Understanding the Impact of Megapixels, Pixel Dimension
Understanding the Impact of Megapixels, Pixel Dimensions, and Resolution on Print Size
Photographers sometimes struggle with how to determine the ideal print size or preferred print dimensions depending upon the resolution and pixel dimensions of the camera or device (smart phone or tablet) used to shoot their photo.
Fortunately, there is a way to answer these questions yourself. You simply need to understand the connection between the image in its digital form and in its printed form.
To start, it is helpful to understand the image, itself. Using image manipulation software, such as Photoshop, it is easy to determine the image size of a file. For the purposes of this explanation, the example of an iPhone 5s image will be used. That device shoots at 8 megapixels and produces a 1.5 MB JPG physical file size.
When looking at the pixel dimensions of an image, you will learn a great deal about what you can do with your file. For example, for our example, the image will be 3264 pixels wide, and it will be 2448 pixels high. Software will be able to use that size in order to determine the size you would like to print. For example, if your goal is to print a 25 inch by 18.75 inch picture, then it would have a 130 pixels per inch resolution, which is sufficient to get a good result in print.
By taking images at the largest possible sizes for your device (camera, smartphone, etc.), you will also obtain its best possible quality of images.
Without software, it is still possible to determine these sizes as long as you have the image file properties and use the right math. Working with the same example of a picture that has a width of 3264 pixels and a height of 2448 pixels, you can use the following for your calculation:
Width (measured in pixels) ÷ Desired Width (measured in inches for the photo size you want) = the Picture Resolution (of the image measured in PPI at that size). So for our example:
3264 pixels ÷ 25 inches = 130.56 resolution. Therefore, this file will create a printed image of 25 inches wide that has a resolution of about 130 PPI.
With that resolution, you can then determine what the height of the image will be in inches. Use the following:
Height (measured in pixels) ÷ Resolution (as determined in the last step) = Desired Height (measured in inches). So for our example:
2448 pixels ÷ 130.56 resolution = 18.75 inches
Now that you understand the math, it’s time to take a closer look at resolution and what it is in terms of what you will require for your printed image. There is no fixed proper resolution for every purpose. The resolution that you require greatly depends on how you want your image to look and how it will be printed. For example, the typical website image needs around 72 PPI. The reason is that most online images are displayed at a relatively small size in order to ensure that the page can load quickly as the file size will be kept low.
On the other hand, printed images will require a greater amount of resolution as they will typically be printed at a bigger size than they would be if viewed on a device screen. Understanding the difference between media in the digital and physical world requires you to know two terms. The first is pixels per inch (PPI) and the second is dot per inch (DPI).
Although these terms are often used interchangeably, they are not actually identical. PPI is the term that is refers to a measurement of monitors, scanners, digital cameras, and other media that use a file in its digital form. On the other hand, DPI is a measurement of the physical form of the image. Therefore, devices such as printers would use image measurements in DPI.
When it comes to resolution, choosing the ideal for printing would require a considerable amount of math – more than is convenient or comfortable for the majority of people, so at American Frame, we simply recommend that you use a minimum 130 PPI as your print size. That said, we will lower image resolution requirements upon request. On the other hand, there is no maximum resolution for printing, though we do have a maximum allowable 100 MB file size. This helps to make certain that we will be capable of serving the widest spectrum of customer needs.
Therefore, if you want to print a 360 PPI image at its print size, we can do so as long as you have a file size of under 100 MB. For added assistance, use the chart available at the following link as your guide. We recommend that you stick to the range of “better” to “superb” for the best results:
If your image is not large enough, then there are some things that you can do to resolve this issue. American Frame can simply print the picture at a lower resolution than is recommended. This will create the image, but it will likely result in more visible pixilation or artifacts.
Pixilation occurs when an image size is increased to the point that the individual pixels that make it up are actually visible. That same image will look smooth when it is reduced in size to the point that the eye can no longer spot the individual pixels that lead to jagged edges instead of smooth ones.
To avoid this problem, we offer the ability to order a “resolution proof” of the print you are ordering with us. Here we take a section of your image shown at resolution of your full size print, which will allow you to determine whether or not pixilation will be visible in your image at its full size. If it looks too jagged for your purposes, you can opt to either choose a smaller print size or, if you have access to image editing and manipulation software, you can boost the resolution of your image to minimize this issue. This process is known as ressing or up-ressing. It provides additional resolution to a digital image that wasn’t actually in its original.
This process should be used with caution and is typically considered to be a last resort as it involves forming pixels where none had previously existed. Using this effect can reduce the crispness of the original image, causing an overall blur that is greater than what it would have been had the image been taken and printed at the quality at which it was taken and printed at its recommended size. Consequently, “upsampling” is best for images that will be viewed from a distance, where the loss of detail will not be noticed by the viewer.
For this reason, it is always easier for you to create a smaller picture size than to try to increase the size of the picture and “create” pixels” during the editing process.
So, the takeaway from this article is this: The more pictures you can capture in your original image, the larger you will be able to print. We always recommend that you use the highest possible settings allowed by your device.
When all is said and done, there is no set resolution or size for a digital image. It is all based on the original pixel dimensions at which it was taken. This will give you far more size options for printing, as it is always easier to start with a larger picture and work your way down, instead of attempting to work in the other direction.
Read more about megapixels, pixel dimensions and printing at AmericanFrame.com.
This article was written by the American Frame Print Department Team for the Ask Mike blog. Mike is the man behind the mission of getting your picture frames produced and out the door quickly, correctly, with custom frame shop quality. Once your order is placed, it is in the hands of Mike and the many people he has trained over his 35+ years at American Frame. Read more framing tips from the team and Mike on his blog – Ask Mike.