Well spotted, George! What my brain instructed my fingers to type was 55mm f1.8, but they disobeyed....

I recently went out and took just the Pentax KM with the SMC Pentax 50mm f1.8. I shot two rolls of Velvia and never felt limited by the one lens. The simplicity of this approach was actually very welcome, and I could just concentrate on the potential subject matter.

It's worth doing this sort of thing now and again - it sort of clears the photographic mind.

I was just mulling over what would be the minimalistic kit I could bear to use if I didn't have all the assorted stuff I have collected.

If it really came down to it, almost any manual body with a 50mm lens would do for a lot of things. By preference an MX with M series 50mm f1.7.

If it could expand to two lenses then the choice would be M series 24mm and 100mm.

Three lenses and it would be 24-50-100mm.

How little could everyone else really survive on? Perhaps it would be a good exercise to go out and just use one lens for a few weeks?

Welcome, Ali, hope you enjoy the site!

This is something that has been argued for years - it was aired very thoroughly in PHOTO TECHNIQUE in the 1970s. Then it was thought that changing to A paper sizes would be the perfect answer.

Frankly I'm not at all sure it makes much difference.

The info regarding the golden mean is an interesting point, George.

Whatever the aspect ratio of any format, it will not necessarily suit the picture you wish to produce. It is rare indeed for me not to crop a picture to the shape I feel is suitable, so within reason I don't mind too much what the format is, from square up to the 35mm dimensions.

Maybe, but it's still true that a 6 MP chip can supply enough information to make a really good A3 print. The 8MP chips are not, at present, any significant improvement.

You've got it. Your example would be closer to being exact with the 24mm though.

The DOF would indeed be the same, but you would be very close and the perspective would again be different.

And following Kim's comment up, don't forget that the 100mm macro will also have the same DOF as the 50mm for a given magnification.

So, if you want to take a picture of a chess piece that fills the frame, it doesn't matter for DOF whether you use the 50mm or the 100mm as the DOF will be the same. The 100mm will of course be twice as far away from the subject, so perspective will change.

In the camera menus you will find the settings you need - the instruction book lists them all, and it is well worth reading so you can see what the possibilities are.

Personally I use centre spot focusing, which enables me to lock on to any subject I want to without any problem.