[Loren E]

I am curious as to why the DA* 16-50 is not an internal zoom design like it's big brother the DA* 50-135. They are of the same series and aperture and have the same weather sealing, so why does one telescope while the other zooms completely internally? I would think they would be of really similar design and this seems like a very fundamental design difference. Also hard to believe a telescoping zoom could be dust sealed, but I have not read one complaint about damage from dust.

Seems like this set would make a really fantastic pair, both fast, and a decent range from pretty wide to some tele ability on the long end. They are the two with the most SDM issues though I understand, so I will hold out until SDM is replaced. I read there was talk of a DA* 11-16 a few years back when Tokina came out with one, but sounds like this rumor died off?

Thanks all! -Loren Elliott

[openyourap]

I'd assume it's related to the fancy retro-focal wide angle optics in the 16-50.

[Rondec]

It might be to allow it shoot as wide as 16mm. The other reason could be that it allows it to be a smaller package, for carrying purposes. Internal zooms are effectively zoomed out all the time, when you are carrying them. It makes them a lot bigger than older, telescoping lenses.

[blockamon]

Interestingly, I don't know of any modern wide-to-normal zooms that do not telescope when zoomed. 16-50 f/2.8 from Pentax, 24-70 f/2.8 from Nikon, 24-70 f/2.8L from Canon, 12-60 f/2.8-4.0, 14-54 f/2.8-3.5, and 14-35 f/2.0 from Olympus...all extend when zoomed (although I believe the Canon and Nikon are longest at the shortest focal length). Must need a pretty long lens to get the wide angle, and I guess the manufacturers didn't want to make the len stay at the max length. Better for the camera bag to have the telescope. However, I might be willing to put up with a longer package to have no telescoping.

[Loren E]

I was just surprised this lens telescoped since the DA* series are fully sealed. I would think the telescoping would make it tough to accomplish that. If telescoping makes the lenses a good bit smaller for travel, then I wish they made the 50-135 telescoping too, assuming it doesn't make them any less well sealed. Seems they would stick to one game plan with these lenses, either external or internal, I guess it just seems odd to me to not stay consistent one way or the other?

[Adam]

assuming it doesn't make them any less well sealed

The more moving parts, the worse.

Unfortunately, zooms in this range are very hard to get to zoom internally. Tele's are easy, which is why lenses such as the 50-135, 80-200, and 250-600 all have IZ.

The 12-24mm also has IZ, right?

[flyer]

The 12-24mm also has IZ, right?

Yes and no. When zoomed in, it extends a few millimeters, goes back to it's shortest in the middle of the range, and extends again when it's zoomed out. So it's not all internal zooming.

[blockamon]

The 12-24 telescopes when zooming too, but not by much.

[vinceloc]

In my experience, zooms with a wider focal length range tend to extend out at longer lengths, while those with short FL ranges have minimal lens extension. Try the FA20-35/4, or the Sigma 17-35 EX DG, or the Tokina 20-35mm. All have a very short extension in their zoom. Like internal zoom lenses, those with short zoom extensions are great in terms of lifespan too. Less zooming length, less dust sucked internally.

Maybe that's why my FA20-35/4 still looks immaculate internally after close to 8 years of use. Same with an '80s vintage Tokina AF 70-210 F4 which I used to own. I was awed at how little dust one could see in its internals