08-08-2010, 02:19 PM
[quote name='Brightcolours' timestamp='1281268694' post='1582']
As you know (you say you have used your 10-22mm with 12mm extension tube), the focus gets shifted to close to the front element, that thesubject is from about 3 cm from the front element to touching the front element.
Now add 2 more CM to the length of the lens, and you get why it matters, the length of the lens. Where with the MK I the subject will almost touch the front element, with the MK II focus can actually shift past the front element inside the lens. Only because of the extra length of the lens.
Now if you would be able to find a 9mm extension tube which routes through the electrical contacts...
[/quote]
It doesn't necessarily have to be like that, as it also deponds on the position of the front nodal point of the lens. With a short lens it always is going to be more cumbersome than with a longer lens, because twice the focal length is always going to be very little compared to a longer lens. However, if you take the EF-S 60 macro, f.e., I've calculated th efront nodal point to eb soemthign in th eorder of 3 mm into th elens, from the glass surface at the front that is.
Often it is a matter of trial and error, although with retrofocus lenses the front nodal point often doesn't lie as close to the front of the lens as with non-retrofocus lenses, as necessitated by the wide angle a WA or UWA needs to cover and the amount of glass elements having to fit in the path as well.
Kind regards, Wim
As you know (you say you have used your 10-22mm with 12mm extension tube), the focus gets shifted to close to the front element, that thesubject is from about 3 cm from the front element to touching the front element.
Now add 2 more CM to the length of the lens, and you get why it matters, the length of the lens. Where with the MK I the subject will almost touch the front element, with the MK II focus can actually shift past the front element inside the lens. Only because of the extra length of the lens.
Now if you would be able to find a 9mm extension tube which routes through the electrical contacts...
[/quote]
It doesn't necessarily have to be like that, as it also deponds on the position of the front nodal point of the lens. With a short lens it always is going to be more cumbersome than with a longer lens, because twice the focal length is always going to be very little compared to a longer lens. However, if you take the EF-S 60 macro, f.e., I've calculated th efront nodal point to eb soemthign in th eorder of 3 mm into th elens, from the glass surface at the front that is.
Often it is a matter of trial and error, although with retrofocus lenses the front nodal point often doesn't lie as close to the front of the lens as with non-retrofocus lenses, as necessitated by the wide angle a WA or UWA needs to cover and the amount of glass elements having to fit in the path as well.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....