Wednesday, 30 December 2009

Macro Extension Tubes

For Christmas I asked for (and was lucky enough to receive) a set of extension tubes for my camera. Having no experience with these before, I started off with the cheapest set I could find on Amazon. Whilst they're nowhere near as functional as the more expensive varieties available they are a decent starting point and would make a great present for any enthusiast.

For the uninitiated, Wikipedia has this to say about Extension Tubes:
An extension tube is an accessory for cameras with interchangeable lenses, used primarily for macro photography. The tube contains no optical elements; its sole purpose is to move the lens farther from the image plane. The farther away the lens is, the closer the focus, the greater the magnification.....


I don't mind using a cheap extension tube because it's just a hollow tube and has no effect on the quality of the image produced. The real disadvantage of this set and the reason they're at least £100 less expensive than the next set (and many hundreds of pounds cheaper than the Canon equivalent) is there are no electrical contacts, they're simply plain tubes. This means you're not able to control the aperture of the lens and must use manual focus; manual focus being no biggie since that's advisable with such a small depth of field.

Here are my first test images to see how they perform (click to see larger versions over on Flickr):
Two Pound CoinTwo Pound Coin





Both of these images were taken using my kit lens at 55mm and F5.6 hence the depth of field is so shallow on the magnified image with the tubes attached which also had a lot longer exposure in order to expose the image correctly.

For greater depth of field there are ways, not recommended by Canon I should add, you can change and lock the aperture of the lens before you add the extension tubes. This means if you're really desperate there's nothing stopping you getting a much better depth of field with these tubes at the expense of even longer exposure times of course.

For me, I think I shall experiment with these a little more. Should I catch the macro photography bug then I'll have to make a decision about whether to get a better set of extension tubes or even at some point treat myself to a proper macro lens. For now though, these will suffice quite nicely.

EDIT: My Amazon Review has now been published.

Upgrading Fedora 11 to 12

After writing recently about my previous upgrade experience, it seems fair to report my latest upgrade experience going from F11 to F12 using pre-upgrade on the same machine at home.

Everything progressed very smoothly, even more so than last time as I'm pleased to report the bug I had written about is now fixed. Fedora now detects hardware raid devices and employs the correct work-around solution to ensure the upgrade proceeds unhindered. So far so good then and I thought I would be sailing through to another smooth upgrade. However, it appears even at Fedora 12 level there are still some small issues as it proved later in the upgrade process.

This time the upgrade was smooth right through to the end of the upgrade process, after all the packages had been installed. Just as the bootloader config was being adjusted I was presented with a rather user-unfriendly Python stack trace with an "unhandled exception" error. By switching to another console I was able to work out the upgrade had in fact completed successfully all except for the final adjustments to the grub menu and removing the pre-upgrade cache. I reported this behaviour in a new Red Hat bugzilla bug report and have been informed this bug has already been fixed upstream in Fedora development and should not occur in pre-upgrade F12 to F13, lets wait and see.

So it seems the pre-upgrade path for slightly more complicated configurations such as the one I have at home is finally starting to look good. I'm slightly disappointed it's still not quite there yet though but all things considered this was another smooth upgrade and one which someone less informed about Linux might be successful.