Digital Hapeman
2010
Introduction: The Problem
While Leica produces a wide selection of wonderful lenses, Leica does not provide a wonderful selection of wide lenses. In fact, there are only two current lenses from Leica wider than 21mm: The 16-18-21mm f/4 Tri-Elmar-M and the 18mm f/3.8 Super-Elmar-M. If you want to go wider, you have to look to either Zeiss or Cosina-Voigtländer.
Because the Leica digital M’s apply corrections to image files based on the lens attached, non-Leica lenses can present some problems with color shifts (specifically a cyan shift shift in the corners, and on the M9 a shift where the left side of the image moves towards red, while the right shifts towards cyan). This problem is especially prominent on wide lenses, and can render the images unusable in many conditions. So what is a Leica digital M shooter to do for ultra-wide angle shooting? Don’t fear, there is a solution at hand.
The Solution: CornerFix
The problems with wide angle lenses and Leica cameras started with the M8, where the corners would drift towards cyan with wide lenses. Fortunately, Sandy McGuffog put together a fabulous software utility to deal with the problem--CornerFix (there are both Windows and Mac OS X versions). Within just a few weeks of the release of the Leica M9, Sandy had released a new version of his utility that corrected the red edge problems of the M9. Unfortunately, using CornerFix is a bit challenging--the documentation is sparse, and the program is not intuitive enough for most people to figure out on their own (although to be fair, if you take the time to read the accompanying documentation, it is very helpful). This article will describe how to use CornerFix properly with the Leica digital M’s and the Voigtländer 12mm and 15mm wide-angle lenses.
The most important aspect of using CornerFix is getting a good profile of your lens-camera combination. CornerFix is so accurate that while a generic lens profile can work, the best results will come from a profile of your specific equipment. While a variety of approaches will work, the most important thing to keep in mind when generating your profile is that you want the lighting to be a even as possible. While this sounds easy, its much harder than you think. My preferred method is to use a large piece of white poster board. This is readily available at most craft and hobby shops, and is very cheap. I set the poster board outside in a location with shaded diffuse light; in my case the shaded side of my house in the early afternoon has a very diffuse lighting that works perfectly.
It’s important to expose correctly so that you don’t have a noisy image to use for your profile. Given that the meter will tend to underexpose pure white, I shoot my profiles at +2EV. Set the camera lens at f/8 and set the focus at infinity (although the focus doesn’t really matter). Hold the camera close enough to the poster board to ensure that the entire image is pure white, but not so close as to cause any shading or shadows.
A good profile image will look something like this, taken with the Voigtländer 12mm f/5.6 Aspherical Ultra-Wide Heliar:
VOIGTLANDER ULTRA-WIDES ON THE LEICA DIGITAL M CAMERAS
7/31/10
Ultra-wide angle lenses can provide a new perspective on old subjects
Note the strong vignetting, cyan shift in the corners and the reddish-magenta lower edge. Those are the problems that CornerFix will correct on your images once you build a profile from this image.
Now, open CornerFix and load this image using the command File -> Open. CornerFix will show the image in the left hand side of the application window. Now you want to create a profile from this image. You do this by selecting Lens Profile -> Create Profile from the menu. CornerFix will very rapidly create a profile from the image and display the resulting corrected image on the right hand side of the window. This image should be nearly perfectly flat and white; this indicates that CornerFix has created a profile that completely corrects for the vignetting and color shifts in the image left-hand side of the application. It should look something like this:
Coding Lenses: What Should You Do?
One other topic should be covered here: Coding lenses. The digital M’s correct for color shifts and vignetting with in-camera profiles and correction algorithms. Many people have experimented with hand-coding Voigtländer and Zeiss lenses as Leica lenses; there are whole websites that show the optimal codes to use on nearly any lens (Here’s an excellent one). I personally like to code my lenses and therefore I have experimented with coding my Voigtländer ultra-wide lenses. What I have found (and others as well) is that using the code for the Leica 21mm f/2.8 Elmarit 11134 with the Voigtländer wides works quite well on the digital M cameras. In the case of the 12mm Ultra-Wide Heliar and the Leica M9, it very effectively corrects out most of the vignetting and color shifts, leaving just a little bit more to correct with CornerFix. It doesn’t correct the red edges on the 15mm nearly as well, but it still helps.
If you do choose to code your lenses, you *must* create a profile of the coded lens. You might want to experiment with your lenses and see if you prefer using them coded or uncoded; the only negative in my opinion is that the EXIF data lists the shots from my Voigtländer wide lenses as all coming from a 21mm pre-aspherical Elmarit, but I can live with that. In my experience with the Leica M9, I get better final results by coding my lenses as indicated above and using a profile of the coded lens.
The final step is to save your profile so you can use it in the future. Select Lens Profile -> Save As from the menu, and give your profile a friendly name that helps you remember what lens-camera combination you used to create it. I typically save the profiles in the same folder as the application, just to keep everything in one place.
Now try the profile you have created on a few images you have taken just to see how well it works. At this point, the profile is now loaded, so if you load any image, it will display the uncorrected image on the left and the corrected image on the right. If the results look good, your work is done. However, if you like a little vignetting in your images, or want to otherwise tweak the output, you can delve further into the options that CornerFix provides. CornerFix will open with the most-recently used profile automatically loaded. If you only use it with one lens, then you will never need to load a profile again. Otherwise, if you need to load a different profile, just select Lens Profile -> Open.
There is a decent selection of options in CornerFix to both alter your profiles and your final corrections. If the resulting images from your profile look pretty good but you want to make a few changes, then I recommend simply tweaking the settings under the “Color” section of the CornerFix preferences. For example, I personally like just a bit of vignetting in my ultra-wide images, so I set the luminance slider to .5. Experiment and see what you think. If you think the profile image is good, but the corrections don’t look quite right, you can try adjusting some of the settings under the “Profile Creation” tab of the application preferences--I recommend enabling the “Multiple Equations” checkbox as a start. If that doesn’t work, you might want to try and re-shoot your profile image.
One nifty final feature of note under the CornerFix application preferences is the “MakerNotes” section; you can check the “Update EXIF” box and CornerFix will update the EXIF fields with the Leica MakerNotes data. This will give you an estimated f-stop for your shot and the lens description information. If you aren’t using Lightroom (which can read the MakerNotes), this can be a very handy feature.
Once you have a good profile, you can use it to correct images any time you use that camera-lens combination. In general, I have found that a profile created with diffuse sunlight will work very well for almost all situations with the exception of fluorescent or mixed fluorescent lighting. I personally dislike dealing with fluorescent lighting anyway, so I avoid shooting in it and haven’t created a profile for fluorescent light. If you do shoot a lot in fluorescent light, you might need to create a special profile to use in those lighting conditions.
Correction of images adds a step to your workflow. Luckily, CornerFix has great batch-processing functionality so you can automate the process. It’s also a fully multi-threaded application, so if you have an newer multi-processor or multi-core computer (like most computers made in the last few years), it is also very fast. When I get back from shooting with my Voigtländer ultra-wides on my Leica M9, I simply put all the images taken by each lens I need to correct in a separate folder. I then open up CornerFix and select the profile I need by going to Lens Profile -> Open (remember that by default, CornerFix opens using the last profile you used, so be aware of that if you have more than one profile). I then select File -> Batch Correct Images and locate the folder I have created and select all the images in the folder and press Open. CornerFix will then correct all images in the folder and save the new version with a _CF appended to the file name.
To see the results of using CornerFix, I have prepared some sample images. The gallery linked below has examples of images before and after correction, as well as some corrected images to demonstrate real-world use these wonderful lenses on my Leica M9.
Leica M9 and Voigtländer Ultra-Wide Lenses
Here are two sample images taken with the M9 and the Voigtländer 12mm Ultra Wide Heliar:
And here are two images taken with the M9 and the Voigtländer 15mm Super Wide Heliar:
Final Suggestions
Finally, I want to make a recommendation about shooting with the Voigtländer wide lenses that will help yield optimal final results. Because the meter in the digital Leica M’s is a center-weighted meter, the corners and edges will typically be underexposed by 2-4 stops. That means that corrected images will show a good bit of noise in the corners. Luckily, CornerFix will correct for both positive and negative vignetting, so you can compensate for this problem when shooting by slightly overexposing your images and letting CornerFix essentially “flatten” the exposure during correction. I typically set the camera to shoot at anywhere from +1EV to +2EV when shooting with the 12mm and 15mm Voigtländer lenses. While the LCD may show a very bright image, keep an eye on the histogram. As long as it doesn’t show any blown highlights, the corrected results will look fine and will have much lower noise in the corners.
Hopefully if you read this you will find it helpful. The Voigtländer ultra-wide lenses are optically excellent lenses, and are bargain-priced compared to any Leica lens. With a little bit of extra effort, they can be used to great effect on the Leica M8 and M9.
I want to thank Stephen Gandy of Cameraquest for loaning me the Voigtlander 15mm f/4.5 Aspherical Super-Wide Heliar used in this review.
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