Macro Photography Lighting Hack

Mmm...gadgets. At last year’s Project Bar-B-Q computer-music conference, sponsor C-Media surprised the attendees by giving each of us an impossibly small audio interface. With its protective cap in place, this tiny digital-to-analog converter is less than 2.5 inches long. Yet plugged into the USB port on my crusty Dell laptop, it made a dramatic difference in sound quality. (The Dell's built-in headphone jack hisses and whines until you move the mouse, at which point it crackles, too.)

With the C-Media interface in place, the background noise and interference disappeared, and music became clearer as well. The interface also works on Macs, and in both cases, no software drivers are required. (If you do install the Windows driver, you can take advantage of simulated surround sound, a 10-band EQ, and reverb.) With an adapter, the analog headphone output doubles as an S/PDIF optical output. Add the right software, and the optical jack can pass true 5.1 Dolby or DTS streams to an external surround decoder.

I’d been meaning to blog about the gadget for a while. But when I got around to taking a photo of it, I discovered a nifty lighting trick, so I thought I’d make this entry an audiovisual one. (More on the audio interface in a moment.)

The Backlight in Front of You

Usually when I take macro photos of gadgetry, I place the subject in front of a curved sheet of white paper and point an incandescent desk lamp at it from the side. But these days my desk is dominated by a 20-inch LCD monitor, so I wondered what would happen if I replaced the paper with the monitor. So I set the screen to all white with Katsura Shareware’s Screenshot Helper, held the C-Media audio interface on front of the screen, and snapped the following photo:

Here's the main EXIF data for the above shot, courtesy of Pixture’s free PhotoToolCM contextual menu plug-in (Mac):

Camera model: KODAK DX7440 ZOOM DIGITAL CAMERA
Flash used: No
Focal length: 5.5mm
Exposure time: 0.033 s (1/30)
Aperture: f/3.4
ISO equiv.: 80
Metering Mode: center weight
Exposure: program (auto)

Note that the screen came out blue—albeit a nice blue—instead of white and with an interesting Moiré pattern. For my second shot, I changed the camera angle and increased the shutter speed to 1/45 second. (I may have moved the camera and lamp a bit as well.) Here, the screen came out much smoother:

I haven’t figured out how to correct colors yet (I’m sure we have a tutorial somewhere on O’Reilly ;-), but I made this interesting variation by clicking on a white spot in the image with the Curves’ white eyedropper:

Other than that, the only processing I did on these images was to shrink them. So I think this backlighting technique has potential, particularly if used with a tripod-mounted camera. In the images above, I was simply holding the Kodak in my right hand.

Back to Audio Gadgetry

According to Scott Snyder of C-Media (who’s also an O’Reilly blogger), the audio interface above is really a “proof of concept” made a few years ago to try to sell the chip/software combination to manufacturers. Turtle Beach’s Audio Advantage Micro and Amigo use a more recent version of the C-Media chip and include audio input. The Amigo includes a microphone and volume wheel as well.

Speaking of volume, I noticed the interface’s headphone output was about twice as loud as the headphone output on my PowerMac G5—more than enough to drive my beefy Beyerdynamic DT770 headphones, whose 600Ω impedance overwhelms my portable MP3 player.

So there you have it: Two tips for the price of one blog.

Come across any interesting audio or photo hacks lately?