Four-thirds Sensors and the Problem of Exposure



Leica Digilux 3
Digital photography has brought with it many advantages, but in general there are two related areas from the film days that have been compromised in the move to a world of ones and zeros: dynamic range and exposure latitude. The negative effects of these two aspects seem to be most apparent in small-sized sensors. Leaving aside the tiny sensors in most point and shoots, I am going to comment briefly on the importance of nailing exposure in four-thirds cameras, which use a sensor half the size of a traditional 35 mm frame.

In brief, Olympus, Panasonic and Leica make cameras conforming to the four-thirds standard, which is a "ground-up" design developed specifically for digital photography (other manufacturers belong to the consortium but have not produced any cameras yet, although Sigma supplies lenses). Four-thirds cameras used in conjunction with their lenses have a number of advantages in a digital world (e.g. reduced vignetting, theoretically smaller sizes - I say theoretically because with the exception of the kit lenses from Olympus, most currently available four-thirds lenses are not notably smaller than those for their bigger-framed cousins); however, they have some distinct disadvantages too (such as the effects of diffraction kicking in at smaller aperture values and degrading the image quality).

It is an oft-quoted maxim of digital photographers to "expose to the right": using the histogram to push exposure as far to the right as possible without clipping highlights and thereby retaining as much detail as possible in the shadows. But getting the exposure right with these digital sensors is more than just about avoiding clipped highlights.

Now don't get me wrong: I love my Leica Digilux 3. It puts me in touch with photography in a way that no other digital camera has. And "touch" is definitely the right word because it is the tactile response that comes from using the old analogue controls of an aperture ring on the lens and a shutter-speed dial on the body that makes the whole act of photography with this camera a much more involving process.

The Leica Digilux 3 produces some lovely photographs with a "creaminess" of tonal ranges that can make photographs really sing...when you nail the right exposure, that is. The four-thirds sensor inside the camera does not have the leeway of film or larger sensors. One has to be very mindful, especially when using the spotmeter, that one is not pushing the exposure for the frame overall too far to the right. It's an easy thing to do: we don't always check the histogram, and the lack of latitude in the four-thirds sensor can produce horrible banding very easily, especially in areas like the sky.



The solution is simple enough. Underexpose and recover shadow details in post. One good thing about shooting Raw files on the Digilux 3 is that they have a reasonable amount of latitude to alter exposure and fix such problems that arise in post-production of the image. So let that be a good lesson on the advantages of shooting Raw all the time. Photographers that shoot only Jpegs with four-thirds cameras like the Leica Digilux 3, better know what exposure settings to use in given situations or prepare themselves for some disappointments.