Chad If that is the problem, why do all my images show up proper? Well, that could be how I go about posting an image. I use the 'scenery' image in the menu, drag and drop. Think that Willie does a copy and paste, I don't remember if any of his have been ..um.. sideways. I do not use a phone or tablet so don't know about those, nor do I need to find out.
L8r
Because the orientation meta data is optional and so your images may not have any orientation meta data. The forum software assumes that the data for the image is always right side up (probably starting from the upper left). This is a WAG but I assume in the old days that JPG did not have orientation meta data -- speaking 20 years ago etc. And a lot of software probably assumes that still.
Apple devices and I assume other modern devices with fancy cameras and stuff do not store the data in that order because when held sideways or upside down the sensors output the data in a way that is not "right side up" so that they detect orientation and add it to the meta data so that the display tech knows how to orient the image for display. That's my interpretation of what is happening from a user perspective but also because I had to deal with it in an app I was helping develop -- we took pictures and if we ignored the meta data we would get upside-down or sideways pics.
To rephrase what I said above -- the sensor in the camera dumps the data to the operating system based on the sensor's default orientation. That default orientation of the sensor may not always be "right side up" for whatever reason (the way the sensor is mounted in the phone/camera, the user holding the phone sideways or upside down*, etc). For performance reasons the phone doesn't move the data around to be right-side up -- if its doing a quick multi-picture burst mode and getting multiple 12 MP or 48 MP dumped all on it in a second or two it can't take the time to rotate that 12 MP or 48 MP image around in memory before storing it. The data is dumped from the sensor to storage. By attaching an orientation meta-data tag to it, the display software can orient it correctly on-screen -- changing the data for only one picture instead of a whole ton of pictures like the camera would have to do. Again, this is my understanding from observing it as a user and also from the software engineer side of interfacing with the camera in an app.
Based on my experience it seems that when you "export" a photo from an iPhone or iPad or Mac into a file, it re-orients and writes the data to the file system in traditional order (right side up). In other words, it looks at the meta data and fixes it on the export. (I can't say I've written a file from my phone or iPad into a JPG on a shared disk but I do export images from the Photo Library that is common between all my devices from my Mac into a file. When I do that the images aren't upside down). When posting directly from the iPhone or iPad, taking the photo out of the photo library, it sends the data the way the camera took it with the meta data for orientation.
* while most people won't purposefully hold their phone upside down to take a picture, if you are taking pictures of stuff on a table from above, you'd be surprised how often the phone tilts to being "upside down" by being tilted slightly lower on the far side... That's the issue I ran into when I was interfacing with a camera in our app.