11-12-2010, 01:48 PM
[quote name='hackmann' timestamp='1289257223' post='4058']
I asked this because I also read somewhere about firmware bugs in some lenses related to effective and nominal aperture, not only with canon but with nikon too.
[/quote]
Got no experience with Canon but AFAIK they show the nominal aperture which normally does not change with focus. Older lenses give nominal aperture on Nikon too; I guess you then have to compensate exposure manually (watch the RGB histogram and roll the EC wheel...). I got used to compensating exposure a lot with the Tamron 60 and Nikkor 18-200VR ;(
[quote name='hackmann' timestamp='1289257223' post='4058']
Does that happens in any aperture?
[/quote]
Yes, the whole aperture range is shifted by 2 stops at close focus compared to inf focus. The name "bellows factor" because old macro lenses would shift the whole lens away from the camera to achieve high magnifications just like bellows or extension tubes. With modern IF designs this is not so simple anymore; there still seems to be the same 2 stops difference at 1:1, but there may be a different curve in between; there are also considerable differences among different IF designs regarding what happens to the effective focal length and the working distance at close focus (compare the Nikkor, Tamron and Canon 60mm IF macros).
I asked this because I also read somewhere about firmware bugs in some lenses related to effective and nominal aperture, not only with canon but with nikon too.
[/quote]
Got no experience with Canon but AFAIK they show the nominal aperture which normally does not change with focus. Older lenses give nominal aperture on Nikon too; I guess you then have to compensate exposure manually (watch the RGB histogram and roll the EC wheel...). I got used to compensating exposure a lot with the Tamron 60 and Nikkor 18-200VR ;(
[quote name='hackmann' timestamp='1289257223' post='4058']
Does that happens in any aperture?
[/quote]
Yes, the whole aperture range is shifted by 2 stops at close focus compared to inf focus. The name "bellows factor" because old macro lenses would shift the whole lens away from the camera to achieve high magnifications just like bellows or extension tubes. With modern IF designs this is not so simple anymore; there still seems to be the same 2 stops difference at 1:1, but there may be a different curve in between; there are also considerable differences among different IF designs regarding what happens to the effective focal length and the working distance at close focus (compare the Nikkor, Tamron and Canon 60mm IF macros).