In this third part of our series on local nature photography we takes a look at the medium telephoto lens in the range of around 70-300mm in 135mm format. This also includes, on cropped dSLR’s, the newer ‘super-zooms’ around 18-200mm. After the standard lens, discussed in part two this is probably the next most versatile and widely available kind of lens.

MTF, or Modulation Transfer Function, is a scientific way of measuring lens performance, 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.

Check out any photographic internet forum, or for that matter any Photographic Magazine's letters pages and you will inevitably come across posts discussing focusing. 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

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.

So you have had a look at the idea of a Backyard Safari and have been out and had a go. Hopefully you have enjoyed the experience and that is why you have come back to find out more.

Having given you an insight on the best way to reach Yellowstone National Park in winter, Roger Reynolds goes on to discuss the issues that surround photographing in the extreme cold.

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.

Over the past half a dozen years or so there have been a myriad of advances in digital camera sensor technology. New advances are still being announced at regular intervals. On top of that, sensor sizes from different manufactures vary from absolutely tiny through to offerings for medium format backs and more.

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.

Yellowstone National Park is rightly regarded as one of the greatest photographic locations on the planet. Yellowstone was to become the first National Park in the United States when it was formed in 1872. The park is the size of Wales and contains over 10,000 thermal features, over 80% of those found on earth. Roger Reynolds explains the attraction.