[Michael Piziak]

Just playing around, comparing the 18-55mm kit lens to my F1.7 50mm M lens, used green button for help with exposure on M lens

Tripod, set both to F5.6, 2 sec delay to avoid shaking, ISO 100 for both, & tried to adjust the kit lens to take same size photo as 50mm lens
Certainly not scientific.....


Without looking into the details/EXIF, see if you can guess which is which from these 4 photos before reading the comments/commenting...
1


2


3


4


---------- Post added 01-06-23 at 06:28 PM ----------

p.s. If anyone wants to download the test chart, which is 2.4MB & I think it's a pretty good one, I placed it at:
resolution test-chart-to-print-to-test-camera-or-camera-le? | Flickr

download the original image

---

Last edited by Michael Piziak; 01-06-2023 at 06:56 PM.

[swanlefitte]

just based on the waviness of the lines I think the bottom is digital. I hope I am surprised.

[Michael Piziak]

just based on the waviness of the lines I think the bottom is digital. I hope I am surprised.

You are welcome to view the EXIF and comment on your findings. I changed the original post to say that people should try to guess then look at the EXIF and then are free to comment... Smiles...

p.s. The photos where the F number is 0 in the EXIF data are the Pentax manual lens...

p.s.s. Of course they are both digital, but I know what you meant - being that by "digital" you meant the APS-C kit lens made for the DSLR's....

[GUB]

You are welcome to view the EXIF and comment on your findings. I changed the original post to say that people should try to guess then look at the EXIF and then are free to comment... Smiles...

p.s. The photos where the F number is 0 in the EXIF data are the Pentax manual lens...

p.s.s. Of course they are both digital, but I know what you meant - being that by "digital" you meant the APS-C kit lens made for the DSLR's....

There is no exif attached. And I am going with the warmer one (bottom) being the M 50mm 1.7

[iheiramo]

I suspect that bottom one with more elegant rendering is M and upper one with stronger contrast is the kit lens.

But in general I think test charts are dull way to compare lenses as it only really shows the sharpness and tells very little about rendering.

EDIT: Checked the exif. It seems I was correct, but otherwise it's very confusing. M lens claims to be 35mm. Kit lens 28,1 and 32,5mm and more over shot with f8 and f9.

[mikesbike]

Yes, I picked the same. However, as already said, such charts don't really tell much unless there is clear deficiency at some point. And there is no doubt, the 50mm f/1.7 prime lens will perform much better at the frame edges than will the zoom lens. It is a very good lens for edge-to-edge quality imaging.

In the real world of use and subject matter, a zoom lens has its advantages, in that the desired framing can be accomplished on the spot with out needing to move forward or backward. You can nab shots otherwise missed. I'm a bit surprised your K-S2 did not come with the standard kit lens for it, the DA 18-50mm RE DC WR, which is even more compact for carrying, and which matches well with the very compact K-S2. It also has a quiet AF that is very fast and accurate. It might be worth considering, getting the HD version of that lens in perfect condition, the HD DA 18-50mm RE DC WR. The HD version delivers better IQ.

That said, although true that a good zoom lens affords versatility of use, and opportunity to get more good shots, a high-performing prime lens can definitely have its own advantages. This is certainly true of your "M" 50mm f/1.7, although I would even more prefer the "F" version instead of the "M" version. Its AF is quicker to get the shot, and it would open up many settings for functions not available to an "M" lens, such as full segmented metering. Many other exposure modes would also be available. I've had this version for many years, bought new when I got my first AF 35mm film SLR, the Pentax SF-1n back around 1990. It is a terrific 50mm lens.

Photographically, it can perform in very important ways your otherwise versatile zoom lens cannot. In addition to its edge-to-edge superiority, on APS-C its 50mm is a very good FL for doing special tasks such as portraits. One of the reasons it is such a good portrait lens, is with its greater aperture capability, you would have much better control of DOF, which is how much or little the background and foreground around your subject will appear sharp- or will be blurred. At 50mm, your zoom lens has a maximum aperture of only f/5.6 wide open. You are stuck with the DOF this aperture will provide, and cannot reduce DOF beyond this, while with f/1.7, f/1.9 or f/2, f/2.4, f/2.8, f/3.5, f/4 etc. etc. all of which are not available to your zoom lens, you can control how much blur you want around your subject to make that subject stand out more from those surroundings. Some setting will blur the background only enough to make that happen, but still recognizable to give the overall photo context. At other times you might want to open up the lens more to make the background less recognizable. Even wide open, this lens can deliver a sharply-rendered subject in the central area of the frame!

At f/1.8 it can also provide around 8x the shutter speed for action shots, compared to what your zoom lens is capable of!! Lets say, same subject under the same lighting and ISO- at f/5.6 max with your zoom lens, you are at 1/60 sec.- not so good for action. Now, with this 50mm lens, you could open to f/4 making it 1/125 sec, or to f/2.8 for 1/250 sec, or to f/2 for 1/500 sec, then say f/1.8 and yet a bit faster!! Huge difference.

[Michael Piziak]

I suspect that bottom one with more elegant rendering is M and upper one with stronger contrast is the kit lens.

But in general I think test charts are dull way to compare lenses as it only really shows the sharpness and tells very little about rendering.

EDIT: Checked the exif. It seems I was correct, but otherwise it's very confusing. M lens claims to be 35mm. Kit lens 28,1 and 32,5mm and more over shot with f8 and f9.

Likely because I didn't select 50mm when camera first turned on, for the M lens.



Addendum: clicking the photos, going to the Flickr page, one can scroll down and select to view the EXIF data...


---------- Post added 01-07-23 at 01:23 PM ----------

There is no exif attached. And I am going with the warmer one (bottom) being the M 50mm 1.7

The photos with F being 0 is the Manual lens. Of course, if one downloaded the original image, all EXIF should be in there.

You have to click on the photos to take you to the flickr page where info and downloading are available....

---------- Post added 01-07-23 at 01:25 PM ----------

Yes, I picked the same. However, as already said, such charts don't really tell much unless there is clear deficiency at some point. And there is no doubt, the 50mm f/1.7 prime lens will perform much better at the frame edges than will the zoom lens. It is a very good lens for edge-to-edge quality imaging.

In the real world of use and subject matter, a zoom lens has its advantages, in that the desired framing can be accomplished on the spot with out needing to move forward or backward. You can nab shots otherwise missed. I'm a bit surprised your K-S2 did not come with the standard kit lens for it, the DA 18-50mm RE DC WR, which is even more compact for carrying, and which matches well with the very compact K-S2. It also has a quiet AF that is very fast and accurate. It might be worth considering, getting the HD version of that lens in perfect condition, the HD DA 18-50mm RE DC WR. The HD version delivers better IQ.

That said, although true that a good zoom lens affords versatility of use, and opportunity to get more good shots, a high-performing prime lens can definitely have its own advantages. This is certainly true of your "M" 50mm f/1.7, although I would even more prefer the "F" version instead of the "M" version. Its AF is quicker to get the shot, and it would open up many settings for functions not available to an "M" lens, such as full segmented metering. Many other exposure modes would also be available. I've had this version for many years, bought new when I got my first AF 35mm film SLR, the Pentax SF-1n back around 1990. It is a terrific 50mm lens.

Photographically, it can perform in very important ways your otherwise versatile zoom lens cannot. In addition to its edge-to-edge superiority, on APS-C its 50mm is a very good FL for doing special tasks such as portraits. One of the reasons it is such a good portrait lens, is with its greater aperture capability, you would have much better control of DOF, which is how much or little the background and foreground around your subject will appear sharp- or will be blurred. At 50mm, your zoom lens has a maximum aperture of only f/5.6 wide open. You are stuck with the DOF this aperture will provide, and cannot reduce DOF beyond this, while with f/1.7, f/1.9 or f/2, f/2.4, f/2.8, f/3.5, f/4 etc. etc. all of which are not available to your zoom lens, you can control how much blur you want around your subject to make that subject stand out more from those surroundings. Some setting will blur the background only enough to make that happen, but still recognizable to give the overall photo context. At other times you might want to open up the lens more to make the background less recognizable. Even wide open, this lens can deliver a sharply-rendered subject in the central area of the frame!

At f/1.8 it can also provide around 8x the shutter speed for action shots, compared to what your zoom lens is capable of!! Lets say, same subject under the same lighting and ISO- at f/5.6 max with your zoom lens, you are at 1/60 sec.- not so good for action. Now, with this 50mm lens, you could open to f/4 making it 1/125 sec, or to f/2.8 for 1.250 sec, or to f/2 for 1/500 sec, then say f/1.8 and yet a bit faster!! Huge difference.

I read all your comments (twice, smiles)...

Thanks so much for the input/info.

As states, I was mostly playing around. I understand that photographing such charts mostly shows which lens is the sharperst, etc...

---

Last edited by Michael Piziak; 01-07-2023 at 01:27 PM.

[GUB]

The photos with F being 0 is the Manual lens. Of course, if one downloaded the original image, all EXIF should be in there.

You have to click on the photos to take you to the flickr page where info and downloading are available....

OK did that - now two questions -
Why did you set the kit to 32mm focal length when presumably you were using the same format(camera) for both lenses?
And why is the kit lens at f8 and f9 ?

[Michael Piziak]

OK did that - now two questions -
Why did you set the kit to 32mm focal length when presumably you were using the same format(camera) for both lenses?
And why is the kit lens at f8 and f9 ?

yea, I thought I had set the kit lens to F5.6, I should probabaly reshoot it then.... The first time I shot it, I did have it all at F5.6, but the camera must have changed this on my reshoots without my knowing...


As far as the 32mm is, I was trying to get the same size image for both. Scientifically, I'm sure I should have shot the kti lens at 50mm, but when I did, it was far off.
For fun, I'll come back later and make sure all is at F5.6, including the M lens, and shoot at 50mm with kit lens - but for some reason the kit lens at 50mm shows much different surface area...

Thanks!

Michael

Addendum: I quickly shot both at F5.6, ISO 800, set the kit lens to 50mm on the lens, used a tripod. Hopefully I didn't miss something again, if so do tell. Oh, I put the kit lens as close as I could at 50mm and turns out I nailed it - apparently the camera recorded this, but I don't see anywhere on the screen or viewfinder where it tells the mm when taking the photo (someone educate me & I started a thread asking about this at https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/451060-mm-autom...ml#post5681218)...


1


2

[GUB]

Good work. And showing the advantage to the 50mm 1.7 as I would expect considering the kit lens is wide open and the prime is 2.5 stops closed down. (not to mention prime vs zoom!!)

[Michael Piziak]

Good work. And showing the advantage to the 50mm 1.7 as I would expect considering the kit lens is wide open and the prime is 2.5 stops closed down. (not to mention prime vs zoom!!)

Yes, we would expect the prime lens to out perform a kit lens, in sharpness anyways, and it did.

I am curious about how one can tell what mm that autofocus zoom lens are at, such as the kit lens, how one can tell via using the optical or live screen viewfinder. I started a thread asking about this at: mm of automatic lens is recorded by the camera - but where on the viewfinder? - PentaxForums.com

Thanks for your input !

[GUB]

Yes, we would expect the prime lens to out perform a kit lens, in sharpness anyways, and it did.

Of course we could be guilty of confirmation bias!! ie retesting till we get the result we want! Given the built in inaccuracies of your setup this is quite a possibility!

[Michael Piziak]

I went ahead and shot 2 more. both F5.6, 50mm, ISO 800, 2 second delay on tripod....

---------- Post added 01-07-23 at 04:12 PM ----------

Addendum:

I think the white balance may give away the M lens.
So, i post processed both and did an "auto levels" on the colors to bring the white/brightness closer together.

Now, one of these is the manual 50mm F1.7 prime lens and the other is the 18-55mm kit lens set to 50mm. You should still be able to guess which is which, as the prime is sharper.




1


2


I'v done similar shots like this in the distant past, and people commented that "still, the kit lens is no slouch !"

[GUB]

And a crop comparison on the two unedited shots show also it is a contrast thing rather than a sharpness thing. I guess the bonus of less glass surfaces.

[GUB]

Also I suspect your chart is too close. Try setting the 50 prime at f8 and moving back until the top bar loses resolution on its right hand side.