Leica is steeped in tradition. Often mistakenly assailed for its slow adoption of new technologies, what you get with a Leica is only the technology that makes sense within the Leica approach to photography. Many things that are great features of, say, a DSLR, simply have no place on a rangefinder.

Leica's M system took a turn after the M9. Whereas the M9 used a CCD sensor, the new M line (just "M"—versions are now designated by a Type specification) uses CMOS. Setting aside a slew of differences between the technologies, relevant here are things that a CMOS can do that a CCD can't that prompted Leica to add a bunch of stuff just because they could. Simply, a CCD produces analog output, and a CMOS produces digital output. Having digital output from the sensor means the ability to use that data faster, meaning you can add things like video recording and live view, and you can clutter up the menus with all kinds of new and exciting (read: relatively useless) options for things.

Cameras are like any other tool: you select a tool because it matches the task you have in mind, and the idea you want to capture. I pick up the Leica when I want the fewest impediments between me and the scene I intend to capture. Aperture and shutter speed immediately adjustable. ISO a button away. With a clean viewfinder, there's nothing left but picking the right lens, and manually focusing.

The capabilities of CMOS over CCD led Leica to include a lot more software and hardware stuff in the M over the M9. In Teutonic fashion, Leica contained themselves to adding one button on the top plate, a thumb dial on the back, and cleaning up the thumb pad. Like any modern digital camera, though, there are lots of menu screens with lots of settings. If you're like me, though, you don't really want all that when you're picking up a Leica. The Leica is for simplicity, and getting to work fast is the goal.

I looked at the indecipherable manual and the menu screens so you don't have to. If you just want to get the M working, and fast, here's your cheat sheet:

1) The battery

The M comes with a big battery. It's lithium ion, and doesn't weigh as much as it looks like it would, but it holds a serious charge. If you are shooting the M like it has film in it (and you should), you can expect the battery to last days. If you're always using live view and spraying and praying, I can't help you.

What you need to know:

When both lights on the front of the charger are on, the battery is fully charged. You can leave it there if you want without harming it.
You check the battery charge with the silver "Info" button.

2) Image Numbering

I like to know which camera I used to make a picture and I'm allergic to EXIF. Like most digital cameras, the M lets you customize its numbering scheme. I set the image numbering prefix to "240M."

What you need to know:

You can set image numbering to your preference on Menu 4->Image Numbering.

3) The 240 Monochrom

I can't afford a new Monochrom. Given the choice between the M9-based Monochrom and converting color files to achromatic with the M (240), I opted for the M (240). (This was an economic choice—not an artistic one.)

A rangefinder doesn't work like the Fuji Monochrom can: you're not going to see any image previews in the viewfinder. That said, you can set the M to make an achromatic JPEG along with the DNG file. When you do, the Live View function will display as achromatic. The JPEG output in Black and White Film Mode on the 240 is superb.

But keep in mind that if set the Film Mode to Black and White and separately set the set the File Format to DNG, you'll get an achromatic preview but only save the DNG file. This can be a considerable space saving if you only work with DNG files but want an achromatic preview while shooting.

What you need to know:

To get both DNG and JPEGs, tap the Menu button. Go to Film Mode and select Black-and-white. Then tap the Set button. Go to File Format. Select "DNG + JPEG fine." Boom. Done.
In Lightroom->Preferences->General tick the box for "Treat JPEG files next to raw files as separate photos. That way, when you import into Lightroom you'll have a set of achromatic JPEGs to review (and work with, if few adjustments need to be made).
To get only a DNG file with an achromatic preview on the LCD, tap the Menu button. Go to Film Mode and select Black-and-white. Tap the Set button. Go to File Format. Select "DNG" Boom. Done

4) Live View

I sometimes shoot with the LCD back in sensitive environments where I don't want to bring the camera to my eye, or when shooting at difficult angles. The M's Live View is well implemented and works well for these tasks. Nicely, the Live View works like the ground-glass focusing screens of old.

What you need to know:

Menu 3->Focus Peaking->Red (shows up really well on the achromatic screen you just set above).
Menu 3-> Focus Aid->Automatic
Menu 4->Exposure Simulation->Permanent

5) The 240 Street Camera

Shooting fast and efficiently is what Leica is about. The 240 had a minor problem when it was first released because (unlike the M9) it couldn't set the ISO automatically in Manual Mode. Instead, the only way to get the camera to set ISO automatically was to also have it set the shutter speed in Auto mode. This was not good.

Luckily, with Firmware 2.0.1.5 and later, the 240 behaves as one would expect a speedy street camera to do. Go to Set -> ISO, and turn AUTO ISO in M mode "On," Now the camera will adjust the ISO to properly expose the image based on your manually set aperture and manually set shutter speed. Hallelujah!

Bonus Bits

Finally, here's two bonus bits of information to get you up and running with the M and out making images:

The Set Menu is where ISO changes get made.
When the camera first powers up (or wakes up), it displays the ISO setting in the rangefinder window.
Menu 5->Auto Power Off->Two Minutes. You can leave the camera's power switch set to "S" or "C" and it will come to life rapidly with a half-press of the shutter while still preserving your battery.