[MJSfoto1956]

So I decided to do some manual "data mining" on the DxOmark website and put together this somewhat interesting chart comparing DxO's concept of "sharpness" (which is really about acuity which they call "Mpix") for DA primes on the K-3.

While I am no Pentax lens expert, the data seems to correlate quite well with the lenses I own and have shot with.

YMMV.

Enjoy!
Michael

Attached Images

 

[rawr]

A useful presentation of that information.

[SpecialK]

I love charts :-)

What I get out of it is the 55 is very soft wide open, and diffraction kicks in for all at f11.

[normhead]

All you have to do to know what DxO mark will say is look at which has the widest aperture. They weight so heavily for low light performance, I don't know why they even do the tests. At 5.6 the DA 35 and 50 1.8 appear to be the best. I'd be happy, except my DA 35 isn't terribly good. For a lens that costs under 200, taking a chance on another one is probably cheaper than sending it in for alignment.

[MJSfoto1956]

Just FYI: these charts are NOT DxOmark scores -- these are "sharpness" scores which are buried a bit deeper in the reports.
A bit different than their traditional DxOmark charts where they bias the result with penalty for slower lenses.

Michael

[Na Horuk]

Wait, can you explain the chart better? So its focal lengths on the vertical exist, and lenses on the horizontal.. and green colour is good vs. red which is bar? Did I get this right?
Interesting indeed. I wish the DFA 100mm would be on there, as well.

---------- Post added 21st Feb 2014 at 21:37 ----------

Also, I find it hard to believe the DA 35mm f2.4 is performing so much better than the DA 40mm? I feel my 40mm XS beats my 35mm in terms of sharpness/detail. I thought the 40mm was known for its sharpness

[johnyates]

Looks like the old adage needs to be adjusted--now it'll be "f5.6 and be there".

[MJSfoto1956]

Looks like the old adage needs to be adjusted--now it'll be "f5.6 and be there".

Yup! actually it makes sense: full-frame DOF and diffraction @ f/8 compares well to crop sensor DOF and diffraction @ f/5.6

For fun here is the same chart with the addition of the superlative Sigma -- basically a lens that is sharp from f/1.8 to f/8 on the K-3 !

Michael

---------- Post added 02-21-14 at 03:55 PM ----------

Wait, can you explain the chart better? So its focal lengths on the vertical exist, and lenses on the horizontal.. and green colour is good vs. red which is bar? Did I get this right?
Interesting indeed.

In DxOspeak, Green represents high perceived acuity (their concept that essentially replaces mere "resolution") and red would represent lower perceived acuity.

M

[wildman]

At first glance it looks to me as though within that important mid-range between 2.8 - 11 the 50mm 1.8 is at least as useful, if not more so, than the 50mm 1.4.

Unless I misunderstand the graph

[MJSfoto1956]

At first glance it looks to me as though within that important mid-range between 2.8 - 11 the 50mm 1.8 is at least as useful, if not more so, than the 50mm 1.4.

If we are only talking about perceived resolution, then yes, one would conclude that the 50mm f/1.8 would be both "sharper" and have a greater range of sharpness across a wider range of apertures.

Here is an enhanced version of the graph that better enhances the "max perceived resolution" for each lens with the pure bluest regions indicating the highest perceived resolution.

Michael

[monochrome]

So I own the DA15 and DA40.

On the basis of percieved resolution what I'm reading is that, within the context of DA Limited lenses, I actually own the two dogs that DxOmark suggests no one should want to own!

Or do I own two lenses dessigned to render pleasing images the classic Pentax way while the others are designed to test well?

[6BQ5]

Nice presentation and data mining! It's a tasty snack of graphics for the number crunchers around here.

Now... if only I owned any of those lenses!

[MJSfoto1956]

Or do I own two lenses dessigned to render pleasing images the classic Pentax way while the others are designed to test well?

I own the 15mm and 21mm (as well as a now-busted 50mm f/1.8 ).
Based on shots taken to date, my 21mm is noticeably sharper wide open than the 15mm.
But stopped down to f/5.6 I find the 15mm quite pleasing -- it certainly is one of my favorite angles of view -- and you can't beat the size or weight.

Given this side-by-side report, I am now leaning towards picking up a 35mm Macro to replace my broken 50mm.

Michael

[wildman]

If we are only talking about perceived resolution

Is there any other kind?
Photography is a visual art so I don't think it's going too far to suggest that in photography perception is reality.
If you can't perceive it for all practical purposes it's not there.

Any difference that makes no real world perceptual difference to the viewer is no difference?

[MJSfoto1956]

Is there any other kind?

I think DxO pisses people off because of this feature of their analysis -- they try very hard to avoid using "resolution" numbers precisely because of what you state. Instead, they add biases that they believe more closely aligns with how people see. Thus, fast lenses generally get higher DxOmark scores because noise is one of those things that detracts from perceived sharpness. (not that noise is bad per se, but when it comes to perceived sharpness is certainly is)

Michael