Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-19-2022, 09:03 AM   #1
Site Supporter
Site Supporter




Join Date: Jun 2020
Posts: 77
Why no real lens measurements at pentaxforums.com

I see lots of lens reviews on the site, but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts.

isn't it possible to determine the lines per inch that the full size K-1 and APS-C K-3 sensors can achieve, then measure every lens of some kind of lens bench, and determine the real resolving power at all the different combinations of aperture and position across the image plane.

05-19-2022, 09:09 AM - 10 Likes   #2
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 22,733
The articles are written by various people with different capabilities. Additionally test methodology is complicated. Read lens rentals blog to get an idea of how that group slowly went down that rabbit hole. Copies vary - most reviewers rarely have access to multiple copies to see what level of variance exists.

Lastly - numbers on the page in these tests don’t define many of the actual factors in what makes a good lens. Bokeh for example has no objective metric. Sharpness and contrast are related and hard to quantify abstracted from each other.
05-19-2022, 09:17 AM   #3
Pentaxian




Join Date: May 2015
Photos: Albums
Posts: 2,841
QuoteOriginally posted by dkpentax Quote
I see lots of lens reviews on the site, but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts.

isn't it possible to determine the lines per inch that the full size K-1 and APS-C K-3 sensors can achieve, then measure every lens of some kind of lens bench, and determine the real resolving power at all the different combinations of aperture and position across the image plane.
Would be great, but that's a massive amount of work and difficult to make consistent set ups.
05-19-2022, 09:31 AM - 7 Likes   #4
Site Supporter
Site Supporter
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 17,136
QuoteOriginally posted by dkpentax Quote
I see lots of lens reviews on the site, but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts.

isn't it possible to determine the lines per inch that the full size K-1 and APS-C K-3 sensors can achieve, then measure every lens of some kind of lens bench, and determine the real resolving power at all the different combinations of aperture and position across the image plane.
Does it really matter? For me, what matters is a) the result, and b) the performance of a system that I can buy.

A test bench with the absolute capabilities of measuring the resolving power, at different subject distances and with sensors that may not be able to actually produce a printable image, only a table of results (perhaps as a guess of what a report might look like) does not go in the field and take images. So who really cares.? Not me.

05-19-2022, 09:48 AM - 1 Like   #5
Site Supporter
Site Supporter




Join Date: Feb 2010
Location: Cincinnati
Photos: Gallery
Posts: 40
Have you seen this?

Pentax K Lens Tests
05-19-2022, 09:58 AM - 1 Like   #6
amateur dirt farmer
Loyal Site Supporter
pepperberry farm's Avatar

Join Date: Dec 2014
Location: probably out in a field somewhere...
Photos: Gallery | Albums
Posts: 32,480
QuoteOriginally posted by Lowell Goudge Quote
Does it really matter? For me, what matters is a) the result, and b) the performance of a system that I can buy.

A test bench with the absolute capabilities of measuring the resolving power, at different subject distances and with sensors that may not be able to actually produce a printable image, only a table of results (perhaps as a guess of what a report might look like) does not go in the field and take images. So who really cares.? Not me.

bingo - those test results aren't going to show me anything about images taken with the lens look, what is the bokeh like, or anything else subjective....
05-19-2022, 11:06 AM   #7
Forum Member




Join Date: Sep 2014
Location: Southwestern Ontario
Posts: 88
Where sharpness is concerned, it's fairly easy to sort the wheat from the chaff. But to measure the sharpness of high-end lenses, which are just about all very sharp to begin with, and obtain reliable results that will withstand scrutiny, really requires a permanent setup, a skilled tester, and ideally multiple copies of the lenses (as UncleVanya alluded to). Even then, I question whether results obtained months apart and for different lenses would be trustworthy.

I restore vintage amps and receivers. After the restoration, I measure distortion and frequency response, but only to ensure the equipment meets or exceeds the original specifications, not for comparing one against the other. I have some idea of what is required to do the latter, and I definitely do not want to go there.

05-19-2022, 11:50 AM - 3 Likes   #8
Loyal Site Supporter
Loyal Site Supporter
BigMackCam's Avatar

Join Date: Mar 2010
Location: North-East of England
Posts: 18,509
QuoteOriginally posted by dkpentax Quote
I see lots of lens reviews on the site, but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts.

isn't it possible to determine the lines per inch that the full size K-1 and APS-C K-3 sensors can achieve, then measure every lens of some kind of lens bench, and determine the real resolving power at all the different combinations of aperture and position across the image plane.
It's possible, sure, but it's a lot of work even just for one lens, never mind the hundreds listed - and since PentaxForums is a privately-owned-and-run user community, not a profit-driven commercial venture, I can't imagine who here would be prepared - and equipped - to carry out that work for philanthropic motives alone...
05-19-2022, 11:59 AM - 7 Likes   #9
Loyal Site Supporter
Loyal Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 5,581
QuoteOriginally posted by dkpentax Quote
but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts
Perhaps Pentax users are less concerned with how "sharp" lenses are, and more concerned with making a good image.
05-19-2022, 12:05 PM - 1 Like   #10
Site Supporter
Site Supporter
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 6,027
I think it tells you something that the manufacturers don't usually provide that information, and they are in the best position to provide it.

You can test your own lenses to learn three things. One, testing is hard to get right. Two, the tests can expose differences that won't be too relevant in photos. But three, you only test your own lenses so copy variation doesn't matter. If you have multiple copies and one is bad, use the good ones.
05-19-2022, 12:13 PM - 3 Likes   #11
Site Supporter
Site Supporter




Join Date: Jan 2013
Location: Hampshire, UK
Posts: 1,477
Maybe it is. Others have suggested reasons why it isn't.

When I (re-) started photography I did find myself paying close attention to lens test data, but over time my view changed. Personally, I think the approach taken by Pentaxforums' detailed reviews are about right. Yes we can't compare with other manufacturer's lenses, but across the Pentax range the test results here do give a helpful idea what to expect. From the tests I can glean a good idea how a lens will handle as well as its resolution qualities. Back this up with users' reports elsewhere and I feel I have enough, eg the HD Pentax-D FA* 50mm F1.4 is sharp across the frame from wide to narrow aperture (as you would expect from a modern, well corrected, but heavy lens), however the SMC Pentax-FA 50mm F1.4 is (very) poor wide open. But here's the thing, for me, at f5.6/f8 for portraits its fine - small & light, and in no way threatening to the subject as a big lens can be. This sort of info comes across perfectly clearly in the detailed tests here.

A lot of this stuff is just subjective. Almost without exception modern lenses are beyond what most photographers "require" to produce a first class photo. An excellent/engaging/memorable photo is is so much more than resolution, in my view. It took me far to long to come to this conclusion. Others will, quite reasonably, have their own view on their own priorities of course...
05-19-2022, 12:59 PM - 1 Like   #12
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 1,785
A good deal of equipment and some technical support is required to do this type of work and then there are a limited number of Pentax lenses to which the effort can be applied. Once all the available lenses are tested, the equipment sits. It requires more than a camera to do these tests since a good number of lenses have capabilities beyond even the best, so the equipment has to be fairly specialized (and $$). Popular Photography magazine did this type of thing but they worked across a wide range of lenses and new lenses were coming out almost every week, but now the situation has changed.

I've found as others have mentioned above, that based on the recommendations of others, quality lenses and the dogs can be identified. It would be interesting to see the kind of information you're talking about, but nowadays I'm less motivated to dig into everything in that much detail. Once a lens gets a good reputation, I simply see if I have something comparable and then if not, start taking my lens buying resisting treatments until I cave in.
05-19-2022, 01:07 PM - 4 Likes   #13
Site Supporter
Site Supporter
MossyRocks's Avatar

Join Date: Nov 2017
Location: Minnesota
Photos: Gallery | Albums
Posts: 2,618
When I really got into photography I found myself really caring about absolute resolution and sharpness. What I found was that for the most part it wasn't the lenses that were the limiting facto in the quality of the shots but that I was. Poor composition, a mess for a subject, not really understanding how the sensor sees light and dark compared to how your mind sees things in real life. Now instead of chasing the absolutely sharpest image (probably the least important aspect of a final picture) and trying to find optics that can do that I focus on what made me notice the thing I'm photographing. I slow down, take time to compose the image, think how I want it to look, and then take the picture. The only 2 areas of photography where I really care about things that might be shown on a test chart is when doing macro or astro photography. With macro I will just stop things down to f/8 with the D FA 100/2.8 WR Macro and use a big heavy tripod, 2s timer and remote release as that solves the sharpness problem and if I want more DoF then I do a big focus stack. With astro I want a fast lens that gets rid of any coma fast and doesn't purple fringe most of which really don't show on test charts that well but a test chart can provide some good guesses. A better question is a lens sharp enough and in almost all cases the answer is yes unless the lens really is a dog or is a defective one.

My 3 favorite daytime lenses to use are the 77ltd, A 50/1.2, and Sigma 300/4 APO Tele macro with the D FA 100/2.8 WR Macro seeing frequent use. The 77, 50, and 100 I love how they render textures and with the 300 I love the close focusing ability and that the background can really get smooshed into nothingness. The A 50/1.2 also can produce some wonderful soft ephemeral feel shots when in the f/1.2-1.4 range. What is interesting is I like my Series 1 Vivitar 135/2.3 for daytime shooting as I like the rendering there more than the Samyang/Rokinon 135/2 UMC but the Vivitar is a dog for astro but the Samyang/Rokinon is fantastic for astro.

For astrophotography things like the amount of vignetting, purple fringing, star bloat, and coma matter and there I will do rigorous tests but there it is specifically looking for those things and where they go away or become not annoying. This involves setting a lens up on the equatorial with a proper polar alignment, getting a perfect infinity focus with a bahtinov mask, and then shooting a lens at all f-stops up to about f/11 while having it pointed at a bright star. However here I am testing a lens not against a synthetic test chart but instead testing a lens for how I would actually use it when shooting the night sky. So it is more like creating sample images so that I know where a lens wants to be run and less figuring out how many pixels across Sirius appears in the frame (what one would get if looking for test chart numbers).
05-19-2022, 01:22 PM   #14
Pentaxian
AfterPentax Mark II's Avatar

Join Date: Mar 2021
Posts: 852
QuoteOriginally posted by dkpentax Quote
I see lots of lens reviews on the site, but why aren't there any real lens measurements for any lenses. im interested in how sharp lenses are, not vague pictures of test charts.

isn't it possible to determine the lines per inch that the full size K-1 and APS-C K-3 sensors can achieve, then measure every lens of some kind of lens bench, and determine the real resolving power at all the different combinations of aperture and position across the image plane.
dkpentax, you describe clearly what you want, from others. Why not start these kind of measurements yourself. I love to see the outcome. Personally I just look at the pictures if have taken. Technically you can have the best lens on earth with dito camera, but do you like the outcome? That is what matters. What about the best lens on earth and the dito camera and a photographer who is just crap? Do you think the lens and camera deliver excellent images? Would not that have to be a lens and camera with photograher correction?
05-19-2022, 01:24 PM   #15
Loyal Site Supporter
Loyal Site Supporter
BigMackCam's Avatar

Join Date: Mar 2010
Location: North-East of England
Posts: 18,509
QuoteOriginally posted by BarryE Quote
... the SMC Pentax-FA 50mm F1.4 is (very) poor wide open. But here's the thing, for me, at f5.6/f8 for portraits its fine...

A lot of this stuff is just subjective.
That's a perfect example. I'd agree, the FA50/1.4 is poor wide open in terms of resolution... and yet, there are folks (I'm one) who like the way it renders at maximum aperture for certain use-cases; so, the value of the lens at widest / wider aperture is relative to the individual's expectations and requirements...

This leads me to wonder what the OP's application / use-case is that would benefit from precise resolution data. It's certainly become fashionable for lens review sources to publish and draw conclusions from MTF data, but aside from a few very specific use-cases, I'm not sure how valuable that data really is. Personally, I find it more useful to know at what apertures a lens is soft away from the centre and in the corners... what aberrations it "suffers" from (and which may actually contribute positively to its rendering, given my own personal preferences)... vignetting... flare performance in strong light... etc.

You're right, Barry... a lot of this is subjective - and knowing not just what you think you want from a lens, but why (i.e. "does it really matter?")...

Last edited by BigMackCam; 05-19-2022 at 03:21 PM.
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!
aperture, data, edge, k-mount, lens, lens measurements, lenses, measurements, page, pentax lens, post, slice, slr lens, tests, web
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K-3 III - Photons to Photos sensor DR measurements Oxygenum Pentax DSLR Discussion 154 05-09-2021 04:49 AM
Pentax DA 200mm 2.8 - is it real APS-C lens or a real full frame lens ? asko Pentax SLR Lens Discussion 31 10-13-2020 08:40 AM
Optical Measurements of Pentax ME Super Shutter Speed AstroDave Film SLRs and Compact Film Cameras 15 07-01-2020 08:49 AM
May 1st, 2012 A Day Without the 99% No Work – No School – No Housework – No Shopping jogiba General Talk 4 05-02-2012 02:48 AM
Why no "real" normal lens for apsc NotaxPen Pentax SLR Lens Discussion 102 02-17-2012 01:09 PM



All times are GMT -7. The time now is 11:57 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