06-21-2012, 03:28 AM
Thank you, Wim. I understand it better now.
Best regards,
Frank
[quote name='wim' timestamp='1340220835' post='18994']
You're wrong there. It does change DoF, by the same factor that it actually dminishes the FL.It also changes the resulting FL. The only reason it doesn't change the aperture is because it uses the diaphragm and aperture placement of the original imaging lens.
Essentially, this works a bit like a static zoom lens, if you like. A zoom lens has an imaging group or groups of lenses, a group or groups of lenses which essentially determine the angle of view, and a group or groups of lenses which image the object onto the sensor. Essentially, a WA (or tele) converter which is front mounted is a new imaging plus static set of lens groups, where the lens this is fixed to behaves like the lens imaging the object as seen through the converter on the sensor.
This means that the imaging part of the convertor needs to deliver a (virtual) image large enough that it will not vignet when imaged by the lens it is attached to.
As to how well it works: it will never work as well as a decent prime lens of the resulting FL, not even with a specific, dediated attachment, for the simple reason that it is an afterthought and therefore not an optimal solution for a specific FL.
Kind regards, Wim
[/quote]
Best regards,
Frank
[quote name='wim' timestamp='1340220835' post='18994']
You're wrong there. It does change DoF, by the same factor that it actually dminishes the FL.It also changes the resulting FL. The only reason it doesn't change the aperture is because it uses the diaphragm and aperture placement of the original imaging lens.
Essentially, this works a bit like a static zoom lens, if you like. A zoom lens has an imaging group or groups of lenses, a group or groups of lenses which essentially determine the angle of view, and a group or groups of lenses which image the object onto the sensor. Essentially, a WA (or tele) converter which is front mounted is a new imaging plus static set of lens groups, where the lens this is fixed to behaves like the lens imaging the object as seen through the converter on the sensor.
This means that the imaging part of the convertor needs to deliver a (virtual) image large enough that it will not vignet when imaged by the lens it is attached to.
As to how well it works: it will never work as well as a decent prime lens of the resulting FL, not even with a specific, dediated attachment, for the simple reason that it is an afterthought and therefore not an optimal solution for a specific FL.
Kind regards, Wim
[/quote]