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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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Interesting answers. DXO as THE reliable source?
In reply to Pixnat2, Feb 17, 2014

Thanks for all those interesting answers.

I think the most interesting thing is the DXO article pointed by Steen Bay :


DXO shows that Tstop (measurement of the effective quantity of light transmitted by the lens at a certain f-stop) is a an effective (versus theoretical) way of measuring the aperture.

If a f/1.4 (theoretical aperture) lens behave like an f/1.7 (effective aperture) lens, the gain of speed is less than the manufacturer advertise.

This may be not so important for f/1.8 and above lenses, but very important for really fast and expensive lenses like f/1.2 or 1.4. Don't we buy them because they are ... fast?

What about the Canon 50mm f/1.2 (1500$) being 1.4Tstop vs the Canon 50mm f/1.4 (350$) being 1.5 Tstop on a 6D? 1200$ for 0.1Tstop difference?

Let's be aware of this when we buy ultra-fast lenses! (If it's important for you of course!)

So, is DXO the realiable source?

Let's see what they'll find about our Nocticron!

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