Why no fixed Super-Tele-Lenses for APS-C?

[torger]

sorry, I did not get it. what does it mean for
30/1.4 ? (filter 52mm)
60/2.8 ? (filter 62mm)

it gives 21mm, why do they have two-three times bigger filter? well, ok, 52mm is the smallest, but why 62mm then?
how do you count for FF?

Thanks a lot

I guess you wonder why 30/1.4 is not smaller in diameter than it is, since tele lenses are quite close max aperture and lens diameter. I'm no optics expert but I think it is because with wider angle lenses you need to take in light from a wider angle to get to the aperture which is sitting a bit back in the lens barrell. Also, there is a design tradeoff too, if let it vignette some more at largest aperture you can have smaller front element, so actually the wider angle lenses would typically vignette less if they had a larger front element.

 

[Loswr]

sorry, I did not get it. what does it mean for
30/1.4 ? (filter 52mm)
60/2.8 ? (filter 62mm)

it gives 21mm, why do they have two-three times bigger filter? well, ok, 52mm is the smallest, but why 62mm then?
how do you count for FF?

Thanks a lot

I guess you wonder why 30/1.4 is not smaller in diameter than it is, since tele lenses are quite close max aperture and lens diameter. I'm no optics expert but I think it is because with wider angle lenses you need to take in light from a wider angle to get to the aperture which is sitting a bit back in the lens barrell. Also, there is a design tradeoff too, if let it vignette some more at largest aperture you can have smaller front element, so actually the wider angle lenses would typically vignette less if they had a larger front element.

Exactly - the numbers I was listing were for telephoto designs. Normal and wide angle designs are different, with different requirements. So are macro lenses - consider the MP-E 65mm, which uses a 58mm filter thread but has a relatively tiny front element.

Check out the article on lens geneaology for an interesting read...

 

[Halfrack]

Doing a Super-Tele for a crop body wouldn't make things easier, rather it would confuse more people than those it helps with a price point. I would like to see a return of F2.8 NON-IS super-tele lenses since I shoot at a high speed - and this may cover part of that market. The other would be a 300/4 that's setup with the built-in 1.4x tele-adapter. Too bad people would see it and say 'well I already have half of it'...

 

[whatta]

sorry, I did not get it. what does it mean for
30/1.4 ? (filter 52mm)
60/2.8 ? (filter 62mm)

it gives 21mm, why do they have two-three times bigger filter? well, ok, 52mm is the smallest, but why 62mm then?
how do you count for FF?

Thanks a lot

I guess you wonder why 30/1.4 is not smaller in diameter than it is, since tele lenses are quite close max aperture and lens diameter. I'm no optics expert but I think it is because with wider angle lenses you need to take in light from a wider angle to get to the aperture which is sitting a bit back in the lens barrell. Also, there is a design tradeoff too, if let it vignette some more at largest aperture you can have smaller front element, so actually the wider angle lenses would typically vignette less if they had a larger front element.

Exactly - the numbers I was listing were for telephoto designs. Normal and wide angle designs are different, with different requirements. So are macro lenses - consider the MP-E 65mm, which uses a 58mm filter thread but has a relatively tiny front element.

Check out the article on lens geneaology for an interesting read...

I will read it, thanks for you both.