low light and shallow dof
 

I am still considering to get the a7s and I was wondering, if the a7s is so good in low light and it also has the full frame sensor, is there really a need to get any lens lower than an f4.0 ? Or, would I still need something like an f1.8 lens for those nice shallow dof shots?

Re: low light and shallow dof
 

In a word: Yes. But you can figure it out yourself. Distance to subject and focal length are factors in addition to aperture. You can use a DOF calculator specifying the sensor size of the A7 to compute the depth of field at a given distance between sensor and subject.

Re: low light and shallow dof
 

that sounds good. I could save $800 since a 24-70, constant f4 lens costs $1200 and the constant f2.8 version costs $2000.

Re: low light and shallow dof
 

To be clear, You asked if an f1.8 lens is needed for nice shallow DOF and I said yes. The 24-70 constant f2.8 is a benchmark lens. But in my experience, for a nice creamy bokeh, you'll want something under f2. The point of the DOF calculator was for you to see the field size of an F4 vs f1.8. Keep in mind it takes distance ahead and behind of the field before it gets real blurry as opposed to just mildly OOF.

Re: low light and shallow dof
 

I should have been clearer and asked if an f4 can make a good bokeh shot. I appreciate you took the time to explain. Thank you, Les.