Is the Panasonic 25mm a real f/1.4 lens?

Started Feb 17, 2014 | Discussions thread
draleks Forum Member • Posts: 76
Re: Take all tests with a grain of salt...

tt321 wrote:

Paul De Bra wrote:

Robin Wong works for Olympus. His tests are completely honest but the choice of what to test has a hint of focusing on the points where the Olympus lens is (objectively) better than the Panasonic.

The test that shows that DOF is not as shallow as a 50mm f/2.8 on FF uses misfocused shots resulting in more or less background blur depending on the focus.

The DXO T-stop measure is very likely to be accurate but f/1.4 is about the diameter of the pupil and corresponding DOF results and does not state anything about light transmission. You cannot assume that the T-stop difference between an f/1.4 and f/1.8 lens is the same as the F-stop difference.

So the Panaleica is really f/1.4 and the Olympus is really f/1.8. That's not a matter of "thoughts about it" but of physical properties.

In the actual case Panasonic's patent says it's 1.44. The FL is also longer than 25 mm so the opening, in absolute mm terms, is reasonably large.

Not too sure what the precise F number the Olympus design has, but the range may be between 1.75 and 1.84


Good point. A lens that is slightly longer but has the same pupil diameter will have a slightly higher f-number, and appear darker. But this is splitting hairs, I own this lens and I love it.

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