Seems like you can pick up the Tammy f/2.8 17-50 or the 28-75 for the same price as a couple of primes to cover the same range. But do the primes provide better image quality?
laydros, short answer yes. Usually they can attain sharper results and smoother background blur.
PRIMEs offer one limitation ... the "ZOOM" is on you. Two-steps forward ... two back ... get the framing right.
The widest aperture currently available in a "Zoom" lens is f/2.8
While this is a good and reasonable bokeh, it does lack that artful flair. You need a wider aperture lens to really get "down & dirty" with smoothing the background blur. Personally, beyond a 50mm f/1.7 or f/1.4 PRIME ... I, personally, cannot say which lens anyone should go with. There are different requirements depending on subject, distance and the amount of bokeh desired. The current Minolta or SONY 35mm f/1.4 G PRIME returns the APS-C sensor camera back to what people used to see using a 50mm f/1.4 (aka "normal"). Unfortunately, the costs involved with owning this lens are three times that of the 50mm f/1.4.
On the other side of the 50mm, there is the Minolta 85mm f/1.4 G or SONY CZ 85mm f/1.4 ... which both react the same way a 135mm did on the film cameras. Both are excellent choices for a portrait lens, when used in concert with the APS-C sensor camera. Also, they come with a significant price tag (~$1100)
Also, there is the added feature of being able to avoid using a flash, indoors. With the wider aperture, your capture of indoor athletic events is much improved, over the zoom. The Depth of Field will be a bit of a struggle, but you can adapt that by distance and being light on your feet. There are plenty of other discussions for that. Wisdom says you should have at least one prime in your bag ... for those times where flash is just not an option.
Which one of those lenses are metal. Glass?
They're all glass inside ;) I remember a post on DPR where someone thought the kit lens was plastic inside (and that's what caused its low quality) lol.
Just a thought, but plastics have been used for high quality lenses as well as in disposable cameras.
A precision ground Aspheric Lens is expensive because, unlike a sperical lens, the grinding process is complex, long and not suitable for mass production.
A hybrid" Aspheric Lens involves the use of plastic molded onto optical glass. They might call it "optical quality resin" but it's still plastic. This method has/is widely used but has drawbacks due to dimensional instability.
In the late 90's techniques for moulding glass to make Aspheric Lenses were developed as an improved alternative to plastic.
I have no idea to what extent this method has replaced the hybrid lens.
Here is a link to very well done list of SONY/Minolta & Konica-Minolta lenses (<- click this link).
Definitely worth a look, in my opinion, just in case you are looking for glass. :D
does the tokina 11-16/2.8 not come in a sony mount ?
So, there it is. I do not believe SONY is crying about it. They get exclusive sales on their own product. SIGMA and Phoenix seem to be the only non-SONY controlled entities that make such lenses.
Thanks for asking. LOL