Scanning Photos and Negatives Resolution
I have began archiving the photos and negatives that are conveniently stored away in boxes. It is a great undertaking, but one that I’m sure I’ll enjoy. I describe my organizing method in my post titled Data Archiving Method. The one issue I have had, however, is determining the resolutions I will use for the digital archives.
There are many questions about resolution with regards to scanning. I haven’t found any conclusive evidence on which resolutions to use, but I have made up my mind as to which ones I will use.
One of the most debated points with regards to scanning pictures, negatives, and slides is the resolution to use. The general consensus is to print at 300dpi (dots per inch), so what should we be scanning the original in at? The answer to that question is it depends. Let’s take a look at how resolution plays a roll in the printing of a picture.
Suppose you have a 4×6 photo that you want to scan in and eventually print. You scan the document in at 300dpi with the size in pixels of the picture at 1200×1800. The size is calculate by taking the size of the photo, in this case 4 inches by 6 inches, and multiplying each number by 300, since you are scanning in at 300dpi.
Now if you want to print the photo at 300dpi you would get a 4×6 photo, which is the same size as the original. If you want to make a larger print of the photo, you can do one of two things: either print at the current resolution by decreasing the 300dpi to something like 180dpi, or rescan the original at a higher resolution.
If you were to rescan the original at a higher resolution, say 600dpi, you will now have a photo that is 2400×3600 pixels. Dividing both numbers by the print resolution of 300, you can now enlarge the photo to an 8×12.
Keep in mind, however, that because you are scanning a photo, and not the original negative, you won’t gain much if you continue to increase the resolution. That only helps to enlarge the photo, and not increase the clarity.
I read somewhere that some think the resolution of a negative is equivalent to a 20-megapixel digital camera. I’m not sure how accurate this statement is, but I can tell you one thing: you can get scan at a much higher resolution and get better prints from scanning negatives than an actual photo. When you do scan negatives, you will definitely need a higher resolution, unless you like really small photos.
The size of a single 35mm negative is 1.42×0.94 inches. If you scan a negative at 300dpi, you will get an image size of 426×282. Printing this image at 300 will give you a picture the same size as the original negative: 1.42×0.94 inches. That is a really small photo. You will need to scan in the negative at a much higher resolution.
Many scanners can now scan above 3000dpi. If you plan on scanning hundreds or even thousands of negatives you may want to go with a scan dedicated to slide and negative scanning. I didn’t have the money for one, so I have invested in a flatbed scanner. Dedicated slide and negative scanners can go as high as 4000dpi, or possibly higher, while my flatbed can go up to 4800dpi, although with results not as good as a dedicated scanner.
If you were to scan a negative in at 3000dpi, you would end up with an image that is 4260×2820 pixels in size. This is equivalent to a 12-megapixel camera. This allows you to print 9×14 inch photograph at 300dpi (4260 divided by 300, and 2820 divided by 300). For most people this will more than suffice for printing.
If I were to scan at the full 4800dpi, the image size would be 6816×4512, or 31 megapixels. The file size would be monstrous to the point where I wouldn’t be able to easily save many photos because the larger the image files, the more space you are going to need to store it. If you do scan at a high resolution, make sure you have the storage space to accommodate all of your files.
To help you determine what resolution to use, please check out Scanning and Printing Resolution Calculator. The Web site also provides great tips on scanning for both photos and negatives.
I have read many posts regarding scanning resolution online, and everyone seems to have there own opinion. For me, when I’m archiving my photographs, I’ll scan them in at 600dpi to leave a little room for enlarging. For negatives I will scan them in at 3200 since it is a nice compromise between file size and resolution. I probably won’t be printing any large photos, but it would be nice to have enough overhead just in case I would like to many years in the future.
In the end, however, scanning resolution will be decided by your requirements, needs and capacity.