[tammons]

SMC Pentax FA AL 24mm F2.0 AF lens

Just bought one from Roberts Camera and not that impressed.

Even at F11 the corners are not sharp on the K1.
Is this typical for this lens?

I have a PK manual focus 24mm F3.5 that is sharper in the center than this AL AF lens.

I am having a heck of a time trying to find a decent AF 24mm lens.

Thanks

[clackers]

Just bought one from Roberts Camera and not that impressed.

I have a PK manual focus 24mm F3.5 that is sharper int he center.

Even at F11 the corners are not sharp on the K1.
Is this typical for this lens?
I am having a heck of a time trying to find a decent AF 24mm lens.

Thanks

I wouldn't expect the corners to be sharp on any smaller 24mm.

But this is a used lens, and you don't know what previous owners have done to it ... have you both microadjusted its focus calibration and checked it for decentering, Tammons?

Send it back if it fails those tests, get another from somewhere else.

[garywakeling]

The lens has a different design philosophy than modern, everything needs to be sharp in the corners and everywhere else. In some ways it is very similar in design to the just released HD DFA 21mm, close up objects in the middle of the frame and at closer distances stands out more from the background than traditional lenses. Whether it is better or worse depends on which photo style works best for you. The three amigos 31 43 and 77 were designed in a similar way. Try it for a week and if it doesn't work for you send it back. I love mine and here are some examples Single October 2018 FA*24mm | Flickr

[tammons]

It is not decentered enough to matter.

This will be a landscape lens so I would prefer it to be sharp in the corners.

I also have a Zeiss 25mm F2.8 M42 lens which is sharp everywhere, but am specifically looking for an AF lens

[stemked]

Funny, I ALSO bought a 24mm FA from Roberts! (mine has a small dent), and I have a K1. I just repeated your image. I would say you are right, at the edges it is not super sharp. It is very sharp across most of the field though.

[tammons]

At F8 the left and right edges are not sharp enough for me and loaded with CA.

My PK 24mm F3.5 manual lens at F8 actually looks better and is sharper at the far edges.

[mikesbike]

If you are not pleased, send it back. Unfortunately, it is very difficult to find specifically a 24mm that is sharp corner-to-corner. Maybe we could see a future large, expensive DFA 24mm f/1.4 DC AW like the 50mm already available. 24mm even has some WA use for APS-C as well- so it makes sense for both formats.

Possibly the FA 28mm f/2.8 might please you, if you find a pristine copy. Quite good even wide open. I bought mine many years ago for 35m film use, and it now does well on my K-1 II. A screw-on lens hood is easy to find new and not expensive. Just be sure to screw it on lightly rather than tightly, as it could become difficult to remove.

[tammons]

I tried an F 28mm F2.8, and it was better than this AL 24mm F2, but the corners still did not come up, so I returned it today.
I do own the FA 35mm F2 and 50mm F1.4 and they are superb.
Think I will just stick with the Zeiss 25mm F2.8.

[clackers]

It is not decentered enough to matter.

Decentreing can be expected to have big consequences at the edges, you don't want that with a landscape.

What you should observe in the sharpness stakes at different apertures:

http://www.takinami.com/yoshihiko/photo/lens_test/pentax_superwide.html

[mikesbike]

I tried an F 28mm F2.8, and it was better than this AL 24mm F2, but the corners still did not come up, so I returned it today.
I do own the FA 35mm F2 and 50mm F1.4 and they are superb.
Think I will just stick with the Zeiss 25mm F2.8.

Yes, the FA 35mm f/2 AL is great, the HD version is even overall better. But the "F" 28mm f/2.8 you tried out is not of the same optical design as the FA 28mm f/2.8 AL.

The new DFA 50mm f/1.4 is superb corner-to-corner, but the older versions like the FA 50mm f/1.4 must be stopped down quite a bit to get very good results across the frame.

[jslifoaw]

While this might be too late, I’ve found the FA24 also has focus shift in my case. For distant subjects, I have to focus slightly closer for the best results and when stopped down, I get the best results with the focus pretty close to the hard limit slightly past infinity.

This has gotten me pretty good results to the corners, but the CA doesn’t go away.

[phat_bog]

Try focusing with live view.
If it gets tack sharp then it means you'll just have to micro adjust the AF.
If not , dsable SR , sometimes it messes around with some focal lengths & lenses
If not again, what speed are you using ? Diaphragm system might be a little worn out, causing a tiny slower closure/opening. Conducting to loss in sharpness.
It not again bis, then there's some minor misalignment -> send it for repair.
Hope this helps.
NB : if you too test a 24mm like brainless testers on the web against a straight brick wall and find extreme corners not in focus, it doesn't mean that the the lens is not a good lens. It's just a 24mm and this is normal. And...actually 24mm are designed more for architecture or photoreporters than for landscapes. For classic landscapes, start with 28mm. 28mm are also way better than 24mm for stiched panoramas. 30-35mm even better.
Anyway, I've seen many photographers disappointed by lenses that are actually excellent (yours has obviously a problem because you seem smarter) just because they don't have enough clues about stuff like front & behind dof limits, not to speak about general optics comprehension.

[phat_bog]

While this might be too late, I’ve found the FA24 also has focus shift in my case. For distant subjects, I have to focus slightly closer for the best results and when stopped down, I get the best results with the focus pretty close to the hard limit slightly past infinity.

Oh god.
It's not a lens that focus shifts. That, supposing the lens is not completely out of calibration.
The phase detection makes AF at 2.0. if you shoot at another aperture you'll always have a slight focus shift.
For example, also, to better undestand too : if you adjust with micro adjust AF with your lens closed at 2.8 , when you open it to shoot at 2.0, you'll get some minor focus shift on your picture.
The marvelous FA* 24mm F2 in good working condition is totally incapable of focus shifting by itself. It's the type of usage and optical physics that creates the phenomenon of focus shifting.

[pschlute]

I am having a heck of a time trying to find a decent AF 24mm lens.

The design philosphy behind the FA* 24mm is subject isolation at wider apertures,not just through DOF but also in the focal plane itself. The centre should always be sharp, even at f2.0, but the edges will be softer. At f8-f11 the edges will be acceptably sharp. If you are not getting this, then your lens may be a bad copy.

Either way it is not a natural landscape lens.

This thread may help....https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/453788-pen...ml#post5721866

[mbukal]

But the "F" 28mm f/2.8 you tried out is not of the same optical design as the FA 28mm f/2.8 AL.

even before when I used the APSC format I had the opportunity to try the FA28/2.8 for comparison with my F28/2.8, and after a short time of parallel use of the F and the FA 28/2.8 I concluded that the F28/2.8 is sharper both in the center and on the edges more than the FA28/2.8 and I remained faithful to the F28/2.8 even today on FF format K1, do you have different experiences on FF or APSC format or in general