www.ukbutterflies.co.uk

I use the above lens for bird photography with some excellent results. I have done some butterfly photography with this lens briefly with differing results. Apart from getting an expensive macro lens, is there any particular part of the zoom I should stick to or just use the full 400mm lens.

Thanks in advance

Marc Heath

Hi Mark, You need to get as close to the subject as focus will allow, and be at full zoom. Have you tried using the lens in conjunction with a extension tube. An extension tube moves the lens away from the camera body and magnifies the image. Not sure why but it does, Eccles, Roger, or Fishiee, will explain. It has no glass, so it does not compromise the image quality, but you may loose AF, you will not be able to use the lens to focus beyond about 30ft, and the lower end of the zoom will not focus either. You should use the lens at full zoom, and you may be able to focus a little closer to the subject, then your usual 150cm. A extension tube is us-full in making a zoom act like a macro, but if you see a Deer, a 100 yards down the track, your be scrambling like a fool to take it off.

Gruditch

For what it's worth, rays of light from a very distant object hit the front glass of a lens approximately parallel to each other. The glass refracts the light, collecting it to focus at the sensor. Light from a closer object will hit the glass with the rays diverging, causing the focus point to move behind the sensor. Moving some or all of the lens elements forward will bring the focus point forward again. As you get closer to the subject eventually you'll run out of adjustment to bring the focus point forward. Sticking an extension tube between the lens and the sensor allows you to continue this adjustment to bring the focus point back into line.
As well as a loss of focus from distant objects, the introduction of an extension tube also reduces the effective 'f' stop.

Another way of getting closer is by using a close up lens. This is a magnifying lens that screws to the front of the main lens bringing divergent rays of light together so that the main lens 'sees' the object as if it were further away. Again, you lose the ability to focus at infinity but the 'f' stop remains the same.

Extension tubes generally give better optical results than close up lenses because they don't introduce additional glass, whereas close up lenses can add chromatic aberration and other distortions to the final image. Using high quality achromatic two or three element close up lenses such as the Canon 500D lens can dramatically improve the results and can be close to extension tubes in image quality. They have the added advantage of being easy to remove to snap the deer that Gary has just missed.