Is one camera application for Android really better than the other?

I encounter the following quite often on forums: "have you tried camera app A? It's way better than app B!" - but barely anyone comes in with tests of these various camera apps to see if there really is a difference in quality. As a programmer who just started his own camera application for Android ("Monochrome", coming soon to an Xperia device near you..!), my best guess is that most -if not all- apps don't apply any algorithms to improve photo quality after taking a photo. Someone who really isn't into programming might think that every camera application starts from scratch and applies their own algorithms, but this is far from the case. With Android, camera applications can very easily be created by simply calling methods, or functions, that do just that - taking photos, focusing, or anything hardware related like that. It is all simply built into Android, ready for developers to easily utilize. I want to be proven wrong (let me know if I am), but so far my instinct tells me that no camera application in the Play Store actually improves image quality with custom algorithms. To be fair, that's quite a tough thing to do if devices don't even allow photos to be taken in RAW format though.

My hypothesis is that popular camera applications in the Play Store do not show a noticeable difference in photo output quality. So far I did some tests on my Sony Xperia Z1 with the following apps and settings, in no particular order:

• Superior Auto mode from Sony devices @ 8MP
• Manual mode from Sony devices @ 20MP, ISO-50
• Google Camera @ 20 MP
• Camera FV-5 @ 20MP
• Camera FV-5 @ 20MP, Night mode (exposure "long")
• Open Camera @ 20MP

Note that any settings which I left out above were set to their defaults. I used Camera FV-5 a second time to see if its night mode made any difference in daylight shots. The photo above shows the scene I set up to take photos with each app at exactly the same location and circumstances. It is vital for this test to not move the camera even the slightest, and I think I managed. Let's see the results, shall we?

Click to ENHANCE!

This is a cropped image stitched together by the 20MP shots. One of these is actually an 8MP shot, from Sony's Superior Auto mode. Can you guess which one belongs to which app? I certainly can't. After taking these, I had a hard time keeping them apart. They all look too similar. In my eyes, my hypothesis holds: between some of the most popular camera applications, there doesn't appear to be a significant improvement over the others. Colour accuracy is the same, brightness more or less too, details seem equal. Any difference in the photos seems due to noise. The lower left photo is the only one that seems a tad sharper though, but since these are fully cropped images, I doubt you'll see a noticeable difference in the full photos. For now, I can only let you in on this: the lower right image belongs to the FV-5's night mode, hence the deviation in brightness from the others. Finally, I have to admit that this is not a professional comparison by any means. I should've taken multiple shots with each app, then either combining the ones from each app or picking the best or worst to make this comparison more fair, and using them at different circumstances. This is a good start however.

If you have a different opinion from mine, please share it in the comments below. I always like to be proven wrong, so try me if you have valid arguments. If one image stands out, let me know why. Can you guess which is which?