If you look online, there seems to be a basic rule about photo scanning that hasn’t changed in around a decade. It is; that 300dpi is totally fine for scanning photos, and that anything above 600dpi is a waste of time. Everyone says this. It’s literally what hundreds of blogs and websites have as the answer to this question. But that answer is wrong.
I know; this sounds crazy. We aren’t going with the prevailing winds here.
But the real answer to this question has a lot of nuances, and we’ll go through all of this with you in this article. First off, if you’re not scanning old photos for posterity or you’re just making quick uploads of things you don’t really care about, then this rule actually holds pretty true. Go ahead and follow it.
Most blogs and websites literally don’t display anything larger than 72dpi. Seriously.
So, there’s no need to do these kind of super-detailed scans for journalism or social media use. Where this stuff comes into play is with printing items, and whether you’ve decided you want to enlarge the original or not.
We’re going to write this in bold for a reason:
Do you want to enlarge the original when you print it? If not, 300dpi is fine.
If you do want to enlarge it, now we need to talk more.
Now we’re going down into the deep rabbit hole that is enlarging things and making prints from small pieces of paper and small images. Buckle your seatbelt.
First, we’ll go through some basics: The higher the resolution (on your screen, on your printer, etc.) the more you can enlarge what you have. This ‘resolution unit of measurement’ is simply DPI aka dots-per-inch. The higher these resolution numbers, the more you can theoretically enlarge stuff.
However, if you’re getting a high-resolution scan of something that is basically not filled with a whole lot of interesting info in that detail (say, the paper of a handwritten note) you’ll have to make your own decisions about how detailed you want that print to be.
Higher-rez photos obviously are larger in size and take up a lot more space on your computer. This isn’t as important of an issue as it was in the past, now that storage is so insanely cheap but it is worth making a note about. If you’re scanning things that you like, and might want to eventually print them out stick to around 300dpi like as stated above.
Even if you don’t print there’s something you may also want to consider in this era of touch-screens and phones; you’ll need to think if you want to enlarge the photo at some point or not.
Say you have a photo that you really like, and you want to eventually have it where it can double in size for on-screen examination. Lots of e-commerce shops have this need. For that photo to double in size without losing any quality, scan it at 600 dpi.
Yes, this does sound crazy, and yes, it will take more time and take up more room.
But do it.
Here’s where things get really crazy; if you want to more than double the size of the original, you’ll benefit from scanning it at more than double the amount of DPI. Say you go 900dpi. This can turn a small 4×6 photo into a 16×24 inch poster. Kind of cool, right?
Why scan at high DPI? What Stuff deserves hat level of scrutiny?
And here are the super-detailed things and media types you might want to scan at a really high DPI; tintypes and daguerreotypes. These are really ancient photo methods, and they’re insanely detailed and even create a bit of coloring and shading in photos that is unique to the medium. You might as well save all of that detailing and shadowing…and again, it is possible if you ratchet your system up to a high-DPI setting.
Another reason to go super big with the DPI is if the original piece you’re trying to blow up is insanely small. Even a 2×3 inch photo if scanned at something like 1200dpi, can turn into a 16x24inch poster. Now, who knows how detailed and good that thing may look; it depends on if the originals are detailed or not.
Tintypes and daguerreotypes have this level of detail, and we say again to go for it.
OK, so now we talk about things like slides and negatives. If you want the ability to make something equal to a photographic slide, something that could live in an archive or a museum you can ratchet up your printer or scanner as high of a level as it goes. A lot of machines can go up to 2000dpi or higher.
This, and basically only this, is what those types of settings are for.
2000dpi is basically a 6MP photo.
4000dpi is a 12mp photo, which is the level of most decent cell phone cameras these days.
The thing with 4000dpi and similar setting is it would allow you to blow up and crop at poster-level sizes. Kind of amazing to be honest, and if you’re looking to have a set of slides from various photos…but in a digital medium, it is these high settings that will get that sort of thing done.
Either way, the point is almost moot depending on what you plan to do with the image. If you’re just printing to paper, yes, you’ll have all the detail of a slide on your image that you print from but the printer you use will have a DPI setting of around 300 so that extra size is literally only good for things like cropping. Just so you know you’re not getting any extra level of saturation happening here.
Once you get things scanned up and ready to go, we recommend you also go ahead and back up to some sort of cloud storage system. Then you’re protected all the way around.