05-08-2019, 08:05 AM
Looking at my very much loved AF 105mm F2.8D micro ....(those were the days) ..... there are two concentric tubes within the front barrel ..... the inner one containing the front element ....
..... Nikon had obviously thought carefully to make sure that when at 1:1 the front element sits very close (0.7mm) from the barrel front (almost no shading)...... cleverly, as you focus towards infinity , both inner tubes retract independently until the outer tube then provides lens shade to the front element which now recessed by 3cms!
..........a very expensive way of doing things in all metal ..... and apparently it uses a complicated series of cams to do it ....... it was the reference macro of it's day
..... and a master-stoke of design!
Sigma 105mm F2.8 macro (another good macro) has only one tube and the front element is always recessed .....at 1:1 that gives you shading when you don't want it.
..... Nikon had obviously thought carefully to make sure that when at 1:1 the front element sits very close (0.7mm) from the barrel front (almost no shading)...... cleverly, as you focus towards infinity , both inner tubes retract independently until the outer tube then provides lens shade to the front element which now recessed by 3cms!
..........a very expensive way of doing things in all metal ..... and apparently it uses a complicated series of cams to do it ....... it was the reference macro of it's day
..... and a master-stoke of design!
Sigma 105mm F2.8 macro (another good macro) has only one tube and the front element is always recessed .....at 1:1 that gives you shading when you don't want it.