About three years ago I waded into the North Willen Lake in Milton Keynes to take pixs of the Hiroshima day ceremony, where floating lanterns are pushed off and float across the lake. I got some good pictures and it's just as well, because I got a nasty leg infection. The calf swole right up, I could hardly get my bike boot on.

It's a balancing lake; it holds flood water then releases it slowly, so there's hardly any current flow. It's clear until you wade through it, then it goes cloudy and stinky as you kick up all the stuff at the bottom, which sits there rotting for years on end and contains a high proportion of duck sh1t.

When I peeled off my trainers and socks, I discovered that fine particles, some of which were you-know-what, had got to my feet. Even washing my feet and calves under an outside tap and changing to clean dry socks and boots didn't prevent the infection.

Look at this site which calculates depth of field and hyperfocal distances: http://www.dofmaster.com/dofjs.html and you will see that with a 2X converter, at the same distance, and at the same aperture set on the lens (so that, say, f/4 is set, but the aperture is f/8 because of the converter) there is less depth of field.

For example:
K20D, 100mm lens @ f/4 and 10 feet: Depth of field is from 9.77 to 10.2 feet.
(Add the 2X converter, change nothing else)
K20D, 200mm lens @ f/8 and 10 feet: Depth of field is from 9.89 to 10.1 feet.

To agree with others, the closest focus doesn't change when a teleconverter is used.

This is a photo the iMac took of me, plus some effect gizmo. If I remember right, it's also upside down. I thought that it would suit the name I've chosen for this site.

After some thought and gently trying various things I managed to get it apart.

Sometimes capacitors can hold a nasty charge and give you a shock. Be wary.

There is no need to remove the cursor. One circuit board is at the back and there are contacts for the various controls that are on the back of the 'gun. It has a row of pins that a socket on the top board plugs into. Careful pulling removes the top board and the two side circuit boards that are joined to it.

The trouble seemed to be in the back circuit board. Some circuit strips and some contacts had green corrosion on them. This would have been caused by leaving the batteries* in until they had burst and sent noxious vapours out. The circuit board is three or four inches away from the batteries but still the damage occurred. Be warned!

I repaired anywhere that looked dodgy, resoldered some wires, and polished then wiped with solvent all the switch contacts.

If you remove the rear board, it's easier to reassemble if it's taken out through the back. Some clips hold the control panel into the back of the flashgun. This area is just full of tiny, easy to loose parts. I know, as when I knocked the soldering iron off the table and when I knocked it back on the table, I lost the ball bearing that allows to cursor to click into the right positions. It was about 3mm diameter, and in the end I used a bit sliced off the ink tube of a Bic biro. Lots of care and patience is required for reassembly of this bit.

I've just got it all back together, and it all seems to be working now.

*Really, the four 1.5 volt AAs that power the flash are not batteries but cells. The four together make a 6 volt battery. When you speak about a 12 volt car battery, you are referring to six 2 volt cells in a common case.

I have the above flashgun. The fractional power control gives me full power on all settings above about 1/16th. I suspect that it's the wiper contacts; they need a clean. The trouble is that I can't get to them.

I have got as far as removing the front half of the case, but I cannot see how to remove the circuit boards from the rear half of the case, though I've managed to remove the transparent cursor.

Has anyone managed to get it apart? Is there anything that I need to look out for? I would ask Braun but they don't make flashguns any more.

There seems to be general light pollution with this shot. It has that yellow tinge from the streetlights, reflected back from muck in the atmosphere. I think that the yellow smears on the bottom and up the left hand side are clouds. About all you can do is adjust your exposure until the sky becomes black, and avoid clouds. Or find somewhere with less light pollution.

The two curved lines are probably flare, perhaps from a couple of streetlights a little way off and about 45 degrees apart from the camera position. It might be easier to stand in the way of the light from the streetlights, or hold a black card to shade the lens.

What seems to be a very small amount of light can cause flare; compared to the light from the stars it will be very bright.

Well, from Milton Keynes actually. I've been a naughty boy and not introduced myself.

I'm actually a Winslow boy. If you don't know, Winslow is a few miles South West of Milton Keynes.

My first camera was a Diana. I was about eight.

I learned to develop black and white films and prints at secondary school. The school had two Zenit 3Ms and a 2X teleconverter. Naturally my first camera was a Zenit, a B. I used black and white and colour print film, and for slide films I used Agfa CT18, Orwo 50 and the old E-4 Extachrome. I think I also used Kodachrome then. I did a lot of street photography in those days. I had a not very sharp 135mm lens, and the Zenit Photosniper. I took photos of the Bell Bellies pub rugby team both on and off the pitch, and learned to handle a Zenit with a preset lens, an off camera, non auto flashgun and a pint of beer to take drunken party photos, something I still do today.

In 1977 or 78 I bought a Pentax ME. In many ways it was the complete opposite of the Zenit; auto exposure only, light, and small. A 28mm Pentax lens and a 105mm lens joined the 50mm that came with the camera. I also had a K2. I found that the 28 was either too wide or not wide enough for me. In the early 1980s I had to sell all my gear because I was skint.

In the 1990s I was a Minolta manual focus man, with lenses covering from 17mm to 210mm. I found that the 24mm was a bit wide for some people shots and the 35mm a bit too long. Some people are never happy! the Minolta outfit left me free to choose whatever DSLR system I wanted, since I wasn't tied to a lens mount.

Hello again Pentax. I wanted a K10D, and watched and waited for the price to drop. It had just got within reach when the rotten bu$$ers at Pentax brought out the K20D. I bought one. I like the 16mm end of the zoom for people shots, though now with a bit more room around them.

The next thing on the shopping list was a new computer. The old one would load one JPEG from the Pentax, then fall over and lie there not moving, just groaning a bit. I bought an iMac.

The longest lens I use is still 210mm, the long end of the 80-210 Tamron that I bought for the Minolta.

Today, I'm nearly 100% digital, though I would like to get a darkroom going again. The fool that designed my bungalow forgot to put a darkroom in so some compromises will have to be made. I had a darkroom until I moved, and if you live in one of the flats in the North corner of Stantonbury you will have a lovely windowless box room just off the living room that's just right for a darkroom. What are you waiting for?

The problem is that the sensor is shaking around while the camera is in live view. This only happens with the 16-50mm lens. Before you ask, yes, I have cleaned the contacts on both the lens and the camera.

Has anyone else had this problem?

Use black card from a craft shop to make a prototype. You may find that a standard food tin will be about the right size and shape, so make your prototype that shape and size (about 74mm diameter by 105mm high) The lens focussed at infinity and set to the minimum aperture will show up any vignetting. The sky in daytime is a good enough target for this.

You might find that the end diameter is a bit big, so you can make a circle to fit on the front.

Once this is proved to work, you are best off with a can that has a pressed on lid at both ends. Remove one end in the normal manner, and fit to it a step up ring or combination of step up rings, where the smallest male thread screws into your lens, and the biggest female thread is just big enough to accept the open end of the can.

Glue it all together. Once it's set and the rings are holding it in shape, remove the other end with the can opener. Remove all burrs and sharp bits as you go along. Paint it with blackboard paint after degreasing thoroughly. You could also use, I suppose, matt black car paint. A coat of spray primer first will make the spray paint more durable. Mask the threads that go into your lens before you start painting.

If you want to put a circle to go in the front, make it to fit the hole, with a row of tags all the way round to fold over at 90 degrees to give you something to glue to on the inside of the can. Use card or plastic card. I wouldn't bother with a petal ended or rectangular ended hood, I don't think it will make that much difference and you have to make sure that it lines up with the edges of the frame.

Having said all this, I did the above, but with one of those cheap 500mm mirror lenses that you see everywhere under various names. It looked great, was solid and did cut out some flare from the very exposed front element. However, I think I was getting flare from light reflected off the sensor, bouncing off the rear (uncoated?) element and back to the sensor again. Your 50mm lens should be better coated, so good luck.

Dwiea, I hope you like the 16-50. I've had one since I bought my K20d in 2008. I've used it in rain heavier than I like to be out in with no problems.