[dkpentax]

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.

[UncleVanya]

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.

[house]

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.

[Lowell Goudge]

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.

[brianmquinn]

Have you seen this?

Pentax K Lens Tests

[pepperberry farm]

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....

[DougieD]

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.

[BigMackCam]

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...

[pschlute]

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.

[Just1MoreDave]

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.

[BarryE]

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...

[Bob 256]

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.

[MossyRocks]

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).

[AfterPentax Mark II]

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?

[BigMackCam]

... 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?")...