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03-30-2020, 02:40 AM   #31
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QuoteOriginally posted by BigMackCam Quote
but why
Default detail/noise/file size compromises. Anyone can push details with sharpening and increase noise. I need to add sharpening to most of my K1 files, at the final stage of image processing, which tends to increase noise.

03-30-2020, 03:00 AM - 1 Like   #32
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QuoteOriginally posted by BigMackCam Quote
Yes, but most people have enquiring minds. We don't just want to know if one combo is better than another, but why - especially since the contributing factors (lens design, sensor resolution etc.) would appear to be so similar. Answering this might not have any practical benefit to us as photographers, but it appeals to our thirst for knowledge.
There's also a discrepancy between numerical tests results and real life results and yes, I merely want to know why.
Or, it's just me pretending my D FA* 50mm f/1.4 doesn't lose in terms of resolution to some Canikony kit lens
03-30-2020, 03:01 AM   #33
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QuoteOriginally posted by biz-engineer Quote
Default detail/noise/file size compromises. Anyone can push details with sharpening and increase noise. I need to add sharpening to most of my K1 files, at the final stage of image processing, which tends to increase noise.
That's certainly possible, but only an assumption. If test shots were captured as raw files at base ISO, then examined in the same software - which should apply the same default sharpening etc. (ideally, it should be manually set to zero for these purposes) - then I think it unlikely.

One person using a common platform to test both lenses in exactly the same conditions, assessing the raw files with the same software, using the same settings, would go some way in removing numerous variables that might be impacting the results...

Last edited by BigMackCam; 03-30-2020 at 03:07 AM.
03-30-2020, 03:01 AM - 1 Like   #34
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QuoteOriginally posted by biz-engineer Quote
Default detail/noise/file size compromises. Anyone can push details with sharpening and increase noise. I need to add sharpening to most of my K1 files, at the final stage of image processing, which tends to increase noise.
The evidence we have (photonstophotos) suggest there is no raw noise reduction at low iso with any recent Pentax model. Why are you insisting on this line? Am I misunderstanding what you are trying to say?

My thinking was the same as Digitalis that the coatings would help fringing as well as other contrast. I agree that the Cameraville has slightly dubious and Pentax tilted reviews but his comparisons of the hd vs smc fa 35 amongst others show increased pf with the new coatings. It's hard to explain away by other means. Pentax even has the same product name in exif for the two lenses so they are most likely identical optically except for coating. Perhaps even the old smc was more fringe revealing than competing coatings?

03-30-2020, 03:16 AM   #35
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What could that be?

- lens copy variation
- difference in choice of micro-lenses on sensor
- mis-calibrated AF, although this should show less impact at smaller apertures
- data processing prior to RAW file making in camera
- shutter shock, should check shutter speeds used for lens evaluation

Seeing a trend for more than one Pentax lens model (15-30, 24-70, DFA*50 and now DFA70-210), could hint at K1 camera maximum possible sharpness slightly inferior to other cameras.

---------- Post added 30-03-20 at 12:22 ----------

QuoteOriginally posted by house Quote
The evidence we have (photonstophotos) suggest there is no raw noise reduction at low iso with any recent Pentax model.
How did you come to that conclusion?
03-30-2020, 03:33 AM   #36
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QuoteOriginally posted by biz-engineer Quote
What could that be?

- lens copy variation
- difference in choice of micro-lenses on sensor
- mis-calibrated AF, although this should show less impact at smaller apertures
- data processing prior to RAW file making in camera
- shutter shock, should check shutter speeds used for lens evaluation

Seeing a trend for more than one Pentax lens model (15-30, 24-70, DFA*50 and now DFA70-210), could hint at K1 camera maximum possible sharpness slightly inferior to other cameras.

---------- Post added 30-03-20 at 12:22 ----------


How did you come to that conclusion?
All known noise reduction can be detected by analysing the raw files since the algorithms leave a "pattern" in the data. This is one if the things the site photonstophotos investigates.
03-30-2020, 03:35 AM   #37
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QuoteOriginally posted by Kunzite Quote
IMO this isn't something we can attribute to sample variation; it's too uniform. Although in case of the 70-210, the resolution drop at the longer end could be sample variation, or a slight misfocus.
I have a different perspective, having tested lenses on a calibrated optics bench for years (regrettably, it's currently mothballed in storage for the moment) Canon,Nikon,Olympus,Carl Zeiss,Minolta(R.I.P),Leica,Konica,Pentax,Voigtlander,Schneider...etc so on an so forth. All great lens makers: There is more to a lens than just its optical performance (which some people place an inordinate amount of significance upon). Remember the sigma 18-35mm f/1.8? optically a brilliant lens, one of the sharpest zoom lenses I have ever worked with..such a shame the AF was plagued with spurious issues and not just on Pentax cameras* Canon, Nikon both had a lot of issues and their cameras have AF modules far more advanced than anything Pentax has. It is wonderful having a class leading High resolution lens, too bad if it has inaccurate AF....and weird bokeh artifacts.

QuoteOriginally posted by Kunzite Quote
MTF50 and no, Pentax doesn't reach the same numbers
MTF@50% measurement can be easily botched even on a calibrated on a Optics bench. Remember the error margin of 20%.

*Sigma SA mount photographers have been curiously quiet about AF performance with the 18-35mm f/1.8, which is strange considering Sigma cameras allegedly have AF systems with all the sophistication of the Pentax K10D.

03-30-2020, 03:46 AM   #38
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QuoteOriginally posted by biz-engineer Quote
Seeing a trend for more than one Pentax lens model (15-30, 24-70, DFA*50 and now DFA70-210), could hint at K1 camera maximum possible sharpness slightly inferior to other cameras.
Testing both the Pentax and other-brand equivalent lenses on a common platform would remove that variable - indeed, anything to do with the camera - from the process. Then, if the results still differ considerably, we'd know there's a difference in the lenses. If, however, the results are more or less equivalent, we'd know it's the camera bodies that have previously caused the difference.

Last edited by BigMackCam; 03-30-2020 at 04:15 AM.
03-30-2020, 04:44 AM   #39
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QuoteOriginally posted by BigMackCam Quote
Testing both the Pentax and other-brand equivalent lenses on a common platform would remove that variable - indeed, anything to do with the camera - from the process. Then, if the results still differ considerably, we'd know there's a difference in the lenses. If, however, the results are more or less equivalent, we'd know it's the camera bodies that have previously caused the difference.
Except for the glass stack thickness in front of the sensor, which isn't correct for all lenses:
Lens Rentals | Blog
03-30-2020, 04:46 AM   #40
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QuoteOriginally posted by Digitalis Quote
MTF@50% measurement can be easily botched even on a calibrated on a Optics bench. Remember the error margin of 20%.
Of course it can. But every single time?
03-30-2020, 05:50 AM   #41
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QuoteOriginally posted by Kunzite Quote
Except for the glass stack thickness in front of the sensor, which isn't correct for all lenses:
Lens Rentals | Blog
It should be a valid approach for the 70-210/4, though. I get that sensor-stack thickness could impact test results on wider angle lenses, but on a tele zoom I'd have thought it would have negligible impact.

On a related note, I seriously doubt that Tamron fine tunes its lenses for the different sensor stack thickness on Canon and Nikon DSLRs - or does it? I'd have thought the glass is exactly the same; only the mount and firmware being different...
03-30-2020, 05:51 AM   #42
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QuoteQuote:
MTF@50% measurement can be easily botched even on a calibrated on a Optics bench. Remember the error margin of 20%.
The fact that there can be a 20% margin of error just means no results can be taken as definitive. Unless, you can differentiate between the good tests and the ones that are off 20% all results will be suspect.
03-30-2020, 06:15 AM   #43
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I would say, from the above, that two things are clear, or getting clearer:

1) Pentax lens coatings might account for increased CA - this is somethng the designers must be aware of and regard as a worthwhile trade-off for the benefits.

2) Pentax (and we know this) aim to produce a particular look in images taken with their lenses, and again it's a question of trade-offs - the classic examples are the FA Ltds where corner softness and CA are traded against 3D pop and lovely bokeh. What we (I) don't know is hat would be lost of they went purely for results that looked good on MTF and other tests, and what they might have done to the 70-210 to reduce measured resolution in that, althogh i's worth noting that in the ephotozine test examples the evenness across the frame is generally higher in the Pentax, and that's something that they have been aiming at in recent releases. I don't personally think in that instance that the camera makes much difference - but I'm alays willing to be proved wrong.
03-30-2020, 06:23 AM - 1 Like   #44
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QuoteOriginally posted by normhead Quote
The fact that there can be a 20% margin of error just means no results can be taken as definitive.
This is pretty much my point, every test published from a single sample is just one data point. Not definitive, unless multiple lenses have been tested on exactly the same testing rig.

Also many lens testers to not mention the distance from the resolution target the sample was taken. Many long zoom lenses do not resolve well at closer focus distances case in point:


100% crops - One of these images was taken from the excellent Sigma 100-300mm f/4 Zoom - compared to a dedicated macro 180mm prime. The differences are visible, but in a 11"X14" print who would notice?

Also, Long lenses are a PITA to test on optical benches due to the distances needed to achieve true infinity focus*, and if the lens extends at all at that setting** then there are stability and alignment issues that need to be taken into account.

*Most benches only extend about 300mm, fortunately mine goes out to 1200mm because it was actually designed for testing LF lenses. The problem is it needs an absolutely immovable platform to deliver accurate and repeatable results, there can be no vibrations.
** depending on the design of the bench Zoom creep/focus shifts can be rather problematic.

---------- Post added 2020-03-31 at 12:44 AM ----------

QuoteOriginally posted by Kunzite Quote
Of course it can. But every single time?
Show me the data.


QuoteOriginally posted by BigMackCam Quote
I get that sensor-stack thickness could impact test results on wider angle lenses, but on a tele zoom I'd have thought it would have negligible impact.
It definitely does affect wide angle lenses, telephoto lenses can be affected in more subtle ways but the sensor stack the telecentricity of the lenses optical design matters considerably.

Last edited by Digitalis; 03-30-2020 at 06:43 AM.
03-30-2020, 09:01 AM   #45
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QuoteOriginally posted by Digitalis Quote
Show me the data.
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)...
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