Hi,

I have been using the Tamron 17-50mm and all in all very happy. To get bokeh I need to be around 1ft or under away from my subject shooting at f.2.8. I would like to buy or hire a lens where I could get good bokeh on a subject which is maybe 4 or 5 feet away. Anything out there which could do that for me? I was hoping that my tamron would.do it but as soon.as I step to around 4ft away from my subject everything is in focus. I then press the magnify button and make sure my subject is in foucs but when I then press record everything including the backgroud looks to be in.focus. I am shooting at 1920, 25fps (50)shutter speed.

Hi,

I have been using the Tamron 17-50mm and all in all very happy. To get bokeh I need to be around 1ft or under away from my subject shooting at f.2.8. I would like to buy or hire a lens where I could get good bokeh on a subject which is maybe 4 or 5 feet away. Anything out there which could do that for me? I was hoping that my tamron would.do it but as soon.as I step to around 4ft away from my subject everything is in focus. I then press the magnify button and make sure my subject is in foucs but when I then press record everything including the backgroud looks to be in.focus. I am shooting at 1920, 25fps (50)shutter speed.

There is no mystery to this. If you wan't a shallower DOF, you need a wider maximum aperture, other things being equal.

Why not have a play with a DOF calculator to help you understand what's going on?

Online Depth of Field Calculator (http://www.dofmaster.com/dofjs.html)

At 4 ft, wide open your lens at 17 should have a DOF of 1.88 ft, going down to 0.2 ft at 50mm.

Things to bear in mind:

1. You will struggle to shoot wide angles with a shallow DOF.
2. You will struggle to keep your subject in focus if you do manage to get a faster lens.
3. What you want to see might not be practical given your constraints - you can't defeat physics.