March 2008

We’ve been experimenting with the camera in the iPhone. It’s an amazingly tiny device, but provides rather more useful photos – 2 megapixel, 1600 x 1200 pixels – than any other ‘phone camera’ I’ve owned.

I’m very curious about the details of the camera. Judging by depth of field and some other clues, I’m guessing the lens aperture is around f 2.8 (in fact, I just did a ‘Get Info’ on an iPhone pic and it reports f2.8, but, curiously no shutter speed or other data).

Which got me to thinking about how this camera must work. I’ve noticed that the low light performance is good – very little shake is visible, even in low light situations (unusal for me because I usually can only manage to hold it with one hand). My guess is that this is really a video camera (it does have a video mode): there’s no mechanical shutter – the pictures are really framegrabs from what may be an analog video stream.

Since framegrabs are essentially instantaneous regardless of light level, low light ’shake’ performance should be good (we’ll be experimenting to see if our hypothesis is correct). Exposure, then, would be handled entirely in software, amping up or down depending on scene brightness.

This in turn means the lens needs to be relatively high quality – with focus fixed just this side of hyperfocus – the closest point to the lens where objects at infinity are also essentially sharp. The lens is noticeably sharper in the center two-thirds of the image (typical for relatively wide apertures like 2.8), which gives many pictures the appearance of being shot with a focusing lens, since the subject of most photos is near the center of the frame. Neat trick, and good use of the physics of optics, if I’m right. Voila 2 pix from iPhone: Peet’s Coffee in Menlo Park and tulips at Stanford Shopping Center…

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Linda’s mother Ede (pronounced ‘Edie’), God rest her soul, used the word ’satisfactory’ to describe things that pleased her. The impatiens in the flower beds around her house were satisfactory because they bloomed constantly and required little fuss once they were established.

Satisfactory is the word I’m choosing to describe my iPhone: I find myself using it a lot more than I used my Treo, which was really a phone with cantankerous contact software. I rarely used its slow, hard to read browser and its email feature was acceptable but not great.

Not only is the iPhone a better phone, but the contact software syncs effortlessly with my Mac, I have music on it (unlike my iPod, I always carry it and thus listen to the music more often) and I’ve used the browser a lot: to find a store and directions for a friend, to post entries to my blog, to check my Google Calendar, to show blog pictures of Grace to friends, and this morning, to read a New Yorker article about Senator Obama while waiting at Menlo Medical Clinic.

I also have a selection of family photos to show friends and acquaintances and have checked stocks and weather a number of times. I can’t wait for developers to come out with new apps… command line, anyone?

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