Yesterday people were complaining on camera blogs about the lack of shallow depth of field of the New Panasonic 12-35mm lens. How it does not compare to the Canon or Nikon full frame 35mm equivalent. What they are thinking of is equivalent focal length not the marked focal length on the lens. I wrote this response.
If we all wanted only shallow depth of field (DOF), we would be shooting with a large format camera at large apertures. Even the full frame 35mm sized sensor does not have shallow with a wide angle lens. What makes low DOF is a longer focal length and a fast aperture. I used to zoom all the way in and open the aperture with my video camera (that had a lot smaller sensor than m43rds) to get low DOF. I would have to back up the camera because it was in full telephoto mode.
A 50mm f2.8 has the same DOF on a large format, medium 35mm full frame, APC crop 35mm, m43rds and a 2/3rds inch broadcast video camera. What is different is the angle of view. 50mm f2.8 is 50mm f2.8.
The new 12-35 has the same angle of view as a 24-70mm on full frame 35mm camera. Because it has a f2.8 aperture means it gathers the same amount of light as the full frame lens that has the same f2.8 aperture. Both cameras can shoot the same subject in the same lighting. Does a photojournalist care about DOF, not as much as about getting the picture in difficult lighting conditions. DOF is used for more artful compositions. At the same distance to the subject the DOF is the same at a given aperture for a given focal length. Just the angle of view will be different.
What I am excited about in the new Lunix 12-35mm lens is it is smaller, lighter, weathertight, less expensive and most important, it has something that Canon and Nikon branded lenses don't have, O.I.S. (Optical Image Stabization) This one of the best lenses for handheld work. If you want less DOF use as faster prime, I have them. That's why I buy an Interchangeable Lens Camera. You can change lenses.
I feel the price will settle to be less expensive the the full frame ones. Think of this lens more like the Canon or Nikon 17-55 f2.8 for crop sensor cameras. They are much larger, heavier, have I.S. and not weather sealed. I also want the other lens the 35-100mm that Panasonic has shown as a prototype. It will be better for video interviews as I have found the 17-55 on my Canon to be too short. It too will have the same DOF of lens for other systems at the same focal length and aperture.
This new Panasonic 12-35mm lens is available for pre-order though Amazon and Adorama.