I’m lucky enough to own a Nikon D7000 camera with a number of very good lenses. I use either a 20mm or 50mm lens for photographing documents with a complicated setup, mostly for family and local history projects. However, it’s not very practical for just walking-around pictures, because carrying all those lenses, and picking the right one, is just too tedious if photography is not the prime purpose of the trip.

Until now, that is.

I very much desired to solve this problem. I have an old Fuji camera which will do for walking around, but the photos are nothing like those that the D7000 can produce. And there is a fine walking-around opportunity in our near future, of which more later. So I read what everyone else has written, and bought a used Nikon AF-S DX Nikkor 18-200mm f:3.5-5.6G ED VR II Lens on eBay.

That’s a DX lens designed for a 2/3-size sensor, which the D700 has. That means it might produce better results for less money than a lens designed for a full 35mm frame, and might be lighter. It does not have the wide aperture of fixed-focal-length lenses, which means that exposure must be longer in low light. However, it does have vibration reduction, which means that longer exposure produces less motion blur. And it has a fast autofocus mechanism, great for snap shots on the street. And it has a very versatile zoom range. So the omens were good.

The lens arrived less than 24 hours after I clicked ‘pay now’. We had a trip to London planned for that afternoon, so the camera and lens came too for some first-class walking around.

We went to the British Museum. I took many pictures, but two stand out for me.

That chap is on a very beautiful urn in the Enlightenment Room. The image processing in WordPress does not do it justice. Click on the picture for the 7Mbyte original unretouched jpeg straight from the camera. That was hand-held with available light through a glass case.

The phrase “available light” is an oxymoron when it comes to the deeper recesses of the Enlightenment Room. There isn’t any. Many of the exhibits are behind glass in unlit bookcases, very hard to make out with the naked eye. Like this exhibit:

Again, click the image for a better look. That one has been cropped in Photoshop and saved at a lower jpeg quality, so is only 1.8Mbytes, but otherwise it is as it came from the camera. Again, that is hand-held, available-light, though glass. The difference this time is that it was very dark, so dark that I didn’t even realise there was writing engraved until I saw the photo. The exposure was 1/10 of a second. That vibration reduction really works!

So, I am very pleased with my new lens for walking around. So much so, I had to tell you about it. For want of writing about anything useful.

Problem – Error – Report

The field broken things is fully of confusing terminology. When I say something, it means precisely what I mean it to say, so here are some definitions of terms. Keep these straight and you’ll be half-way there.

I use the word problem here to mean, “The cause that made the system produce errors.”

A Problem could be

• A Fault
  Something that is broken or worn out, that is repaired by replacing the broken part
• An out-of-calibration event
  Something that is repaired by making an adjustment (like putting more air in a tyre if the pressure is low)
• A design flaw
  Something that is fixed by changing the design
• An upset
  Something that goes wrong, but isn’t evidence that the system is breaking down. The cosmic-ray-induced soft errors in computer memory are an example of an upset. Provided they don’t happen too often, we just learn to live with them.
• and other stuff

so ‘problem’ covers all sorts of causes. We tend to give different names to the causes depending on what action we need to take to make the system work properly. But, all these different sorts of problem share the fact that they cause the system to produce errors rather than working properly.

I use the word error here very carefully, too.

An Error is

• A signal or datum that is wrong.
  For example, low air pressure in the tyres, high temperature in the engine, zero RPM when the engine is supposed to be running.

An error is internal to the system. It might propagate within the system and cause more errors. For example, low tyre pressure might cause tyre overheating. However, we won’t notice anything is wrong (we’ll be under the misapprehension that the system is working properly) until the error is detected by some error detector and produces a report.

A Report is

• The output of an error detector that says “There’s an error!”
  For example, the warning light that tells that the engine is overheating
• The result of a specific test
  For example, when you measure the tyre pressure and find it is low
• Some human error detector
  For example, you notice the smell of burning rubber.
• Anything else that causes the procedure of diagnosis and repair to start.

At least, I hope that’s the domain name. It doesn’t make a lot of sense, but I happened to own the name, so it didn’t cost me anything!

Hi, I’m Emrys Williams in the real world, and I live in Eversholt, Bedfordshire, England. This site is a place to store all sorts of odd things that should be on the web. I manage another site at www.eversholt.org for news about the village. That site is provided by Google Sites, which was very nice when I started it but is very restrictive now. I shall be moving content from there to here over time.

This is also a place for me to post information that’s not about the village. The first item is a birthdate calculator, for people poking around in their family tree.

Please feel free to comment on anything you see here. It’s fully moderated because of the spam, but I should approve posts the day you make them.