{mosimage width=125}SFR, or Spatial Frequency response, is another way of expressing MTF, or Modulation Transfer Function. But isn't that just stuff for Geeks?

 Well, no, it does have a bearing on a lens' ability to produce sharp images that goes beyond the photographers technique and goes a long way to explain the difference in prices between apparently similar lenses.

{mosimage width=125}Check out any photograhic internet forum, or for that matter any Photographic Magazine's letters pages and you will inevitably come across posts discussing focussing. The terms 'Back focus' or 'Front focus' crop up regularly, and often it is the lens that is blamed. But is it always the case? We decided to look a little further.

{mosimage width=125}Many publications, both in print and on the web, will test a product and give you, the reader, a definitive rundown on how good the product is from that single test. Often the results are at a variance to one another and sometimes they can be totally contradictory.

The arguments of the last few years concerning Film versus Digital look likely to be replaced with a new, and probably just as contentious battle, that of full frame versus cropped sensors.

Do you fancy yourself as a wildlife photographer, but don't know where to get started?

Do you think it will be expensive to get the equipment together? Don't have the time to go to all those exotic locations? Well specialist equipment and time away in far flung places just aren't necessary as Ian Andrews explains.