Ho John Lee's Weblog

These are my links for April 12th from 17:02 to 19:13:

• Dubai bashing and ‘what-aboutery’ – Joi Ito’s Web – Joi Ito comments on various recent negative articles on Dubai.
• A VR Geek Blog » Diva – Exploring your database in 3D – Visualization tool for looking at relational database structure in 3D, with optional data glove VR interface. Wonder if they ship with the cool techno music that's playing in the demo videos.
• Polar Rose | Naming is sharing! – Face recognition service, currently scans Flickr photo collections for tagging to Facebook names.
• iSerenity – A collection of background / ambient noise, including ocean, rainforest, city street, library, etc
• A Bunch of Great Strategies for Using Memcached and MySQL Better Together | High Scalability – Notes on approaches to data caching in web applications.

A team at Honam University in Korea has developed a low cost wide angle lens that provides the wide field of view associated with fisheye lenses, but with much lower distortion. The image above is from a wide angle camera mounted on the ceiling of a university book store. Notice the relatively straight lines of the book shelves, in contrast to the curving distortion associated with a fisheye lens.

There are already various software solutions for remapping lens distortion from captured images, but this is a much more elegant approach performing the mapping in analog space before the image is sampled. There is still a blind spot at the center of the image, where the camera blocks the conical miror.

Optics.org says the lens costs around $100, although I suspect that may be the cost of materials for the development team, and probably doesn’t include the cost of the camera. The lens assembly looks more fragile than a typical security camera, but I could also see this making a nice webcam, especially if they come up with a way to minimize/mask/move the blind spot.

Speaking to optics.org, Prof. Gyeong-il Kweon of Honam University said: “We have successfully designed a wide angle lens that can provide a FoV of over 150 degrees with less than 1% distortion, and are very excited about its potential in the security arena.”

Dubbed as a “catadioptric” wide-angle lens, it is made up of a mirror that reflects the light from a wide area (catoptric), and lenses that focus this light on the sensor of a small camera (dioptric).

The setup consists of cone-shaped mirror fixed inside a hemispherical glass dome. At the top of the dome are a series of lenses leading up to a slot for connecting a small camera. Light entering from the dome strikes the mirror and is directed toward the lens. Here, it is focused to form a sharp image at the exact location of the camera’s sensor.

Looking at some of the sample images one can’t help but notice a small black spot at the centre of every picture. This phenomenon, called central obscuration, is actually a reflection of the camera appearing on the mirror. Kweon and his research partner Milton Laikin are looking for ways to overcome this problem. Currently, they have designed a purely dioptric lens that doesn’t suffer from this problem and has a FoV of 120 °.

Link (requires free registration)

I seemed to have missed this feature when the most recent line of Photosmart cameras came out a few months ago:

They say cameras add ten pounds, but HP digital cameras can help reverse that effect. The slimming feature, available on select HP digital camera models, is a subtle effect that can instantly trim off pounds from the subjects in your photos!

Just the thing for making your own Katie Couric-style portraits…

I dropped my subscription to the ACM Graphics SIG some time back, so this is the first I’ve heard of this project, which is very cool. Take your photos now, and decide what to focus on later.

From Wired News, via A Venture Forth:

A computer science Ph.D. student at Stanford University has outfitted a 16-megapixel camera with a bevy of micro lenses that allows users to take photos and later refocus them on a computer using software he wrote.

The system works by capturing information about the direction of the incoming light, as well as the intensity. This is then used to compute the image that would have been formed if the sensor was in a slightly different plane, effectively changing the focal length. The paper published by Ren Ng and team observes:

As an aside from the biological perspective, it is interesting to note that our optical design can be thought of as taking a human
eye (camera) and replacing its retina with an insect eye (microlens / photosensor array). No animal has been discovered that possesses such a hybrid eye [Land and Nilsson 2001], but this paper (and the work of Adelson and Wang) shows that such a design posseses unique and compelling capabilities when coupled with sufficient processing power (a computer).

The system works best with more data, 16 megapixels appears to work pretty well. They indicate that 8 megapixels would still work but with a narrower computed focus range. As shown in the schematic, the effective output resolution is limited by the microarray lens, not the sensor resolution, but it needs the high resolution sensor data to determine the direction of incoming light. The prototype is built in a medium format (Contex) body to make it easier to build the sensor assembly.

It doesn’t look like this is going to turn up in consumer devices any time soon, but I’m sure there are some interesting applications that can afford the cost and physical bulk of the system already.

Links:

• Light Field Photography with a Hand-Held Plenoptic Camera (project page at Stanford)
• Light Field Photography with a Hand-held Plenoptic Camera (Stanford Tech Report CTSR 2005-02, PDF)
• Gallery of movies demonstrating digital refocusing (Windows Media)
• The Plenoptic Camera (1992 project at MIT)

I’m not very good at Photoshop, but this portfolio of photo retouching projects by Glenn Feron nicely illustrates the disconnect between reality and the beautiful Photoshop-enhanced images that fill today’s advertising and print media. You can view his before-and-after images by moving your mouse back and forth, some of the differences are quite striking. These images were all part of various commercial projects, but if you have a favorite photo you can apparently send it to him for the full treatment. I’m not sure how well this works when you start with normal-looking people, though. All of the “before” photos are of professional models who look pretty good to start with.

For those who want to play along at home, you can read more about how to remove wrinkles, and blemishes, plump up lips, whiten teeth, tidy up loose hair, add contours, and generally glamourize your photos in these articles:

• Beauty Retouching in Photoshop
• Beauty Retouching

Maybe there should be a service splicing the Amazon Mechanical Turk with Gimp and HotOrNot to help people who need to boost their photo appeal?

Stopped by the Mobile Monday meeting at Yahoo this evening. This evening’s session looked like fun, as the theme was “Mobile Photos”, combining a couple of my current interests. Quick notes:

Some the general trends targeted by mobile photo services:

• Mainstream arrival of digital photography
• Impending arrival of megapixel+ phone cameras
• Increasing availability of network connectivity
• Rise of social software applications
• Changes in online attitudes and habits of society – it’s not considered weird to meet people online
• Change from photos mostly documenting events to photos of incidental, serendipitous memories

The slate of speakers / demos:

Erik Weitzman, Shutterfly (http://www.shutterfly.com)
Heather Champ, Flickr (http://www.flickr.com)
Rich Gossweiller, HP Labs/Plog (http://www.richgossweiler.com/projects/Plog/PLOGPage.htm )
Chris Dury, ScanR (http://www.scanr.com)
Mike Prynce, Mobido (http://www.mobido.com)

Flickr guy (standing in for Heather) commented that at present around 30% of their uploads are from mobile phone cameras, versus near zero when they started. Shutterfly guy brought a set of sample prints from phone cameras of various resolutions, showing that more megapixels are definitely better, although the phonecams suffer from no flash or bad flash, and mostly terrible lenses. The Sony phonecams shown in the ScanR demo had visibly better quality than the Treo sample images.