Search this site
All things Photography by Thomas Tempelmann
Disclaimer: I am no photographer. I'm a geek that likes the technical aspect of photography.
On this page... (hide)
I have two DSLRs, both from Pentax: K20D and K-5, along with an ever growing set of lenses, mainly from Pentax and Sigma. I also own the Gigapan EPIC Pro to take highly detailed panomamic shots.
A few AppleScripts (for Mac OS X) that assist in identifying missing and duplicate (RAW+) images: AppleScripts
I own the Sigma 150-500mm OS lens, which has a 86mm filter thread. What's little known, apparently, is that there are different kinds of threads used for 86mm: Sigma uses a 1mm pitch, which Sigma also calls 86C ("coarse"), while on eBay you may find a lot of filters and adapters that use a 0.75mm pitch, making them not fit on the Sigma lenses. Furthermore, filters get rather expensive at this large and rare diameter.
Now, this lens is made for full format (FF) cameras, and I use it on a APS-C format camera. Which means that the front diameter is layed out for a wider opening than what's necessary in my case. So I figured that I might try a so-called Step-Down ring to reduce the filter thread to 77mm, for which I own fitting equipment already. I got myself a cheap 86mm-to-77mm step-down ring. Even with a 77mm filter screwed into it, I cannot tell any vignetting at 150mm nor at 500mm focal lengths. Making this a bargain over having to purchase new filters for the 86mm diameter.
The only issue is the aforementioned thread pitch issue: The step-down ring won't fit into the Sigma's filter thread. And I could not find any step-down filter that uses the 1mm pitch. What I found, however, is a 86C (1mm pitch) to 86mm (0,75mm pitch) adapter on eBay. With that, everything fits now, and I saved quite some money on not having to buy a new set of filters.
Apple (and 3rd parties) offer adapters for the iPad for importing taken pictures into the iPad, both for viewing and for temporary storage.
If you're using such an adapter, here's a tip:
If you like to shoot in RAW mode, you may find that importing your pictures into the iPad takes quite a long time. To speed this up significantly, take your pictures in RAW+ (i.e. RAW plus JPG) mode. While this increases the overall memory usage a little, it makes importing into the iPad much faster. That's because the iPad needs a JPG image for viewing. When you give it only the RAW images, it has to generate the JPGs itself, and the iPad's rather weak CPU is taking a long time for that process. But if you give the iPad a set of RAW and JPG images, it'll use the JPG, not needing to reprocess the RAW image. The iPad will import both images, so you won't lose your RAW images this way.
I know, taking panoramic shots usually is done with a preset focus, not with auto focus. But when you have a good reason to rely on the camera's autofocus, you might find this not to work with the Gigapan EPIC system, despite their documentation suggesting that it should work. Instead, using the supplied shutter cable, the camera will shoot without focusing first.
The reason for this misbehavior is related to the design of the shutter cable and how cable remotes on the Pentax cameras work: The Pentax has two independent circuits that can be controlled via the remote cable: One for activating the autofocus, and one to activate the shutter. The problem with the shutter cable from Gigapan is that it only serves the latter of the two circuits.
There's a simple work-around, though: Get a mono audio extension cable with a 2.5mm jack. If you use that to extend the shutter cable, you'll effectively shorten the two circuits, causing the camera to apply the autofocus before releasing the shutter. Just don't be surprised that you'll take a picture if you plug this cable into the camera if it's turned on - you'll effectively press the shutter button while pushing the jack inside the plug. Or just remember to turn off the camera before you insert the jack. There's no other harm to expect from doing this, as the cables do not carry their own electrical power but only close open circuits, for which the camera is well prepared.