Studio/Portrait Lens

Hey Guys,

I've been doing lots of studio stuff recently, however i find i need to change lens loads throughout the shoot.. And what i would really like is a lens that can do it all for me.

http://stejones.deviantart.com/

You can see some of my work there...

I've been looking at the Sigma 18-125 f3.8-5.6 DC HSM, and the Sigma 17-70mm f2.8-4 DC Macro OS HSM... What are your thoughts on these?? and what other suggestions would you have??

Thanks in advance, steve.

I think the SP AF28-75mm F/2.8 is better in the studio and for portrait because of the constant F-number and the range is perfect although I like longer lenses better like the DA*50-135 or Sgima 50-150 but that's me. =]

The price of the Tamron is £100 more than the lenses you name but worth it I believe.

Also the Lenses you name don't have HSM or OS on the Pentax mount so don't buy them for that.

I recently helped out a pro photographer in setting up and taking some studio portraits. This is not his normal type of shot, he was using a c***n 1D mark II with a 70-210mm lens fitted.

Only added this as a suggestion as to a lens, I used his lights with my K10d and Kit 18-55mm lens, these can out OK (comment from the pro)

Regards

As Stefan suggested, constant aperture zoom would be ideal.
The Tamron he recommended has great reputation. I never had it (nor anything similar) but personaly I'd go with Sigma 24-70. Those 4mm on wide end make a big difference on wide end and the lens is still constant f2.8.