It's a Carl Zeiss 135mm f/3.5 lens – a little old, and with a huge thumbprint on the front element (now removed), but nonetheless obviously worth more than the £9 it was selling for. I snapped it up just to see if I could get it to work, and happily it did:

In fact, as it turns out it's amazingly sharp – certainly as good as my Nikkor 24-85mm zoom, and possibly better. Using it isn't easy – it needs an M42 to Nikon adapter, which is stiff and hard to fit, it won't focus beyond ten feet or so because of the Nikon mount distance, and there's no metering, autofocus or automatic aperture control – but still, on the D80 it's the equivalent of a 200mm telephoto for £15 all in. Bargain.

I really should learn to use a camera properly; you know, buy a book or something. Instead I've been slowly working things out over the years, which is satisfying but often frustrating in a "wish I'd known that when I was in…" kind of way. Case in point: lately I've been having problems with lens flare.

Having attended a lovely wedding at which I was pretty much unable to photograph anyone inside because of the dark (can't afford an external flash to bounce and my zoom lens is large enough to obscure the built-in one) I decided to buy a simple, bright lens. In the end I picked up a really old Nikon E 50mm f/1.8, and it's great: almost twice as bright as the zoom, and easy to focus because it was made in the days that auto-focus didn't exist. It's also tiny – on the D40 it barely protrudes beyond the prism/flash housing – and stupidly light. Oh, and cheap. Cheap is good.

The problem, though, is flare. Point my modern zoom lens, with hood, pretty much anywhere other than directly at the sun and you'll get a clean picture. When pointing the 50mm lens pretty much anywhere outdoors I was getting the most amazing light effects: blobs, swooping arcs, upside down headlights in the sky where they'd obviously reflected somehow inside the glass (there are probably technical terms for these things, but I don't know them). Sometimes they're pretty, mostly they're a pain.

Anyhow, today I finally figured it out, and the answer is simple: just stop the lens down. At anything wider than f/4 you get crazy flares. f/5.6 or higher and things get better. Stop it all the way down to f/22, if you can, and there's no problem even with bright light sources in the frame. The photo above was 5 seconds, f/22 at ISO200.

So, there you go. Simple. And it only took me three sodding weeks to figure out. Nuts. For my next trick, maybe I'll learn how to actually take some interesting pictures.