Sigma vs. Nerd (Part 2: The BW Merrill)

In Part 1 of this article, I discussed why, as a black and white photographer, I became intrigued by the upcoming Sigma Quattro cameras. This intrigue lead me to contact Sigma — arrogantly offering to help them insure the Quattro line achieved its full potential as a tool for dedicated BW photographers. Although my interest in Sigma cameras lies primarily in the upcoming Quattro series, Sigma generously lent me their current-generation DP3 for two weeks. Who knew such a loan, so simple in intent, would result in such a dense and weighty tower of words? With Part 1: Sensor School fully occupying the tower’s ground floor, it’s time to add another couple of stories to the Sigmascraper. In this article, I’ll discuss how Sigma’s DP Merrill cameras require altering one’s BW processing techniques, and how these techniques result in some significant differences in the tonality of black & white images. Later, in Part 3, I’ll report on the overall handling and ergonomics of the Sigma DP3 Merrill camera. It will be a report utterly tainted by the subjective viewpoint of someone (me) who prefers cameras that fulfill the curious and specific requirements of “street” photography (or, as I dubbed it in my Roadkill article, “observational” photography).

Shades of Grey

When working with any BW capture medium (film or digital), one of the first things I want to know is this: How does the film/camera translate color into tonality? In other words, what shade of grey will each color create? The following image illustrates four different versions of a photogaphed X-rite Color Checker chart:

• On the far left is the chart as shot with the DP3, and processed in Sigma Photo Pro (SPP).
• To its right is the same photograph after converting it to BW using the standard Adobe Lightroom (LR) default.
• To the right of that is, again, the same photo — only this time converted to BW using Sigma Photo Pro’s default BW setting inside its Monochrome processing panel.
• To the far right is a similar color chart, photographed with a film camera loaded with Tri-X and exposed at ISO 400.

What does this tell us? First, it illustrates some significant differences between grey tones when Lightroom and Sigma Photo Pro each employ their own default values. For example, we see that blues are rendered much darker (by default) in SPP than in Lightroom (LR). Conversely, we see that SPP renders red and orange much brighter than LR. Finally, we see that neither renders tones in exactly the same way as my “go to” film — Tri-X, but there’s little doubt that Lightroom’s default conversion comes substantially closer.

Shading the Shades

Of course, default values are just that — defaults. In the case of BW film, photographers affix colored filters to their lenses — changing the scene’s tonal balance by modifying colors before they ever reach the film. For example, a BW landscape photographer might use a red filter on the front of his camera lens. This makes anything that’s red photograph as a much lighter grey, while everything blue photographs as a much darker grey. Obviously, by darkening the greys that correspond to blue, the landscape photographer effectively darkens the sky — making clouds stand out, and giving photos a more dramatic appearance. In the case of BW digital, photographers apply the colored filters after the image is shot — as part of their post-processing workflow. Specifically, the typical (non-Foveon) BW digital workflow is:

1. Point camera at shiny object, and release the shutter. Your camera photographs the scene using its imaging sensor — usually some variant of a color filter array, as described in Part 1.
2. Convert all this raw color filter array data into a color image using the demosaicing algorithms built in to your RAW processing software of choice.
3. Convert the color image into BW by selectively applying a series of colored filters in varying amounts — thus altering the relative grey luminosities in the BW image.

This is how the left-most BW rendering was created in the previous illustration. If desired, one could employ this same color-to-BW conversion technique with any of Sigma’s Foveon-based cameras. But to do so would be to completely ignore a significant imaging advantage of the Foveon sensor: its lack of a color filter array. It’s this very absence of the traditional color filter array that makes the Foveon sensor so appealing for BW photographers.

Monochrome Mode in Sigma Photo Pro

As described in the Sensor School article, the Foveon sensor eliminates the standard color filter array used by most cameras to derive a color image. Instead, Foveon sensors contain three “monochromatic” sensors, which essentially use the thickness of the sensors themselves to “filter” out certain colors. Because Sigma knows the exact spectrum of light capable of reaching each sensor layer, their Sigma Photo Pro software can derive a color image by analyzing the luminosity data contained on each of the three layers. But unlike a color filter array, which must always be demosaiced into a color photo before BW conversion can occur, Sigma Photo Pro software has a special “monochrome” mode. This mode allows BW photographers direct access to the monochromatic data recorded by each of the Foveon’s three stacked sensor layers. Since all three layers see every color in the visible spectrum (but in varying proportions), each layer effectively gives a photographer a different monochromatic version of the same scene — varying only in tonality (and noise, which I’ll discuss later). Within Sigma Photo Pro’s Monochrome editing panel is a little color mixer that lets you combine outputs from these three different layers to create a monochromatic image with the tonality you desire. You can create a BW conversion using only the “blue” layer, only the “green” layer or only the “red” layer. And of course, you can mix these layers in any desired proportion (the default being 33% from each of the three layers). Below is a very pedantic example that illustrates exactly this:

Notice how the monochrome image’s tonal balance changes depending on which sensor layer one chooses to display. There is, however, one significant caveat: noise. Specifically, since the so-called “Blue” layer is the top layer of the sensor stack, it contains almost no noise whatsoever. Conversely, the so-called “Red” layer is derived mostly from the bottom layer of the sensor stack and therefore contains significantly more noise than the “blue” layer.

Personally, I don’t mind the Sigma’s red “layer” noise at all, but then I also really love film grain. The noise is much less ‘offensive’ than the sort of noise created by the demosaicing algorithms necessitated by color filter arrays and, in general, it’s something I just don’t worry about. However, there is a very significant difference in noise level between layers, so depending on what your photographic needs are, this might affect how much of the red “layer” you’re willing to include in your BW images.

Hue-bris

You might be tempted to assume that choosing between Sigma’s blue, green and red layers correlates with using these same colored filters during the more typical color-to-BW conversion performed by Lightroom, Photoshop and others. Do not succumb to this temptation. The tonal renderings resulting from Sigma Photo Pro’s color mixer are, in fact, substantially different than those from a standard image processing program. The following examples should effectively illustrate the difference between red, green and blue filtering in Sigma Photo Pro versus the same red, green and blue filtering applied by a popular BW conversion application (in this case, Nik Software’s Silver Efex Pro 2). The first image (shown below) illustrates four different BW conversions of an X-rite Color Checker chart, as performed by Silver Efex Pro 2 (SFX). Specifically:

• On the far left is the color version of the chart.
• The left-most BW version was converted using a red filter in SFX.
• The middle BW version was converted using a green filter in SFX.
• The right-most BW grid was converted using a blue filter in SFX.

The second image illustrates four different BW conversion of the same X-rite Color Checker chart, this time performed by monochrome “layer mixing” in Sigma Photo Pro:

• On the far left is the color version of the chart.
• The left-most BW version was converted by setting SPP color mixer to 100% red.
• The middle BW version was converted by setting SPP’s color mixer to 100% green.
• The right-most BW version was converted by setting SPP’s color mixer to 100% blue.

What do these two illustrations show us? They show us that the blue, green and red “filtration” used by SPP is much more subtle than when the filtration is performed on a fully rendered color file. This is to be expected, since the so-called “blue,” “green” and “red” layers in a Foveon sensor are actually panchromatic — capable of recording a full spectrum of colors, but in varying proportion that simply skew toward blue, green or red. Below is a less clinical (though still pedantic) illustration of this effect. There are three columns to look at:

• On the left is the color scene as shot with a Sigma DP3.
• The middle column contains three different BW renderings from a cropped region — the top taken with Sigma Photo Pro’s “blue” layer, the middle from its “green” layer, and the bottom from its “red.”
• The right-most column contains three different BW renderings from the same cropped region — this time performed by Silver Efex Pro 2 on the previously-rendered color image. The top is SFX’s default blue filter, the middle is its default green filter, and the bottom is its default red filter.

Look first at the upper-left corner of each crop — where the graffiti is painted onto a red building. Notice how drastic the differences are between each of the Silver Efex Pro conversions. Note how the conversions aren’t nearly so severe when performed by Sigma Photo Pro. Next, look at the colored banners in the lower right corner, and make note of the same tonality differences. It’s up to you to decide which tonalities you prefer. Personally, I much prefer the less-drastic renderings from Sigma Photo Pro — I can always further-amplify the contrast in Lightroom or Photoshop if I need to.

New Camera, Old-Skool

Since there are basically three monochromatic sensors inside each Foveon-based camera, and since each sensor gives us a different tonal balance, does this mean Sigma’s DP Merrill cameras are 3 times better than Leica’s Monochrom? No. Not by a long shot. First and foremost, there’s the issue of ergonomics. I’ll discuss this aspect in Part 3 of this article, so let’s move along to the next issue: tradition. This is one of those “nebulous” fundamentals that, intellectually, seems completely insignificant — until you actually try adhering to it. One of the wonderful things about shooting BW film (and a benefit that’s shared by the Leica Monochrom), is that the photographer never once sees a color rendering of his photograph. There is a purity to working in BW that simply cannot be replicated by a workflow that injects color into the equation. This is what I mean by “tradition.” It’s a psychological aspect that many (who are not BW photographers) ridicule, but it’s a mindset shared by many true BW photographers. One of the main reasons I’ve been shooting film for the past couple of years is that, after reviewing the Leica Monochrom (and falling in love with the all-BW workflow), I detested returning to a color-conversion workflow. So I didn’t. I started shooting mostly BW film instead. There are ways, using Sigma Photo Pro, to mostly prevent yourself from ever having to see a color representation of a photograph. But there is a complexity to it that seems utterly unnecessary. Here, specifically, are my issues:

1. You need to run a separate program (Sigma Photo Pro) that converts Sigma RAW files into TIF files, which you then must import into Lightroom, Aperture, or whatever other standard workflow software you use.
2. Sigma Photo Pro is highly unstable. Rarely was I able to process more than 1 or 2 images on my Mac Pro before needing to reboot the program. Expect to restart SPP dozens of times for each hour you spend working with it.
3. Sigma Photo Pro is in serious need of a User Interface designer. I know. I spent 20 years designing User Interfaces for Macintosh professional music programs. Using SPP is like taking a trip to the 1990’s — the bad 1990’s, and not the retro-cool 1990’s. I could easily write a 3 part article describing only those things wrong with the user interface and how Sigma should correct them.
4. Because of the whole post-processing layer filtering thing, there’s way too much fiddling required in order to extract the BW image you want.

Fortunately, I have a solution: Sigma could get rid of all four issues if they simply offered users the ability to record images in a BW RAW format. Through an on-camera menu option, users could select whether they wanted the camera to record a standard color RAW format or a BW RAW format (much like selecting whether to load a camera with color or BW film). By offering a BW RAW format, it’s no longer necessary to run each file through Sigma Photo Pro. The whole complicated 3-layer Foveon calculation is removed from the equation. Instead, the BW file would be a single layer file (exactly like a Leica Monochrom file), which could therefore be read by standard image editing programs, like Lightroom and Aperture. The convoluted and frustrating step of translating every file through Sigma Photo Pro disappears. Not only that, but having a BW RAW format means us BW photographers are never forced to view a color image — meaning we’ve restored purity (and a sense of integrity) to our image making. Alas, while this suggestion removes the pain of SPP from the BW photographer’s lifestyle, it would still remain for color photographers. Here, too, I can help. Sigma could definitely use some organized beta testing to address issue #2 (something I’ve done in the past), and issue #3 is a direct match for my previous (pre-photography) career. In other words, I’m suggesting that Sigma solve these issues by doing something else old-skool — hire me to work on it.

Finally (returning to the topic of Sigma’s Foveon sensor vs. the Leica Monochrom), there’s the issue of color filtering. Leica’s Monochrom, in spite of being a digital camera, allows BW photographers to work with filters exactly as they would with a film camera. Because the Monochrom is a rangefinder, the photographer frames and focusses the scene through a viewfinder window that’s separate from the lens. This lets Monochrom photographers place colored filters on their lenses without colorizing their view of the scene. The sensor sees the altered tonality, not the photographer. Alas, with an SLR (like the Sigma SD1 Merrill) or a mirrorless camera (like the DP1, DP2 and DP3), photographers view their intended scenes by looking directly through the lens. This means, if you use colored filters with a Sigma camera, you’ll be looking through that filter when you shoot — something I find truly discombobulating. But using filters on lenses is the essence of BW photo purity and, as I opined, this purity is one of the things that makes the Leica Monochrom so desirable. Fortunately, I have a solution for this, as well… Sigma should offer “in camera” filters that emulate the look of various colored glass filters used by traditional BW photographers. Specifically, rather than screwing filters onto their lenses, BW photographers would select a “software” filter prior to shooting. This would change the way the Foveon’s three layers are mixed together to create the single BW RAW file. In other words, it restores the purity of BW photography, including the use of filters before an image is taken, further helping turn Sigma cameras into BW dream cameras. For BW photographers, Sigma’s cameras offer truly spectacular resolution, gorgeous (and pliable) tonality, an unbelievably noiseless top layer sensor, and a much noisier (but ultimately inoffensive) bottom sensor layer. The way I see it, there are only two things preventing Sigma cameras from “owning” the BW photography market:

• The myriad issues, complications and hassles surrounding Sigma Photo Pro and the resultant workflow impact.
• The handling and function of the cameras themselves… but that’s for Part 3 to dissect.