What We Know so Far

This has been really interesting. Well, interesting for me… if you're actually reading these words I'm impressed ;-) But what we now know is that the camera make and model have to match certain criteria, and we know that “Apple” and “iPhone 6 Plus” will work. It would seem obvious that any iPhone model that shoots panoramas will work, or perhaps even just the word “iPhone” will do it (it won't; I tried). But both names do need to be changed. I'd guess that a variety of Android-related camera make and model names will work too, but I can't test those. If you want to… go for it and let us know in the comments. The rest of the EXIF data and the file name does not matter.

We also know that the ratio can not exceed 5.75:1, and that the file height has to be at (or under?) 3,082. That said, there could be other criteria… it could be a total pixel count. A wider but less tall image might work that doesn't exceed the current 17,722 × 3,082 (54,619,204 pixels) size. 

That's actually quite interesting… and what I'll try next.

I've created a new starting point that is the original file with just the camera make and model changed. I'll keep returning to this one for each ratio test.

15 Let's change the ratio but not the pixel count

I created a new table to calculate sizes and ratios, ensuring that I've maintained the same pixel count all the way through. I may not get past the first one… but this is what I have in mind. The first row is what we've already tested the works. From there, the height and aspect ratio are calculated from a fixed total pixel count and a manually entered width. The widest width here, 29,919 is the actual width of my test file. You can also see the ratios of each calculation. Finally, I'll always round down on the height to ensure I don't go over the total pixel count.

I'm also scaling these differently than before. I'll change the Image Size of the un-cropped image to the calculated height listed below, then crop the sides off using the Canvas Size tool to match the width.

These are the ratios I’ll try, starting with a known working size

17,772 RESULT: Worked, of course… this is what worked before. But I had to do it again as a control test.
18,000 RESULT: Well that was a short test… this didn't work!
19,000 RESULT: Oh I can't test this… when I drop the vertical resolution to 2,874, the width reduces to 18,766; less than the 19,000 I'm meant to test with. Maybe not important, but still…

Could that 5.75:1 ratio really be the limiting factor? Or…

16 Could it be file size?

Looking through my test files, every file that worked was 6.1MB or smaller. The last test file was 6,099,930 bytes. Could file size have something to do with it?

I'll take the last fail, so the 18,000 pixel wide 5.93:1 aspect ratio image which is currently weighing in at… hmm, still 6.1MB but 6,142,747 bytes — well what the heck let's test anyway. I'll compress as a smaller JPEG, to quality 6 instead of 7 (file size now 5.6 MB), and see what happens. 

RESULT: Nope… alright then. It's not file size.

And just to prove that, I'll go the other direction, taking the last known working file from 6.1 MB up to JPEG quality 9, making it 8.2 MB.

RESULT: Yes, that worked… affirmation that file size is not an issue (at least not to this degree).

I'm going to try one more aspect ratio test, not that I expect it but I must try. I'll take go for the max 29,919 width and crop that down to just 1,825 vertically.

RESULT: Ha! That just crashes facebook… so that'd be a big nope.