Photo Scans: What Resolution?
Updated: Oct 25, 2020
You have hundreds of printed photos, transparent slides and film negatives that you need preserved for your kids and grandchildren. What is the optical scanning resolution recommended and what file formats should you use to future-proof your time and effort? Before you take on a large archiving project of your photo collection, we'll cover a few basic guidelines.
A simple rule of thumb is the smaller your printed photo, the higher the optical resolution is needed for the scan. So if you have small 3x5 prints, you'll want to do at least 600 dots per inch (dpi). For a larger print such as a 5x7 or 8x10, then 300 dpi may be fine. In general, 600 dpi is a good optical resolution that will bring out the details of your loose photo prints. Resolution choice depends on your use. For scans that will be used for social media posts, 300 dpi is sufficient but use a higher resolution if the photo is important and will be archived. Also, if you plan on printing a large photo from a scan, make sure your original was scanned at a high enough resolution that will look good when enlarged.
For 35mm film negatives and slide transparencies, you are working with a small image that will most likely be enlarged when viewing or printing. 2400 dpi to 3200 dpi is a recommended resolution for negatives and slides. If you plan on printing 8x10 or larger prints from your original media, you may want to consider up to 4800 dpi. For the highest quality archival scan, always use the film negative if you have both the print and the negative for your images.
What about Polaroids and old film formats such as 126, 828, 620 and 110? For negatives of these formats from earlier this century, make sure your scanning vendor has the capability to properly scan these film negatives. Without the proper templates to hold the negative flat to the scanner, it is very difficult to obtain a quality scan. 110 format has a very small negative so it's recommended to scan this format at 3200 dpi or higher.
Once you have decided on the optical resolution for your photo scans, what is the best file format for your digitized photos? The National Archives recommends the TIF format which is uncompressed. While not as common as the compressed JPEG format, having your scans in TIF gives you a 'golden' uncompressed file that you can edit in Photoshop or other photo programs and then save in JPEG. If you scan to a JPEG file, any edits to that already-compressed file will result in a lower quality compressed and edited JPEG file. For scans that will not be archived and do not require editing, JPEG is sufficient.
So which resolution and file format is best? That really depends. Your optical resolution and file format choice hinges on the size of your photos, the importance of the pictures (archiving or social media posting), and whether you plan to tweak the scanned images in a photo editing program.