[house]

Pentax seems to do well resolution and IQ wise in the various studio scenes.

[normhead]

See ephotozine's latest Pentax reviews, those for which they're giving numbers rather than "excellent/good/etc" - no lens will get close to 3500lw/ph.
Yet Nikon's best lenses can approach 4000lw/ph, on a D810. Even a zoom like the 70-300 will reach 3500 (@f11)...

"Lenses for the way people take pictures, not for the test charts."

Pentax wasn't even competing on the sphere of test chart scores. They tested their lenses on based on whether or not people like the enlarged images. It's not all that surprising that Pentax doesn't compete in that area given their design philosophy.

No one has ever confirmed with images that more lw/ph is correlated to more enjoyable images.

My favourite image from the summer isn't all that sharp....


yet there is is up on my wall printed 24x16.


It gets really annoying, people going on and on about lw/ph as if it were the sole definition of image quality.

It gets really really annoying with titles like this one. "Pentax lenses measured worse?"

If you isolate a factor that is perhaps 1/4 of IQ, but is focused on because a machine can measure it, then you dismiss the opinions of actual people and claim the machine knows best, that is truly irritating.

It would seem to be that the research of Pentax engineers has shown that super high resolution and the kind of rendering people prefer in field cameras are not possible in the same lens. And we do have evidence that Pentax did this kind of research.

I have to say, if you can find my posts from 10 years ago, you can find Rondec and others telling me MTF was a small part of the equation.
It's taken me 10 years but I finally get it.

I guess everyone has to work through this at their own speed.

SO for you who think different.

I defy you to find even one double blind test of enlarged photos that shows a correlation between lw/ph and how much people enjoy the images. It's just not a factor taken on its own.

It's painful watching people get conned by this nonsense. Now I know how Rondec felt 10 years ago.

MTF... it doesn't mean what you think it does.

[house]

The pentax jp site with the various special content, testimonials etc give some idea of Pentax priorites. They tend to speak of optics in unusual terms.

[normhead]

The pentax jp site with the various special content, testimonials etc give some idea of Pentax priorites. They tend to speak of optics in unusual terms.

As far as I can tell Pentax tends to focus on appropriate contrast. High MTF lenses tend to be high contrast lenses.
But high contrast accentuates noise in out of focus areas.
Both high contrast and high MTF numbers tend mean transitions are not as smooth.
The extra sharpening in in-camera processing also tends to add noise (and MTF performance.)

So your choice is
High MTF numbers with poor transitions, messy out of focus areas, noise in out of focus areas or softer lenses that render better.
I'm sure all companies deal wth these trade-offs.

Pentax seems to have adopted the MTF isn't worth what you give up to get it philosophy. Although with new releases they seem to be doing a lot more testing to produce lenses that have both higher MTF numbers snd still keep the Pentax focus on user appreciation of the end product.
Looking at the DFA* 50 1.4, I'd say they have a pretty good idea what they're doing.

And given that I'm likely to use these lenses for 20 years, it doesn't bother me at all that it takes them longer to get them out than people think it should.

[c.a.m]

No one has ever confirmed with images that more lw/ph is correlated to more enjoyable images.

While I don't have a credible answer for the questions posed in the first post, I think the above point is important.

Consider the various elements in the chain from the subject to the final display of a finished image. The photographer controls many of these elements. If a photographer is keen to improve their output, I would suggest that several key areas are more important than absolute lens sharpness.

• The Subject: location, subject and scene selection, lighting, composition
• The Camera System: focus control, signal processing, lens AF calibration, selected exposure settings
• Optical path: lens, filters, sensor
• Camera and sensor stability: shake reduction, including hand-holding technique and tripod system
• Colour management: sensor calibration, monitor calibration, white balance, printer profile
• Image processing: In-camera parameters, RAW developer software, post-processing technique, 'finishing touches'
• The Print: printer, media selection, ink, dimensions, frame and mounting, ambient lighting

"Some photographic issues seem to defy precise explanation. Visual impressions are difficult to assess in verbal form, and we grope for words that encompass the qualities of the medium. One such elusive concept is sharpness. It is worthwhile in this volume to consider sharpness and related concepts in physical terms, but in discussing mechanical or optical issues we must not lose sight of the much greater importance of image content -- emotional, aesthetic, or literal. I believe there is nothing more disturbing than a sharp image of a fuzzy concept!" - Ansel Adams; The Camera; Little, Brown and Company; 2003; p. 73

- Craig

[Kunzite]

Pentax seems to do well resolution and IQ wise in the various studio scenes.

And in the real life.

[Kunzite]

"Lenses for the way people take pictures, not for the test charts."

Pentax wasn't even competing on the sphere of test chart scores. They tested their lenses on based on whether or not people like the enlarged images. It's not all that surprising that Pentax doesn't compete in that area given their design philosophy.

The pentax jp site with the various special content, testimonials etc give some idea of Pentax priorites. They tend to speak of optics in unusual terms.

I know you folks are trying to be helpful and I truly appreciate it... but please, pay attention to the question when answering.
"Same" lens (under Pentax and some other brand), different test results on Pentax vs. e.g. Nikon. This cannot be about lens design philosophies.

And you won't see me claiming this is important. OK, it is somewhat important for brand perception but that's it.

[normhead]

I know you folks are trying to be helpful and I truly appreciate it... but please, pay attention to the question when answering.
"Same" lens (under Pentax and some other brand), different test results on Pentax vs. e.g. Nikon. This cannot be about lens design philosophies.

And you won't see me claiming this is important. OK, it is somewhat important for brand perception but that's it.

Because the same design philosophies apply to their cameras.
Look at the folks who were whining and crying about the loss of resolution when the accelerator chip was introduced. Most people totally don't get it.

It's not about charts, it's about the final image... period.

Test chart scores are only meaningful for those whose photographic interest is confined to reproducing test charts. No one else. They are
a very specific photographic niche who's relevance to anything has never been established.

My favourite lenses are not my sharpest MTF lenses.

Example my DFA 28-105 doesn't even touch the resolution of the Sigma 70 on my K-3 but my really picky wife loves it. It's Ephotozine test chart.


When you can explain why everyone who uses it loves this lens despite it's apparently poor MTF, I'll be happy to give you a listen.
That's real life. I have no idea what the heck that test chart means
I have plenty of images to show it has little to do with IQ.

[BigMackCam]

I know you folks are trying to be helpful and I truly appreciate it... but please, pay attention to the question when answering.
"Same" lens (under Pentax and some other brand), different test results on Pentax vs. e.g. Nikon. This cannot be about lens design philosophies.

And you won't see me claiming this is important. OK, it is somewhat important for brand perception but that's it.

Because the same design philosophies apply to their cameras.
Look at the folks who were whining and crying about the loss of resolution when the accelerator chip was introduced. Most people totally don't get it.

It's not about charts, it's about the final image... period.

Test chart scores are really meaningful for those whose photographic interest is confined to reproducing test charts. No one else. They are
a very specific photographic niche who's relevance to anything has never been established.

I do get where Alex is coming from here, though. He's not a test chart junkie... Nor am I... MTF numbers really don't bother me, I'm all about the rendering and, as you say, the final image. But in future, when someone levels criticism at Pentax for the 70-210/4 (or any other lens) being less sharp in tests than its Tamron cousin - which, so far as we know (though never 100% confirmed, as I recall), is optically identical save for the coatings - it would be nice to know why that's the case and have an explanation for it. Not a defence... just an explanation...

[house]

People are going overboard with these comments. Of course mtf's are one of the most important metrics for judging lens design. Both for designers and consumers. Just because of a perceived over emphasis on mtf doesn't mean it makes any sense to start running the other way suggesting it's somehow bad or not very important at all.

Even "are bure boke" photographers want sharp lenses.

[normhead]

Not a defence... just an explanation...

The explanation would be Pentax values image quality as defined by humans rather than test charts interpreted by machines. Or is that a defence? What's the difference?

The reason for a defence is the original proposition was in some way offensive.

What's offensive about the question?

The word "worse". That word contains a value judgement.
If you said why are Pentax MTF scores are different.... no problem.

The first thing that has to be addressed in this thread is that higher MTF and other test scores are better. Using the term "worse" in the title complicates that enormously. You're starting from a position of bias, and then have to fight your way uphill.

So I seriously don't understand what you're recommending, especially since you've added more value judgments with "defence" and "explanation" as if one can't be part of the other.
The thread title is offensive. How do you deal with that without a "defence?".

[Serkevan]

Potentially very dumb comment: what about the colour profile and software? I know for a fact that trying to use any of the "standard" Pentax presets in Lightroom leads to horribly butchered details, when compared to AdobeRGB. The Canon profiles are SO much better for example.


Now I have to do JPEG conversions from RT and DT to compare with LR's demosaicing... I have the impression the RT images look more detailed.



Also, sharpness is for the bourgeoisie.

[c.a.m]

I know you folks are trying to be helpful and I truly appreciate it... but please, pay attention to the question when answering."Same" lens (under Pentax and some other brand), different test results on Pentax vs. e.g. Nikon. This cannot be about lens design philosophies.

The ePhotozine review and test methodology (as of January 2019) is described at: Lens Reviews - Find Out How We Review Lenses | ePHOTOzine

In particular, they provide the following insight into their technique:

"*LW/PH = Line Widths / Picture Height. To quickly summarise, LW/PH shows the sharpness of a lens, and the higher the figure, the better sharpness. In our charts we show the sharpness in the centre of a lens and at the edges, at various apertures. The LW/PH figures are now shown in the graphs to help you more clearly compare sharpness between lenses reviewed from late 2015 onwards, and descriptions are used in the text, so that you can compare with reviews made before this."

and (my emphasis):

"Technical tests use a very large Imatest slanted-type test target, which has been mounted on what is effectively a small portable wall. Lenses up to around 200mm can be accommodated in the studio, after which we have to move outside. When outside, a dry, bright overcast time is chosen to make lighting as consistent as possible. Any focal length can be tackled in this way, the biggest challenge in the winter being snatching a suitable break in the weather.

The camera/lens combination is mounted securely on a Manfrotto 055 tripod with Manfrotto 115 three-way head and aligned very carefully on the target. All lens corrections in camera are switched off and the highest resolution possible chosen. The base ISO is used, often ISO 100, but sometimes ISO 200, depending on camera. No in camera sharpening is allowed. The self-timer is used to make the exposures, to avoid all possibility of shake, but any in-camera or in-lens shake reduction is switched off.

AF lenses are focused using Live View and for prime lenses, three runs are recorded, shooting at every aperture. For MF lenses extreme care is taken to focus accurately using whatever aids the camera offers, plus magnifiers on the screen if necessary. MF lenses are given at least four runs, and up to seven might be used if a lens proves tricky to focus accurately."

I assume that out-of-camera JPEG images are used for the Imatest analysis. The ePhotozine articles do not appear to indicate exposure parameters or specific test conditions such as lighting or target distance, so it would be difficult to reproduce their results or reveal any deficiencies or weaknesses in the methodology.

I can think of several issues that could arise:

• Shutter shock
• Inaccurate autofocus using CDAF. They take only 3 or 4 shots at each setting, but we have seen from the data at Lens Rentals, for example, that focus precision and accuracy can vary considerably across shots.
• Pentax default sharpening. Other cameras may provide more intense sharpening for OOC JPEG images as a default.

Note that the Imatest site indicates some hints for data reliability in comparing sharpness of several digital cameras: Sharpness Comparisons for several digital cameras | imatest

Note the item related to RAW conversion and sharpness setting (my emphasis below).


"These measurements are limited to

• One lens. For DSLRs this is usually one of the sharpest available, such as the 50mm f/1.4 prime (non-zoom).
• One focal length. Sharpness is a strong function of focal length for zoom lenses. The sites aren’t very consistent in their choice of focal length for zooms in compact digital cameras; long, short or intermediate focal lengths may be chosen.
• One aperture, typically around the optimum: f/8-f/11 for DSLRs; f/4-f/5.6 for compact digital cameras.
• One ISO speed, which strongly affects noise and dynamic range, but has little effect on sharpness.
• One sharpening radius, typically 2, used in standardized sharpening calculations, indicated by (corr.) and red columns.
• One or two vertical edges (in most cases), resulting in horizontal MTF measurements. Sometimes vertical MTF (from horizontal edges) is different.
• One RAW converter (usually the JPEG converter built into the camera) with one setting, usually the default. The choice of converter and sharpness setting has a strong effect on sharpness measurements.
• Gamma assumed to be 0.5, typical for digital cameras. A 10% gamma error results in about a 2.5% MTF50 error. Though gamma error is rarely severe, gamma should be measured with Stepchart or Colorcheck for greatest accuracy.
• Exposure and lighting are not always optimum. If the image is too dim or bright there may be some clipping on data (where it goes pure black or white), which reduces the accuracy of the sharpness measurement. Lighting may not be as even as it should be."

- Craig

[Kunzite]

Because the same design philosophies apply to their cameras.
Look at the folks who were whining and crying about the loss of resolution when the accelerator chip was introduced. Most people totally don't get it.

It's not about charts, it's about the final image... period.

Norm, I paid for the upgrade after pixel peeping until my eyes bled (and deciding there's no detail loss to talk about). I totally get it. I'm also a happy owner of the D FA 28-105, and on APS-C I used the DA Limiteds.

But this is about charts... not photography, but this thread and my question.

[normhead]

Just because of a perceived over emphasis on mtf doesn't mean it makes any sense to start running the other way suggesting it's somehow bad or not very important at all.

I like my DFA 28-105, I don't like my DA 35 2.4. One is a test chart champion, the other is a test chart failure. How do you reconcile that?