Pixiq

If you don't make a habit of shooting in dark alleys at night, then you may feel this post is irrelevant to you. Certainly, compared to working for days – or even weeks – with high key snowy landscapes, you won't encounter predominately dark-toned low key scenes so often.  Nonetheless, there will be times, early or late in the day, when most of a landscape will be in deep shadow before or after the sun bathes the whole area with light. Dark sombre skies above backlit mountain ranges are another low key scenario.

Tiger Leaping Gorge in Yunnan China is one of those places that is often inaccessible after heavy rain because falling rocks block the road. Twice I have had to turn back, but the third time I was lucky. Early in the morning, the sun broke through the angry sky as we rounded a corner resulting in a dramatic mountain scene above the gorge. I manually spot-metered the grey clouds on the left of centre. The two main peaks on the histogram are from the silhouetted foreground peaks and the second from the dark grey clouds and more distant peaks. Note that the base of the graph continues to the far right without any clipping of the highlights. 

The classical gardens in Suzhou are a very different type of location in China. Here, low-angled light shines through ornate lattice windows punctuating corridors to create striking low key cameos. Others include rocks, such as obsidian and lava, while there are plenty of black birds as well as a few black apes.

Low key subjects are invariably ones where black predominates, but dark red or deep purple subjects can also be low key. Their correctly exposed histograms will show a high peak in the shadows over to the far left, with some mid tones and even a smattering of brighter ones.   

It isn't rocket science to look through the viewfinder and gauge whether the frame has an average tone all over; or that half is darker than average, or the whole frame is darker than average. Any animal which is black all over, such as a black swan or a crow standing on snow so that half the frame is black and half is white, is not a low key image.  Like the black and white stripes on a zebra, if an in-camera matrix or multi-segment metering is used, this will work fine, because the white area compensates for the black one.

But when there is only a sliver of light or colour on an otherwise all over black scene, an uncorrected in-camera reading will appear overexposed (the opposite to the grey snow syndrome when white subjects appear underexposed). Viewed against the light, the rim-lit mossy base to a beech tree is the sole area lit by morning sunlight. I turned around to manually meter a larger patch of moss lit by the sun and used this for the exposure. The main peak on the histogram is over to the far left with a low level of a complete tonal range right up to the far right.

A black deep water oceanic fish was the nearest I could find to the cat in a black coal hole scenario. The black body of a deep-sea angler functions in the same way as a green grasshopper on green grass – namely as camouflage. It lives at depths around 1000 metres, where there is no visible light, so it is invisible against the dark ocean water.  I cannot tell you how the fish was metered, because one of our photographers– the late Pater David ­– took it on a research ship. However, I do know it was alive when it emerged from the depths in a net before being transferred to a specially made aquarium on the ship. 

How to meter

From the comments I have already made about how I metered various shots, it will be evident that I try to find an average-toned subject lit in the same way as the brightest part of the frame. This I manually meter to use as the exposure for a low key subject.

Typically, correctly exposed histograms of low key subjects will have a full set of tones, with a high peak over to the far left, and successively lesser peaks moving across towards the right-hand highlights side of the histogram.  

So. there are several options for getting a correct exposure with a low key subject.

1) Manually spot meter off a known average tone, such as a matt green leaf or a gray rock. If the shot is framed looking into the light, you may have to turn around to meter green grass or leaves that are front lit. Go with the manual average-toned reading.

2) If using a P, S or A exposure mode choose center-weighted or spot metering. If using center weighted metering, select the center focus area with the multi-selector and use the AE lock to hold that exposure for each shot. If you want to repeat it you will have to use the AE lock again.

3)  Use a hand-held light meter to take an incident light reading of the light falling on the subject, by pointing the meter towards the direction of the light source with the white diffusion cone in place for a front lit. Set the exposure manually using the correct combination of shutter speed and aperture given on the light meter.

4) To over-ride the automated camera reading, use the exposure compensation (need to use a - value to decrease the exposure to compensate for the dark tones). Take a shot, check the monitor and make any further adjustments necessary. I don’ t use this because I find it all too easy to forget to reset the exposure compensation back to 0.

You may like to read my post on high key subjects.