Cheap and decent quality don't rest easily together.

The monitor will affect everything you do, so the best is the best option.

The easiest lens to make in a range is one slightly longer than a standard, so in 35mm film terms a 58mm is often found for faster lenses in the early days of SLRs.

But all lenses in a range should be sharp.

It would be a good idea to post both images, so we can see exactly what you shot.

As a general principle I would expect at close distances both to be sharp, but the 100mm macro to have the edge. However, this shouldn't be an issue in general photography, so seeing the images would be very useful.

I don't understand that either....:

The important thing for me is that all my versions of Photoshop work fine on Windows 7.

Sue is currently enjoying her new Sims 3 and that runs fine on W7 as well.

Happiness all round.

I see images of Windows 7 have been firmly excluded from the brief....

In that case, the field of view of both lenses is the same, but a 400mm lens has more DOF than a 600mm one.

You get the same effect over different film formats. For a given field of view, such as a "standard lens" for example, larger formats have less DOF because they need longer lenses.

An extreme example is that 110 format needs a 24mm standard and 6x6cm needs a 75mm or 80mm standard.

This is why tiny format CCds in compact digital cameras have immense DOF and putting the background out of focus can be well nigh impossible.

A 400mm lens has the same DOF regardless of the format. Why would that change because of what you put behind it?

I agree with Yves.

Lens design principles haven't changed, so read it with confidence!