Using colour filters with the Leica M Monochrom alters the M Monochrom’s tonal response, as it happened with B&W film in the good old days. It is a well-known fact that the Leica M Monochrom can only shoot black & white images, so the question is: what kind of B&W does the Leica M Monochrom output? What about its tonal response? How do the Monochrom’s images compare with “regular” colour digital images converted to B&W? And what about using colour filters to modify the cameras B&W tonal response vs. using digital colour filters on a colour image? Read on to find out!

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Let’s start by saying that, just like in the glorious old days of film different stocks used to have different tonal curves, the Leica M Monochrom’s default tonal response is not neutral. Neutral, in the case of the Monochrom’s B&W images, would mean being perfectly panchromatic, or equally sensitive to all wavelengths of visible light.

Photographers using B&W film used to pore over the way different film stocks responded tonally to colours, in order to choose whichever one best suited their vision for the job at hand. As well, they’d use colour filters on top of that to get exactly what they wanted, such as dark(er) skies, pearly(er) skin tones, and so on.

When converting digital colour images to B&W in post-processing, you can tune the tonal response of your B&W images playing with the amounts of different colours in the B&W mix in post.

With the Leica M Monochrom, obviously, you cannot do that. Using colour filters with the Leica M Monochrom is the only way you’d be able to change the camera’s default tonal response.

When creating a B&W image, either adding colour filters to the Leica M Monochrom or via the channel mix on a colour image, there is no right or wrong, there is no better or worse.

Like with all artistic choices, there is just you, the photographer, trying to realise your vision with the tools at hand. To do so, you need to know what your tools can do.

So, what I set off to do was very simple: take a colour image of a Gretag chart, convert it to black & white, apply digital filters and compare the results with shots taken with the Leica M Monochrom, both unfiltered and using physical colour filters.

For the colour shots, using a Leica M9 would have been the best choice: it features exactly the same sensor as the Leica M Monochrom, plus the Bayer colour filter of course. Alas, I don’t have a Leica M9 at hand anymore, so the Nikon D800E had to do.

Methodology. All images in this article have been shots in daylight, diffused window light coming from camera right. In order to compare metering between the two cameras I shoot them both in “A” mode with -1/3 exposure compensation, since I was also interested in seeing whether using colour filters would trick the Leica M Monochrom’s meter.

On the Nikon D800E, I used the Nikon 24-70mm f/2.8G ED AF-S at 70mm and f/5.6. On the Leica M Monochrom, on the other hand, I used the Voigtlander Heliar 75mm f/1.8 at f/5.6.

Spot white balance has set on the Nikon D800E’s colour image in Capture NX2, clicking on the third grey spot from the left in the lower row. Nikon’s “Standard” colour profile has been used, and the black and white conversions have been done using the “Black & White” layer in Photoshop. The Leica M Monochrom’s images have been developed in Capture One. PhaseOne’s “Film Standard” profile for the Leica M Monochrom has been used and obviously no digital filtering has been applied in Photoshop. The same Level settings have been applied in Photoshop to all B&W files, to preserve eventual differences in camera metering.

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Let’s have a look at the images now. For those of you unfamiliar with a Gretag chart, here is a rather uninspiring shot of it. I suggest you’d use it as a reference to see what colours look like with the Nikon D800E’s Standard profile and to know which colour is where in the B&W images (click on the image to enlarge):

Let’s first see what a straight, untouched B&W conversion of the above shot would look like, compared with a Leica M Monochrom shot without the addition of any filter (click on the images to enlarge):

First of all, you’ll notice how the Leica M Monochrom outputs a lower contrast file than the Nikon D800E. As well, you’ll see how the Leica M Monochrom’s meter exposes more generously than the Nikon D800E’s.

As far as the cameras’ interpretations of colours, the Leica M Monochrom reminds me a bit of Tri-X, probably my all-time favourite film (although I might be biased here). Comparing the two images, it is immediately evident that the Leica M Monochrom is more sensitive to Yellow & Cyan and less sensitive to Red than the Nikon D800E. The B&W tonal response of these two cameras is definitely very different.

Let’s now see what filtered images look like. First, I simulated a Yellow/Orange filter for the Nikon D800E’s image using Photoshop’s “Black & White” layer, and compared it with a Leica M Monochrom image taken with a real, B+W #40 Multi Coated Glass Filter, Yellow/Orange (click on the images to enlarge):

The differences between digital and physical Yellow/Orange filters are evident. While the effects of both filters are similar in the Blues and Cyans, in the Oranges and Reds the digital filter behaves very differently, outputting much lighter tones that the B+W #40 glass filter. For instance, you can see how the Yellow in the Nikon D800E’s shot is now lighter than the one in the Leica M Monochrom’s.

Finally, I simulated a Light Red filter for the Nikon D800E’s image, again using the B&W layer in Photoshop, and compared it with a Leica M Monochrom’s image shoot with a real, B+W #090 Multi Coated Glass Filter, Light Red (click on the images to enlarge):

I’ll leave it to you to draw your own conclusions.

During this test, I noticed that using colour filters with the Leica M Monochrom indeed fools the camera’s meter. The camera progressively underexposes the darker the added filter is, which theoretically shouldn’t happen since the meter itself is TTL. In particular, the camera meters through the lens, and therefore through the filter, off diagonal grey strips painted on the shutter curtain. Since the filter’s darkening effects should be already accounted for, it is clear to me that the meter’s cell is differently sensitive to different wavelengths, progressively underexposing when using redder filters. This is something to keep in mind when using Orange and Red filters: the darker the filter, the more exposure compensation you’ll need to add to get perfectly exposed images.

CONCLUSIONS | As we all know, when converting digital colour images to B&W we basically can push and pull the monochrome tones whichever way we please. Simulating colour filters for digital B&W conversions is a very easy and flexible way to get your monochromatic images to look the way you want. More, since you are doing so in post-processing, you won’t incur in any of the metering problems that using colour filters on-camera might trigger. However, with the Leica M Monochrom this is not possible. You’ll either have to use colour filters with the Leica M Monochrom, or you’ll be left with what Leica in its wisdom thought good B&W tones would be.

Whether this is good or bad really depends on what look and feel you are trying to achieve with your monochromatic images. Personally, I found Leica’s own interpretation of a B&W image to be very pleasant to the eye out of the box. I find the Leica M Monochrom files to be wonderfully detailed and rich.

More, I find that Leica’s conservative approach to contrast helps you to decide for yourself how you want your images to look, allowing you to go from a very ethereal look to a very gritty one on the same file in two clicks in post-processing. Last, while for a long-time film user like me the idea of adding physical colour filters to my lenses sounds quite natural, I understand that for other people this might not be the case. However, if you have the camera or are planning to get one, I’d definitely suggest you try and experiment with colour filters with the Leica M Monochrom. First of all, it’s fun; more, the flexibility of the results could be surprising.

Disclaimer: At the time of writing, I am not affiliated with Leica in any way. I am a professional photographer looking for the best equipment for my work, I buy all my gear with my hard-earned cash and I don’t get paid by anyone to write articles for my blog.

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