The Ultimate Guide to Digital Photo Resizing
How to Enlarge A Photo for Print Without Losing Quality
Digital image enlargement, or resizing, is the process of increasing the resolution of an image to produce larger prints, posters, wall art or even billboards. Even with today’s high resolution full frame digital cameras that have 45-60 megapixels, photographers often need to resize their images. If done improperly, the resulting image enlargement may be grainy, soft and generally of poor quality. However, with the advanced software tools available today, images taken on low resolution cameras, iPhones, or old film scans can all be transformed into detailed enlargements. Maybe you want to take an iPhone photo and create a 12x18” print, or perhaps you have 36 megapixel image file and need to create a 100” print for a client. You do not have to be a pro or pay a lot of money to get amazing results. This article will discuss the best software, methods and limitations for image enlargement.
Digital Image Enlargements
There are no concrete rules when it comes to image enlargement. Anytime an image is resampled and enlarged it will reduce quality; the key is to preserve as much detail and sharpness as possible. There are numerous factors that each need to be considered before determining if an enlargement is possible, which include:
- Original Image Resolution
- Quality of the Original Image
- Cropping and Aspect Ratio
- Output Size Needed
- Type of Output Medium
- Viewing Distance of the Finished Product
Original Image Resolution
Digital image resolution is usually discussed in terms of the number of pixel rows (height) and pixel columns (width), for example 4000px x 6000px. Another way to describe this is to multiply the height pixels by the width pixels and divide by one million to define the megapixels of the image. In the example above, the image would have 24 megapixels ((4000x6000)/1,000,000)=24.
For reference, here are some of the latest model cameras’ resolutions:
- iPhone 12 Pro Max - 12 megapixel sensor, with image resolution of 3024 x 4032
- Nikon Z7ii Full Frame Mirrorless - 45.7 megapixel sensor, with image resolution of 5504 x 8256
- Nikon D850 Full Frame DSLR – 45.7 megapixel sensor, with image resolution of 5504 x 8256
- Canon EOS R5 Full Frame Mirrorless - 45 megapixel sensor, with image resolution of 5464 x 8192
- FUJIFILM GFX 100 Medium Format - 102 megapixel sensor, with image resolution of 8736 x 11,648
Quality of the Original Image
The quality of the original image has to do with many factors related to the camera, lens and equipment, but also the photographer’s technique and the conditions in which the image was taken. Higher resolution cameras have the potential to create massive enlargements, but poor technique, conditions or other negative external factors can greatly reduce this capability. The images with the most potential for enlargements are tack sharp (or lack details altogether, like moving water or clouds), are noise-free, and have not been edited too heavily. The best technique for achieving this typically includes a quality camera and lens, stable tripod or fast shutter speed, low ISO, proper focus, and sufficient light. The cleaner the original image is, the bigger the enlargement can go.
Cropping and Aspect Ratio
Oftentimes the image must be cropped to fit the intended display. For instance, an image taken with a standard 2x3 aspect ratio camera will create native output sizes such as 8”x12” or 20”x30.” If you want to fit the image in an 8”x10” frame, the image will have to be cropped. This reduces the resolution of the file since you are deleting a portion of the pixels. Depending on the amount of cropping needed, this can greatly limit the output size.
Output Size Needed
There are many resources available that describe the maximum size prints you can make with any given megapixel camera. These charts are a basic resource, but do not take into consideration the many factors that impact the decision. The best way to know if an image can be enlarged to a specific size is to create the enlargement digitally and review it. Additionally, a crop of the enlargement can be printed on small paper to review the actual output quality prior to sending for the final enlargement.
Type of Output Medium
Typically, enlargements are performed to create a print, poster, billboard or other physical product. There are many different papers and mediums to choose from, and each has its own characteristics. For fine art prints, mediums such as Fujiflex or Lumachrome retain the ultimate in detail, color and sharpness. If your enlargement is not great quality, these may not be the best choices. However, canvas or cotton rag papers oftentimes lack the same level of detail and can be great solutions to less than perfect image enlargements.
Viewing Distance of the Finished Product
One of the most important factors with enlargements is the distance the final image will be viewed at. A small 12x18” print will usually be viewed within just a few inches, so it should be very sharp throughout. As prints get larger, for example an 80”x120,” they are generally viewed from a greater distance. The sharpness will degrade as images get larger, however, from a proper viewing distance this is not an issue and the image will appear very sharp. On the extreme end of the spectrum, billboard images are printed 14’x48’ and upon close inspection appear to be a collection of large dots. When viewed from your car or the sidewalk, they still appear to be sharp and detailed. It is all about proper viewing distance!
Photo Enlargement Software
There are numerous software options available for image enlargement today with the most popular being the following:
- Adobe Photoshop – The gold standard for image editing and enlargements with several options for resizing and enlargement methods.
- Topaz Labs Gigapixel – A standalone program for image enlargement that uses AI (artificial intelligence) and machine learning technology to create enlargements.
- On1 Resize – A standalone program that uses a fractal image enlargement algorithm.
- Shutterstock – A free online image resizing resource for anyone to use.
To understand which one is best for your needs, you will want to review the side by side comparisons below which show the different resizing methods and results.
Best Settings for High Quality Image Enlargements
In this section we will look at the different resizing options included in my favorite enlargement programs, Adobe Photoshop and Topaz Labs Gigapixel. As mentioned above, Adobe Photoshop is the gold standard for photo editing, and image resizing is no exception. With numerous options to choose from depending on need, Photoshop consistently and quickly produces stellar results. On the other hand, Topaz Labs Gigapixel can also produce excellent enlargements, but in my experience can sometimes be unpredictable. Regardless of which enlargement method used, you will need to sharpen the image after enlargement, but before printing. Sharpening is a separate topic not covered in this article.
Topaz Labs Gigapixel
For best results, it is recommended to use an uncompressed image format, such as TIFF versus JPG, PNG, etc. Open the desired image, and the program will display a preview of the before and after results. This is only a quick preview, so do not be discouraged if the results do not look the best. On the right-hand side panel, there are basic settings for enlargement. Start by choosing the resize mode, which is either by specifying a percentage to enlarge by, or by entering the exact width/height and pixels per inch needed. Below that, you can select face refinement and image type (manmade or natural). The machine learning algorithm in Gigapixel is based on thousands of other images, so make sure to select the proper type. Finally, the last section includes two sliders for suppressing noise and removing blur. I have had the best success with leaving these both at zero, but experimentation is key since every image enlargement is different.
Adobe Photoshop Image Resize
With your image open in a Photoshop window, go to the top navigation bar and open the dropdown under Image and select Image Size. A dialog box will open, which is where you will specify all your settings for the enlargement.
The first thing you want to do is make sure that the link between width and height is selected; if this is turned off your image will not retain its aspect ratio when you enter a new size. Next, tick the resample box. Resampling adds pixels information into your image when it is being enlarged and must be checked. After this, specify the desired output size (e.g. 40x60” or 4000x6000px, etc) and the resolution (300 DPI is best if possible). Finally, you must select the interpolation method for how the pixels will be added in the enlargement. There are eight options in the dropdown menu, but for enlargement purposes you can select from three: Preserve Details, Preserve Details 2.0 or Bicubic Smoother. Both Preserve Details options also have a slider for reducing noise, which I always leave at zero (its usefulness depends on your image).
These three interpolation methods all produce exceptional results, but again you must test each out to see how each affects your image. My preference is Preserve Details (the original, not 2.0), as it produces predictable and clean enlargements with fine details and edges rendered exceptionally well.
Comparison of Image Enlargement Software Results
Below we will look at a comparison of two images enlarged by using four different interpolation methods in Adobe Photoshop and Topaz Labs Gigapixel. When comparing results, it's important to review the images at 100% or higher magnification. Quality enlargements will maintain high levels of detail, sharpness, contrast and edge fidelity. In the two image enlargement examples below, I started with incredibly detailed and sharp files from professional cameras that had previously been post-processed.
Image Enlargement Example #1
All four of the enlargement methods used below produced acceptable results. The comparison image is shown at 100% magnification. The Bicubic Smoother is slightly softer than the others, but still produced nice results. Gigapixel produced sharp results, but also had strange artifacts around some of the edges (this is the unpredictability I mentioned above, red circles show these areas). Preserve Details (original) produced the most impressive results, with sharp edges, no artifacts, great details and no noticeable noise.
Image Enlargement Example #2
In this image there are several manmade elements, including buildings, lights and a bridge. Again, each of the four resampling enlargement methods produced quality results. Gigapixel may have produced the best results overall, if it were not for more unexpected artifacts. These are seen most prominently when magnified to 200% or higher. In the image below, Gigapixel produced squiggly, wormlike lines in some areas. These could potentially be seen on a high quality print, which is why I typically stick to Photoshop Preserve Details or Bicubic Smoother. However, the rest of the results from Gigapixel were quite stellar.
Conclusion – The Best Choice for Image Enlargement
After several years of enlarging images for high quality fine art prints, I have found that Adobe Photoshop is consistently the most predictable and reliable tool for resizing. Topaz Labs Gigapixel is also quite good, but sometimes shows artifacting that would be cause for concern in large prints. Nonetheless, Photoshop and Gigapixel are my top two choices for enlargements. Based on your individual needs, there are several enlargement options to choose from. If you want to quickly upscale an iPhone image to print as a 12x18, a free option like Shutterstock may be sufficient. For more professional results, Adobe Photoshop and Topaz Labs Gigapixel both produce amazing results, are easy to use and are relatively inexpensive.