TK! Posted March 31, 2016 Share #1 Posted March 31, 2016 Advertisement (gone after registration) Hi all, I heard/read several times that the lens correction information is not coming from the software (Lightroom) as I thought but is already contained in the DNG-Files. I would be quite interested in learning more about this. Maybe this is a chance to correct the pictures in OpenSource-Software. (I nearly gave this up, starting to run Lightroom in a virtual machine on my Linuxbox...) Would also be great to have the colour profiles being contained in the DNG-Files... Best wishes TK! Link to post Share on other sites More sharing options...
Advertisement Posted March 31, 2016 Posted March 31, 2016 Hi TK!, Take a look here Lens Correction Contained in DNG-Files?. I'm sure you'll find what you were looking for!
jaapv Posted March 31, 2016 Share #2 Posted March 31, 2016 http://www.l-camera-forum.com/topic/246312-q-28mm-lens-design/ Link to post Share on other sites More sharing options...
Jared Posted April 3, 2016 Share #3 Posted April 3, 2016 Here is a little info... There are three ways that lens corrections can be dealt with in Lightroom. By lens corrections, I mean distortion, chromatic aberration, and (optionally) vignetting. 1) The camera manufacturer can figure out all the information required to correct the image and tag the DNG or RAW file with the actual corrections themselves. Lightroom will apply these corrections automatically when the image is imported--they are not optional in Lightroom. Some other raw software readers will only apply these corrections if you want. However, the recent trend is for camera manufacturers to consider these corrections "mandatory", i.e., the design of the lens/camera assumes that these corrections will be made in software since otherwise the overall image quality would be noticeably inferior. The "Q" is an example of this type of approach. So is the SL/24-90 combination. For that matter, so is the use of "R" lenses on the SL camera--the corrections themselves are embedded in the file. This is becoming more and more common since it allows the camera/lens manufacturer to design the system as a package, and you can end up with better overall performance if you don't need to make all corrections in the lens. 2) The camera manufacturer can simply make sure the image is tagged with the lens and camera used. The combination of camera and lens can then be used to manually choose a "profile" in Lightroom or any other software package to make corrections. The corrections are not applied automatically--the user must choose the correct profile (though Lightroom will often default in the correct values). This is how distortion and chromatic aberration corrections are made for most "M" lenses. Someone (Adobe? Leica?) creates a profile that is available in Lightroom and the user chooses whether or not to apply the profile. Typically, this is used in situations like the "M" cameras where the same lens might be used in lots of different cameras--from an M3 to an M(240). Since the lens designer can't assume much of anything about how the lens will be used, aberrations like distortion and chromatic aberration are generally better controlled in the lens than in situation 1 above. These lenses weren't meant to NEED correction, but they may still benefit from it. For example, my 16/18/21 Tri-Elmar has a fair amount of distortion if I don't apply the profile. Enough that the lens would be useless for architectural purposes without the profile, but still pretty good for landscape work. This method is also used to address "Italian Flag" type issues where some lenses with some sensors create color casts on the edges of the frames due to the angle of incidence of light on micro prisms. Non tele-centric wide angle lenses are particularly prone to this issue. 3) Lens corrections can be performed manually by the user in Lightroom. Generally, the toolset is not as good as in situations 1 and 2 above. For example, simple barrel and pincushion distortion can be fixed, but not more complex "mustache" type distortion. This is also the best way to get rid of any final vignetting in the system--either through a flat field or through a slider tool. While profiles often contain SOME vignetting correction--even a fair amount in scenario 1--they rarely try to get vignetting down to zero. Especially wide open, you will usually find there is significant vignetting with most camera/lens combinations even after the profile is applied, but you can remove it completely in Lightroom by hand if you want to. Most images don't need this correction, but it depends on the subject matter and the desires of the photographer. A couple other things I will mention... Lots of people seem to think they need the "true" RAW file. You don't really. At a bare minimum, I can't think of a situation where you wouldn't want your software package to perform demosaicing on the image--assignment of color values for all pixels. In addition, most camera manufacturers embed maps in their cameras noting dead and hot pixels and the like, and raw files generally have these pixels already "fixed" by the time you see them in Lightroom or anywhere else. So, outside of astronomy cameras, you are never really seeing a completely "raw" image. I certainly wouldn't want to. The big debate here seems to be about scenario 1 above. Is embedding software corrections in a file a sign of poor optical design on the part of the manufacturer? Or a way to make a cheaper product perform better? Is it cutting corners? There are pros and cons to this approach. In the case of the Leica Q, where the lens will never be used on a different camera, I think it's an extremely smart decision for Leica or any other manufacturer in a similar situation to do less of the correction in the optics and push some of the correction into software. This must be done intelligently, of course. If too much interpolation is required, image quality will suffer, but there is no question that this gives the designers an additional degree of freedom in the design so that they can pick the best combination of features--physical size, weight, cost, responsiveness (autofocus), handling, distortion, chromatic correction, spherical correction, near focus distance and quality, on-axis performance, off axis performance, etc.. Designers are constantly trying to come up with the right balance, and embedding corrections in the raw file provides an additional tool to achieve this balance. - Jared Link to post Share on other sites More sharing options...
mgrayson3 Posted April 3, 2016 Share #4 Posted April 3, 2016 The problem with LR is that the correction can't be turned off. Not all images require perfect rectilinearity, and there is a decent amount of information that is cropped in LR which *is* available in, for example, Capture One. I have more than once used a crop of a Q image that went into this region. LR is not usually stingy in providing manual control. It's odd that it is forbidden in this context. --Matt Link to post Share on other sites More sharing options...
Jared Posted April 4, 2016 Share #5 Posted April 4, 2016 I agree that I would prefer if Lightroom had the ability to disable the embedded profile correction. I suspect that the camera manufacturers collectively have asked Adobe to NOT provide this function since it might result in owner dissatisfaction due to exactly the type of discussions that have occurred on this forum. Leica in the past has shot themselves in the foot by claiming that they were not relying on software corrections when, in fact, they were. I believe that happened with the initial release of the 'T'. Nothing wrong with using software correction in my opinion--they should use all the tools at their disposal--but they should be more transparent about it. I have found one easy way to guess whether software correction is embedded in the DNG's... If the tech spec includes a distortion graph, there is no software correction embedded; just the lens is included in the exif to allow manual profiles. If the tech spec DOESN'T include distortion numbers, then there almost certainly IS software correction since the graph would look horrible otherwise. - Jared Link to post Share on other sites More sharing options...
jaapv Posted April 4, 2016 Share #6 Posted April 4, 2016 Leica in the past has shot themselves in the foot by claiming that they were not relying on software corrections when, in fact, they were. I'm interested. Could you please provide a reference for this? Link to post Share on other sites More sharing options...
Jared Posted April 4, 2016 Share #7 Posted April 4, 2016 Advertisement (gone after registration) Sure. Here is where I got it, I think... http://www.dpreview.com/reviews/leica-t-typ701/7 According to DPReview, Leica had informed them during the pre-launch briefing that the optics did not require software correction of distortion. It could just have been an overly zealous rep trying to emphasize optical quality, but it sounds like it was a pretty specific claim. Oops. The mention on DPReview was picked up by several other sources and described as either a conspiracy, a controversy, or a non-event depending on the perspective of the writer. - Jared Link to post Share on other sites More sharing options...
jaapv Posted April 4, 2016 Share #8 Posted April 4, 2016 Ah yes, that was about the T. I recall now. A bit of a storm in a teacup at the time. Link to post Share on other sites More sharing options...
marcobellardinelli Posted May 4, 2016 Share #9 Posted May 4, 2016 As I have personali verified, Affinity Photo doesn't actually read and interpret lens correction information that is embedded in Leica Q DNG files. Does someone have news about it, and is there a way to bypass this serious software bug? Link to post Share on other sites More sharing options...
pico Posted May 4, 2016 Share #10 Posted May 4, 2016 Cannot the OPCODEs be stripped from the DNG? I do not use LR, but I do have a utility to strip OPCODEs from DNG, kept from my former employment. Link to post Share on other sites More sharing options...
Herve5 Posted May 5, 2016 Share #11 Posted May 5, 2016 I agree that I would prefer if Lightroom had the ability to disable the embedded profile correction. Am I really the only one NOT using Adobe here? IMHO, all the other raw processing softwares open Q DNGs without correcting them (and, when needed, I correct the barrel myself)... Link to post Share on other sites More sharing options...
xenar Posted May 5, 2016 Share #12 Posted May 5, 2016 Cannot the OPCODEs be stripped from the DNG? I do not use LR, but I do have a utility to strip OPCODEs from DNG, kept from my former employment. Stripping the WarpRectilinear opcode will remove the embedded lens correction, yes. Link to post Share on other sites More sharing options...
TK! Posted May 5, 2016 Author Share #13 Posted May 5, 2016 Stripping the WarpRectilinear opcode will remove the embedded lens correction, yes. And how to get software other than LR to rely on the opcode? I still would like to use my opensource tools (darktable, gimp, rawtherapie, ...) It's a pitty... (and a pain with LR in a virtual box on my Linux system) - TK Link to post Share on other sites More sharing options...
soizic Posted May 6, 2016 Share #14 Posted May 6, 2016 Hervé said : Am I really the only one NOT using Adobe here? No I also (Capture One) Link to post Share on other sites More sharing options...
stevieboy Posted May 7, 2016 Share #15 Posted May 7, 2016 I use Aperture. I've used Lightroom in the past (pre Q) and it's okay but Aperture I like much better. We'll see how long I can keep using before it becomes obsolete. I haven't had my Q very long but I've taken a fair number of photos with it, in different situations. I haven't noticed any aberration, not saying it isn't there, but nothing that stands out enough for me to notice. I'm not going to make an effort to look for it and then become unhappy with the camera! Link to post Share on other sites More sharing options...
Bart van Hofwegen Posted June 13, 2016 Share #16 Posted June 13, 2016 Am I really the only one NOT using Adobe here? IMHO, all the other raw processing softwares open Q DNGs without correcting them (and, when needed, I correct the barrel myself)... Of course you are not, Adobe seems to make it easy for other RAW converters to carve out a market share, however small. I am not particularly happy with ACR in general. I actually use different raw converters depending on the camera and type of shoot and finish off in Photoshop. For the Q, I find that colors come out best using Raw Photo Processor (RPP), combined with a couple of custom profiles made with a ColorChecker test chart. RPP has an excellent option for that, performing better than XRite or Adobe DNG editor. It has some other nice features too. However: RPP does NOT perform the lens correction opcodes at all. Sometimes that is Ok, sometimes not. Does anyone know if anyone went through the trouble of making a custom Photoshop lens correction profile (or action) yet ? I have been unable to find one up till now. Herve5, you mention doing barrel correction yourself. As that is is what I would like to do (although I think the opcodes actually code for more than just barrel correction), could you please share the settings/steps you use, or any any other suggestion? TIA! Link to post Share on other sites More sharing options...
GiantTristan Posted June 13, 2016 Share #17 Posted June 13, 2016 I routinely use DxO Pro 11 for photo editing and they have a correction module for the Leica Q. If you disable the correction module, you get the image without correction. I attach an example for a file without correction (upper picture} and with correction applied (lower picture). The barrel distortion is very apparent at the vertical door frame. Whether DxO uses the Leica correction or their own, I do not know. I believe they prefer to use their own correction algorithm. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/258812-lens-correction-contained-in-dng-files/?do=findComment&comment=3060908'>More sharing options...
Bart van Hofwegen Posted June 13, 2016 Share #18 Posted June 13, 2016 Thanks Tristan, but I am looking for settings / custom profile / action to perform the correction in Photoshop. I use a raw converter that does not have lens corrections. I might go back to Adobe Raw Converter but I simply do not like the colors (even with custom made profiles). Link to post Share on other sites More sharing options...
Herve5 Posted June 13, 2016 Share #19 Posted June 13, 2016 Thanks Tristan, but I am looking for settings / custom profile / action to perform the correction in Photoshop. I use a raw converter that does not have lens corrections. I might go back to Adobe Raw Converter but I simply do not like the colors (even with custom made profiles). Ah, but I don't use Photoshop either For removing the barrel effect, I just use the associated command in Macintosh GraphicConverter, which superimposes a frame over the picture, which allows very easily to cross-check whether the straight lines are really straight -and once the correct setting is found, as the software spontaneously defaults to the previous setup each time this function is called, and the Q, well, only has a single lens, nothing more needs to be done : select barrel correction, and carriage return on the proposed setting... DarkTable and RawTherapee propose the same (-0.1 setting in RawTherapee, DarkTable I don't remember) Link to post Share on other sites More sharing options...
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