Photos – semifluid.com

Backpack and Canon T3i lost/stolen in Frankfurt (Main) Hauptbahnhof

December 31, 2014February 8, 2015 Steven A. Cholewiak Leave a comment

I had a red and black The North Face backpack/Rucksack taken from a train in Frankfurt, Germany this past Monday, so I’m posting this online with the hope, however remote, to contact the individual(s) who removed the bag from the train and to see if they can contact me to return it. It contained my DSLR camera, lenses, and a number of personal keepsakes that have really hurt to lose.

Here is a short run-down of what happened: On Monday, December 29th, 2014, I went down to the Frankfurt central train station (Hauptbahnhof) with my wife and friends to go ice skating at the Eissporthalle Frankfurt. We took a Deutsche Bahn (DB) train from Giessen, Germany to Frankfurt, Germany, departing at 3:22 PM and  arriving at 4:02 PM. At the beginning of the trip, I placed my backpack on the  luggage rack above the seat. About 10 minutes after exiting the train, after having taken an S-Bahn train to Hauptwache, I realized I did not have my bag. I immediately took another S-Bahn back to Frankfurt Hbf, ran up to the train platform, and found my train still waiting at the track (total time from departing the train to returning was approximately 20 minutes). I quickly searched the train because it was about to leave to head northward, but the backpack was gone.

I immediately notified the DB lost property office (Fundbüro) and made a  claim. I also notified the police but will need to wait 1 week before I can officially file a police report (which I plan on doing on Monday if the bag has not been found).

Unfortunately, I don’t know how much identifying information was in the backpack (it did not contain any IDs), but in the future, I will make sure to include contact information on the camera to help the person who finds my things to reach out to me, if this were to ever happen again.

Full Moon – December 6, 2014

December 7, 2014January 23, 2016 Steven A. Cholewiak 1 Comment

Last night there was a great full moon, so I tried to capture it with my DSLR, a Canon T3i (which is discontinued, replaced as of today with the T5i), and a Tamron 18-250mm F/3.5-6.3 Macro lens.

To capture it, I setup a tripod inside, facing out an (admittedly) dirty window, disabled the len’s optical stabilization, turned on the T3i’s 3x digital crop zoom, and composed the shot. Only post-processing was to speed up the captured clip because the original was ~10 minutes long, shifting the movie to vertically center the moon’s precession, and adding an ambient background track. I’m impressed with what I was able to capture with such an inexpensive lens.

FoodieTV adds Johannisbeeren Pastries to this week’s episode

June 20, 2014January 26, 2017 Steven A. Cholewiak Leave a comment

Since my Johannisbeeren (red currant) Pastries video on Vimeo is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike license (CC BY-NC-SA 3.0), anyone is free to share, modify, and adapt it, as long as they make sure to note that I created it (and as long as it is not used for commercial purposes).

The FoodieTV app, from Glam Media, took advantage of the open nature of the licensing and just included my video in their latest episode (S2E12):

If our kitchen had time-lapse, we'd be eating “Currant Puff Pastries” now! S2E12 http://t.co/XDBmTddpNM cc @semifluid pic.twitter.com/LYNM7G7wqt

— FoodieTV (@foodietv) June 19, 2014

Cool! FoodieTV is a free app on the Apple iTunes Store (unsolicited shout-out and thank you for the free exposure).

GoPro SuperView-like adaptive aspect ratio

March 16, 2014May 31, 2018 Steven A. Cholewiak 1 Comment

For Christmas, my parents got me a fantastic gift for photographers and outdoors enthusiasts, a GoPro Hero3+ Silver Edition digital camera (Amazon). If you are not familiar with GoPros, they are small action cameras that have a very wide-angle lens and come with a water-resistant case. It’s a fantastic little camera that packs a lot of punch for such a compact package.

There are a number of GoPro editions, but the newest one are the Hero3+ Silver and Black. The Silver Edition is very similar to the GoPro Hero3+ Black Edition (Amazon), but omits a few features, including some very high-resolution video recording modes and a feature that GoPro calls “Superview”. This post talks about a way that I attempted to emulate their Superview mode in MATLAB and put together an adaptive aspect ratio function that allows one to change the image’s aspect ratio while maintaining “safe regions” with minimal distortion.

This function allowed me to resize 4:3 images and video, like this one:

To a wider aspect ratio, for example 16:9:

Click through for info on how I implemented the code.

Effect of repeated JPEG compression on image quality and content

August 5, 2013January 21, 2016 Steven A. Cholewiak Leave a comment

There are a number of videos online illustrating the effect of increasing JPEG (JPG) compression on both file size and image quality (see example 1, example 2, or example 3). I wanted to try recompression on my own data because the effect can be recreated quickly using a simple MATLAB script. It is a very simple demonstration of the effect of lossy image compression. For a simple demonstration of the effect of compression, I load an image into MATLAB and then progressively increase the JPEG compression (by decreasing the ‘Quality’ parameter in imwrite), saving each incremental image as a frame. I then load all of the frames and assemble them into a video file. Here’s an example of increasing image compression at 10 frames per second:

In addition, I tried recompressing the image to see the effect of repeated JPEG compression on the output. An initial image is loaded, it is compressed, then that image is loaded and compressed at a lower quality, then that image is loaded and compressed at an even lower quality, and so on and so forth. Here’s the output at 10 frames per second when we do this from the least amount of JPEG compression (‘Quality’,100) to the most amount of compression (‘Quality’,0):

Just to be artistic, we can then repeat the cycle 10x and observe the effect of repeated compression. Here is an example at 30 frames per second with 10 loops of the repeated recompression:

Click through for the MATLAB code and a couple more example videos.
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AMC7135 Driver Boards & Luxeon K2s

January 29, 2008July 28, 2014 Steven A. Cholewiak 1 Comment

I know it’s been a looooong time since I’ve posted any new electronics projects, but that’s primarily been due to my increased course load now that I’m in graduate school. Well, I’ve finally picked up some 1050 ma constant current driver boards for the Luxeon K2 LEDs that I mentioned a while ago and hopefully I’ll get these up and running in just a little bit. I just wanted to post some pictures because I think they’re nice little boards.