In some posts dating back to last year I discussed the Leica M9's by now notorious red edges problem, starting with this post. At the time, I thought, and commented to that effect on the Leica User Forum, that while Leica wouldn't be able to 100% solve the problem given manufacturing variations in both lenses and the M9, they would be able to make substantial improvements by tweaking the M9's firmware corrections. However, there's been a deafening silence out of Solms, and the silence is growing more deafening by the day - no firmware update, no statement about what the issue actually is.

What's concerning is that its now been quite a while. CornerFix V1.3.0.0, which was capable of correcting the red edges in most cases, shipped in early Novemeber last year. CornerFixV1.3.0.4, which fixed some early bugs, and extended "most cases" to "pretty much all cases", shipped in late November. So its now nearly three months since a version of CornerFix that unambiguously nails the problem shipped, but Leica haven't got anything out of the door.

The question is, why haven't Leica shipped a new firmware version? This is actually a major issue, and it's not as if it just impacts 50 year old lenses, or lenses from other manufacturers - it impacts the vast majority of Leica's own 18mm lens, which was introduced in past few years, as well as a good number of examples of other lenses, e.g., the 21 mm and the WATE.

Well, I can only speculate, although it's somewhat informed speculation in the sense that I know exactly how CornerFix solves the problem. It seems to me that there are only a limited number of possible explanations:

Explanation 1: Leica's just busy with the S2, etc.  Well, maybe. The S2 is probably Leica's view of its future. But the M9 is today's cash cow. Neglecting getting it right seems like a big risk, even if production hasn't yet caught up with demand.

Explanation 2: The red edges just can't be fixed much better than they are now. This is the "doomsday scenario", and not a pleasant one, and certainly not one that I had considered up till recently. But there is some evidence that supports it:

• The Kodak DCS PRO 14n suffered from what was known as the "Italian Flag" problem (green on the left, red on the right!) with some lenses. That was never solved in firmware - it took a next generation Kodak DCS with a revised sensor to solve the problem. And the M9 uses a Kodak sensor.....
• Stephan Daniel referred in a recent interview to vignetting correction as being "more of an art than a science", which discourages me. I'd be a lot more confident if this was being described as an engineering problem. In my opinion, Leica should be viewing this as a matter of science, and statistical variations in production. Trying to make corrections by "feel" seems unlikely to result in an optimal solution, and will maybe result in no solution at all.
• I'm starting to have a lot of trouble believing that Leica didn't know about the red edges before the M9 shipped, which in turn implies that they had ample opportunity to find a fix, if they could. What we know today, and didn't know three months ago, is that nearly all 18mm lenses show red edges. In fact, every one that I'm aware of does, and I know of at least one M9 user that tried all three that his local dealer had available. And when I specifically asked in a post on the Leica User Forum a few days ago whether anyone knew of an 18mm that didn't have red edges on the M9, nobody responded. So to believe that Leica didn't know about this, we need to believe that either the 18mm wasn't tested for vignetting, or the test was so hopeless incompetent as to miss the problem.

Explanation 3: Red edges are a lot more difficult to fix in firmware than anyone thought. This is a more hopeful scenario, and fortunately one that we have some reason to believe might be true. The reason is the following. If you consider what computations CornerFix has to do in order to correct an image as a proxy for what the M9 firmware might have to do, the answer is very different for the M8 and M9:

• For the M8,  a simple symmetrical radial devignette, centered on the physical center of the sensor is sufficient for CornerFix to correct any lens, up to and including the CV12 and CV15. That amounts to what is in effect a "half of a radius computation" and a look-up for every pixel.
• For the M9,  an offset asymmetrical correction is required. What that amounts to is an (a) offset computation, (b) a full radius calculation, (c) multiple look-ups, and (d) a complex interpolation process for each pixel.

Now Leica may be able to do something clever to simplify that process - they have the advantage of presumably knowing in detail what the root cause of the problem is, and thus having a mathematical description of what's going on, which I don't. However, two things are near certain - firstly, the M9's vignetting correction code will need a total rewrite, and secondly it will absorb far more processing power than the M8's algorithm, which also appears to be the current M9 algorithm. However, we know that the M9's processor is already heavily loaded, so unless some really efficient code gets written, the M9 may be slowed to a crawl. And writing really efficient code takes time. And there's a complication - the original code was written by Jenoptik for the M8, so its likely they will have to create any new code, or a new set of programmers will have to understand the old code.

What happens if the M9's processor just can's handle the load, no matter how efficient the code is? Well, there a solution to that, but a solution that will be very unpopular in many quarters. Leica could simply give up on doing the corrections in-camera, and embed correction op-codes into the DNG image, using the DNG 1.3 specification. That means no processing the image pixel by pixel. However, there are two problems with that. That means the in-camera JPEGs aren't fully corrected, and that DNGs can only be processed in Adobe Lightroom or ACR. No other raw developer implements DNG 1.3 opcodes. Which will drive the Capture One enthusiast crazy, and could seriously cut into the "rich snapshot" market. And given the somewhat strained relationship between Phase One and Leica at the moment, it's not clear that Phase One would go to the trouble of writing correction code.

So we live in hope.......

UPDATE: Part 2 here.