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03-01-2022, 01:39 AM - 2 Likes   #1
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Test charts vs. real life performance

Here's an interesting video that many are already aware of. I started in the middle because that's the best quote about the debate between test results and actual performance that I've ever heard in my entire life! Enjoy...

https://youtu.be/ktyzkSRxdFE?t=117

//Joe

03-01-2022, 04:17 AM - 4 Likes   #2
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QuoteOriginally posted by Shupienis Quote
Here's an interesting video that many are already aware of. I started in the middle because that's the best quote about the debate between test results and actual performance that I've ever heard in my entire life! Enjoy...

https://youtu.be/ktyzkSRxdFE?t=117

//Joe
A nice and succinct video. When I look at a picture that I really like, sharpness per-se is usually well down on the list of attributes. Look at the great photographers today or in history.... we don't appreciate their work because the images are sharp, we appreciate them because they tell a story.

In the same vein as the video, folk can often get hung up on differences between individual lenses. You hear derisive comments about "kit" lenses or cheaper, slower lenses. In the hands of a good photographer, a cut-off bottom of a bottle glued to the camera mount can produce a good image

I leave you with one of the iconic images of WWII by Robert Capa.........
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03-01-2022, 05:09 AM - 3 Likes   #3
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It just reinforces what I have maintained all along. Since I have never seen a test chart hanging in a gallery, I don’t shoot at them. Going out to see how your lens works in the real world is always the best
03-01-2022, 05:41 AM   #4
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I’ve never shot a test chart with digital.
I’m missing out I think!


Hang up and DRIVE!

03-01-2022, 05:55 AM   #5
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The video is referring to photographic cases with out of focus / blurred image areas (such as portraits, macro,,), to conclude that best sharpness aperture is practically useless. That's technically and practically incorrect, because there are plenty of photographic cases where everything is in focus, hence knowing the lens aperture that deliver sharpest results is useful, and Pentax even has an MTF Program Mode for such situation.

---------- Post added 01-03-22 at 13:56 ----------

QuoteOriginally posted by pschlute Quote
I leave you with one of the iconic images of WWII by Robert Capa.........
Why not take a daguerreotype image from the 19th century to claim that sharpness (and/or resolution) is not necessary?
03-01-2022, 06:11 AM - 3 Likes   #6
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QuoteOriginally posted by biz-engineer Quote
The video is referring to photographic cases with out of focus / blurred image areas (such as portraits, macro,,), to conclude that best sharpness aperture is practically useless. That's technically and practically incorrect, because there are plenty of photographic cases where everything is in focus, hence knowing the lens aperture that deliver sharpest results is useful
The reviewer said exactly the same thing. If you watch it a second time you'll probably find where he mentions it. It is a useful metric to know, in portraiture for example, but not the most important attribute of the lens. Nor is distortion charts or edge results or really test results in general.

IMO, what the real point he was making is: Don't place much emphasis on test charts, look at real life results.

EDIT: As an example the FA77 does not lab test as wonderfully as the images users get with it.

Last edited by gatorguy; 03-02-2022 at 05:51 AM.
03-01-2022, 06:23 AM - 2 Likes   #7
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QuoteOriginally posted by gatorguy Quote
It is a useful metric to know, in portraiture for example, but not the most important attribute of the lens.
I'm writing most reviews for Pentaxforums (and elsewhere), and I agree with this.

That is why we supplement the test charts with real-life samples.

I would say that there is a minimum level of sharpness required, beyond which it's a matter of diminishing returns.

It's not useless (better sharpness makes it easier to crop, and is required when your sensor resolution increases) but not the only thing of importance.

A soft image will be annoying for viewers (except if there is intent) but beyond a certain point, no one is going to look at an image and say "so shaaaarp!". They'll look at other things.

That is also why lens tests cover sharpness, aberrations, bokeh, distortion, vignetting, etc.

03-01-2022, 08:00 AM   #8
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This is probably something that seems to get way more importance then it actually gets. It is easier to measure and talk about. However the same lens can be sharper at infinity or minimum distance.

We don't buy every lens but use the lens we have at every distance. You don't see these tests done and therefore talked about.

We have tests of every aperture to determine the exact sweet spot at a given distance. We talk about the sweet spot. With zooms we measure maybe 3 fl out of several. No one cares the measure didn't determine at what fl the exact sweet spot was.

My 55-300 PLM lens probably has a sweet spot around 124mm f/8 at 8 meters. The fact no one really knows or talks about it, tells me it really isn't important to people. It is just easy to make small talk about.

It is like the weather. It is easy to talk about. Judging by how much we talk about would seem like it is the primary factor that controls our day. Sure I might choose a different weather to go swimming or a different lens to use. If its 30c or 40c the swimming days are fine. If its 30 or 40 MTF it is probably fine.
03-01-2022, 08:12 AM - 1 Like   #9
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The author of the video says that "Understanding a lens's sharpest point is really great if you have a career photographing test charts, but it really doesn't matter as much in practical application."

Certainly, controlling the depth of field is important, and it's good to understand the parameters that affect DoF.

Attaining a desired sharpness in an image depends on DoF and focus accuracy. However, it also depends on the resolution characteristics of a lens across its aperture values. Although we don't need test charts per se in our everyday shooting, or precise knowledge of a lens's 'sweet spot', we often follow a rule of thumb that maximum sharpness may be attained at a couple of stops narrower than wide open.

We often read suggestions to "stop down a bit and the lens will sharpen up nicely."


- Craig

Last edited by c.a.m; 03-01-2022 at 08:24 AM.
03-01-2022, 08:36 AM - 3 Likes   #10
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Sharpness isn't always that important but one thing holds true, having a very sharp lens won't prevent one from getting excellent shots whether in focus or not, however a poor IQ lens will prevent some shots from being possible. You rarely hear someone complaining that their lens is too sharp (although it happens). Art is not hampered by lower IQ.
03-01-2022, 08:37 AM - 1 Like   #11
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It's not easy to suss out lens performance from a couple of "real life" photographs. The complexity of the scene and the settings used means you have many variables at hand that are difficult to analyze. Most available photos won't show issues because those images were culled.

For dof limited photography it's less of an issue but for pan focus (as Pentax calls it) photography it gets very complicated. I don't really know a lens until I've used it for a month or so. Test charts, mtf curves and photographs designed to provoke issues really help with understanding what to look for in those "real life" photographs and helps prevent surprises.

You have to read those chars and tests with your use case in mind. Otherwise it makes no sense.
03-01-2022, 09:15 AM - 1 Like   #12
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QuoteOriginally posted by Bob 256 Quote
Sharpness isn't always that important but one thing holds true, having a very sharp lens won't prevent one from getting excellent shots whether in focus or not, however a poor IQ lens will prevent some shots from being possible
I am not sure I follow you. If I miss the focus with my DFA 50mm or DFA 85mm (two of the sharpest lenses I own), I get a rubbish image that will be sent to the recycle bin in double quick time. If I use my old M series 50mm f2.0 (not highly regarded) and nail the focus, I get an excellent image I can then send to the printers.
03-01-2022, 09:16 AM - 5 Likes   #13
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The importance of sharpness varies with the type of photograph.

Many types of photos can be just as good with a less-than-perfectly-sharp lens because those photos are defined and judged by the overall macroscopic shapes, orientations, and juxtapositions of the larger-scale objects in the scene. Many images with people only need to show the overall posture and facial express of the subject in the context of other people or objects in the scene. If anything, detail can detract from communicating the overall story or emotional state of the subjects.

Some photos even benefit from poor sharpness like that Robert Capa image posted by @pschlute. In that image, blur and lack of resolved detail captures the essence of the "fog of war." Some lenses are actually too sharp for some types of imagery such as macro lenses that would too-accurately render every pore, blemish, and wrinkle in a portrait subject's face.

However, some types of images do benefit from sharpness. Many nature and macro images look much better when you can see the full detail of the subtle patterns in animal fur, bird feathers, butterfly wing scales, flower petals, etc. Some landscape images benefit from corner-to-corner sharpness to show the details of trees in the forest, granulation of rocks, fruit on distant trees, or the presence of a distant speck-sized human figure. Those gigapixel panoramas of cityscapes or landscapes create an immersive experience because they sharply resolve all the details of a large, complex scene. Astrophotography, especially, really does require lenses with extremely good sharpness wide-open and corner-to-corner. Of course, technical photos such as archival images of paintings, textiles, and old documents need sharpness. For some photos, the beauty is in the microscopic details, too.

As for test charts, they provide a more objective and repeatable testing environment for people who want to find the sharpest lens or get the most sharpness out of the lenses they have. In the field sample images do a poor job of testing and communicating the sharpness of a lens because the viewer of the image does not know how sharp the image could be or should be. Trial-and-error in the field takes too long and it's often impossible to review the corner-to-corner sharpness of an image in the field. For photographers who want sharpness, test charts can give them the confidence that the equipment will do the job when they go out. Moreover, test charts are the only way to tell if a lens you plan to buy is better than the copy of a lens you already have.


TL;DNR: some images require sharpness, some images don't require sharpness, some images require softness. If sharpness really is required, then test targets provide objective and comparable data across lenses and settings.
03-01-2022, 09:27 AM   #14
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QuoteOriginally posted by photoptimist Quote
TL;DNR: some images require sharpness, some images don't require sharpness, some images require softness. If sharpness really is required, then test targets provide objective and comparable data across lenses and settings.
Good points.

I think the video author is suggesting that it's worthwhile to try your lenses in the field at various subject distances, focal lengths, and apertures, mainly to get first-hand insight into Depth of Field effects.

Like you, I think that understanding a lens's resolution characteristics is also important.


- Craig
03-01-2022, 12:07 PM   #15
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I often make sure to never know the operating parameters of my tools. Things always turn out better that way.

Regardless of how I use my lenses, when I get them, I many, many test chart shots and then a set of many shots of my front yard. I also have all my camera P-lines set to MTF. I want to know how my lenses work then check that in the real world of my front yard and distant trees and mountains.
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