Mark's Blog about Tech and Cool Stuff

In February 2010, I purchased an 82mm Fader ND Filter (ND2 to ND400) from the official eBay store for Light Craft Workshop .  The label on the filter reads "82mm  Fader ND [W]  HL-OPTICS". The purpose of a Neutral Density (ND) filter is to reduce the amount of light, therefore allowing for slower shutter speeds.  A variable ND filter allows you to vary the amount of light by rotating the front of the filter. When shooting video, the shutter speed is normally fixed - it is tied to the frame rate giving the required Shutter Angle (e.g. 180 degrees) controlling motion blur.  When shooting video, the only way to prevent over exposure in bright light is to Stop Down the aperture.  This limits your ability to use the aperture to control depth of field. A variable ND filter is particularly useful for video, since it allows you to control exposure independently of the aperture and ISO.  Specifically you set your fixed shutter speed, choose your depth...

We've now got five chickens, having purchased another two today. This is our family of hens. "Beatrice" is a Silver Laced Wyandotte , purchased 13th June 2010. "Snowball" is a White Wyandotte Bantam , purchased 13th June 2010. "Dotty" is a Cuckoo Pekin Bantam , purchased 1st November 2009. Sadly she had to be put-down on 7th March 2011 after developing paralysis from a virus. "Edna" is an Isa Brown , purchased 1st November 2009. "Dora" is an Australorp , purchased 1st November 2009. Click here to view more photos of our hens.

Recently I wrote about how I had designed an automatic door opener for our chicken coop by modifying an alarm clock.  Refer to this post ( Building an automatic chicken door opener ) for more details of the design. The automatic door opener has been installed into the new chicken coop, here's a video of it in action. Our three hens come out in the order Dora first, then Dotty the bantam and then finally Edna pushes past. The new chicken coop is much larger than the old one. Note the chicken coop is a one-off, home-made design purchased off eBay, which we've then modified to suit our needs. There's plenty of space in the nesting boxes for our hens .  In fact it's probably too big now, so we'll definitely have to get some more girls. Plus the most important thing, I've converted my automatic door opener to suit.  Now it operates vertically, and hence why the clock is on a 90 degree angle. The operating mechanism is much less prone to error.  Specifica...

I bought a FOSCAM FI8908W wireless IP webcam off eBay recently. It has lots of features for the price. However, I've had problems with being unable to connect to the camera after a period of time (an hour or so). Power cycling the camera would fix the problem. I've tried upgrading to the latest firmware (version 11.14.2.17 is supposed to fix WiFi disconnection problems), but it did not fix my problem. Problem analysis The problem is not related to my browser or the wireless network. I've tried disabling DHCP (router based static IP). It turns out the problem is that the webcam simply ceases to respond to ARP  (Address Resolution Protocol) requests (once in this broken state). ARP is a mechanism to translate between IP addresses and device MAC addresses. It underpins all IP communications over both Ethernet and WiFi, since at the lowest level it relies on exchange of packets between device MAC addresses. The ARP protocol allows a network device to discover t...

A photographic light tent or cube is invaluable for product photography.  It allows you to light a photographic subject with soft shadows and a non-distracting background such that a photograph will look its best.  It is ideal for product photography such as when you're selling things on eBay.  These eggs were photographed using the light tent: The tent is sold in a folded/collapsed shape, but when you open the package it springs open.  It is very difficult to collapse back into the original shape - if you don't know the technique. I purchased my light tent from DealExtreme here:     http://www.dealextreme.com/details.dx/sku.5224 Many of the customer comments say that they can't figure out how to collapse the light tent for storage or transportation.  Taking note of this, I was very careful when I first opened the light tent.

Any modern DSLR camera supports (or should support) predictive autofocus tracking. While they might have this capability, there is an art to using it effectively, and therefore getting in-focus shots of moving subjects. This is actually something I only learnt on the 19th of August, 2009.  Yes, I remember the date, it's an important date.  This is after having a DSLR many years, and never being able to effectively shoot moving subjects.  I would resort to doing things like: Stopping down , therefore increasing the depth of field, such that the moving subject might still be in focus. Increasing the shutter speed ('cause clearly I didn't understand the difference between motion blur and just plain out-of-focus). Pre-focusing in front of a moving subject. These can give acceptable results, but why not get the camera do what it's supposed to do.

I've been looking at Creative Commons licensed music for use with my videos.  There are a number of licenses, but typically they allow sharing and use in non-commercial products. There is a lot of web sites dedicated to free music, and I've found some music by Manolo Camp that I really like.  Here's two web sites with his music for download: Opsound.org ccMixter.org For example try Morning Coffee or Ships in the fog .  I'm already picturing some video that I can shoot for that second track.  Anyway, hope you like it. Update 11/12/10: I've published my first video using Manolo Camp's music "Medieval". I think the music really adds polish to the video.

Time-lapse movies are cool.  Especially when they are really professional looking.  Some of my favourite time-lapse movies are made by these people: Tom @ TimeScapes Philip Bloom Ross Ching I've made a couple of time-lapse movies which you can find in high-definition on YouTube .  Perhaps not in the same league as those guys, but it's still fun and rewarding anyway. I hope to do a lot more, and have recently learnt some new techniques to maximise battery life and minimise wear on the camera. On a SLR camera, every photo causes the mirror to flip up, the shutter opens and closes, then the mirror flips back down.  Being moving components, the mirror and shutter have a finite lifetime.  During a time-lapse you may be taking thousands of photos, therefore reducing the life expectancy of your camera. These techniques can be used with the Canon 7D and 5D mk II cameras (and possibly others) to reduce mirror and shutter activations. Live View mode eliminate...

Remember when you were young and you used to know everything.  Yeah, me too! Now, even when I'm an expert on a subject, I'm constantly learning new things.  I guess it seems more profound or gratifying when you do have an in-depth subject knowledge, and then discover a new dimension. This is a collection of things that I've learnt, and hopefully they're things you'll find interesting too. I'll add to this post when/if I learn anything else. The index: Part 1: Fractional ISO   Part 2:  Time-lapse battery, shutter and aperture life Part 3: Using Predictive Autofocus That's it for now.  Check back later.

The ISO setting on a digital camera controls the gain applied to a digital sensor (making it appear more sensitive to light) - in the same way that ASA film speed specified the film sensitivity. Having previously owned a Canon 20D, I was familiar with traditional ISO values (associated with powers of two), for example: ISO 100, 200, 400, 800, 1600. Due to my computer background I had assumed that boosting the ISO was achieved through bit-shifting - or digital amplification/gain.  It turns out that this is wrong.  ISO gain is achieved by analog means prior to analog/digital conversion.  That said, ISO expansion modes such as ISO 12800 on the Canon 7D and ISO 3200 on the Canon 20D are achieved by digital gain (bit shifting). My Canon 7D supports fractional ISO values such as 125, 160, 250, 320 etc.  There has been discussions circulating on the Internet saying that the 2/3 of a stop values result in less noise.  While there is an apparent loss of noise, t...

TVersity has built-in support for photographic raw files, using dcraw to perform transcoding/conversion on the fly. Unfortunately the dcraw (version 8.88) included in TVersity version 1.7.4, does not support the Canon 7D camera. Pukkita's Digital Darkroom Corner has more recent builds of dcraw.  There are actually two versions, and type which works on my system (the file dcrawMS.exe ) still does not contain Canon 7D support. Instead, I've got a version from LibRaw .  This is not exactly the same.  The file dcraw_emu.exe is mostly compatible - but does not support the -c option (which TVersity uses).  This option is used to force output to stdout.  I've modified dcraw.bat to handle this incompatibility: @echo off echo TVersity is converting a raw digital camera image ... dcraw_emu.exe -w -h %1 move %1.ppm %2 Of course, once TVersity is updated, then this will no longer be necessary.

TVersity is a digital media server that can share media over your home network using UPnP/DNLA. This is kind-of like Windows file sharing/SMB, except that a digital media server can be a lot smarter.  You get access to traditional media such as picture, audio or movie files, like you would through network file sharing.  TVersity though can take things further, supporting: On-the-fly transcoding of media into a format suitable for your media player, Downloading content from the Internet, Streaming media as it is being downloaded or transcoded, Tagging of media to present a smarter content view instead of just a traditional directory structure, Improved network performance compared with normal network file sharing.  I'm able to stream 1080p video rather than having to copy it to the internal HDD My media player is a Astone AP-300 and is similar to many others in that it has network connectivity, HD video support, and of-course acts as a UPnP Media Player/Render...

We recently got chickens and found them to be noisy in the morning because they wanted to be let out of their coop.  Of course, we just wanted to sleep in.  What we needed was an automatic door opener. Here's our 3 hens (Edna, Dora and the bantam Dotty).  Click for more photos. Here's the chicken coop, with the addition of an automatic door opener.  The chicken coop was purchased from Pets Station . There are some (expensive) automatic chicken doors that are available for purchase, but I decided to design and make my own.  You are welcome to copy or adapt the design to suit your own requirements.