After the M4, Leica started with embedding their cameras with light meters, or Leica TTL. Here’s everything you need to know about them.

Leica TTL Table Of Contents

What is TTL in Leica?

TTL stands for trough-the-lens and refers to the capacity of the camera to judge the exposure from inside the lens as opposed to an external light meter. This eliminates the need to have an extra accessory and is a more accurate way to judge light because it samples the subject directly from the lens.

While that might not be much of a “feature” nowadays with live view, back then when using film cameras you either had to eyeball the exposure or use a Leicameter or similar. The first Leica to have a built-in light meter is the Leica M5.

Leica M6 light RFI

Is Leica M6 TTL?

TTL can refer to either the light metering capacity OR it can also refer to the camera’s capacity to pass on information to an attached flashlight (TTL flash). So the Leica M6 has TTL metering (in other words, has a built-in light meter like the M5) but if you want to use automatic flash only the Leica M6 TTL has that capacity.

Is Leica M7 TTL?

Yes it is. Just like the previous M6 TTL, the Leica M7 has both trough the lens metering AND trough the lens flash.

Leica TTL Comparison

SpecificationLeica M7Leica M6 TTLLeica M6Leica M5
BatteryLithium (2), 3V eachSilver oxide (2) or 1.55V oder Lithium (1), 3VSilver oxide (2) or 1.55V oder Lithium (1), 3VMercury Oxide (1) 1.35V
Metering CellSilicone PhotodiodeSilicone PhotodiodeSilicone PhotodiodeCadmium Sulfide photoresistor
Metering Diameter12mm12mm12mm8.5mm
Metering range cd/m20.03 to 12,50000.03 to 12,50000.06 to 12,50000.03 to 12,5000
Exposure valueISO 6 to 6400ISO 6 to 6400ISO 6 to 6400ISO 6 to 3200
SS Manual4 secs to 1/1000, B1 secs to 1/1000, B1 secs to 1/1000, B1/2 secs to 1/1000, B
SS Automatic32 secs to 1/1000NANANA
Aperturef/1 to f/32f/1 to f/32f/1 to f/32f/1.4 to f/32

How does Leica TTL work?

Leica M5 meter
Leica TTL: Illustration of the Leica M5 light meter “arm”

If you’ve ever wondered WHY on earth does the Leica M5 doesn’t look like any other M camera, that’s because of the TTL metering. There’s a little “arm” inside the camera that meters the light and that takes a lot of space, making the M5 necessarily larger than it’s other siblings.

leica M6 metering
Illustration of the Leica M6 TTL with location of reading cells

From the M6 however, another way was used. In front of the shutter is a large white spot that a light meter is constantly aimed at and reads. For the Ms with flash TTL two photocells are used at opposite ends.

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