Sony Zeiss Vario-Tessar T 24-70mm f4 ZA OSS (FE): Question

[fotomatix]

Apologies if this is not the most intelligent question. Novice here.

 

The above lens is a highly rated lens. I have seen images produced and they are very sharp and capable of producing creamy bokeh as well. Interesting for a minute if you think that it's an F4 lens. I am curious to know if an f4 FE lens on a Full Frame sensor camera is behaving like an f2 on an APSC sensor?  In other words, you don't necessarily need f2 or brighter to get desired results (DOF bokeh) since you are using a FF sensor.  

[Pierre]

You're correct, the larger the sensor, the deeper the DOF at an equal aperture. If I'm right, F4 on a full-frame sensor will have roughly the same deep of field as a F2.8 on an APSC sensor.

 

Regarding DOF, it's not always the good way to shoot, and doesn't always "enhance" a photo. It depends on the result you want.

But i have to say, since I shoot some portraits with the A7 full-frame sensor plus the 55mm F1.8, I felt in love with such combination !

[Philber]

I am sorry to respectfully disagree with Pierre. Depth of field decreases with sensor size. Full-frame cameras have less DOF than comparatively specced APS-C ones. This is why, as he correctly states, f:4.0 on a full-frame has the same DOF as f:2.8 on APS-C (f:2.8 has less than f:4.0 on the same setup, so if f:4.0 on FF has the same as f:2.8 on APS-C, it entails that FF has less DOF than APS-C).

But this is only DOF, not field of view (obviously you have less on APS-C) and bokeh (the blurring effect is the same irrespective of sensor size, so a f:4.0 FF zoom will blur less than a DOF-equivalent f:2.8 APS-C zoom, both used wide open to get the same DOF.

This as regards depth of field. There is another aspect, that of aperture and light metering. A FF sensor being larger will accumulate mor ephotos than APS-C. Thus, for the same level of lighting, you need to use one stop more with APS-C. Meaning that, in low light, you will have to use f:2.8 on APS-C to achieve the same lighting (shutter speed being the same) as f:4.0 on full-frame. Thus the larger sensor gives you a one-stop advantage in low light.

Hope this helps