I have the 35 & 90 APO SLs. At f/2 both are as sharp in the corners as at the center. Both also vignette a bit at wider apertures. Stopping down reduces vignetting and increases contrast (and depth-of-field of course).For landscapes I usually go for deep DOF, so any good lens that sharpens up in the corners at f/5.6 or f/8 does the job for me.-Dave-

Thanks Dave.I have my eye on the APO 28sl. There doesn’t seem to to be any constructive reviews of this lens other than Jono Slack’s, which is quite excellent. MTFs are slightly less on the edges and perhaps corners as compared to the APO 35. A quantitative testing approach might win me over. Coming from an anachronistic “f64” philosophy, f11 is a most frequent aperture for many of the intimate landscape work I do, and even sharpness into the corners is preferable. I haven’t quite convinced myself that “wide open” landscapes are appealing enough. I continue to find it gratifying to see every detail in focus.

This SL APO 28mm review is good:The One You Want. Leica 28mm f2 Summicron SL Review (thephoblographer.com)

Red dot forum’s video on these lenses is very instructive including detailed sharpness comparison with APO summicron sl lenses and 24-90.as expected the APO lenses win in the edges and corners. The 24-90 performs remarkably well.The poster of one comment to the video states that they spoke to Karbe who said the Leica version has glass changes as compared to the Panasonic S versions. Interesting intervention if true, which may account for performance deltas, and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.

……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.

JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?

koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.

JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)

koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?

JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.

koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.

JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.Wow, now you stoop to this?Normally, I'd ask a MOD to come clean this up, like they've had to do in the past. But, I'm going to let this ride as I feel bad they are getting kicked to the curb in a couple weeks.And in the meantime, we'll just leave it here for all to see how low you're willing to stoop when you get called out.

koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.Wow, now you stoop to this?Normally, I'd ask a MOD to come clean this up, like they've had to do in the past. But, I'm going to let this ride as I feel bad they are getting kicked to the curb in a couple weeks.And in the meantime, we'll just leave it here for all to see how low you're willing to stoop when you get called out.You still can’t show one rebranded lens.

JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.Wow, now you stoop to this?Normally, I'd ask a MOD to come clean this up, like they've had to do in the past. But, I'm going to let this ride as I feel bad they are getting kicked to the curb in a couple weeks.And in the meantime, we'll just leave it here for all to see how low you're willing to stoop when you get called out.You still can’t show one rebranded lens.And I still never said rebranded. And you still never backed your claim up.My grandpa used to say "if you find yourself in a hole, stop digging". Although, it might be fun to see how far you want to keep digging.

koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.Wow, now you stoop to this?Normally, I'd ask a MOD to come clean this up, like they've had to do in the past. But, I'm going to let this ride as I feel bad they are getting kicked to the curb in a couple weeks.And in the meantime, we'll just leave it here for all to see how low you're willing to stoop when you get called out.You still can’t show one rebranded lens.And I still never said rebranded. And you still never backed your claim up.My grandpa used to say "if you find yourself in a hole, stop digging". Although, it might be fun to see how far you want to keep digging.You didn’t have to say it. I replied to a poster and you saw fit to stick your nose in where it wasn’t invited.

JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:koweb wrote:JDLaing50 wrote:……….., and one wonders if Karbe is testing prototypes and requiring changes by Panasonic and Sigma to the Lmount versions raising the bar? Speculative but a potential comforting thought.They most definitely are.Curious, how do you know that?Leica invented the L mount. Leica started the L mount consortium. Leica and Panasonic (LUMIX) formed the L2 alliance. Leica is the optics expert in the formula and LUMIX is the electronics expert as admitted by both parties. Leica, at the outset, developed the standards for the coalition. Easy peasy.Yes, but that wasn't the statement you responded to, nor the context of this thread.What definite information do you have that Leica is 'raising the bar' when it comes to the lenses that start out as a Panasonic or Sigma brand, then get rebadged as a Leica lens? Can you share a link to where Karbe said that? (this was also part of what you quoted when you responded)Can you show me one of those lenses that are rebranded to a Leica lens?Nice deflection... It seems your opinion has no solid backing, so just another example of an unhelpful opinion trying to masquerade as fact. I'm done.You were done a long time ago.Wow, now you stoop to this?Normally, I'd ask a MOD to come clean this up, like they've had to do in the past. But, I'm going to let this ride as I feel bad they are getting kicked to the curb in a couple weeks.And in the meantime, we'll just leave it here for all to see how low you're willing to stoop when you get called out.You still can’t show one rebranded lens.And I still never said rebranded. And you still never backed your claim up.My grandpa used to say "if you find yourself in a hole, stop digging". Although, it might be fun to see how far you want to keep digging.You didn’t have to say it. I replied to a poster and you saw fit to stick your nose in where it wasn’t invited.Umm, I started this thread, so I think it's you who is sticking their nose in uninvited. And I was actually curious if you had genuinely helpful information to share. You continue to prove that you do not.Want to keep digging? What else you got?

Your banter is age old - between belief and fact, religion and science.if we consider Leica the source of all things 35mm camera, and Mr Karbe the “god” of lens design, then one might believe that the hand of Karbe can/should be found in all Leica lens designs.On the other hand, there is no proof other than circumstantial. Looking more carefully at the Ephotozine imatest  of both the Panasonic 35mm f1,8s and the Leica asph 35mm f2 sl, the resolution bell shaped curves iare very similar, albeit the former is tested with a 24mp camera, the later on the 45+mp Leica SL2.My guess is if ephotozine was to test the “s” lens on the higher mp Leica camera, the resolution graph would match.Apples to Apples, it appears to be the same lens.Either way, the results are pretty good if you shoot portraits, street which is where many of the non-APO m series lenses seem to be favored.For landscape work, the APO sl lenses appear superior, but I have no first hand experience there though I hope to remedy that soon. The CA numbers for the non APOs are really quite excellent, so if you can live with the much lower res numbers at edges (confirmed by red dot team) these lenses should satisfy.In my experience, accurate focus is far more critical to sharpness than the resolution differences between top lenses from different manufacturers at the same apertures, especially between f5.6 and f11 where I normally shoot. You pay a premium to obtain a lens with less CA and across the field sharpness wide open.