I received this email a few weeks ago from Jennifer E, one of my subscribers:
“Hi David, I need to download some of my photos to a CD. My question is, if I resize the photos to a smaller size, so I can get more of them on my CD, then I reinstall them into my computer and size them to the size when I took the photo, will I lose any quality? (size 3264×2448 down to 640×480 then back up to 3264×2448) Thanks, Jennifer
P.S. Your books and info are great. Every time I go through them again, I always find something new. I am so glad I found you.”
Here’s my reply:
First off, thanks so much for your kind words. I’m really glad you’re enjoying my books!
The short answer to your question: Yes, you will lose image quality. If you resize your images down to a smaller size, and then size back up again, your image will be a lot less clear. When you resize the image back to the original size, you won’t get the original image back.
Why is this? The amount of detail stored in an image depends on two factors. The first is the number of mega pixels in the image. The more mega pixels, the more detail your photo has. That’s why newer model cameras boast larger mega pixel numbers – these cameras capture a more detailed photo.
The mega pixel count is (simply) the total number of pixels in the image, and thus is related to the number of pixels in the width and the height of the image (pixels wide times by pixels high equals the number of million (mega) pixels in the photo).
By resizing the size of the image, you actually reduce the mega pixel count of the photo. When you reduce the megapixel count, the computer can’t store all the detail any more (there simply aren’t enough pixels to do so). In Jennifer’s example, she was reducing the size from 3264×2488 (8 megapixels) to 640×480 (about 0.3 megapixels). Thus removing detail from the image.
Resizing the photo back to 8 megapixels means there are a lot more pixels in the image again, but the computer no longer has all the pixels needed to reproduce the original image. So it copes the best it can and makes an approximation.
So to store images for the long term, do not resize your images to save space. You’ll lose valuable detail in your photos that you’ll never be able to get back.
Oh, the other factor that controls the amount of detail stored in an image is the method you use to store the photo. See my tip on file formats for more information.
So thanks for the question Jennifer.
If you have a photography related question that you’d like to ask, post it on the comments below and I’ll do my best to answer it for you!