I was making a soundslide in Premiere with a sequence of 1080p 24. I've noticed when I use a photo with the extension .jpeg, the photo doesn't automatically fit within the sequence. When I use a photo with the extension .jpg, it automatically fits within the sequence. I've used the same photo with the same size dimensions, 1920x1080, but with different extensions, (.jpg and .jpeg) and this routinely shows up. I know there's no technical difference with the extensions, but is the .jpg and .jpeg difference the reason for the size issue?
The reason for the different file extensions dates back to the early versions of Windows. The original file extension for the Joint Photographic Expert Group File Format was ‘.jpeg’; however in Windows all files required a three letter file extension. So, the file extension was shortened to ‘.jpg’. However, Mac OS was not limited to three letter file extensions, so Mac users used ‘.jpeg’. Eventually, with upgrades Windows also began to accept ‘.jpeg’. However, many users were already used to ‘.jpg’, so both the three letter file extension and the four letter extension began to be commonly used, and still is.
By opening both a JPG and a JPEG file with an hex editor, you will notice that they share the very same heading information.
You shouldn't be seeing any difference on a sequence however I recommend you stick to the .jpg extension of it works for you