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

Started Feb 17, 2014 | Discussions thread
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Pixnat2 OP
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At those apertures 0.1ev is significant
In reply to tt321, Feb 17, 2014

tt321 wrote:

007peter wrote:

I share the same thought as you (for the most part). However, you must keep your Expectation Realistic & Reasonable. A slight 0.3ev lost in T-Stop is to be expected. AFAIK, no lens live up to their T-Stop claim (or very very few do). Most manufacture measure them under the best LAB CONDITION, so in everyday "Real World", a slight 0.3ev lost isn't outrageous.

For example, the DXO Tested T Stops are:

  • 2.0 T-Stop for Panasonic 20mm F1.7 (II) | -0.3ev
  • 2.1 T-Stop for Panasonic 20mm F1.7 (I) | -0.4ev
  • 2.2 T-Stop for Olympus 12mm F2 | -0.2ev
  • 2.0 T-Stop for Olympus 45mm F1.8 | -0.2ev
  • 2.0 T-Stop for Olympus 75mm F1.8 | -0.2ev

Based on DXO results, I would say Olympus is more consistent with narrower gap between Lab Tested "claimed" vs real-world tested results. It would surprise me if the new Olympus 25/1.8 is tested exactly at 2.0 T-Stop.

Either way, I wouldn't worry about it. Since Olympus is the cheaper of the two, I just buy it over Panasonic.

You are right.

I looked at a number of FF 50/1.4 lenses (Canon, two versions of Nikkors, and a Sony) and they are all T1.6 so the PL25 is a bit worse in class, but not too radically different.

When we think about the price difference between, a f/1.4 and f/1.2 lens, it's like 500$ for 0.1 EV

More seriously, the claimed difference between f/1.4 and f/1.8 is 0.4ev. It's not a good surprise if it's reduced to 0.3EV in reality (supposing the Oly 25mm will be 2 Tstop)

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