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SL 24-90 digital corrections


dgktkr

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I don't know Sean, but people I respect do know him, and they say he's a nice man.  

 

He has apparently been a professional photographer for over 30 years, and has studied photography at all sorts of important sounding places (I don't know much about this stuff).  However, what I do know is that he does reviews on a paid site, and is keen to protect that income stream.  I have subscribed a couple of times - first with his dreadful old site (and I didn't resubscribe), then his new site (for the SL and 28 Summilux reviews, and again didn't renew my subscription).  His reviews are interesting, but they do tend to take what I consider to be reasonably irrelevant issues to the extreme - I would find myself jumping to his conclusions because in setting out his methodology and his comparisons, I was actually learning absolutely nothing I needed to know about the lens or camera.  I guess therein lies the fault of a dilettante (for you professionals out there), but I spend a lot of time and money on my photography and it has been a life long journey of learning and discovery.  I learn more from Jono's posting, I'd have to say (and I like his photography too).

 

So, when (if) he says that it would be better if the lens was more optically correct, and relied less on digital corrections baked into the DNG files (which you should be able to switch off or on in LightRoom - isn't this an Adobe problem?), I rather think - meh!  More critically, I think to myself that there must be some gain for Leica to do this, and not just a cutting corners/cost saving thing as the uncharitable might suggest.  Because, the truth is, the images taken with the zooms are pretty amazing.  My experience has always been that zooms are very inferior to primes, but these lenses really blow that idea out of the water.  The 50 Summilux also looks very nice, but it is a lens I don't need (having 3 M mount 50s)

 

Anyway, Sean the photographer - his site doesn't give much of an idea of anything but fruit and veggies and mushy B&W photos of the backs of people's heads at various fetes.  I know this is not very complimentary, but this is a photography forum, and surely I can say that a much vaunted photographer produces nothing at all that does anything at all for me.  Just my opinion.  But then, I thought I might be a little harsh based on photos taken for the purposes of reviewing equipment (though I'd be a bit more careful about the images I posted, I'd have to say).  So, I went looking, and I found Sean's FaceBook page - https://www.facebook.com/pg/seanreidphotography/photos/?ref=page_internal

 

Judge for yourselves about the quality of the professional photographer.  Doesn't do it for me.  Why post this, when I'm not posting a link to my empty flickr page?  Well, I'm not holding myself out as any sort of photographer, let alone someone whose opinion should be cherished.  I'm not bashing Sean, just trying to understand where he's coming from.  If there is a better source of Sean Reid Fine Art photography (he is a fine art photographer), I'd be keen to see it.  I appreciate this is a fine line, but to say "Sean Reid says ..." and we should listen because "he does photography for a living" isn't really enough for me, when the photos I've taken and seen look pretty good.

 

Perhaps the test would be to some comparative shots taken with the Summilux-M 50 (reasonably optically corrected) and the SL-50 (or the zoom at 50mm) of heads to see if there's a problem?  Having spent more time than I really wanted to testing Ming Thein & Lloyd Chambers' focus shift issue, I'm probably not the best person to do this.  That particular rabbit hole had been filled in by Leica, it seems.

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That Facebook page is for a different Sean Reid.  Not the photographer in Vermont.

 

 

Ha! Good to know.

 

I found this one - http://www.still-photo.net/northeastern/architectural.htm  If you click on the "Special Events tab, the page only loads if you have Flash (sigh!) and the Home Page link is broken.  The Architecture images are viewable (in thumbnails). Had a look at the Upstate New York and Ireland ones from 30 years ago - what do you think?

 

I looked at some of the architecture photos, and they seem to be missing their foregrounds - my personal preference would be to use a wider angle of view ...

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Guys,

 

STOP

 

FEEDING

 

THE

 

TROLL

 

...Wish him well with his Canikony or whatever and let's just ignore him...You can't win with this guy...Let him dwell on this very first world problem while we go out and take photos.

This is the Leica forum at its absolute worst. Deviate from the pack view of Leica worship and be denounced as a troll (I've no idea why the moderators find this kind of abuse acceptable).

 

Zlatkob has been incredibly polite given the insults people are heaping on him for questioning the wisdom of enforced digital corrections. I don't think it's a big deal. It's true that Canon, for example, give the option of turning off corrections, but the degree of correction isn't so great to begin with; if it was, framing would be tricky with an optical viewfinder. Software correction for EVF cameras is just a fact of life and all of the manufacturers appear to be taking the same route as Leica. The world moves on and we shouldn't be surprised that lens designers take advantage of any additional tools that become available to them.

 

None of that makes me want to burn Zlatkob as a heretic.

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Here are 100% crops from the corrected and uncorrected images. Blue (purple?) fringing is prominent in the uncorrected one, while even the corrected one shows some color at the edges of the black features.

 

dgktkr

You can't ever have perfect correction for lateral chromatic aberration in a lens profile because the LCA is only consistent if the subject is perfectly flat. If things are at different distances, the LCA is going to vary a bit. Then throw in the fact that chromatic aberration will also vary with f/stop--values that aren't available to put into the exposure if you at shooting an 'M' lens and things get even more approximate. That's why you may still want to make small corrections to chromatic aberration adjustment even after a correct profile is applied.

 

- Jared

 

- Jared

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This is the Leica forum at its absolute worst. Deviate from the pack view of Leica worship and be denounced as a troll ...

Really?

 

I don't think that's even remotely accurate. At what point did Zlatkob really do much more than repeat the same point over and over again? He expressed his opinion in his first post (on another thread). The point about a forum like this is not so much how people express themselves (thought it helps), as the nuggets of real information you can glean from the exchanges (or the entertainment - that's always fun). Anger, moral outrage (yawn), fawning admiration (please!), boasting "professionals"( get over yourself) and aspiring for consensus is a complete waste of bandwidth.

 

The alternative reality? Gee, Zlatkob, youre right! Naughty Leica! Hmm, maybe not. Sure, Leica makes a number of decisions for us - they get to make the cameras, and very good they are too.

 

Every so often someone who knows something interesting posts - that's worth wading through quite a lot to get the benefit of. Too much noise, the people with interesting things to say find something else to do.

 

The trick is, learn when to let it go ...

Edited by IkarusJohn
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Interestingly, my biggest concern with the digital corrections is NOT the distortion correction.  It's the vignetting correction.  And I don't see it so much as an issue with the 24-90 as I do a potential issue for other lenses.  If you don't incorporate vignetting control into the lens itself and brighten things up on import, you lose dynamic range in the corners because you end up raising your noise floor.  With the 24-90 I don't think it's too bad, but if you depend on it too heavily (presumably in an effort to make your lens(es) smaller) you could end up with an image that looks great in the middle but noisy in corner shadows.  I have seen it with some of my pictures with 'M' lenses when I'm the one applying the vignetting control manually!  Of course, it is always possible to increase vignetting after the profile has lessened it in order to address the noise, but it would be better still for the illumination wide open to be a bit more even.  

 

My 21mm Summilux has roughly 2.5 stops of vignetting when shot wide open

The 24mm Summilux is actually a touch worse

The 50mm Noctilux is similar

Even the 35mm Summilux has over 2 stops of vignetting

 

I don't object to any of the above numbers on an 'M' lens.  Obviously, one of the key design criteria for an 'M' lens is keeping things small, and that means higher vignetting numbers.  But the SL lenses are physically much larger and so not subject to the same design constraints.  Leica has decided not to publish vignetting numbers for any of the SL lenses, probably because of the software correction available.  I would hate for them to become so dependent on the software correction that they start allowing 'SL' lenses to be more 'M' like in their vignetting.  Again, I haven't seen any pictures with my 24-90 where this was an actual issue, but I see it frequently with my 'M' lenses.  If I am shooting wide open with my 21mm or my 35mm I need to recognize that if I choose to correct the vignetting (which I may or may not want to do, depending on the subject), I run the risk of noise levels in the corners becoming visible when they weren't an issue in the center of the field.  One lens I am looking forward to in the SL roadmap is the wide angle zoom.  It's the lens where Leica will be most tempted to rely on the software vignetting correction.  I hope they aren't too aggressive.  

 

- Jared

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This is the Leica forum at its absolute worst. Deviate from the pack view of Leica worship and be denounced as a troll (I've no idea why the moderators find this kind of abuse acceptable).

 

Zlatkob has been incredibly polite given the insults people are heaping on him for questioning the wisdom of enforced digital corrections. I don't think it's a big deal. It's true that Canon, for example, give the option of turning off corrections, but the degree of correction isn't so great to begin with; if it was, framing would be tricky with an optical viewfinder. Software correction for EVF cameras is just a fact of life and all of the manufacturers appear to be taking the same route as Leica. The world moves on and we shouldn't be surprised that lens designers take advantage of any additional tools that become available to them.

 

None of that makes me want to burn Zlatkob as a heretic.

 

Had this been his first post, or even sixth or seventh on this topic I would agree with you. But it's been many many more than that and from someone who does not own or use the SL or its lenses. Of course you can have a look back through his recent posts and verify how many, exactly, for yourself. I have no doubt he means well but it's not seeming like anything other than an obsession for him with this topic and with gear he doesn't use. Maybe it's unintentional. Maybe not. But I'm not the only one who thinks he's gotten to the point of argument for arguments sake. And I'm not the only one who thinks he's more than made his point and should just let it go. Or better take it up directly with Leica instead.

 

Gordon

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Had this been his first post, or even sixth or seventh on this topic I would agree with you. But it's been many many more than that...have a look back through his recent posts and verify how many...it's not seeming like anything other than an obsession for him...Maybe it's unintentional. Maybe not. But I'm not the only one who thinks he's gotten to the point of argument for arguments sake. And I'm not the only one who thinks he's more than made his point and should just let it go

He's not arguing with himself in an empty room. Maybe you should all 'just let it go'.

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Oh, I don't know. Some of it was interesting.

 

Like any internet discussion, you could always just ignore discussions that don't interest you. That's certainly what I try to do. There have been significant and interesting contributions as a result.

 

Leica discussion at its best is where you learn something. The educational benefit of this exchange is sorely limited, so I'll leave you to it.

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People often make the mistake of thinking that if an issue doesn't bother them then it shouldn't bother anybody. I've no idea how problematic automatic software corrections are to Zlatkob for his uses. I suspect not overwhelmingly problematic, but nothing about his posts suggests he's 'trolling' or 'bullshitting'. He's just calmly making a case for the option of easily turning corrections on or off in Lightroom. It's not an outlandish position and with, for example, Canon conversions I decide on a picture by picture basis whether I enable corrections or not. As I said in an earlier post, I think the shift from OVF to EVF cameras changes everything. You can't have crazily distorted uncorrected lenses on an OVF camera because framing would become impossible, whereas a corrected EVF leaves all options open for lens designers.

 

I'm sympathetic to Zlatkob because I've had abuse hurled in my direction for asking a really straightforward question that mattered to me but clearly not to others. In my case I asked if anybody had ascertained whether a SLOOZ 28mm finder aligned properly on the Q. Nobody answered my question, but a number of people pointed out that I must be an idiot because the Q already had an EVF. No matter how many times I politely pointed out that I don't find EVFs great in bright tropical sunlight, the response was the same: 'You're an idiot, the Q already has a viewfinder'.

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I downloaded "DNG Cleaner" and stripped the opcodes from the dozen or so SL50mm DNGs I had collected, and did the same for a number of SL24-90 DNGs set to 50mm that I had. I compared the corrected and uncorrected files from both. My perceptions:

  • The DNG Cleaner tool was written by the same person who wrote PhotoRAW for iOS. The new app, for macOS, is well-written app that works simply and easily, costs $10.
  • Regards the lenses, in both cases some rectilinear correction is taking place. The zoom shows a bit of 'mustache' shaped aberration, the SL50 a bit of simple barrel distortion (probably 5%). 
  • A small amount of image area is lost around the edges due to the correction. 
  • I am unable to find any evidence of egregious stretching in the corners or sides of the image.  
  • In no case would I prefer the uncorrected image over the corrected image even though the corrections are truly quite small in both cases.* 
  • Lining up and comparing the SL lenses photos with 100 similar photographs made with Summilux-R 50mm, Color Skopar 50mm, and Nokton 50mm, they all produce pleasing photographs. The SL series lenses produce photographs that on average show slightly better correction—but in all honesty, if you weren't specifically looking for rectilinear correction, I doubt very strongly that you'd even see it. 

* This is my judgement call, others might see differently. 

 

Like so many of these controversial thread discussions, the debate here is just "much ado over nothing." Obviously, if eliminating the corrections is important to you for some reason, just do it with the tool (which is cheap and easy to use) and enjoy yourself. They're your pictures, do what you damn please with them. 

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I downloaded "DNG Cleaner" and stripped the opcodes from the dozen or so SL50mm DNGs I had collected, and did the same for a number of SL24-90 DNGs set to 50mm that I had. I compared the corrected and uncorrected files from both. My perceptions:

  • The DNG Cleaner tool was written by the same person who wrote PhotoRAW for iOS. The new app, for macOS, is well-written app that works simply and easily, costs $10.

This one is for free:

http://www.l-camera-forum.com/topic/226978-tool-to-remove-dngraw-software-lens-correction-instructions/

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Sandy's DNG cleaner does a few extra things, besides removing the WarpRectilinear opcodes from an SL file.  It also removes the Adobe profile templates and the full-sized jpg embedded for in-camera sharpness of focus testing, and then has a compression option.  If you want some subset of those functions, it is probably worth the $10.  But you just want to override the opcodes, using CaptureOne or Iridient is perfectly capable of doing that or of changing the extent of that correction with a slider.  AccuRaw will ignore them as well.

 

Incidentally, in discussing software corrections, we should be aware of some important distinctions, as they affect whose software or firmware is causing or concealing the problems.  Vignetting  corrections are most naturally performed in the camera on the Bayer image, 24 million RGGorB pixels, each at a specific location and behind a specific filter.  Post processing corrections (now we're in Adobe's grip, or using some third party software) can be made on the Bayer image or on the demosaiced RGB image before outputting it as a TIF or JPG. The distortion corrections, when combined with lateral chromatic aberration correction in a single transformation which is different for each color, have to be done at the second stage.  That's how the opcodes for "WarpRectilinear" work, and I suspect that is a very good method.  The SL uses these opcodes to correct things left uncorrected optically in their latest designs, and also provides these corrections for a number of highly regarded M and R lenses.  The M10, working more closely with Adobe, seems to have left the M and R corrections only available in Adobe's profiles.

 

scott

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I downloaded "DNG Cleaner" and stripped the opcodes from the dozen or so SL50mm DNGs I had collected, and did the same for a number of SL24-90 DNGs set to 50mm that I had. I compared the corrected and uncorrected files from both. My perceptions:

 

  • The DNG Cleaner tool was written by the same person who wrote PhotoRAW for iOS. The new app, for macOS, is well-written app that works simply and easily, costs $10.
  • Regards the lenses, in both cases some rectilinear correction is taking place. The zoom shows a bit of 'mustache' shaped aberration, the SL50 a bit of simple barrel distortion (probably 5%).
  • A small amount of image area is lost around the edges due to the correction.
  • I am unable to find any evidence of egregious stretching in the corners or sides of the image.
  • In no case would I prefer the uncorrected image over the corrected image even though the corrections are truly quite small in both cases.*
  • Lining up and comparing the SL lenses photos with 100 similar photographs made with Summilux-R 50mm, Color Skopar 50mm, and Nokton 50mm, they all produce pleasing photographs. The SL series lenses produce photographs that on average show slightly better correction—but in all honesty, if you weren't specifically looking for rectilinear correction, I doubt very strongly that you'd even see it.
* This is my judgement call, others might see differently.

 

Like so many of these controversial thread discussions, the debate here is just "much ado over nothing." Obviously, if eliminating the corrections is important to you for some reason, just do it with the tool (which is cheap and easy to use) and enjoy yourself. They're your pictures, do what you damn please with them.

Thank you Godfrey. As you say, much ado ...

 

I can understand philosophically, people wishing the images were the result of perfect optical design and not electronic trickery, but:

 

(1) the lens is designed only for use with the SL; it's not a generic lens for use on multiple platforms like the Otus series

 

(2) as others have said, by not compromising some aspects to achieve the best optical performance, and relying on digital correction for those aspects, we might be getting the best of both worlds

 

(3) in all honesty, it's the end result that interests me. I don't actually care how I got there.

 

I'm assuming that, having invested in the two zoom lenses, Leica will continue making a full frame L mount to take them long term - I expect to use the SL till it breaks; and it will break eventually. I've broken just about every other camera.

Edited by IkarusJohn
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