Resolving power of lens

[jabatama]

I haven't a clue about if this is within your budget but it is a lens that provides you with a much wider perspective.

Yes, I was looking at this lens at the camera store today.
I can buy it … just have to think it over and see if the 18mm on the 18-140 will be sufficient, because I’m saving for Z5ii and I hope I can get some good deal around Christmas time.

 

[sirhawkeye64]

I always wondered what "Resolving power of a lens" is.

Is resolving power same as more details ?

Here is what answers I'm after.

Currently I have Z50ii with Z 18-140 DX VR, Z 50-250 DX VR and FX 24-120/4 S.

In 2 months we are going on a Mediterranean cruise trip and I would like to take the best possible pictures with my current gear.

I wonder if FX Z 24-120/4 S on my Z50ii will give me more details than the other lenses that I own ?

We will also go to Amalfi coast, Capri, Positano, DOLOMITES and lake Como in2026 and I really want the best quality photos for this second trip in 2026.

.

But generally speaking what is the Resolving power of a lens ?

The pictures below I took on our trip to Rocky Mountains in 2023 with Zfc + 50-250, will the outcome be better if I use the FX 24-120/4 S ?



View: original size



View: original size



View: original size

.



View: original size

I think in short, some lenses may give you sharper images than others, such as using the Z 24-120 on a DX camera versus the 16-50 (which itself is good in its own right) but I think there are a lot of variables that can impact the appearance of sharpness and thus resolving power as is perceived visually (things like atmospheric haze, lighting, etc).

But I'd say if you're using a Z lens on the appropriate format (meaning a DX lens on a DX body, and an FX lens on an FX body, or an FX lens on a DX body) you should have sufficient resolving power. This was more of a concern with DSLR lenses (particularly older ones) that were designed with lower resolutions in mind. But I think all of the modern Z lenses and even some late-model F-mount lenses (like the F-mount 24-70 2.8E VR) were designed with higher-resolutions in mind and thus have sufficient resolving power. It's the older ones (say ones from 2010 or earlier that were designed with lower resolutions in mind, like 16-36MP) that may be of concern. But with modern Z lenses, I feel that they are designed to resolve enough resolution on the respective format they were designed for and this isn't as much of a worry. Obviously some lens characteristics like field curvature will impact the appearance of sharpness across the frame but this starts to get into the nitty-gritty details and I don't know that that would necessarily be the same as lack of resolving power, it's more an optical deficiency as some lenses have more of it than others. That's just my take, but again, I don't put too much emphasis into resolving power and the other "technical" stuff more so than I need to as it's the composition that's really important to me, not the shear technical sharpness. Some of my best photos (and even those of the greats) were not particularly sharp, but you remember them because of the composition, not necessarily the technical aspects of it (sharpness).

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* PLEASE NOTE: I generally unsubscribe from forums/comments after a period of time has passed, so if I do not respond, that is likely the reason. *

 

[anotherMike]

I would *never* consider 36mp "low resolution" in todays world.

There was a HUGE difference when the D800/E came out at 36mp in how much that camera challenged the older F mount lenses.

 

[sirhawkeye64]

I would *never* consider 36mp "low resolution" in todays world.

There was a HUGE difference when the D800/E came out at 36mp in how much that camera challenged the older F mount lenses.

well, yeah, it's not exactly "low" resolution necessarily but again, my piont is that lenses designed for older cameras may not be suitable for the higher-res ones (like the modern 45-60MP sensors). They'll "work" but you may observe some optical degredation as a result when compared to a "lower" resolution for which they were designed for (such as 24-36MP). Or rather should I say that any optical deficiencies in older lenses designed for lower-resolutions will become more apparent on higher-res bodies, regardless of age.

--
* PLEASE NOTE: I generally unsubscribe from forums/comments after a period of time has passed, so if I do not respond, that is likely the reason. *

 

[David Kieltyka]

I would *never* consider 36mp "low resolution" in todays world.

There was a HUGE difference when the D800/E came out at 36mp in how much that camera challenged the older F mount lenses.

well, yeah, it's not exactly "low" resolution necessarily but again, my piont is that lenses designed for older cameras may not be suitable for the higher-res ones (like the modern 45-60MP sensors). They'll "work" but you may observe some optical degredation as a result when compared to a "lower" resolution for which they were designed for (such as 24-36MP). Or rather should I say that any optical deficiencies in older lenses designed for lower-resolutions will become more apparent on higher-res bodies, regardless of age.

I can't say I've seen any of this.

The big shift in my experience was switching in the mid/late 2000s from APS-C cameras to models like Canon's 5D and Nikon's D700. This exposed the weaknesses of many previously acceptable lenses, especially their corner performance. And these are low-res models by currrent standards. I sold a lotta lenses during that period.

With higher-res sensors I've found some lenses kinda "top out" in that they don't resolve much if any extra detail compared to their performance with lower-res sensors. But I've never such seen a lens degrade in performance. Instead the degree of improvement levels off.

I took the two photos below with a ~90-year-old uncoated Zeiss 40mm lens designed during a time when that company optimized their optics for contrast at the expense of some resolving capability. This made sense considering the tech limitations of the era. And because the contrast is good the lens holds up well with current sensors, even higher-res than the 40mp model used here. I wouldn't choose this lens for technical work but for general use it's just fine.


Stitched pano.





-Dave-

 

[anotherMike]

Nope. A 36mp camera, which I still shoot, is still VERY demanding on lenses. There isn't much difference in actual resolution you achieve going from 36 to 45, but there was quite a bit going from 12/16 to 36/45.

Your general concept is correct - lenses designed for film era/early digital may not be as good on higher rez bodies, but your goalposts are wrong. A lens designed for 36mp era is likely still an excellent performer on 45, but one designed for 12 (or even 16) may not be.

 

[sirhawkeye64]

I would *never* consider 36mp "low resolution" in todays world.

There was a HUGE difference when the D800/E came out at 36mp in how much that camera challenged the older F mount lenses.

well, yeah, it's not exactly "low" resolution necessarily but again, my piont is that lenses designed for older cameras may not be suitable for the higher-res ones (like the modern 45-60MP sensors). They'll "work" but you may observe some optical degredation as a result when compared to a "lower" resolution for which they were designed for (such as 24-36MP). Or rather should I say that any optical deficiencies in older lenses designed for lower-resolutions will become more apparent on higher-res bodies, regardless of age.

I can't say I've seen any of this.

The big shift in my experience was switching in the mid/late 2000s from APS-C cameras to models like Canon's 5D and Nikon's D700. This exposed the weaknesses of many previously acceptable lenses, especially their corner performance. And these are low-res models by currrent standards. I sold a lotta lenses during that period.

With higher-res sensors I've found some lenses kinda "top out" in that they don't resolve much if any extra detail compared to their performance with lower-res sensors. But I've never such seen a lens degrade in performance. Instead the degree of improvement levels off.

I took the two photos below with a ~90-year-old uncoated Zeiss 40mm lens designed during a time when that company optimized their optics for contrast at the expense of some resolving capability. This made sense considering the tech limitations of the era. And because the contrast is good the lens holds up well with current sensors, even higher-res than the 40mp model used here. I wouldn't choose this lens for technical work but for general use it's just fine.


Stitched pano.



-Dave-

I'm not really talking about lenses themselves degrading necessarily (if that's what you meant), but as the original post implies, that you reach a point where the sensor may start to show the limitations of the optics, but mainly with older glass that was not designed specifically with the high-res sensors we have today, in mind.

But I also think there is a couple of things that need to be taken into account, with one being the optics themselves. Even some newer third party lenses are this way -- they do fine on APSC or lower-resolution (20-24MP) FF sensors, but on the higher-res FF sensors you may start to see more issues due to the optics of the lens (or as I said in my other reply, some of the optical flaws start to become more apparent) but the lens itself doesn't degrade. But I think this is also more of a concern when you start getting into adapted lenses more so than modern/semi-modern lenses (lenses made in the last 10-15 years) as I have some film lenses that simply would not hold up well against a high-res sensor like a 45MP sensor, and even on my 24Mp Zf, it might be iffy just because of the optics.

I have pretty much upgraded all of my lenses to Z lenses so the question of resolving power is not a huge concern anymore again, as all of the Z lenses I believe are designed with the high-res sensors in mind.

But again, this is something that is somewhat not relevant at least to me and there are more important things to me regarding photography than these "technical" aspects.

--
* PLEASE NOTE: I generally unsubscribe from forums/comments after a period of time has passed, so if I do not respond, that is likely the reason. *

 

[anotherMike]

Note to Mike. The prints sizes that I refer to are based on the standard viewing distance for a rectangular image. Just checked Google again and that is 1.5 to 2 times the diagonal of the "print". Doing the 345 rule for a rectangle this means the diagonal for a 36 x 48 inch print is 60 inches. So the typical viewing distance is 90 to 120 inches or 7.5 to 10 feet. At these distances the visual acuity of 20/20 Human vision is 75 to 56 line pairs per mm. Basically Human Vision has rather poor "resolving power". It's also why the pixel peeping we all do is more about Stroking our Ego rather than if a lens is "good Enough".

This is actually a subject that is more complex than I have time for at the moment, but I wanted to tackle this a bit now.

First off, I understand the general gist of your sentiment in that there are far too many people who are zealots of chart tests, but at the same time, saying pixel peeping is stroking our ego is frankly insulting to a lot of people and doesn't really represent what is going on.

I'd also want to say that the viewing distance of a print is actually a bit *closer* when a good photographic print is in play. It's not uncommon for me to look at a print at 1.25X diagonal, but it varies, and that's not really enough to change a lot of this anyway.

Point #1 of course is that we all have different standards for image quality. All of us. That runs the gamut from folks who think a 20"x30" poster print from Kodacolor X is good enough to those of us (not me) who need 150mp Phase One systems for their work. One thing that is too prevalent in forum discussions is the pushing of everything to the binary side, the poles, where it's either "this" or "that", when reality is there are gradations, and image quality absolutely one of those..

What I generally try to do here is explain the "why" a lot of the time - why a chart test number isn't the final answer to a lenses optical performance, and in this post, why I believe you are incorrect with your print assertion you so commonly make. While I am deeply educated in the technical of photography, I also test for a living, and one thing I often do is take a look at a myth, concept, saying, or supposed truism and test it out. I'm not retired, so I don't have the time someone like Jim Kasson does, but it's something I like to do. And then I try to work through the "why is this so" when what I find might fly counter to the supposed truism, and in this post - your thoughts about lenses needing only to be good enough to produce a large print - I will do so.

Back when the D800E came out, while in the process of long term evaluation of my lenses since I wasn't happy with the output from many of the F mount Nikkors of the time, and this process included looking at third party glass, I ran through extensive/thorough testing - not "I shot this lens in a camera store so now I can talk about it with certainty in a forum", and then made prints. Like you, I believe a medium sized print tells us a lot about a lenses image quality, and if I didn't have competing things for my time, I'd also say I'm trying to work through an exercise of *which* image quality parameters/differences in lenses show up in print versus on a good monitor, but I do have some thoughts based upon experience.

One of the things I did was take two lenses - the Nikon 24/1.4G, and the Sigma 24/1.4 Art, on the D800E, and shot a scene with side to side/front to back detail at F/9 - you know, the aperture where everything should be equal (not) and made 17x22, 16x20 and A2 prints (I tested on different paper types) and then did a BLIND print test. To say that was interesting would be an understatement, because even at SANE viewing distances - about 1.4X diag distance, EVERY participant could EASILY see which print was better. Note that the "loser" was not a "bad" print, but there always was a winner. In other words, my blind print test - which I later repeated with another set of lenses and then once again in the D850 era, showed your assertion to be wrong. Now you can get all worked up about that, but that's that and you can't argue against that. What I think you should do is think precisely what I did, and that is to ask "Why is this so?" because it shocked me.

And that's because of a few things, which I don't really have the time to expound on beyond this post right now:

1. Your concept of print size and eye resolution is based IMO on 1970's thinking in the film era. Things are different in the digital era, and there are also other factors that explain why you can see differences at smaller sizes. This is a key point - we are both older, both grew up on film, but I've taken the time to do the research and the tests because I quickly realized a lot of things I knew from RIT in the film era had to be re-evaluated in the digital.
2. The primary differences in the lenses that caused this were:
   1. Better mid/high frequency structure (think in classic optical bench MTF) performance (say the 30-50lp/mm area roughly speaking), which leads to better output. It's not that one print showed more detail, but rather that the overall image looked more realistic. Subjectively, several participants noted the better print "looked livelier, and more realistic". Very long ago I remember a discussion between noted dye transfer printer/tech expert "Ctien" and Michael Johnson, back when they got along, where they talked about the visual impact of better high frequency performance (assuming of course, the subject had such fine detail and it was captured), and IIRC, the sense of reality and liveliness was mentioned. Anyone who remembers this better is free to chime in and correct me as it's been a long time.
   2. More even performance across the frame. One thing I've found repeatedly in my print-based lens evaluation is that the human eye/viewer will always prefer an image from a lens that is more consistent across the frame as opposed to one with peaks and valleys, even if subtle/moderate, from wave field curvature or wave astigmatism. I believe this is so because consistency is natural, while hot/cold is not. So a lens gamed for a test chart to score well in the corners but right next to it a zone that isn't tested and the lens isn't so good - doesn't work out so well in real life.
      1. Related to the above, I then researched lens performance and found that some aberrations went away as you stopped down, and some didn't, and the troublesome ones for landscape photographers, field curvature and astigmatism, do not. That's why the "every lens is the same at F/8" myth is false.
   3. Less of the pesky aberrations (see 2.1 above). If you've got astigmatism creeping in, and now you sample it when you capture it, it's not going away. It may or may not "add more detail" to the image, but you certainly will prefer looking at an image that has less of it. Again, the better vs more concept is in play.
3. Now we have to talk about the digital world we live in today. I'm not an engineer, and I don't design sensors, but from research as well as looking at what folks like Panavision in the cine world have to say, my *current* thinking is:
   1. More data is better than less
   2. Corollary to the above: BETTER data is better to have
   3. Acquisition quality should exceed exhibition quality, because in a digital system, where we're sampling and reconstructing, higher resolution, less lens artifacts, less "problems" equals a more natural result. Again, note that this is not about being able to necessarily see more detail, but that the overall image is better. More and Better are different. And it's this concept that is ignored in your more simplistic print size/eye resolution paradigm. Why did an 11x14" print I saw in 1980 from a Hasselbad look better than mine from a Nikon? Surely the increased resolution mattered some, but that wasn't the full tale, and now that we have sampling and reconstruction and so forth, plus we want the ability to perform operations in post on an image, where more/better information is desirable, more/better is certainly valuable.
      1. Interestingly, there is an older Panavision video from when they announced the 8K DXL or something cine camera, and they showed where even when the output was downsized to a "small" resolution (a 2K or even HD screen), the image from the higher resolution camera was noticeably better. Again, it's a different world than when we were squarely in the film days.
4. The complicated part comes next. There is a thought pattern and research being done on what's called hyper-acuity. While human vision is typically thought to only resolve 1 arc/minute (which I believe is like 5-7 lp/mm at 20", not your numbers, but if someone has the math to correct me, I'm open to it), the brain has additional processing that "knows" shapes/patterns/tones, and thus infers things. This was also references in the old Panavision video, so there are odds that there is more than just core resolution going on - the human vision system is both basic and complex at the same time.

At the end of the day, this is why I strongly disagree with your particular print size assertions. In my testing, for my standards, at 13x19 you can barely see differences, but at 16x20 you certainly can. Your standards might be different, and other readers again different. But they are there, and I do firmly believe most can tell, for the reasons I put forth. It's what the blind tests I've done showed too.

Where we likely AGREE is that there is a definite point when good enough is good enough. For the OP of this thread, it would be pointless to get a 45mp camera or even 8K video camera; it's overkill because there is a zone of efficiency, for lack of better wording, between the maximum achievable and what's good enough. And we agree prints are excellent to judge image quality, although I add that careful evaluation of on screen images augmented by printing is the best way. And I'm sure we agree that too much focus on test chart numbers isn't useful.

Respectfully, from another old-time

-mike

edit: PS, my current thinking is that 36mp "got us there" with excellent lenses and print sizes that weren't large format gallery sizes, and 45/50mp gives us some headroom to crop for compositional reasons and a bit of "leeway" in post processing. However, I met a guy pre pandemic who made 12 foot prints and needed everything the phase one could give him; his standards were higher. But I've been at this for a while, and I think for the shooter who has standards that merit a "high" to "very high" level, 36mp to 45mp is a very nice place to be. But that doesn't mean I'm going to knock the guys who moved to the Fuji or HB 100mp medium format backs. But at some point, the gains are getting mini incremental for all but the largest work. IMO anyway.

 

[TechStrider]

Once again, Thank you anotherMike.

Yes and Yes many times over.

Worthy distillation of many related details.

We see what we expect to see given the clues accumulated from our personal life experience, which are different for each of us, along with the clues we gather in the now in real time.

It is called a Visual System for a reason.

Continuous processing.

Well done in a short entry.

Also from another Old Timer

 

[jabatama]

I always wondered what "Resolving power of a lens" is.

Is resolving power same as more details ?

Here is what answers I'm after.

Currently I have Z50ii with Z 18-140 DX VR, Z 50-250 DX VR and FX 24-120/4 S.

In 2 months we are going on a Mediterranean cruise trip and I would like to take the best possible pictures with my current gear.

I wonder if FX Z 24-120/4 S on my Z50ii will give me more details than the other lenses that I own ?

We will also go to Amalfi coast, Capri, Positano, DOLOMITES and lake Como in2026 and I really want the best quality photos for this second trip in 2026.

.

But generally speaking what is the Resolving power of a lens ?

The pictures below I took on our trip to Rocky Mountains in 2023 with Zfc + 50-250, will the outcome be better if I use the FX 24-120/4 S ?



View: original size



View: original size



View: original size

.



View: original size

I think in short, some lenses may give you sharper images than others, such as using the Z 24-120 on a DX camera versus the 16-50 (which itself is good in its own right) but I think there are a lot of variables that can impact the appearance of sharpness and thus resolving power as is perceived visually (things like atmospheric haze, lighting, etc).

But I'd say if you're using a Z lens on the appropriate format (meaning a DX lens on a DX body, and an FX lens on an FX body, or an FX lens on a DX body) you should have sufficient resolving power. This was more of a concern with DSLR lenses (particularly older ones) that were designed with lower resolutions in mind. But I think all of the modern Z lenses and even some late-model F-mount lenses (like the F-mount 24-70 2.8E VR) were designed with higher-resolutions in mind and thus have sufficient resolving power. It's the older ones (say ones from 2010 or earlier that were designed with lower resolutions in mind, like 16-36MP) that may be of concern. But with modern Z lenses, I feel that they are designed to resolve enough resolution on the respective format they were designed for and this isn't as much of a worry. Obviously some lens characteristics like field curvature will impact the appearance of sharpness across the frame but this starts to get into the nitty-gritty details and I don't know that that would necessarily be the same as lack of resolving power, it's more an optical deficiency as some lenses have more of it than others. That's just my take, but again, I don't put too much emphasis into resolving power and the other "technical" stuff more so than I need to as it's the composition that's really important to me, not the shear technical sharpness. Some of my best photos (and even those of the greats) were not particularly sharp, but you remember them because of the composition, not necessarily the technical aspects of it (sharpness).

This a practical advice that I like.



Short and sweet explanation of the difference between the DSLR F-mount lenses and the current mirrorless Z-mourn lenses.



I agree that some of my best photos for some odd reasons were from 2012 with my wife’s G15 (which we still have) and were taken on “Auto” mode on out first cruise trip ever.
I guess the moments on that trip matter more than the sharpness of the image.

Or may be the CCD sensor on that G15 … who knows.



Lighting, composition and hitting the shutter on the exhale



Thanks and have a great day !

 

[Leonard Shepherd]

What a non-sense this is.

Everybody is entitled to their own opinion.

When judging photographic competitions one of the "basic issues" is - is it clear what the photographer wants a viewer to look at.

Often, but not always, this involves avoiding shooting situation where background clutter et cetera compete for attention with the subject.

There is the opposite point of view that taking subjects with lots of conflicting background detail as often occurs in real life is more representational of reality.

To some extent there is pressing the shutter button without taking much thought about what is in front of the camera (some referred to as snapshots) and the separate approach of making a photograph by carefully selecting the components in an image.

In the art world painters can learn to focus on the detail they wish to record – partly perhaps because it can take hours to paint a picture.

Whether or not a photographer could or should do something similar when taking a picture is in my opinion personal choice rather than nonsense.

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[NiVoak]

Most lenses from serous manufactures are pretty good these days. I get great looking pictures from my Z24-200 and 28-400. Even pictures from my old Nikon PC lenses look good on a big screen, and would print well.

To get good pictures a photographer needs to do the following:

1 Take pictures of interesting subjects, and things that he/she is interested in.

2 The ability to make well composed photographs.

3 To take one's pictures at the right time, with the right good light, and for monuments, a less crowded time of year/day.

This is just a partial list. Lens resolving power, is very far down the list. It is only of interest to other photohraphers.

 

[jtr27]

What a non-sense this is.

Everybody is entitled to their own opinion.

When judging photographic competitions one of the "basic issues" is - is it clear what the photographer wants a viewer to look at.

Often, but not always, this involves avoiding shooting situation where background clutter et cetera compete for attention with the subject.

There is the opposite point of view that taking subjects with lots of conflicting background detail as often occurs in real life is more representational of reality.

To some extent there is pressing the shutter button without taking much thought about what is in front of the camera (some referred to as snapshots) and the separate approach of making a photograph by carefully selecting the components in an image.

In the art world painters can learn to focus on the detail they wish to record – partly perhaps because it can take hours to paint a picture.

Whether or not a photographer could or should do something similar when taking a picture is in my opinion personal choice rather than nonsense.

I read some time ago that photography is the "Art of Exclusion," and that was an epiphany for me. A painter decides what to put into their painting, and a photographer decides what to leave out.

It is an important consideration in composition, and composition in my opinion is more important than the gear being used, and unlike gear, cannot be bought. Buying stuff, even very expensive stuff, is actually the easy part.

 

[NiVoak]

Why's that? Personal perception I believe. I like it this way, more the way my eye would see it without the camera. If I looked at this and the structure behind subject was blurry, it would look unreal or like something was wrong with my eyes.

As it is, the dolphin photo is a record shot. “I went to a marine park; here is what the dolphin pen looked like, with the nice scenic background. Oh, and there is a dolphin jumping after some toys there too.”

If your goal is to take a recording of what your eyes see, this is a perfectly fine example.

But from the perspective of trying to capture the dynamic event of a dolphin playing with its toys, this is not a good photograph because there is too much clutter in the scene stealing away from that beautiful animal.

And as we are now talking about recording what your eye sees, how many times, as you were first learning your craft, did you point your lens at a subject and think you were taking a fantastic picture of a dolphin playing with its toys, only to find out once you had the roll of film developed that what you actually caught was a lake, and a stadium, and a body of water, and a tiny dolphin in in the middle of the frame?

The wonderful thing about the human eye/brain combination is that if you want to zero in on some tiny thing quite a ways away you can do that, to the exclusion of all the clutter around you. Your brain helps you create your own zoom lens. You “see” only that dolphin breaching 100 yards away, and you don’t even notice the other pair 20 feet from you and 5°away from your field of view, because you weren’t paying attention to them.

So … no. Likely this photographer saw only the dolphin clearly separated from all that background clutter, as if he was pointing a 300mm f/2.8 lens at it, because that was the only part of the frame he was paying any attention to. His inexperience as a photographer meant hi]e took a mediocre action shot not because he wanted to, but because he was blind to all the clutter away from the center of the viewfinder. And when he got home he may well have said, “huh. I clearly saw much more dolphin, and much better separation from the background, than what this picture shows.” So he went on a photography site and asked how he can do better next time.

What a non-sense this is.

Spare it next time.

I have just taken a look at the dolphin picture. PLS has a point and has made some valid criticisms of your picture.

No finer resolving lens is going to improve a shot like that. It is what it is a record shot of a nice day out. You need to work on lens focal length, depth of field, shooting position and lighting, to make a photograph that will stop people in their tracks and say wow, what a shot.

 

[Leonard Shepherd]

Most lenses from serous manufactures are pretty good these days. I get great looking pictures from my Z24-200 and 28-400. Even pictures from my old Nikon PC lenses look good on a big screen, and would print well.

You raise an interesting conundrum.

I get the impression a score of 1000 LW/PH is enough for a sharp printed A3 image - based on comments by those who test at some testing websites

Many modern 35mm format lenses can score twice as high as this using MTF 50 - and sometimes three times as high.

Whilst there are numerous higher scoring lenses than the two you mention, a good A3 print was possible though challenging IMO from an 18–200 DX lens on a 17 MP sensor.

To get good pictures a photographer needs to do the following:

1 Take pictures of interesting subjects, and things that he/she is interested in.

2 The ability to make well composed photographs.

3 To take one's pictures at the right time, with the right good light, and for monuments, a less crowded time of year/day.

This is just a partial list. Lens resolving power, is very far down the list. It is only of interest to other photohraphers.

+1 - though defining "good" is similar to defining how long is a piece of string

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[olyflyer]

Currently I have Z50ii with Z 18-140 DX VR, Z 50-250 DX VR and FX 24-120/4 S.

In 2 months we are going on a Mediterranean cruise trip and I would like to take the best possible pictures with my current gear.

In my opinion, the "best" in your case is the 18-140, that's what I'd bring. Why? Not because it is the highest quality lens, but because it is the most comfortable to use. The 24-120 is just not wide enough for such trip with a DX body, and on the long end it is already covered by the 18-140. On any trip, comfort is the key of enjoyment for you and your company. Personally I hate to look like a Christmas tree, so I always only carry one lens on normal trips. If I'd go on a safari, I'd brake that rule because I'd carry a long tele zoom also, but otherwise, for trips like the ones you are mentioning here, the 18-140 is all you need, unless you plan shooting wildlife also, in which case the 50-250 would also be needed, but I don't mean visiting a zoo, but real wildlife.

I wonder if FX Z 24-120/4 S on my Z50ii will give me more details than the other lenses that I own ?

Maybe and maybe not. It's the best lens you have, but "more details" is more than just the best lens. Apart from the already discussed things, "detail" is also about your own abilities, if you use a lens in a more or less optimal way, or if you are able to fill the frame with your subject better with another lens, than the 24-120 is maybe outclassed by your other lenses. Remember that 250 mm is more than twice of 120 mm, so if you take an image which requires the 250 mm, then the 120 mm would be beaten by your 50-250, even if the 24-120 it technically better. Also, if you stop down too much then the ISO will go up (unless you match it with the shutter speed), and if the ISO goes up the noise will also increase and that will reduce the details. On the other hand, if you always stay in the range of the 24-120 then the 24-120 will beat your other lenses, and will also allow you to use f/4, which you can't do with the others. The 18-140 starts at f3.5, but my guess is that it is less than f/4 by the time you are at 24mm. So there is no real answer to your question because it depends on a lot of things.

We will also go to Amalfi coast, Capri, Positano, DOLOMITES and lake Como in2026 and I really want the best quality photos for this second trip in 2026.

Again, from the lenses you have, the 18-140 would be the one in my bag. You won't have use for the others. Europe is about walking, even if you cruise or drive part of a trip, once you are on land or park the car you will be walking. No point making a trip less enjoyable than necessary.

But generally speaking what is the Resolving power of a lens ?

Don't worry about that, you haven't reached the maximum resolving power of your lenses.

The pictures below I took on our trip to Rocky Mountains in 2023 with Zfc + 50-250, will the outcome be better if I use the FX 24-120/4 S ?

That is again impossible to answer, since it depends on many things. However, one advice is not to use P, because it will give you weird apertures and shutter speeds. I can not really understand the reasons for the choice of shutter speed/aperture in those images. Diffraction can be an issue, and that will reduce resolution also, not just haze, air pollution or weather.

The best lens is the one you have on your camera. What you have in your bag wouldn't have done a better job if it is in the bag.

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https://www.youtube.com/@AdaptingCamera/videos
https://adapting-camera.blogspot.com/2022/05/auto-focus-light-extender-for.html

 

[Leonard Shepherd]

I read some time ago that photography is the "Art of Exclusion," and that was an epiphany for me. A painter decides what to put into their painting, and a photographer decides what to leave out.

It is an important consideration in composition, and composition in my opinion is more important than the gear being used, and unlike gear, cannot be bought. Buying stuff, even very expensive stuff, is actually the easy part.

Adding to this a painter is free to change the spacing between a key elements in a composition without moving his position/easel - helping with achieving the composition that the artist prefers.

To achieve similar results a photographer may have to change position if possible.

A third photographic option is change the size, position and maybe clarity etc of individual key elements in the composition - using what can be moderately complex post processing.

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Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.