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04-12-2012, 09:50 PM   #1
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DXOMark results I don't understand

Hi guys,

Maybe someone can enlighten me. Because I for one can't understand this:

The DA 35mm F2.4 AL is considerably better than the DA 40mm F2.8 Limited.

So is there a mistake. And if so, where is it and what is it?

04-12-2012, 10:31 PM   #2
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basically, it wins out cause its faster.
04-12-2012, 10:34 PM   #3
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From what I see, DA 40 has better light transmission, better distortion, and better CA so it is a better lens.
04-13-2012, 02:18 AM   #4
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QuoteOriginally posted by Doanh Quote
From what I see, DA 40 has better light transmission
Really? The numbers aren't high enough resolution to say as far as I can tell. 2.6 is about a quarter stop from 2.4, 3.1 is about a quarter stop from 2.8. In absolute numbers the DA 35 obviously wins, which I assume is how it got the higher summary score. Or maybe they score for some subjective usefulness of focal length thing?

04-13-2012, 04:05 AM   #5
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I questioned how DXO scores too:

QuoteOriginally posted by JinDesu Quote
Lens score should be considered with the testing platform (camera). The top lenses scoring 30-34 are on full frame cameras. All their lenses appear to get a +10 or +12 factor when shown on a full frame. If you take the lenses tested on the D3x and drop to the D7000, you'll get a -12 to the score, putting it closer to what the Pentax lenses are scored at.

Now, that being said - the top scoring Pentax lens is the DA 35 F2.4 on the k-5. It outscored (at 15, so full frame would be 27-28):

DA 70mm Limited
DFA 100mm WR
DFA 50mm F2.8
DA 40mm Limited

Just a quick comparo of the 35 F2.4 and the 100 WR, both reached 46lpmm, the 100 WR has 0% distortion vs 3% on the 35mm, the 100 WR has 0.5ev less vignetting than the 35 F2.4, and it's chromatic abberations are 3 micrometers smaller.

The only thing the 35 F2.4 has on the 100WR is light transmission, which seems to be at .6Tstops better. Now, the general mark of the Limited lenses are the lower light transmission, and it seems to be the big factor in the DXO score. In fact, the 40mm F2.8 is also 46lpmm, 2% distortion, same vignetting, and less chromatic aberrations, but lower light transmission and it scores 4 points lower than the 35 F2.4.

It's weird.
It does seem that light transmission is a big factor for them - which is unfair towards Pentax Limited lenses.
04-13-2012, 04:44 AM   #6
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Yes, their final score heavily relies on the light transmission (just look at how unfair this score is towards the very good 55-300), but neglects other factors, which may not even be taken up in a calculation, such as micro-contrast. The DxO score has little to do with how pics taken with a certain lens look.
04-13-2012, 04:52 AM   #7
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I too really don't like how DXOMark rates lenses. The only thing of any value in their lens tests are their MTF graphs, in my opinion.
04-14-2012, 09:54 AM   #8

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The DA35/2.4 is a good lens, especially at the center of the image. The DA40 has better resolution off-axis, and is what I would choose for landscape work, that is, if it had a depth of field scale.


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