iOS6: Panorama mode against Microsoft Photosynth

One of the stand-out features Apple promoted with iOS 6 is a new Panorama mode in the Camera (available on "all dual-core iPhones and iPads" - effectively only iPhone 4S and 5, and the retina iPad).

I'm interested in this because for a couple of years now I've been using the actually quite excellent (you've no idea how much it pains me to admit that) Microsoft PhotoSynth app to capture panoramas.

Functionally, there's no point in performing a comparison: PhotoSynth can take full 360-degree horizontal and vertical panoramas and can post them online using a viewer app that corrects for distortion and allows for interactive display. Whereas the iOS native functionality just captures a horizontal 180-degree strip as a single wide photo. So there's no way I'd ditch PhotoSynth just yet anyway.

Having said that, though, I am still interested in the technical differences: Very often with PhotoSynth the choice of stitch points and overlaps is less than perfect (or in English: You Can See The Joins). I've used this a couple of times to deliberate effect (a favourite of mine being capturing a helicopter taking off twice; less favourite being the appearance of my daughter no less than 8 times in a single panorama), so it's a Bug that's also a Feature. But it makes casual use harder.

With Photosynth, the gyroscopes / position sensors are used to detect the orientation of the camera; when it's moved sufficiently outside of the current frame another shot is taken (with plenty of overlap). For mostly horizontal scans this works well enough (although one does have to remember to only rotate the iPhone and try and avoid moving one's body or even just arm in an arc). The orientation sensors work less well taking deep vertical shots and tend to mis-align shots straight up or straight down, although the app's tap-to-take feature mostly allows one to work around this.

The iOS app works by just getting the user to follow a horizontal arrow across the screen held in portrait mode from left to right. There's no discrete shot-taking going on, it operates more like a video mode. As long as one rotates at the correct speed and keeps the camera horizontal, the shot works. Attempts to move or rotate the camera vertically either abort the panorama (big moves) or just clip the top and bottom of the vertical movement (small moves): the end result is always just a horizontal panorama with centre point and height determined by the starting position.

So really the only meaningful technical comparison that can be made between the two techniques is to compare the accuracy of the stitching and the compensation for focus distance and exposure across the apps.

I captured the same (or nearly so) 180-degree panorama sat on a bench outside my local leisure centre yesterday on a bright sunny day, moving from down-sun at the start straight into the sun at the finish. Because of orientation glitches and PhotoSynth's auto-start, I've had to crop the PhotoSynth panorama at top and bottom to reflect approximately the same strip as the iOS Panorama. As I took my time with both apps (particularly PhotoSynth which I more normally use in a discrete rotate-shoot-rotate movement), there was less difference in the results than I was expecting (or in English: I got better-than-normal stitching from PhotoSynth this time). But what I do find interesting is that both modes of panorama have considerably more softness to the results than I was expecting.

Here's the PhotoSynth capture (Scroll right for more of it):

Taro Leisure Centre 2012-09-21; Microsoft PhotoSynth, cropped to close to iOS Panorama output dimensions

And here's the iOS Panorama (pretty much untouched from as-taken):

The Same, only taken with iOS 6's Panorama function

My verdict (yours may vary): iOS does a better job of blending the frames together (there's some obvious exposure differences in the PhotoSynth example whereas the only obvious example on the iOS panorama can be explained away as Lens Flare if one's of a mind). Focus is also sharper in the iOS photo, although to be absolutely fair I may have over-cropped the PhotoSynth example and we're seeing some interpolation instead. I prefer the colour balance and exposure of the iOS example except for directly into sun which is better handled by PhotoSynth (which is taking multiple shots so can adjust the exposure to suit).


I don't have a conclusion: I thought I'd ignore iOS Panoramas as they're nowhere near as versatile as PhotoSynth, but the difference in quality is enough to make me reconsider for certain use cases.