Why zoom lens never go wider than f2.8

[vaga2681]

Hi,

Anyone know why zoom lens never break the f2.8 barrier regardless how many times zoom?

 

[elcap]

Actually not really true, there are zoom wider than 2.8 except it is not full frame. Olympus has Zuiko Digital ED 35-100mm/2.0 and Zuiko Digital ED 14-35mm/2.0 lenses.

 

[vaga2681]

Actually not really true, there are zoom wider than 2.8 except it is not full frame. Olympus has Zuiko Digital ED 35-100mm/2.0 and Zuiko Digital ED 14-35mm/2.0 lenses.

I see, didn't know that been too engross with C,N and S being a Sony user myself... I have not seen any zoom lenses for C, N and S wider than f2.8... Thanks

 

[stvc11]

Zoom Lens with bigger than F2.8? The lens will be damm heavy then. 70-200 @ F2.8 already near 1.3kg. if F2 maybe 2kg?

 

[flipfreak]

cost and size does not allow.

 

[flipfreak]

Actually not really true, there are zoom wider than 2.8 except it is not full frame. Olympus has Zuiko Digital ED 35-100mm/2.0 and Zuiko Digital ED 14-35mm/2.0 lenses.

the 4/3 cameras can get away with such lenses because in usage, the dof is more like a f/4 lens wide open.

 

[pipo999]

Technically difficult, commercially not feasible.

 

[egnaro]

the 4/3 cameras can get away with such lenses because in usage, the dof is more like a f/4 lens wide open.

Ya DOF is like F4 if based on 35mm format. btw in this case is it true that since 4/3 is 2x more DOF then 35mm, Sony non FF body will have 1.5x more DOF then 35mm?

(is sony 1.5 crop factor?)

 

[yokechye]

can.. but i think u hv to be very rich to own it... ;p and will be big

 

[flipfreak]

Ya DOF is like F4 if based on 35mm format. btw in this case is it true that since 4/3 is 2x more DOF then 35mm, Sony non FF body will have 1.5x more DOF then 35mm?

(is sony 1.5 crop factor?)

yep. on the cropped bodies, a f/2.8 lens gives abt a f/4 dof. conversely a 645 medium format body gives a f/2 or so dof on a f/2.8 lens.

 

[vaga2681]

Zoom Lens with bigger than F2.8? The lens will be damm heavy then. 70-200 @ F2.8 already near 1.3kg. if F2 maybe 2kg?

May be not on telephoto lenses. At 200mm with F/2 means the aperture have to me 100mm :bigeyes: U can imagine how big the lens will be..

But if you have a 16-50mm F/2, the aperture diammeter only needs to be 25mm at the 50mm end. Size wise still sound practical and feasible..

 

[egnaro]

yep. on the cropped bodies, a f/2.8 lens gives abt a f/4 dof. conversely a 645 medium format body gives a f/2 or so dof on a f/2.8 lens.

thks... clear some of my doubt...