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Welcome to Dijemeric Visualizations

Where photography and mathematics intersect with some photography, some math, some math of photography, and an occasional tutorial.

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Monday, October 31, 2011

Wildcat Creek in Time Lapse

Wildcat Creek did not run dry this year and still has a respectable flow. As I watched some leaves floating slowly by, I thought ahead when heavy rains will fill the creek above the rocks I was standing on. I also wondered how fast the leaves would be moving with the increased flow. One way to visualize this would be to take a time-lapse sequence!

Using the iPad I shot two sequences of 200 frames each. The first sequence was shot at 10 fps and the second at 1 fps. The two sequences were combined into a 40 second video using iMovie for the iPad and a soundtrack was added from a recording made a few years ago using a Sony MD Walkman. The first 20 seconds of the video shows the flow at normal speed and the second 20 seconds shows the flow at approximately 10 times normal speed. When the rains come, I can take a standard sequence and compare them. Perhaps not the most direct way to determine the comparative speed of flow in a creek, but it offers an alternative approach.

Saturday, October 22, 2011

di Rosa Art Preserve

3808 Don't Call Me Bullwinkle3766 Low Maintenance3772 The Victorian Garden3774 di Rosa Reflections3777 To Catch the Sun3790 Pipe Collection
3794 Racing the Clock3801 Puppet Masters3815 The Shadow Knows3825 A Matter of Balance3838 Not So Ancient3841_2_3_4_ Heavenly
3873 Designer Desk with an Attitude3875_6_7_ Mirror Mirage3882_3_More Than Mirrors3886 Mirrors as a Painting3903 Don't Try This at Home3900_1_2_ Ring at Your Risk
3926 Peacock Portrait3909_17_Mezzanine View3931 Meadow for Art3934 Meadowphoric Art3938 Drought Tolerant3939 Artemesia
di Rosa Art Preserve, a set on Flickr.
Located near Napa, the di Rosa Art Preserve is 200 acres of the selected works of Northern California artists and includes metal work, ceramics, photography, paintings, and other categories that I cannot identify (e.g., 50's vintage cars adorned with a collage of collected items).  For more information and tours see

Thursday, October 13, 2011

Light to Sound with an iPad

Back in the early days of digital computing it was possible to design reasonably simple interfaces to convert analogue signals into digital inputs to a computer, like the Apple II or Radio Shack Tandy Model 100.  An investment of a few dollars could bring an evening or more of entertainment to the digitally amused.

In 1986 I designed a simple A2D converter for the purpose of capturing a varying light source as a digital input to a computer.  The heart of the converter was a '555' chip which was essentially an opto-isolator in a simple, small, and cheap package.  With the addition of a power supply, a capacitor, and one fixed and a variable resistor the A2D converter was created.  The variable resistor was a photocell for measuring the light source but could be any other variable resistor, such as a thermo-resistor.

The 555 generates a pulse with a rate dependent on the value of the input resistance.  As the resistance drops, the frequency of the pulse increases.  When the photocell is aimed at a light source, the resistance drops and the 555 generates a pulse stream that increases in frequency as the intensity of the light source increases.   The output from the A2D circuit is entered into the iPad via an iMic and Camera Connector. This combination is what I used to accommodate my original design using RCA jacks: the iMic has an RCA jack input end and a USB output end.  The USB output of the iMic is connected to the Camera Connector on the iPad.

Once everything is hooked up, the sound of the pulses can be captured using an app such as 'FiRe' for recording the output.  An example is in the link below.  The sounds are from moving my hand between a light source and a photocell connected to the A2D converter.

The schematic below shows the essential components: a 555 chip, input voltage (9V), variable resistance (R1), fixed resistance (R2), and a capacitor (C1).

 Figure 1: circuit diagram schematic
Input ('In Resistance'), output (Out RS232), and power (to 9V Source) connections used RCA jacks available inexpensively at electronic supply houses, shown in Figure 2.  The output was originally designed for an RS232 hookup, but here was connected to the iPad via an iMic interface, seen in Figure 3.  Figure 4 shows details of the hookup of the iMic to the iPad using the iPad Camera Connector.

Figure 2: A2D converter

Figure 3: Connection to iMic

Figure 4: iMic to iPad 

Friday, October 07, 2011

Capturing Sounds on Your iPad

There are iPad apps, such as FiRe, which can be used to record audio using the internal iPad mic.  There are other apps that create music or special effects sounds, such as Bebot, but do not record what has been created.

It is possible to create sounds using one app while recording those sounds with another app.  I have done that using FiRe to record while making a bit of something sounding like music with Bebot.   Click the link to hear a recording of the Bebot in Therimin simulation mode.

The process is fairly simple, though perhaps not so easy to explain.  First, open the recording app, in this case FiRe, and put it into record mode.  Then immediately hit the home key twice in quick succession.  This will bring up a scrollable row of apps.  Scroll to the sound/music creation app and open it.  The recording app will record any output you now create.  Once completed, return to the recording app and stop the recording.  You will need to edit out the lead and ending portions that were recorded during the intervals when the sound creation app was not in use.


FiRe demonstration on YouTube:
FiRe app at App Store:
BeBot at App Store:

Blue Angles from Lawrence Hall of Science

3350 Blues Over Sutro Tower_KEO3347.JPG_KEO3346.JPG_KEO3349.JPG3345 Whoosh3304 Four in Formation

The choices - close up shots and mingle with the crowds in The City or find a distant overlook on a Berkeley hill where you and a binocular equipped Chicagoan look into the sun to view the Blue Angels doing their stuff.

I chose the bad light, distant view, with no crowds and enjoyed it thoroughly!

Wednesday, October 05, 2011

Photo Phun with an iPad - UCB Stadium, Bowles Hall, IHouse

IMG_1040 Stadium Work 3IMG_1038 Stadium Work 1IMG_1039 Stadium Work 2IMG_1036 Bowles HallIMG_1030 International HouseIMG_1058 Girton Hall
1038_9_40Colliseum.jpgIMG_1037 Bowels Hall

The iPad 2 camera is not up to par if compared to the iPhone camera, but you can do a lot with it that is creative, fun, and even useful.

One nice app (FieldCam) emulates an pre-digital (and pre-35 mm) dry plate camera. It produces a sepia toned image. And it has two shutter releases, readily accessible on the sides rather than at the bottom of the iPad. So if you want to take your favorite scene thru the way-back machine, try this app on your iPad.