Post by Harold on Aug 27, 2006 10:19:22 GMT -2
From the Newsletter 11 August 06:
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Your Say
Advice on Canon lens needed
My telephoto lens is Canon’s bottom of the range 75-300 mm. Cost £165.00.
Small blue butterflies look like dots on leaves when I’m zoomed in.
I’ve got some cash coming in January and want a lens that when I’m 5 or 6 feet away from a small butterfly, it will fill the frame.
I have a horrible feeling this is going to be expensive. Any suggestions welcome – it probably won’t be a Canon!!!
Andy Murphy
Reply To Andy Murphy's Enquiry
So would I! In my dreams!
The longer the focal length, the smaller the angle of field. The trouble is that the longer focal lengths of lens are generally not made to focus close up.
You can halve the angle of view (aka doubling the magnification) by placing a x 2 converter between the back of the lens and the camera. You can also make such a lens focus closer by placing an extension tube behing the lens. For example, a 30mm tube behind a 300mm lens brings the closest focus down to about what you require but we are talking about a large dragonfly, not a small butterfly, filling the frame. Using the converter and the tube brings us down to large butterfly size at the same working distance. Another x 2 converter and we would be at twice the magnification again.
The bad news comes in two forms. The teleconverter, as with any lens, brings my lens down from the normal aperture of f1:2.8 to an effective aperture (i.e. the one for exposure purposes) of 5.6 with either of the arrangements and probably to 11 with the combination. Not many telephoto lenses are so fast, so you are going to be into f1:16 or less. As you need a shutter speed of the reciprocal of the focal length to prevent hand shake you go from 1/300 (or nearest faster available) with the lens alone to 1/600 with the teleconverter or extension tube and 1/1000 with the combination. With one teleconverter, you might just scrape through with ISO 100 and are going to have to use 200 and 400, respectively. You may not get the definition you want with these speeds.
Further bad news is that aiming at a small target is difficult due to the small field of view and the weight of all that glass. (My lens weighs 2.5 kg by itself). It would be akin to hand-holding a bellows for macro work.
As for costs, my lens, for film, manual focus, would cost 2,000 to replace. (You don't say what equipment you use).
What I actually do is to use a Tamrom 70-210mm lens with good macro performance and a teleconverter. At six feet that combination gives half life size and a maximum aperture of f1:7. Stealth in the approach permits the magnification to be increased.
I can't speak for Canon lenses but I have always used Tamron multi-fit lenses for macro work, at least until I recently obtained a Zuiko 50mm macro for my OM system.
I hope some of the above helps.
Harold
--------------------------------------------------------------------------------
Your Say
Advice on Canon lens needed
My telephoto lens is Canon’s bottom of the range 75-300 mm. Cost £165.00.
Small blue butterflies look like dots on leaves when I’m zoomed in.
I’ve got some cash coming in January and want a lens that when I’m 5 or 6 feet away from a small butterfly, it will fill the frame.
I have a horrible feeling this is going to be expensive. Any suggestions welcome – it probably won’t be a Canon!!!
Andy Murphy
Reply To Andy Murphy's Enquiry
So would I! In my dreams!
The longer the focal length, the smaller the angle of field. The trouble is that the longer focal lengths of lens are generally not made to focus close up.
You can halve the angle of view (aka doubling the magnification) by placing a x 2 converter between the back of the lens and the camera. You can also make such a lens focus closer by placing an extension tube behing the lens. For example, a 30mm tube behind a 300mm lens brings the closest focus down to about what you require but we are talking about a large dragonfly, not a small butterfly, filling the frame. Using the converter and the tube brings us down to large butterfly size at the same working distance. Another x 2 converter and we would be at twice the magnification again.
The bad news comes in two forms. The teleconverter, as with any lens, brings my lens down from the normal aperture of f1:2.8 to an effective aperture (i.e. the one for exposure purposes) of 5.6 with either of the arrangements and probably to 11 with the combination. Not many telephoto lenses are so fast, so you are going to be into f1:16 or less. As you need a shutter speed of the reciprocal of the focal length to prevent hand shake you go from 1/300 (or nearest faster available) with the lens alone to 1/600 with the teleconverter or extension tube and 1/1000 with the combination. With one teleconverter, you might just scrape through with ISO 100 and are going to have to use 200 and 400, respectively. You may not get the definition you want with these speeds.
Further bad news is that aiming at a small target is difficult due to the small field of view and the weight of all that glass. (My lens weighs 2.5 kg by itself). It would be akin to hand-holding a bellows for macro work.
As for costs, my lens, for film, manual focus, would cost 2,000 to replace. (You don't say what equipment you use).
What I actually do is to use a Tamrom 70-210mm lens with good macro performance and a teleconverter. At six feet that combination gives half life size and a maximum aperture of f1:7. Stealth in the approach permits the magnification to be increased.
I can't speak for Canon lenses but I have always used Tamron multi-fit lenses for macro work, at least until I recently obtained a Zuiko 50mm macro for my OM system.
I hope some of the above helps.
Harold