Tech Question: JPEGs

Hello, I have joined this site because it seemed a fantastic place to find great assistance. I’m having trouble understanding an issue with Jpeg images. It’s an issue I need to resolve before continuing my project with confidence.

The first image is the original image numbered 2297. As you can see, image 2297 was created on January 25, 2020. You’ll note it has a small “.jpeg” identifier or extension.

The second image is a copy of the same image, Image 2297, dated April 26, 2022. You’ll note it’s identifier is a large “.JPEG”.

Unless I’m missing something, the “.jep"and “.JPEG", along with the “Color profile” of each photo are the only pieces of information that are different between the two images. All other data is identical.

What is very confusing for me is that the original photograph, dated January 25, 2020, is 2.3 MB. But a copy of the same image, dated April 26, 2022 , is 3.1 MB.

How can the copy be better, meaning more Megabytes, than the original?

Many Thanks for your consideration to address.

Best,
THN19

How did you create the "copy"?
JPEG images use a "lossy" compression algorithm. This means some information is lost while compression the image so it takes less space in storage or to transmit over the internet. Different programs allow for greater or lessor loss of information, and some programs allow the amount of loss to be set by the user. The different file extensions suggest that different programs were used to create the two files from possibly the same source such as a RAW image.

How can the copy be better, meaning more Megabytes, than the original?

Larger file size does not mean better quality. It usually will, but it's not a given.

This pic saved Level 10 in Photoshop (Level 1 = minimum file size and quality, Level 10 = largest file size and best quality)
File size is 116kB.

Then pic saved as Level 1, resulting in 32kB size.

If you open a high quality JPG file and then re-save it, often artifacts will form. They can take the form of haloes around objects. The effect can be subtle, so you might not notice unless you look very carefully. Anyway, those artifacts take additional data, so the file size gets bigger. The quality is less, but there is more (undesirable) data.

Original pic saved Level 6, resulting in 55kB file size.
Much better than the 92kB file.

Knowing how these results were achieved, this is all very predictable, but does show that while file size usually indicates quality, sometimes does not.

Hello CapnJack, Choderboy, and Archibald, Thank you so much for taking your valuable time to answer my question. It is really appreciated. I’m now able to move on. Wishing you all a great day, full of “blue skies and golden sunshine all along the way!” Cheers!, THN19

You never answered the question on how the copy was created. If you simply copied the file and pasted using Windows copy/paste function, or drag and drop, the file sized should be the same thus I am suspecting that you opened the file using some application and re-saved it. If this is the case, the reason for the difference in file size is because you re-compressed the file. When you read in a jpeg into an application, it de-codes the compressed file into an image. If you zoom in to greater than 100%, you can see the jpeg compression as squares. Depending on the compression level, they may be subtle or very noticeable. When you re-save the image creating the copy, the jpeg engine of the application you are using goes through the compression algorithm again re-compressing an compressed/expanded image. Because of the jpeg artifacts, the image will compress differently. Do this enough times at a low enough quality level and the artifact becomes very evident.

Below is a random image i brought up. The top 1/2 is the uncompressed file and the lower 1/2 is the same location from a jpeg at a 5 quality level. You can clearly see the 8x8 jpeg blocks. If I were to re-save this, it would re-compress the photo and because of the blocking can/will cause a larger file size than the original.

btw, the pic above is zoomed in 400% and I too a screen shot. At 100% it is barely noticeable and if I view the whole image, you cannot see the compression artifacts at all.