Fast sensors have made fast lenses obsolete Locked

Started Jul 31, 2013 | Discussions thread
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Anders W
Forum ProPosts: 19,064Gear list
Re: "Preconceived ideas"?
In reply to amalric, Aug 4, 2013

amalric wrote:

Great Bustard wrote:

amalric wrote:

My contention is that almost any lens is good at f/2.8 so the sensor's difference kicks in.

That explains the v. good performance of the Sigmas.

Conversely almost anyfast lens, witness the PL 25/1.4 or the CV at 0.95 have bad resolution at full aperture (see Lensrentals) therefore if the aim is to have max resolution there is an alternative strategy. Choose the best sensor, both in terms of per pixel sharpness and SNR.

As I recall, Sigma also makes a 35 / 1.4 that's sharp right from wide open, as well as an 18-35 / 1.8.

Huh.

I also recall that Olympus makes a 45 / 1.8 and 75 / 1.8 that are also quite sharp right from wide open.

Huh.

Not m4/3 lenses.

The last two are.

Distance to flange must be almost double. That explains.

No it doesn't.

First, the interesting thing about flange distance is not how large it is in absolute terms but how large it is relative to the sensor diagonal. For the Sigma 35/1.4 on a Canon FF camera, we have

44/43.2 = 1.019

and for a native MFT lens on an MFT body

19.25/21.6 = 0.891

In other words: very similar.

Second, and more importantly, a short flange distance is always an advantage, never a disadvantage, from an optical design point of view. It just means that you can put the rearmost element closer to the sensor if you want. But there's nothing forcing you to do so. You can also put it as far away as you like.

Now for some facts about MTF from your favorite source, LensRentals. The figures are line pairs per image height at MTF 50 for center/average based on unsharpened output from E-M5 RAWs.

First a couple of your favorite 2.8 lenses:

Olympus 17/2.8

2.8 720/590

Sigma 19/2.8

2.8 850/745

And here are some faster alternatives for comparison:

Olympus 12/2

2.0 860/730

2.8 1000/845

Panasonic 20/1.7

1.7 870/735

2.8 1050/875

Olympus 75/1.8

1.8 880/765

2.8 1020/925

In other words, the fast lenses do about as well wide open, at f/1.8 - f/2.0, as the better of the two f/2.8 lenses you advocate do at f/2.8. And when stopped down to f/2.8, the faster lenses all do significantly better.

Good that sometimes I open up the files of a plonked carrion bird.

Shrieking lies.

As everyone can see for themselves, you do your best to maintain your reputation as the epitome of rudeness and ignorance combined.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +21 more
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