Whenever you hear the word Leica, say the word Leica, or even think the word Leica, you think of quality. The quality of the product, the quality of the lenses, the quality of the image and surprisingly, also the quality of the colors. But why is it that when you think “Leica”, you think that the colors should be breathtaking. What does Leica know about colors? They’ve never designed color previously; all they did was to let you load any color look you wanted inside their film cameras.

Once camera makers started to switch to digital, color suddenly became a top priority. This was some task because there is not a single camera that reproduces colors faithfully by default. This is not because of technical limitations, but is a way of thinking.

Back to the Leica M8. When I loaded Leica’s M8 colors to our color transformation database, I was excited to learn what Leica has done with the colors. By looking at JPEG images from the M8 I noticed that when the WB is correct (which does happen from time to time) the colors are quite unique. I am now able to describe with words and numbers what I have noticed from the real world images I took. Below you’ll find the same LAB and delta C plots from our color database.

Apparently, Leica has engineered the colors so that most of the colors are close to real life colors, somewhat more than other DSLR cameras on the market. However, yellow and orange are twisted towards the greens and are brought close together. Browns however, are turned more to the oranges. I find this to be very interesting! Those colors are usually not twisted that much in other DSLRs.

Next are the greens. Greens are one of the colors camera makers generally twist and saturate. Deep greens and yellow green are slightly saturated in the M8, but not very twisted. More pure Green colors get twisted towards the blues; this is not something we often see in digital cameras.

So surprisingly, we may infer that Leica knows what they are doing with colors. I find their color decisions quite brave. I can’t imagine Canon or Nikon giving us colors like that by default. And there is probably a very good reason for that, Nikon and Canon are trying to please as many photographers as possible, so the colors are tuned to be something most users might like. Leica on the other hand, thinks differently

Getting the white balance correct is essential to get those colors. The auto white balance isn’t something to be proud of. For our color database, we struggled with the custom white balance to try and get a possibly good balance . So there you go, The M8’s colors are distinctive, no other camera has such interesting colors. Enjoy.

Leica M8 colors vs. Nikon D200

In order for you to decide whether you like the Leica M8 colors or not, we compared the colors to the Nikon D200 Mode I colors. Personally, I just love Nikon Mode I colors, which you can get with the Nikon D2x/h and Nikon D200 cameras. But I do feel the Leica M8 should be somewhat more unique and distinctive.

In order to compare colors we needed to make sure the white balance, exposure and sensitivity of those cameras are the same. This is essential in order to receive genuine output colors that are written into the camera’s color table (LUT). Color tables (assuming Leica uses them), or color lookup tables can only be compared when the chromatic balance and input level that insets into the table are the same.

Before taking the images below with both cameras at the same time, we custom measured white balance off a white card. Even if the image we took was not at the same color temperature as the white card when we measured it, the white balance from both cameras should be the same. So the result will be genuine to the color LUTs (but not for the scene of course, which does not matter).

Leica M8	Nikon D200

Well, as you can see, the Leica M8 really renders green and blues more yellowish. Interestingly, skin-tones are more real to me than with the Nikon D200, which look as if the skin was painted a bit to look more human. You can also take a look at our color database with those two cameras here.

But wait

But wait, there is one more essential to get those colors: you have to use the JPEG file of the camera. Frankly, the image quality of the JPEG file is also not something of which to be proud. So if you want to get those distinctive colors with RAW, you have a little problem.
That problem is with the way the DNG file is designed. Adobe, being no camera maker, haven’t left room for the DNG using camera maker to design colors as they wish. All there is for the camera maker to work with are two color matrices, which might be not good enough for flexible color reproduction. But, if Leica know what they are doing and if the color components are not twisted in an extreme manner, two color matrices might just do. For the record, I think Adobe should really rethink about colors with DNG.

Fortunately, there is one RAW software that has been designed by a camera maker and also supports the Leica M8. The Phase one Capture One is clearly designed by someone who understands how a Raw software should work from the image processing aspect. With Capture One you’ll get an ICC file that describes the M8 colors, it also installs other camera profiles for other cameras. This is how all RAW software should work. Technically, with ICC color and LUT support, Capture One should easily match the Leica M8 colors exactly. However, this isn’t exactly the case.

Capture One

The plot below maps colors from the M8 JPEG files and the colors from Capture One using the supplied Leica M8 ICC profile. The file was processed under Capture One LE with Film extra shadow setting, because there are far too many Gamma differences between Capture One and the JPEG file with the standard setting.

An average of delta C 5.25 between the JPEG file and the C1 ICC is okay. By looking at the LAB plot you can see that all the orange and yellow colors have ‘lost their charm’. They seem to be a bit off. Lets see how ACR 4.0 is doing (remember that we processed the file under default settings in ACR).

Adobe Camera Raw 4.0

• ACR Default
• ACR with Gamma correction

Leica M8 sRGB JPEG Adobe ACR 4.0 ColorChecker 24 reference

Leica M8 sRGB JPEG Adobe ACR 4.0 with gamma correction ColorChecker 24 reference

When looking at the results you have to remember that Leica is the one that designed the two color matrices of the DNG files. Because of that, ACR will perform very differently when using M8 DNG files than when using other Raw images. This is because Leica, the camera maker, has designed the colors.

Matrices are very limited in comparison to color LUTs, it’s like trying to cover your self with a small blanket. Pull to one side and the opposite side retracts. I am sure Leica would like some more freedom to tune DNG colors more freely.

ACR is the only software that lets us manipulate the Gamma curve quite freely. As gamma has a large affect on colors, using ACR we could correct the default gamma to the gamma of the Leica M8 JPEG. You can see the results by clicking on the “ACR with gamma correction” tab above the plot.

By looking at the results it could be seen that orange yellow, yellow green, foliage and green are all twisted towards the yellows, this will make any nature containing image look yellowish, even more yellowish than Leica has designed in the jpeg file (short blanket?). Other colors look a bit more saturated than the M8 jpeg file. When using our gamma correction we could get closer to the M8 JPEG colors with most of the non green and yellow colors. You can download the XML file containing the Gamma correction file for ARC 4 here. Please note that the exposure index shifts as a result.

Let’s look at Apple Aperture next.

Aperture

Aperture seems to be quite close in terms of the relationships between the colors, only that the entire space needs to be rotated a bit. This is called “hue” as in hue, saturation and brightness. There are some colors that need some more shifting to fit.

RAW color comparison

We thought it would be nice to come up with some way to display Leica M8 colors of various RAW software applications, so they could be compared. This should help you evaluate which color of which RAW software you like best. So we gathered up a few images in various situations and color temperatures. All of those images were processed with default settings, Capture One images were processed with Film extra shadow and ACR GC images were processed with our special gamma correction configuration. Click the tab below to show the images.

Click here for RAW color comparison

Choose first color images	Choose second color images
M8 JPEG ACR ACR GC C1 LE Aperture	M8 JPEG ACR ACR GC C1 LE Aperture

It is interesting to see that Apple Aperture and Adobe Camera RAW with our gamma correction are quite similar. This means they both use some of Leica’s DNG matrices, but Apple has tuned their Gamma to be more similar to the Leica M8 native JPEG. So there you go, just pick witch software you like best. I think I’ll go for Capture One. Note that you may, of course, twist and change colors inside each software to a limited extent. But frankly, how many colors do you think you can handle? Three? Four? Picking the colors you like best from a software will shorten your workflow considerably.

A word on Raw and color

Most photographers think that with RAW, colors can be manipulated to fit whatever the photographer wants or needs. While this is true in some extent, there are a few problems. Firstly, at present there is no true flexible tool that allows the user the manipulate colors to a very fine resolution. Capture One goes as close as possible, and I suggest trying their color editing tool. However, their tool is quite hard to work with.. Photographers never used to tune colors in the past. That was the job of the chemists. Today, the color tuning work has been transferred to the engineers, who have the tools and knowledge to truly implement what a photographer requires. This brings us to the second problem: what exactly does a photographer wish the colors to be? Does a photographer know what he or she wants? Photographers were never required to design colors, and only a very few could design a good color scheme for a camera. A painter? maybe. Photographer? Just a few of them.

So the task of colors lies on the camera makers and RAW software makers, which should bring to the photographers a basic color scheme that they can then adjust, using the available tools on the market (Photoshop for JPEG – RAW software for RAW).

Color is tough

Color is one of the most problematic issues in digital imaging. Mainly because it is easily misunderstood. I don’t think that even the experts (RAW software makers) really understand how to approach colors. Leica, however, does know how to approach colors. Mathematically I can see that they didn’t just throw in some fancy LUT’s and hoped for the best. I am really happy that Leica has chosen not to fall in to the “colors should be faithful” cult, but chose to create a really unique combination of faithful and twisted colors for the Leica M8. If you do not like those colors, by using RAW you can change the colors to some extent to your liking.

RAW is the next issue I’d like to talk about. It is seems that Leica could not fit the colors of DNG to match the M8 JPEG, it’s a short blanket as I said. However, Capture One, which is the software that is compatible with the Leica M8 should be able to reach the same color as the Camera (using ICC). As of today, Capture One’s colors are not very similar to those of the camera, nor is the Gamma that is being used. I think it’s in Leica’s best interest to make sure these two match. After all, most of us are using RAW with the Leica M8 and some of us are using Capture One. Moreover, both Nikon and Canon are tying to match their RAW software to the camera colors. After all, we bought those cameras to also get those colors. So Leica, please note.

The image on the left is the RAW data at its bayer format from the Nikon D200. The image on the right is the RAW data at its bayer format from the Leica M8. one is brighter then the other even though they both will look the same with any Raw software, such as Adobe Camera Raw. In this article we will explore the 8 bit riddle of the M8 DNG files.

Nikon D200	Leica M8

Yes, those are 8 bits

Right around the time first Leica M8 cameras reached the hands of some of the more advanced digital photographers, reports that Leica’s new M8 RAW files are 8 bit started to come in. This is actually a fairly easy thing to notice as all Leica M8 RAW files are 10.1MB, no matter what is actually in the image. So, if all RAW files are 10.1MB, this means there is probably no compression going on.

With computers, each byte is equal to 8 bits. So, if we have four pixels each holding 8 bits of data, we will have a file size of 4pixles X 8bit = 32bit = 4byte.

A simple calculation of the M8’s 10 megpaixels sensor reveals that with a resolution of 3936 x 2630 where each pixel is holding 8 bits, we will have a file size of:

3936×2630 = 10,351,680pixles X 8bit = 82,813,440bits = 10,351,680 bytes = 9.8MB (when kilobyte is 1024 bytes).

So, here is a proof that Leica’s DNG RAW files are really holding 8bit of pixel data. But, it is not as simple as that.

Understating the role of Gamma

Image sensors operate in a linear way. This means that for every time the amount of light is doubled the sensor also doubles it’s output. What you need to understand is that humans see the world in a logarithmic way, and so this is one of the reasons you see the image below as too dark. What’s more, our computers screens project light in a non-linear way.

Historically, to compensate for those problems camera makers have applied a gamma curve to the image, making it appear correctly on computers and TV screens. Today, camera makers not only use the gamma function for compensation, but also to design the image to look as the camera maker thinks it should look. In other words, every camera has its own gamma function rather then a standard value.

The image on the left is a linear image taken with the Canon EOS 30D. The image on the right has been applied with the Gamma function we have managed to extract from the Canon standard picture style profile.

16 or 14 bits?

Although Leica insist that the M8 is “16 bit-color resolution”, there isn’t any proof that this is actually the reality. What we are about to describe in this article is leading us to think the M8 is really a 14 bit camera, which is already not bad at all. Moreover, the chip that determines how many bits per pixel a camera has is called the AFE chip, or the A/D chip. As it turns out, dual cannel chips with 16 bit output are not very easy to come by. In fact, Analog Devices, one of the biggest AFE chip maker, hasn’t got any AFE chips with 16 bit output, but they do have some dual cannel 14 bit AFE chips.
We are going to assume in this article that the M8 is an 14 bit camera.

Leica M8 DNG files

Obviously, the reason the M8’s DNG files are 8 bit is because leica wanted to have small files that are easy to store and process. Leica is using a software processor on the M8, which is a good thing for a company with no experience with image processing. But this also means its power to energy ratio is quite bad compared to the hardware image processor in most DSLR cameras. So 8bit RAW data is going to help Leica get more battery life and processing time when the images are viewed.

The principle of Leica’s 8bit files is based on the fact that the data will need to be applied with Gamma. As discussed previously, humans see in a logarithmic scale. Human vision tend to have ability to distinguish shadows better then highlights, this could be exploited when 14 bit in linear scale are converted into non-linear 8 bits data.

A bit of reverse engineering

Leica’s DNG files are holding a DNG tag called “Linearization table”. This tag holds a lookup table with 256 entries where each entries is holding 14bit values. Lookup tables, or LUT in short are just big tables with input output values. Leica’s LUT is used to convert 256 input values into 14 bit output values.

There is a lot we can do with this LUT, and we’ll get to the actual use of it in a minute. Using a simple matching function we were able to reverse leica’s LUT to produce the actual LUT that maps 14 bits of linear data into 8 bits non-linear. The curve below exhibits Leica’s curve, reversed, in a 8 bit (with rounding)/8 bit scale.

Obviously when converting 14 bits (or 16 bits) into 8 bits, data gets compressed all over the scale. This LUT compresses data in such a way that data from the shadows gets compressed less than data from the highlights. The table below illustrates some key entries from the LUT (reversed) and the ratio of compressing.

As you can see, the ratio in the shadows is lower then the ratio in the highlights. For example, in the shadows (6th stop) every 19 bits in the 14 bit data are mapped into 1 bit in the 8 bit data. Wheres at the highlights, every 111 bits are mapped to 1 bit in the 8 bit data. So steps in the shadows are more expressed.

Square root, a simple Gamma

Leica performs a Gamma function in order to transform the linear 14 bit data into non-linear 8 bit data. Normally, a camera manufacturer would use a Lookup table (LUT) to perform a similar function. A simpler way to perform the same task is by raising the pixel value with a power. Using exponentiation (power) is a limited function, capable only to shape the data in a single form. A LUT however, is completely flexible.

The term “Square root” has been used by leica to describe what is being done to transform 16 bit (according to leica) linear data into 8 bit non-linear. And indeed, the Square root of 65536 (16 bit) is 256 (8 bit). Also, because the way Square root is acting, by applying Square root on all the 16 bit data range, we would get a nice gamma curve similar to gamma 2.0.
This is because a gamma function is similar. Gamma is performed by raising a number with a power of gamma. For example, gamma of 2.0 would be: 65536^1/2.0 = 256.

Having explained that, I do not think Leica performs a Square root function on the data, because that would require 16 bit input data. It is more likely that Leica is applying a Lookup table (LUT) that performs a function that acts like a Square root, mapping 14 bit data in to 8 bit data. The chart bellow demonstrates Leica’s LUT along with the sRGB standard. Please note that part of the CIE lightness curve is being used by Nikon with their NEF compression method.

How it works

After Leica applies all necessary corrections on the RAW data, such as vignetting correction and cyan correction, Leica then applies the Gamma LUT on the data. The data is converted from what appears to be 14 bit of linear data into 8 bits of non-linear data. Leica then writes a reverse LUT, also called DeGamma, into the DNG header. This reverse LUT has 256 entries for input and 14 bits values for output.

The first step the Raw converter has to do, before it can continue with its normal image pipeline, is to reverse the data back into the linear domain. It does so by applying Leica’s stored LUT on the data, after which it can continue with its image processing pipeline. The diagram below should help you understand this process.

	Capture 14 bit
	LUT 14 bit => 8 bit
	Result
	Raw software
	LUT 8 bit => 14 bit
	Result
	Proceeding
	Color & Gamma
	Final image
	* use your mouse to roll over the above buttons

The negative

Other then small files, faster writing time and better battery consumption, there are no an other benefits. Although by using Gamma 2.0 Leica is taking advantage of the human vision and industry standards, the RAW data will always have 256 input bits. After applying DeGamma on the 8 bit non-linear data there are going to be gaps between the linear 14 bit data. Even if our eyes and computer screens can’t pickup those data gaps, there are still going to be problems with some issues:

Noise!

In the Poisson distribution light behaves, photon noise is larger as the data becomes brighter. By applying Gamma function on the data, noise is being averaged down in the highlights and starched out in the shadows, after which the DeGamma operation will reverse the function. Once the data has been manipulated that way, noise is being averaged down to tonal levels with no consideration of the structure of the image. Noise reduction algorithms are smart, and treat noise differently according to the surroundings of the pixel. For example, a simple algorithm will treat human hair differently than it would treat a flat surface.

The table below is the outcome of an experiment we tried. Using the Canon EOS 30D, we took a CR2 image of a B&W step chart. We then striped the CR2 file from any Canon headers and remained with pure 12bit Raw data in it’s bayer form. Using matlab, we then shifted the data to 16bit, and preformed a simple sqrt on all the data with rounding. The result was a 8 bit image of the chart, still in bayer form. The next step was to bring the data back to 16 bit, this was done by raising the values with a power of 2. The last step was to measure the standard deviation on each step in the image (still in bayer form).

Above: the step chart we used – evey step is 0.3EV.

Quantization problems

The M8’s files will not tolerant much of under exposure corrections. You are likely to see quantization quite easily when correcting your under exposed images. Also, post processing is likely to show some quantization problems. The histograms below are the actual photoshop histograms from the experiment we have done (described above). The histogram on the left is the full linear 16 bit Raw data and the image on the right is the decompressed image, also 16 bit linear. As you can see, there are gaps in Raw tonal data.

Highlights

Because of compression in the highlight, the M8’s DNG files would not have as much details as the next DSLR to recover by sliding the exposure tools of different RAW converters. Please note that ACR/Lightroom are using smart algorithms to recover details automatically once the slider is pooled into negative values – so ACR/Lightroom are not very suitable softwares to test this.

White Balance

In very extreme lighting temperatures, where the red channel or the blue channel are highly saturated, M8’s DNG files are most likely not holding much details at the highlights after the Green channel. Therefore, correcting white balance will likely result clipping and quantization problems of the dominant channel, red or blue.

Future improvements

We can’t be sure what people could think of next. Smart local toning? HDR printing? better smarter noise reduction? Maybe adobe will surprise us with something extra cool? Some of those could be relying on the RAW data being full 12 bits. The M8 DNG files might not have the ability to take the advantage of the next cool feature.