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03-13-2018, 04:32 PM - 2 Likes   #16
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@BruceBanner

As long as we’re reading historical film era lens sharpness tests, here’s Yoshihiko Takinami’s test results (and methodology) for lens resolution tests of various Pentax lenses. The results are quite similar to the K-mount Page Table. Many volunteer hours by posters on the Pentax Discuss Mailing List_Share (PDML) went into these various old tests. Be sure to read Yoshi’s Test procedure. It is more comprehensive than recent commenters give credit for.


I put a little sticker on the rear cap of my K lenses like this - K50/1.2 f/11 - rather than carrying a table in my camera bag.


Last edited by monochrome; 03-13-2018 at 07:03 PM.
03-13-2018, 04:45 PM - 3 Likes   #17
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Get to know the sweet spot for each of your lenses. Learn their quirks and qualities. Use them accordingly.
The Single In challenges are a great way of doing this, with the advantage of independent feedback from peers
03-13-2018, 05:05 PM - 1 Like   #18
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QuoteOriginally posted by monochrome Quote
@BruceBanner
I put a little sticker on the rear cap of my K lenses like this - K50/1.2 f/11
I am doing somewhat the same. No scientific test, just my own test at min & max distances then take a note on a sticker and stick it to the lens. I used to take note on a phone but find out that technology didn’t help speed up the working process but slow me down (true in many things). Simple handwriting on a sticker is the way to go.
03-13-2018, 05:11 PM - 3 Likes   #19
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QuoteOriginally posted by pakinjapan Quote
I am doing somewhat the same. No scientific test, just my own test at min & max distances then take a note on a sticker and stick it to the lens. I used to take note on a phone but find out that technology didn’t help speed up the working process but slow me down (true in many things). Simple handwriting on a sticker is the way to go.
Analog Rules. Digital . . . .

03-13-2018, 07:54 PM   #20
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QuoteOriginally posted by BruceBanner Quote
Just quickly can I ask on that chart what 'MTF50 in LW/PH' stands for?
"Modular transfer function 50% in line widths per picture height."

I'm glad you didn't ask what it means.
03-14-2018, 05:11 AM   #21
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Here's a site I find interesting. Most of the Pentax lens tested here show max resolution at f8 or better.

http://www.takinami.com/yoshihiko/photo/lens_test/pentax_28-30.html


P.S. I see Monochrome has already posted a link to this site.
03-14-2018, 05:33 AM   #22
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Interesting... Yoshiihiko tests using T-max,

The FA 50 macro test as a pretty much flat line from 4 to ƒ22 taking off at ƒ22,
The DFA 50 macro 2.8 OpticalLimits (Photozone) is nowhere near flat.

Is this a film vs Digital issue?

I wonder if it's possible to compare these metric by dividing lw/ph by 24mm.

At ƒ4 the Yoshiihiko has the lens at 98
Klaus has it at 2668/17mm= 156 lines per mm

At ƒ22 the Yoshiihiko has the lens at 98
Klaus has it at 1733/17mm= 101

Just one of those things I guess. Does Imatest test differently than whatever they used for film?

Different lenses, different testers, unknown method, discrepancies between testers suing the same lenses and software.... it's a crap shoot.

Perhaps about 110 line/mm is the most the film could resolve. That would explain the flat line on film, but much higher resolutions on digital. It doesn't matter what the lens resolves, the film can't get past 110. Where as the 16 MP sensor is resolving 152 lines/mm and shows more of a curve... just a guess.


Last edited by normhead; 03-14-2018 at 08:46 AM.
03-15-2018, 12:45 PM   #24
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The FA 31 and FA 43 lenses were tested on a K-5 camera at 16MP. This would the effective resolution of the K-1 in APS crop mode. What is not known is how the lens would perform outside those 16 MP's. Sadly, we can only guess it would be worse. That's not a big deal in most practical applications like portraiture. Landscape photographers who want edge-to-edge performance may disagree.
03-15-2018, 12:59 PM   #25
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QuoteOriginally posted by normhead Quote
Interesting... Yoshiihiko tests using T-max,

The FA 50 macro test as a pretty much flat line from 4 to ƒ22 taking off at ƒ22,
The DFA 50 macro 2.8 OpticalLimits (Photozone) is nowhere near flat.

Is this a film vs Digital issue?

I wonder if it's possible to compare these metric by dividing lw/ph by 24mm.

At ƒ4 the Yoshiihiko has the lens at 98
Klaus has it at 2668/17mm= 156 lines per mm

At ƒ22 the Yoshiihiko has the lens at 98
Klaus has it at 1733/17mm= 101

Just one of those things I guess. Does Imatest test differently than whatever they used for film?

Different lenses, different testers, unknown method, discrepancies between testers suing the same lenses and software.... it's a crap shoot.

Perhaps about 110 line/mm is the most the film could resolve. That would explain the flat line on film, but much higher resolutions on digital. It doesn't matter what the lens resolves, the film can't get past 110. Where as the 16 MP sensor is resolving 152 lines/mm and shows more of a curve... just a guess.
I don’t think the individual test results matter. What matters - where we have multiple testing regimens on the same lens (or formula like the FA/DFA50/2.8 Macro) - is that the highest resolving lens gives that result consistently, then 2, 3 and so on. There are too many variables for any single test Index to be meaningful.

Last edited by monochrome; 03-15-2018 at 01:10 PM.
03-15-2018, 01:14 PM   #26
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QuoteOriginally posted by angerdan Quote
There are other test sites with resolution measurements of film era introduced AF lenses.
Most lenses reach their maximum resolution at 2-3 steps stopped down.
My impression has always been most lenses achieve maximum resolution at f/8 - f/11 rather than f/4 - f/5.6. What structural factors skew the lenstip tests to f/5.6? Is this test bias consistent across other known outstanding lenses?

The lenstip tests comments are biased toward ranking sharpness across the frame. Jun Hirakawa wrote he intentionally designed the 43 and 77 for edge softness (or intentionally did not correct it). That’s part of the charm of the lenses. Consequently the raw test comments are not particularly useful ranking film era lenses to a false value standard.

Last edited by monochrome; 03-15-2018 at 01:35 PM.
03-15-2018, 02:29 PM   #28
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At least photozone doesn’t use words (for the 43, referring to edge resolution) such as ‘not at all useful.’

[EDIT] See robbiec’s coment next re: testing on APSc sensors causing drop off at f/8+ (and not revealing true corner resolution). That was what I was asking for when I questioned whether there might be something structural in the lenstip tests causing the deviation from the older film tests. Lenstip and Photozone were done on APSc sensors (K10, K20 and K-5)

Maybe that’s why I was taught in HS to just stay at f/5.6

Last edited by monochrome; 03-15-2018 at 03:59 PM.
03-15-2018, 03:48 PM - 1 Like   #29
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I second Sandy's suggestion in getting to know each of your lens by taking it out and trialling it in different scenarios. Most of the more recent Pentax lens tests have been on APS-C format and will be hit by diffraction sooner than FF so lower resolution at f/8-f/11 than would be possible if tested on a K-1, corner strengths will also test very differently in some cases. Lens tests while valuable should be seen as a guide rather than gospel. At the end of the day, it is up to you to recognise and play to a lens strengths to return the image you want and or deserve.

Also sensors play a role as well strangely enough, the DA35/2.8 Macro is sublime on the K20D perhaps due to the fact that it was developed at around the same time as Pentax was using Samsung as its sensor supplier and the development teams swapped notes. The FA43/1.9 behaves quite differently in the corners using the Samsung (K20D) vs the Sony (K-5). So to have a valid test database, all lenses would need to be tested as a minimum on a K-P and K-1 to have a current sensor type and size to cross reference. Sample variation of lens will also play a role so a minimum of 3 per lens type and pretty soon you will have a fairly major job on your hands. Next thing is where do you stop? Do you start with current models? DFAs, DAs, FAs? and then pick some of the more interesting lens in each subsequent series? A series for example would have the 50/1.2, 85/1.4 & 135/1.8 as stand outs? Or take the 50/1.4 and test every model from first to last and map out the changes in coatings? Anyone know where to find 3 x FA*200/4 Macros?

Last edited by robbiec; 03-15-2018 at 04:27 PM.
03-15-2018, 04:12 PM   #30
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QuoteOriginally posted by robbiec Quote
At the end of the day, it is up to you to recognise and play to a lens strengths to return the image you want and or deserve.
Yes, once you have done two things:

(1). Bought the lens (or rented it for a longish time),
and
(2). Used the lens for long enough, in enough different situations, to "recognise ... [the] lens' strengths".

Good tests (what this thread is looking for) come in earlier,
when you're trying to decide whether it's worth your while to do (1) and (2).

Unfortunately, most of the tests out there have their flaws and gaps,
so they don't really help you that much.
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