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New Website New Blog!

Jun 29, 2013 | General | Comments (0)
An entry welcoming people to my new website and a new set of blogs.
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Red Kite’s in August

Aug 15, 2012 | General | Comments (0)
Red Kites's at harvest time in mid August 2012, the first bit of sun that we have had all summer.
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Tawny Owl Chick, 2nd Attempt and Sigma 400mm lens.

Jul 29, 2012 | General | Comments (0)
Here is a later attempt at photographing a Tawny Owl chick.
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Tawny Owl Chick.

Jul 15, 2012 | General | Comments (0)
My first attempts at photographing a Tawny Owl chick.
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An overview of a couple of local reserves.
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Spring Walks: Llyn Briann, Tywi Forest and New Quay.
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General information on the following blog entries.
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A blog looking both at the Wildlife of West Wales and those who are working to conserve it.
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Tawny Owl Chick, 2nd Attempt and Sigma 400mm lens.

on Jul 29, 2012 | General | 0 comments
This image was taken with a Sigma 400mm f/5.6 lens:
Tawny Owl Chick

Here is a little more information on the Sigma 400mm f/5.6 lens:-

This lens was on the market in the late 1990's and was been as an upgrade from the more standard kit lenses for the keen amateur photographer. It is optically a very good lens, has as a fixed aperture and is extremely light weight, for a 400mm lens.
Sigma 400mm f/5.6 lens
I am using this lens with my Canon EOS 60D DSLR; unfortunately this lens was never designed for use with this particular series of camera. These Sigma lenses were generally designed for Film Cameras using an autofocus system; in the case of Canon this was the EF system. When digital came out they started using EFS lenses alongside their existing EF lenses, third party manufacturers such as Sigma had not seen this coming and the existing lenses did not always work with the new camera bodies. As well as problems with the focusing systems, these lenses will not 'stop down' and allow the photographer to change the aperture. Sigma did try and get digital users to return the lenses to the factory to have a new microchip put in, but ultimately many lenses were never 'chipped' and in the end Sigma just replaced the whole range. This has resulted in a complicated second-hand market where some lenses are 'chipped' and work fine with new DSLR's and others, more commonly do not operate as they should.

The above does not sound great on paper; but a few other points should be taken into consideration. There is often no problem with another camera system, such as Pentax (where the electronic system is more straightforward), I have used this lens on a Pentax K20D and autofocus's perfectly and stops down. Being able to control the aperture is particularly important in regards to this lens as it does suffer from a bit of *'colour fringing' with the aperture fully open. Stopping down (closing) to an aperture of f/8 or f/11 significantly reduces this fringing.  The other important point is that it is extremely good value for money. It can be picked up for as little as £70 on ebay, although better examples will sell as much as £250 second hand, this is still not very much money when compared with modern, new lenses. I have also compared this lens with other lesser telephoto and tele-zoom lenses in field tests. For example it easily outperformed the Sigma 70-300mm APO kit lens regardless of what aperture you chose.

I will at some future point go into a little more detail on other telephoto lenses. I am extremely interested in comparing these lenses to try and find those that are of exceptional value; I may well try and get some other (test) examples of our Tawny Owls.

By the way the above image is a bit grainy this is mainly because the ISO had to kept high (around 1600 ISO) as these Owls will not come and sit on the telegraph poles until a good 20mins after the sun has gone down! Maybe a faster aperture lens is required?

*As regards 'colour fringing' this is just one of the optical distortions caused by the curvature of the lens. The light is split as it passes through the optical element; this causes a coloured halo to appear around the subject in the photograph. This halo is often there but is usually very slight and the image has to be magnified for it to be seen. It is more obvious in high contrast subjects particularly where the subject is shown against the sky (such as a bird on a wire). It will be reduced when you use a smaller aperture and only the centre of the lens is used (the centre of a lens is normally of better optical quality - will produce a sharper image with fewer distortions).



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