digital displays; for example, a television or computer screen, smartphone, scanner, or digital image.
A screen resolution of 72 PPI is the industry standard for online use. While that implies a low resolution image, it is considered optimized for the web. It combines good image resolution with a small file size and fast load time.
A Measure of Quality in Print Images
The photo resolution of print images is stated by dots per inch or DPI. This refers to the number of ink dots contained within a square inch of a printed image, whether that is printed on paper, canvas, acrylic, metal, or any other surface. DPI is also expressed as a measure of printer resolution.
While DPI is similar to PPI, they’re not the same. However, the two terms are often used interchangeably and incorrectly. Both define image resolution; dots for printing photos and pixels for rendering digital images.
Here is our comparative analysis of DPI and PPI.
A 300 PPI digital image is the industry standard for photo prints. To render the highest quality for larger prints, printing equipment should be capable of a print resolution of 300 DPI or higher.
Image Resolution for the Web
Images for online use come with a variation of the rules. Pixel dimensions take precedence over image resolution. An image that is 600 x 900 pixels at 300 PPI will display exactly the same as a 600 x 900 pixel image at 72 PPI.
Pixel density for display on a computer monitor is considerably less than the pixels per inch necessary for printing. So two images with different resolutions but the same pixel dimensions will display as the same image when viewed online.
Online organizations strive to maximize photo quality and minimize image file size. Many social media platforms resize images or compress them. This allows them to store millions of photos of relatively small file sizes and still maintain the acceptable quality of the images.
Resolution in Camera Sensors
Camera manufacturers market their devices by the size of the image sensors.
For example, a popular digital camera features an image sensor with a pixel resolution of 5,760 x 3,840. The pixel count, achieved by multiplying image width by image height, equals 22,118,400 pixels. Rounded off, that’s 22.1 million pixels. One million pixels equals one megapixel, so that camera comes with a 22.1 MP sensor.
While the various brands race to add more megapixels, photographers should instead concentrate on what sensor size meets their specific needs.
If your photography is intended for posting online images or for small prints, a 10-12 MP sensor will suffice. For photographers who specialize in landscape, wildlife, or weddings, a camera with a sensor of around 20-30 MP will be needed.
Ultra-large printed images require a sensor size of 36 MP and up, with a price that rises with each additional million pixels.
Sensor Size and Pixel Size
While we’re on the topic of sensors in digital cameras, we should distinguish between sensor size and the physical size of the pixels.
Two cameras may have an identical resolution. But one comes with a larger sensor. That means that the size of the pixels is also larger. Larger pixels capture more light than smaller pixels. This results in higher quality images and an enhanced ability to keep noise levels low.
That’s a minor difference when there is sufficient light, and you can shoot at low ISO levels; however, the difference becomes more obvious when shooting at high ISOs of around 800 and up. Larger pixels result in improved low-light performance.
The Advantages of High Resolution
High resolution cameras perform better than low end cameras. This includes lower noise, greater dynamic range, and enhanced low light capability.
A larger sensor also allows for cropping, an important consideration for wildlife or sports photographers. Taking the viewer closer to the subject, changing the perspective, or removing details that distract from the subject may require major cropping. An image with more pixels can withstand cropping without a noticeable loss of detail.
Higher resolutions also present better options for resampling or resizing, such as downsizing to improve focus. Large format printing, such as billboard advertising and fashion photography, requires high resolution cameras.
Advances in monitor technology created a demand for images with higher resolutions that have greater detail and color rendition.
Achieving High Quality Photos from High Resolution Sensors
High resolution cameras deliver images that are high quality if other factors are right. Lighting, proper exposure, and lens quality combine to determine image quality.
How important is the lens? The quality of the lens determines how much information reaches the camera sensor.
High megapixel cameras cannot compensate for low quality lenses. And if the lens produces anomalies such as chromatic aberration or excessive diffraction, those flaws will be even more obvious when rendered by a higher resolution camera sensor.
A high resolution image allows for more latitude when we get to photo editing software, such as Adobe Photoshop or Lightroom.
A cropped image may be a great improvement over the original. And higher resolution means that you have no great drop-off in image quality.
The same is true if an image needs a change of perspective or an adjustment to its aspect ratio. Both result in some loss of detail. But an image with more pixels can withstand losses and still maintain high quality.
Set Your Camera for its Highest Resolution
When it comes to editing, it’s good to have the highest resolution possible. Set your camera to the maximum image size and shoot in the RAW file format to get the most out of your recorded pixels.
RAW files contain more data, so they are the preferred format for editing.
You can always export or save at a lower resolution. And if you save an image for online use, optimize it to achieve a balance between image quality and fast load time.
Where to Find Image Data
The size of a digital image is contained in the EXIF data. An EXIF (Exchangeable Image File Format) file stores critical information about the photo. In addition to image size and pixel dimensions, this data includes camera and lens settings for each photo. Most digital cameras record this data whenever you take a picture. The screenshot below shows an example of an EXIF file.
You can view EXIF files from your computer.
With Windows PC, right-click on the file. A new window appears with options. Click on Properties, then Details to see the EXIF file.
On a Mac, right-click the file, then click Get Info to view the EXIF tab. Or from Preview, click Tools, then Show Inspector for a more limited EXIF tab.
A Quick Review in Closing
How much detail is present in a photo is determined by how many pixels are contained in that image. An image displayed on a computer monitor is optimized at 72 PPI, while a photograph intended for print will be around 300 PPI.
High megapixel cameras improve image detail; however, knowledge of the camera and specialized skills combine to maximize photo quality and realize the camera’s potential.
The term resolution should be used with understanding. It does not guarantee a compelling online image or a high quality print. A low resolution image looks good online or in small print. But you’ll want more detail as the print size increases.
I hope this article clarifies the subject and guides you in achieving the best resolution and photo quality for your photography niche.