With only 136mm of extension
This was less than the first ( i cannot remember how many tubes i added for this )
This is a shot with 446mm worth of extension with a 55mm micro of the greenback
No sharpening, slightly soft but I do not think i have achieved the critical focus yet.
Sorry, IMHO, it is not sharp.
Last edited by Leong23; 11th January 2008 at 03:26 AM.
Some layman term on diffraction.
Diffraction is happening when light is travelling through the lens.
The glass elements inside the lens help to control diffraction
(that way pro lense is sharper - more lens elements)
When stack with too much extension tube hence creating a big void with no glass elements, the light will run wild and some never make it to the sensor (loss of detail in photo)
Last edited by Leong23; 11th January 2008 at 02:25 AM.
extension tube as we all know, makes a lens possible for closer focusing aka reducing the minimum focusing distance, in such, create magnification.
as compared to macro lenses, macro lenses have full range of focusing distance from 1:1 to infinity, but normal lenses have a much further minimum focusing distance then to infinity.
So if add extension tube to normal lenses, makes it function like a macro lens but minus the infinity.
your 1st question, i wonder why would anyone wanna put extension tube on a wide angle lens. Wide angle lens already have the ability to focus a shorter distance in MFD as compared to normal lenses. normally an extension tube is attached to lenses more than 50mm. thats the norm.
And i wonder how would you be able to take group shots with an extension tube, you get close, and you want wide angle?
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A good quality closeup filter such as the Canon 500D will cost almost the same as a set of third party tubes. Closeup filters do not cause any light loss and are best used with longer focal length lenses. Its a filter so it only screws onto similar diameter lenses.
Extension tubes can be used with any lens and the major disadvantage is light loss and if stacked, diffraction can be a big issue.
IMHO, a dedicated macro lens is still the way to go. A secondhand Tamron 90 or Sigma 105 costs not much more than a Canon 500D but offers a way higher mag rate and top image quality.
Canon 5D mkII|24-105 F4 IS L|70-200 F4 IS L|135 F2 L|580EX|