Category Archives: How-To

How to check a lens for decentering

There are many things that can be wrong with a photographic lens. Optics require tight manufacturing tolerances in order to produce high resolution images. Copy to copy variation is a serious issue, even (or especially?) nowadays. While most lenses leave the factory in good condition, a non-negligible percentage reaches the market with unacceptable optical flaws. One of the most common issues is decentering.
Since this happend to me a few times already, I decided to write a short article about it. I will first explain what decentering means and then continue with a simple procedure on how to test a lens.

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Equivalence: How to compare different camera systems

As you may know, to compare lenses of different camera systems in terms of angle of view, the focal length often needs to be converted to an equivalent value. What about aperture and depth of field or the expected amount of noise? Are those values also comparable and if so, how?

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How to backup your data, properly

I guess most people know that it is important to regularly backup important data. However, only few do it and even fewer do it properly. Fact is: No storage medium is safe, it is only a question of time before it fails. So what is the best way to store data? What is the most reliable backup medium? Harddisc, SSD, DVD or something else?

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How to migrate a Linux partition to a new PC

Last week I got new hardware and therefore, I was faced with the task to move all my data to the new PC. Well, the clean way would be to start from scratch, i.e. install the operating system and all the applications that I need, then copy all my data. This of course takes a lot of time and sometimes you would prefer to continue right where you left off.
Now the fast – or lazy – way is to simply copy the whole partition from the old to the new PC, including the OS and all applications and settings.

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Basic Room Correction for your Speakers

frequencyIn this short tutorial, I’d like to explain a simple but effective method to achieve basic room correction when using a Windows computer as playback source.
Basically, several filters are applied to the digital audio signal before it is forwarded to the amplifier and speakers to “ameliorate unfavorable effects of a room’s acoustics”. This can sigificantly reduce or even elimiate unwanted vibrations due to bass, improves the overall listing experience and even reduces the amount of sound that is emitted through the walls.

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Raspberry Pi Server


Since I had a spare Raspberry Pi 2 lying around, I figured I could use it as a webserver. The idea is to host a simple webpage and implement a functionality to wake and shutdown devices in the LAN from the Internet (Raspberry acts as an intermediary). Besides, the Raspberry shall also monitor the state of some devices in the network (e.g. my Synology NAS).

Due to the lack of computational power and fast memory, the Raspberry is certainly not suitable for services that require highspeed I/O capabilities such as large databases, but for personal use it will do just fine!

What makes the Raspberry Pi particularly interesting to be used as a server – apart from its affordable price tag – is the low power dissipation of just 2W. So even if you keep it always on, it won’t be heavy on your pocket. Besides, it is fanless and thus inaudible during operation.

Here is what you are going to need for the following tutorial:

  • a Raspberry Pi (obviously), I recommend the version 2 or 3
  • a micro USB power supply with at least 700mA
  • a micro SD card with at least 2GB
  • an Ethernet cable

You can get all of this for less than 50 bucks. Besides, you will need a monitor with HDMI and a keyboard for the initial setup.

Now let’s get started!

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How to backup photos when traveling


I’m a person who really likes to take photos on vacation, and I would be frustrated if I lost some (or even all) of them before I get home. When you think about it, there are many things that could happen to your camera and memory card: You could lose it, or it could get damaged, stolen or experience a hardware failure. Therefore I think it’s important to make a backup of your photos on a daily basis. But how?

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The ultimate media player for 60€


I’ve been using a Raspberry Pi 2 and a Blu-Ray player to play movies and music in my home cinema. Recently, I found that those devices can’t play everything. Specifically, they fail to play files that are encoded with HEVC (H.265) or videos in 4k resolution (UHD 2160p). So I decided to look for a new media player, one that could handle all kinds of files… and doesn’t cost more than 100 bucks.
This article consists of the following subsections:

  • hardware selection
  • software selection
  • installation
  • configuration

Ok, let’s get started!

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How To: Room correction for Stereo Speakers with a DSP

_mg_0561In this article I am going to show you how to leverage a digital signal processor (DSP) to add room correction to your stereo or 2.1 speaker system.

Here’s what you are going to need:

  • a DSP (e.g. the MiniDSP 2×4 with a plugin)
  • a measurement microphone (e.g. the MiniDSP UMIK-1)
  • 2x stereo audio cinch cables (or 3x if you have a subwoofer)
  • REW software installed on a computer

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How To: HiFi Network audio receiver for 50€


Let’s assume you have a nice set of speakers, but your amplifier doesn’t have any network features. In this article I’d like to show you how you can add network features such as Upnp/DLNA playback to an arbitrary amplifier, an analog input is the only requirement.
This will allow you to select music from your digital collection directly from your smartphone to play it back on your speakers in hifi quality.
The best thing about it: It will cost you only 50€!

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