A Guide to Image Resolution: Scanning Edition
In the world of fine art imaging, scanning resolution plays a crucial role in capturing and preserving the intricate details of artwork, photographs, and documents. At the highest level, resolution is used to communicate the quality of an image as it relates to detail, sharpness, and colour.
Through many consultations with clients, however, we have found that resolution is one of the more confusing concepts, especially because resolution can be communicated differently depending on whether you are talking about optical, digital, or print resolution. And since the quality of your scan will have an impact on the quality of your output - whether for on-screen viewing or printmaking - understanding resolution is essential to making informed decisions about your fine art scanning needs.
In this guide, we will unpack some of these concepts with a focus on how resolution plays into fine art scanning.
What is Image Resolution?
In digital imaging and photography, an image’s resolution is the total number of pixels it has and is most often communicated in mega-pixels. This can be calculated by multiplying the number of pixels in the width by the number of pixels in the height.
The number of pixels you can get in the width and height of your image will be determined by your capture system’s optical resolution, which represents the device’s ability to capture data and details. Generally, the more pixels you have, the higher quality your image will be. This is because each pixel is a tiny square of a single colour that makes up an image so the more pixels you capture, the better the image; so when it comes to fine art scanning, reproductions, and archiving where details are critical, you will want to ensure that your scan is done at a high enough resolution.
That’s why camera and smartphone manufacturers always highlight increases to their cameras’ resolution in mega-pixels - because it represents an improvement to the quality of the image that will be produced! The same applies to scanners. With our Cruse Synchrontable scanner, for example, we can capture a maximum of 14,000 pixels in the height of the image, with images up to 800MP in resolution.
The total number of pixels in the image doesn’t tell the whole story of image quality though. To get the full picture (pun intended), we also need to care about how the pixels are distributed within the image’s physical dimensions, most often measured and represented as pixels-per-inch (ppi).
Ppi is what most people think of when it comes to image and scanning resolution. Just like how more total pixels will generally give you better images, the higher your ppi, the smoother, more detailed and colour-accurate your image will be. When your ppi resolution is too low, your images may end up looking blocky/pixelated.
Determining the Optimal Scanning Resolution:
So how do you determine the optimal scanning resolution for your images? Many clients come to us with the idea that there is a universal magic number, with 300ppi as THE benchmark for an image to be considered ‘high-res’. And while it is a good standard for most scans (all of our standard scans are done at 300ppi, size permitting, unless requested otherwise), there are a number of factors that can influence whether a higher or lower resolution scan is suitable for you:
Size of the original: For smaller originals (ie. 8”x10”), you may want to scan at a higher resolution than 300ppi. On our Cruse, we can scan this size at up to 1,700ppi. Scanning at a higher resolution gives you more pixels to work with for any post-production you may want to do, as well as giving you the option to print at an enlarged size. At the same time, you may not want to go too high since a higher resolution can also show more of the imperfections. For example, we have scanned some very old photographs with dust and scratches that aren’t visible to the naked eye, but showed up clearly in a very high-resolution scan.
For large originals, we may actually need to scan at a resolution lower than 300ppi due to the architecture of the scanner. If you remember our Cruse having a limit of 14,000 pixels in the height, for any images larger than ~45” tall, the scanning resolution will be below 300ppi. And while it doesn’t meet the 300ppi threshold, there will still be more than enough pixels (14,000pixels x whatever width) to produce a scan that can be used for a high-quality reproduction. Remember, pixel density is only one part of overall image resolution. If you are ever skeptical of a resolution below 300ppi, ask about the total pixel count.
Intended use (digital, print): The optimal image resolution for on-screen viewing is between 72-150ppi. This resolution provides the best balance of image quality and short loading time. If you are using your image to print from, you will generally want a file with 300ppi, but the specific value will also depend on a few factors such as the final print size and the printer’s resolution (this is a separate concept which refers to the number of dots of ink that a printer can print per inch of the image). With certain sizes and/or printers, you can still achieve a beautiful, high-quality print with a file that is lower than 300ppi.
Larger viewing distances with large prints/pieces means that 300ppi isn’t always needed for an image to still look crisp and sharp.
Output size: Just as the size of the original will impact your scanning resolution, so too will the desired output size. If your output will be the same size as the original, then a 300ppi scan will give you a high-resolution, quality image. If your output size will be enlarged, then you will need to scan at a higher resolution so that you have enough total pixels and pixel density when the pixels get distributed across a larger physical area in the image resizing process.
However, for larger originals and outputs, such as for a 60”x90” image, you do not necessarily need 300ppi for a high quality image. In our experience and with our printers, we can print a high-quality image with a 150ppi image (part of this is related to the printer’s interpolation capabilities, which we’ll discuss in a separate article). Of course, there will be an objective difference between the 300ppi image and the 150ppi image, but the reason a lower resolution image is acceptable is because of viewing distance.
Generally, someone viewing a 60”x90” piece will not be standing a few inches away and studying each detail with a magnifying glass, just as how you wouldn’t sit a foot away to watch a 72” TV. Instead, they would be standing a few feet back so they can take in the entirety of the piece. With a larger viewing distance, the lower resolution is not noticeable and the image can look just as good as a smaller, 300ppi image.
Complexity of the artwork/original: Art that has a lot of fine detail (fine lines, edges, etc.) will require a high enough resolution to be able to capture and reflect the details of the image at the final size. Art that is quite busy, on the other hand, although it does have “detail”, can get away with slightly lower resolutions since the busy-ness of the piece will mask off certain elements that are not as sharp.
Condition of the artwork/original: Scanning at higher resolutions allows you to capture more details from a piece. If the original has any dust, scratches, or other fine imperfections in the surface of the piece that may not be visible to the naked eye, scanning at a very high resolution can act like a magnifying glass in bringing these out in a scan. This can, of course, be touched up in post-production, but if you don’t have a specific need for scanning at a very high resolution and you want to balance the amount of work that needs to be done on the file, then the original’s condition may factor into choosing the best scanning resolution.
Budget: Scans at higher resolutions are typically more expensive, though this can vary from business to business. With our Uberscan services, the scanner moves more slowly as the resolution increases, and because a lot more detail is captured in the scan, the processing time by our technicians to remove imperfections and perform colour-optimization also increases.
Conclusion:
Starting with a high-quality capture at the right resolution is a critical aspect of fine art imaging, and plays a vital role in preserving and reproducing the details and essence of artworks. By understanding the concept of image and scanning resolution, you can make informed decisions about your fine art scanning needs.
With the Uberscan by Colourgenics, we combine the industry-leading imaging technology of the Cruse scanner with our imaging experience and expertise to provide artists and photographers the highest-quality scans with stunning detail and colour-accuracy for originals up to 60”x90”.
You can learn more about our services at our website, and if you’d like to schedule a free consultation to discuss scanning your work, fill out our contact form.