Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-31-2016, 07:34 PM   #31
Loyal Site Supporter
Loyal Site Supporter
clackers's Avatar

Join Date: Jul 2013
Location: Melbourne
Photos: Albums
Posts: 9,192
And where are the 645Z's figures, that we know DxO tested but have hidden the results?



05-31-2016, 07:58 PM   #32
osv
Pentaxian




Join Date: Mar 2007
Location: So Cal
Photos: Gallery
Posts: 2,080
QuoteOriginally posted by MadMathMind Quote
Seemingly most of them, actually.
actually, no sensor is out-resolving legacy pentax glass, not even close.

your dxo numbers are a mishmash of undocumented procedures for measuring and averaging who knows what into one overall p-mpix number:

"The DxOMark resolution score shows sharpness performance of a lens-camera combination averaged over its entire focal length and aperture ranges.
The resolution score is computed as follows:
For each focal length and each f-number, we first compute sharpness and then weight it throughout the field, tolerating less sharpness in the corners than in the center. This gives one number for each focal and aperture combination.
Then, for each focal length, we select the maximal value of sharpness over the range of available apertures. We average this value over the whole range of focal length to obtain the DxOMark resolution score that we report (in P-MPix)." Metric Scores - DxOMark

if you want to see the math for calculating the point when sensors don't matter any more:

"I figure that some of the finest lenses that we use are close to diffraction-limited at f/8. If thatís true, for 0.5 micrometer light (in the middle of the visible spectrum), a Q of 2 implies:
Pitch = N /4
At f/8 we want a 2-micrometer pixel pitch, finer than currently available for any available sensors sized at micro 4/3 and larger. A full frame sensor with that pitch would have 216 megapixels."
How much sensor resolution do we need to match our lenses?
06-01-2016, 12:35 AM - 1 Like   #33
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,246
Do Sensors Out Resolve Lenses?

Short answer: "No".
06-01-2016, 12:50 AM   #34
Pentaxian




Join Date: Jul 2009
Location: TromsÝ, Norway
Photos: Albums
Posts: 973
I also have the impression that DxO resolution "P-Mpix" is far off the reality. I discovered large inconsistencies with lenstip.com and photozone.de data. I tried to figure out what was going on and could not find a direct flaw in their claimed methodology (here and here), which makes the inconsistencies even more mystique. For example, its easy to see that the Mp increase from K10D to K-5 gives a real perceived resolution increase, and that the removal of the AA filter for K-5 IIs gives another perceived resolution increase and that K-3 gives even better resolution, all with the same DA*55mm. Its also easy to see that K-1 competes to D810 with the same 3. party lenses, and that K-1 beats it hands down when turning on the pixel shift mode. DxO just isn't in line with reality. I don't know why, but I trust my own eyes and numerous test sites more then mystic DxO scores without images.

06-01-2016, 01:48 AM - 2 Likes   #35
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,878
QuoteOriginally posted by MadMathMind Quote
The only place who really measure this stuff is DxO
The problem is their testing methodology is, as far as they have publicly disclosed so far: highly questionable.

QuoteOriginally posted by stevebrot Quote
My understanding is that it involves equal parts of peyote and mezcal...and dice...
I hear that is also a great way to get into D&D

QuoteOriginally posted by Class A Quote
Do Sensors Out Resolve Lenses? Short answer: "No".


Fundamentally
this is correct. However there is a limit on the frequency of contrast a lens can reproduce this is why MTF is widely accepted the benchmark test for lens contrast attenuation - and contrast is a characteristic that is determined by optical design and the number/quality of lens coatings and number of lens elements used in the design. Resolution is different from contrast, but they are intrinsically linked in a similar way that spherical aberration is to astigmatism* and coma. A lens that resolves 20lp/mm @ 50% contrast is going to appear sharper than a lens that can resolve 20lp/mm @ 35%. The actual resolving power of the lenses in question can be identical.

*in a well designed lens they are carefully corrected and balanced so neither aberration can dominate, however under extreme conditions one of them will invariably make its presence known. Coma is often left uncorrected as it is only visible under very specific circumstances.

Last edited by Digitalis; 06-01-2016 at 02:01 AM.
06-01-2016, 02:38 AM   #36
Site Supporter
Site Supporter




Join Date: Mar 2009
Location: Gladys, Virginia
Photos: Gallery
Posts: 16,426
It is clear that certain lenses will be unable to take full advantage of resolution of a given sensor at some apertures. That is a sufficiently vague statement, but clearly, the DA *55, since it has been brought up, is kind of soft at f1.4, while at f4 it is really sharp, even on full frame. I see a lot more vignetting and soft edges on my K-1 photos than with K3 photos, if I am not stopped down, but it isn't that hard to stop down a stop and everything is fine. And edge sharpness isn't even that important in a lot of photos.
06-02-2016, 03:58 AM   #37
Site Supporter
Site Supporter
Clinton's Avatar

Join Date: Feb 2010
Location: Salt Lake City, UT
Photos: Gallery | Albums
Posts: 1,827
QuoteOriginally posted by Kozlok Quote
Sadly, the biggest disappointment most feel when getting the K-1 is that they don't suddenly become better photographers.
It is? Well...!

Last edited by BigMackCam; 06-23-2016 at 12:42 PM. Reason: Removed minor vulgarity
06-03-2016, 01:14 PM - 1 Like   #38
Veteran Member
jsherman999's Avatar

Join Date: Dec 2007
Photos: Gallery
Posts: 8,228
QuoteOriginally posted by clackers Quote
Yep, a variant of the 'If I buy a Nike top, I'll be able to play like Roger Federer" effect.
I know, right? Everyone knows it's the Nike shoes that bring the game up to that level.

06-03-2016, 01:21 PM   #39
Loyal Site Supporter
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: Kirkwood (St. Louis) MO
Photos: Gallery | Albums
Posts: 20,602
UnderArmor.
06-03-2016, 05:27 PM   #40
Pentaxian
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 4,300
Weren't some lenses designed to be soft at wide open or near wide open apertures or in the corners?
06-03-2016, 06:03 PM   #41
Loyal Site Supporter
Loyal Site Supporter
Quartermaster James's Avatar

Join Date: Nov 2015
Location: Anchorage, Alaska
Posts: 618
QuoteOriginally posted by Wild Mark Quote
It is worthy to note that the price of some legacy lenses on ebay seems to have risen of late - perhaps news is spreading that the good legacy stuff is worth having?
Shhhh!!!!! Hush!!!
06-03-2016, 06:16 PM   #42
Site Supporter
Site Supporter




Join Date: Jun 2013
Location: Newcastle
Photos: Gallery | Albums
Posts: 1,571
QuoteOriginally posted by Quartermaster James Quote
Shhhh!!!!! Hush!!!
Lol. I took the punt years ago buying up the legacy stuff on the risk that it was not going to be any good. Looks like I got lucky (but you make your own luck in my book).

Of course the latest coatings make a difference but the optical differences are marginal. One clear difference between legacy and modern lenses is the design imperative of modern lenses to be sharp across the entire FoV. Some want this, but as pointed out here and elsewhere, it is not important to have sharp across the whole frame as the 'content' worth looking at is meant to be in the centre not the edges.

I am embarking on a project (with lots of risk) involving the repair of a K28/2. It has a busted rear element in need of replacement. I will be getting it made with new glass with the element coated with modern coatings. I might even get a few of the existing elements recoated in the process. If it works (in my favour) I will be comparing the then two copies I have of this lens. It will be interesting to see what differences emerge as a consequence of new coatings.
06-03-2016, 06:32 PM   #43
Pentaxian
noelpolar's Avatar

Join Date: Oct 2013
Location: Goolwa, SA
Posts: 3,096
QuoteOriginally posted by Wild Mark Quote
Lol. I took the punt years ago buying up the legacy stuff on the risk that it was not going to be any good. Looks like I got lucky (but you make your own luck in my book).

Of course the latest coatings make a difference but the optical differences are marginal. One clear difference between legacy and modern lenses is the design imperative of modern lenses to be sharp across the entire FoV. Some want this, but as pointed out here and elsewhere, it is not important to have sharp across the whole frame as the 'content' worth looking at is meant to be in the centre not the edges.

I am embarking on a project (with lots of risk) involving the repair of a K28/2. It has a busted rear element in need of replacement. I will be getting it made with new glass with the element coated with modern coatings. I might even get a few of the existing elements recoated in the process. If it works (in my favour) I will be comparing the then two copies I have of this lens. It will be interesting to see what differences emerge as a consequence of new coatings.
Will be interesting to hear (and see) how it goes....... also a bit about where you get this done down here...... always thought about getting some rear elements coated to reduce sensor reflections.
06-03-2016, 06:42 PM   #44
Site Supporter
Site Supporter




Join Date: Jun 2013
Location: Newcastle
Photos: Gallery | Albums
Posts: 1,571
QuoteOriginally posted by noelpolar Quote
Will be interesting to hear (and see) how it goes....... also a bit about where you get this done down here...... always thought about getting some rear elements coated to reduce sensor reflections.
Not far from you - Salisbury Heights (Jung Precision Optics)
06-03-2016, 08:25 PM - 1 Like   #45
Veteran Member
zoolander's Avatar

Join Date: Dec 2012
Location: Gold Coast
Photos: Albums
Posts: 337
QuoteOriginally posted by normhead Quote
Does anyone actually know exactly how DxO comes up with their numbers?
It is extracted from their back side !

QuoteOriginally posted by normhead Quote
The cool thing is, at Imaging Resources, you can look a the test swatches, and see exactly what they are talking about. DxO. Not so much. Given the wealth of available "check it out yourself" data at Imaging Resource, and the complete poverty of such data over at DxO, no credible person could take their claims seriously. It's sad to see someone building such a complex analysis on such shoddy data.
DXO (and Photozone) is a load of bolony. Other lens testers show different results. That DA* 55mm 1.4 is a lot better then what DXO is saying, and in fact they are over stating Canon and Nikon Lens resolution.

To me the DXO lens thingo is a web widget. If a brand new lens comes out for Pentax, they don't literally re-test it on every old Pentax camera body. If a new camera body comes out, DXO isn't going to literally re-test every single lens on that body to see the perceptual pixels. For Pentax there'd be 20-30, Canon there's maybe 80 plus, Nikon maybe 80 plus. DXO is pretending that this is what they do to get the perceptual mega pixels. They're not going to do that for every new camera and lens. They make a website widget, make it biased in favor of Canon and Nikon ........budda bing budda boom, every big shot pro photographer refers to it thinking that its valid information when its a huge stinking pile of poop.

For crying out loud, DXO lens perceptual mega pixel widget is a widget and unscientific. DXO is a joke, and I can't believe so many youtubers refer to this crappy widget - perceptual mega pixels ! Who uses this term .......nobody but DXO.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
24x36mm, bit, course, design, edge, exceptions, film, focus, full-frame, images, legacy, lens, lenses, lots, pentax, pf, price, sensor, sensors, sharpness, time
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Isn't this getting out of hand... mattt Pentax DSLR Discussion 4 03-25-2016 06:58 AM
Who designed/manufactures the 36.4 MP sensor? *Rich Pentax Full Frame 79 03-02-2016 10:43 PM
New to Pentax - Legacy glass & auto focus Senko Pentax SLR Lens Discussion 9 02-12-2016 07:15 AM
Why GoProís Success Isnít Really Isn't about the Cameras interested_observer General Photography 16 07-01-2014 05:05 PM
Sensor Stack (glass in front of sensor) and legacy vs modern lenses carrrlangas Pentax SLR Lens Discussion 8 06-24-2014 11:27 AM



All times are GMT -7. The time now is 02:27 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top