The iPhone 4 introduces a brand new camera, increasing the resolution from the previous 3GS' 3MP sensor to a 5MP sensor. Video recording has also gone up in resolution to 1280 x 720 pixels (720p) from the previous 640 x 480 pixels. An LED flash has been added to the rear camera and a new front facing camera has been added for FaceTime. This front facing camera can also be used to snap photos at a resolution of 640 x 480 pixels.
The challenge with increasing resolution while keeping more or less the same sensor size is image noise. You see this happening in compact cameras; to keep up with marketing, manufacturers increase this year's megapixel rating while keeping last year's sensor, when the megapixel count really has nothing much to do with better image quality. At the extremes, you end up with either overly aggressive noise reduction giving you weird artifacts, or too much noise in your photos. Somewhere down the middle, a pleasant trade-off is sometimes achieved. So where does the iPhone 4 sit?
We took an iPhone 3G (2MP), an iPhone 3GS (3MP) and the iPhone (5MP) out into the field for some challenging subjects, and we have to say we came back impressed. It's worth remembering that these cameras don't come with any manual controls for ISO or white balance, and only the iPhone 3GS and 4's cameras come with manual tap to focus (it's purely up to luck on the 3G). Since we can't lock down the controls, you might get different results from the same scene if the iPhone decides to change exposure or white balance settings for some reason. Okay, caveat over.
While the 3G and 3GS' colors look more neutral, the iPhone 4 bumps up the contrast and saturation for richer photos. Whichever you prefer is up to you, but for us we'd prefer the richer hues of the iPhone 4, since we'll likely be using these photos 'out of the box' for simple situations like Facebook, tweaking saturation/contrast for the 3GS would be an added step.
The iPhone 4 is the first iPhone to not feel like a mobile phone camera. It gets exposure and focus settings more accurately and faster than previous iPhones, and the results look like they were shot with a simple compact camera rather than a mobile phone. While upgraders from iPhone 3GS will be pleasantly surprised by the difference, iPhone 3G users will be astounded! This isn't a camera you're using to make do, it's a camera you can reasonably trust to take some decent photographs.
Leaves are a nightmare for any camera to capture, due to their fine detail and complexity. In this comparison between the iPhone 3GS and the iPhone 4, we see that the iPhone 4 captures more detail than the 3GS - where some leaves have been reduced to a muddy mess with the 3GS, the iPhone 4 retains their fine edges.
Digital zoom has been improved on the iPhone 4, although like digital zooms everywhere, the result is horrid and we'd advise against using it (if you must, zooming halfway gets a better result than zooming all the way in). Digital zooms, unlike optical zooms, don't involve lenses moving to get a closer picture, they're just crops performed on the photo by your iPhone in-camera. To be fair, we couldn't get much better results cropping and scaling ourselves in Photoshop CS4.
Low-light performance has improved with the iPhone 4. You won't beat a capable compact camera, but you'll get better results than the iPhone 3GS, with finer grain. The LED flash (which can be turned on and off) is an added advantage in those places where there just isn't enough light.
Video has been improved as well. The higher, more filmic resolution is welcome as you see more with the larger sized videos, while details that were fuzzy with the 3GS are clear with the iPhone 4. Sound is noticeably better, louder and more distinct. Unfortunately, the rolling shutter effect is still apparent, where things seem to tilt if the camera moves while shooting.
Compare and contrast this video shot with the iPhone 3GS (click here for the full resolution video):
And this video shot with the iPhone 4 (click here for the full resolution video):
It's not just about the better image quality though, the experience of shooting with the iPhone 4 and the earlier iPhones is a difference as clear as night and day. Not only are the colors richer in the JPEGs, they're richer on screen. The Retina display is so vivid and bright that you feel like you're looking right at the world when framing with the camera, and makes the 3GS' screen look dull in comparison (the 3G looks dull and blurred). It's not just for the sake of a better viewing experience, you take better pictures too because you're looking at the scene more accurately. Launching the camera app is almost immediate, auto-focus is faster, the shutter is much snappier, so is saving the shot, so there's a higher chance of getting the next shot sooner.