By Werner Ruotsalainen on Mon, 05/21/2012
Back in the iPhone 4 times, I very happily reported on the phone having very good video resolution: something very-very-very-very rare in the digital stills camera / camcorder / smartphone world.
Now, Apple seem to have repeated the same feat with the iPad 3: it has way better video resolution than 99,9% of the current consumer-category (-priced) stills cameras (with 1080p video) and (1080p) camcorders. Based on my measurements, I can safely state that very few other cameras come close to it, resolution-wise. (Note that I wasn't allowed to test the video resolution of the Nokia 808 PureView (last article HERE) in Barcelona this February. Based on the information I have, I assume it'll match the resolution of the iPad 3, but, again, it's an early assumption.)
Now, let's see how the iPad 3 renders the ISO 12233 resolution chart! A correctly focused, well-light grab of some footage of an absolutely steady iPad 3. (Original video footage HERE; note that the first second was out of focus; then, I re-focused and kept the focus after that)
Here's a thumbnail:
(click it for the original, uncompressed image! Don't even try to judge the resolution based on this dumbed-down, heavily resized thumbnail! (The other thumbnail, visible images in the article are also clickable and lead to the original ones.))
In the image, I've annotated the Nyquist limit, which is equal to the vertical output pixel count of 1080p videos – that is, 1080 pixels/LPH. (It's a vertical red line in almost the middle of the screen). Everything to the left (higher resolution than 1080 line pairs) is “false detail”; to the right (lower resolution) is almost correctly rendered. The same stands for the horizontal resolution (horizontal red line: everything under is false, aliased detail; the lines over it, on the other hand, can be rendered by a decent camera.) Note that I've also provided an unmodified, non-annotated version of the framegrab HERE.
Now for the bad news: the Field-of-view (FoV) problem
As has been explained in my previous articles (for example, THIS) dedicated to enhancing the iPhone 4 / 4S video recording, the problem with most current camera phones (except for some high-end ones engineered keeping photo / video enthusiasts in mind: the Nokia N8 and the Nokia 808 Pureview) is that they simply don't have the computational power to correctly downsize ALL the horizontal pixels 30 times a second while recording video (no such problems exist with stills shooting!). This is why in the iPhone4, 4S and the iPad 3, only part of the sensor's width is used when recording video. (The iPad 2 and iPod touch 4, the other two camera-equipped model, don't suffer from this problem as their sensors was selected to just be of 1280 pixels – that is, 720p – wide. The old iPhone 3GS uses the entire sensor to shoot video – after all, the resolution of the sensor is 3 Mpixels only, which means downsampling to 640*480 can still be done using the comparatively fast CPU of the phone.)
For example, the iPhone 4, which records at 720p (1280-wide), uses only the center 1280 pixels of the otherwise 2592 pixel-wide sensor. This is why the video it records has a FAR narrower field-of-view (appr. 43 mm in video mode vs. appr. 28 equiv. in stills mode) than the still shots it takes, as the latter make use of the entire 2592 pixels. The same stands for the iPhone 4S: it has a 8 Mpixel sensor, of which only a 1920 pixel-wide area is used when shooting video. And, unfortunately, the iPad 3 also belongs to this category.
In order to see the difference between the different field-of-views, let me present four video framegrabs taken from the video footage recorded with FiLMiC Pro. (More on this app later.)
(480x360; original video footage HERE)
(640x480 (VGA); original video footage HERE)
(1280x720 (720p); original video footage HERE)
(1920x1080 (1080p); original video footage HERE)
What can you see? Apart from the first two shots (which have the same FoV), the higher the resolution, the narrower the FoV (that is, the less area the camera records). Also, you can clearly see the brightness of the images gradually decrease with the resolution increase. The latter is very easy to explain (and you already know the answer for the why's): 2592 pixels (the width of the iPad 3 sensor) divided by 480 = 5 (dropping the non-integer part of the result); 2592 / 640 = 4; 2592 / 1280 = 2; 2592 / 1920 = 1. That is, while you can combine 5 pixels into one target pixel when recording 480x360 footage, 4 pixels for VGA, 2 pixels for 720p, only one pixel can be used for 1080p recording. The more pixels combined into one target pixel, the better light sensitivity and less noise.
What does this mean? Exactly the same as was explained in my iPhone 4S camera hacking and FiLMiC Pro review article: without jailbreaking (which is still impossible on the iPad 3), the only way to gain a much wider FoV OR much better low-light performance is using a third-party app (for example, FiLMiC Pro) that allows for recording in 480x360, VGA or 720p resolutions. Unfortunately, you'll still need to trade in the (excellent) resolution.
Speaking of FiLMiC Pro (iTunes link; also has a free trial / lite version), the current version runs great on the iPad 3. Both the aperture and the focus setter reticles are active and usable (as opposed to the iPad 2 and the iPod touch 4) and all lower-res modes, directly writing to the camera roll, work just fine. The bugs I've very thoroughly elaborated on in my previous article seem to be all fixed; now, all you need is going to the Settings menu (the tools icon to the left of the red (shutter) button) and select the desired resolution under the “Resolution” menu item. Nothing else need to be set – just leave everything on their defaults. (I do NOT recommend decreasing the frame-per-second from the default 30 as it'll result in having to use the app's own encoding not necessarily having the same robustness and quality as that of Apple.)