RSS Feed of latest blog postsOctober 2011 - Settings, Exposure & Focus : The Nitty Gritty
| Category: Despatches | 01 October 2011 |
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The location was found yesterday and I’m now in position now overlooking Preci, The colour in the fields in Umbria in late spring defy belief. The farmers plant purple sainfoin and yellow jobbies I have no idea the name off as fodder, and these blocks of vibrant colour on the hillside are peppered with random blobs of scarlet poppies and blue cornflowers. In amongst this Italian colour I’m all set up; the camera is on the tripod with cable release and hot shoe mounted spirit level fitted. I’m pleased with the strong lines, depth and simplicity of the composition. All I need now is light to illuminate the scene. There are gaps in the cloud to the west, it may happen. When the Gods of Light do oblige I need to be ready, the Decisive Moment may well be fleeting. I’ve done the leg work to be here and frame up the shot, now I need to knuckle down and concentrate on the nitty gritty; the camera craft that will ensure this is a well exposed and crisp image. That may seem basic stuff, but it doesn’t matter how many times I’ve done it before I still need to concentrate and be meticulous. Like a pilot going through pre flight checks I go through my list while waiting for the light; camera settings, exposure, focus. I go back to basics every time.
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Whether I need to or not I prefer to use a tripod for landscapes. It helps me to be much more analytical with my composition, and I’m lousy at getting horizons straight so rely heavily on the spirit level. I check the tripod is firmly rooted and all the collars and knobs are tight before moving onto the camera settings. Obviously I’m shooting RAW; we all know the advantages of that format. I’m a control freak; I like to have as much tonal and colour information as possible. Shooting RAW gives me the undiluted uncompressed information straight from the camera’s full frame sensor. If you’re serious about your landscapes there’s simply no other way. The white balance is set to daylight; that way any warm golden rays or cool ambient light will appear as such without the camera’s software trying to neutralise it. Yes, I’m shooting RAW so the camera’s WB setting is somewhat arbitrary, the colour balance can be controlled in post production. But to tell you the truth I hardly ever alter the colour balance of my landscapes. I keep the camera on daylight WB and apply no adjustments at the RAW conversion stage. That’s my style, and ultimately a subjective call. We all work differently, thankfully, but I don’t think I can improve on the subtleties of light Mother Nature serves up, so I don’t interfere.
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The ISO is set resolutely to the default 100; I’ll only change that reluctantly if there’s a good reason to, like having to work hand held in low light. Our cameras are capable of producing astounding results at previously considered sky high ISO settings, but there is a price to be paid; noise. We’re landscape perfectionists, right? The thought of whopping up the ISO ‘cos we can’t be bothered to lug a tripod would never occur to us, would it? That is a slippery slope; before you know it you’re shooting in Program mode and suffering the associated devastating loss of self esteem. It doesn’t bare thinking about; which brings me handily to exposure modes. Aperture Priority exposure is by far the most useful mode for landscape work, I use it 90% of the time because when a composition has been framed up the first thing I consider is what depth of field I need, which determines my choice of aperture. Many think going fully manual is mandatory and the mark of a serious photographer, but Manual mode gives me nothing that Aperture Priority doesn’t; I’m still reliant on the through the lens meter but have to set both shutter speed and aperture, which can be ponderous as light levels fluctuate due to stray clouds or the dipping sun. I do however use manual when exposing stitched panoramas or when using tilt and shift lenses. Shutter speed priority is handy when panning on an F1 car at speed but for landscapes is of limited use. And as for P for Program, or Plonker Mode; don’t even think about it.
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Next up; metering mode. I use evaluative, or matrix metering all the time. The choice is subjective, familiarity with a camera’s system and evolving a way of working is the key and many prefer centre weighted or spot metering, but I find using evaluative metering in tandem with the camera’s highlight alerts and histogram display a quick and fail safe way of ensuring perfect exposures. The metering system divides the image area up into numerous segments and evaluates the light levels in all of them to give an exposure which records the full range of tones in the scene. Any one sector which is way off the others due to, for example, the bright sun in shot, is discounted. In practise it works well, as long as I always consider what the metering system is doing. If I were to take numerous spot meter readings of the scene and average them out, as I used to do when exposing large format film, I would merely be replicating what evaluative metering is doing far more quickly. Speed is of the essence, when the clouds part briefly and light paints the landscape I need to expose and evaluate quickly, not be fussing about with camera settings. Working this way I can be toattly confident of my exposures; there is simply no need to bracket anymore.
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Eilean Donan Castle, nr Dornie, Loch Alsh, Wester Ross, Western Highlands, Scotland. Canon 1Ds mkII, 24-70mm f2.8 L lens @ 51mm, 1/125 sec @ f6.3. With the camera set to aperture priority exposure mode with evaluative metering I could take advantage of the momentary light illuminating the castle. Checking the histogram and highlight alerts quickly I could be totally confident of my exposures and make the most of the fleeting opportunity. |
It’s easy to believe the manufacturer’s marketing and think that all you have to do is point the camera in the right direction and the technology will sort out the rest. But to get the very best results we need to understand what the camera is doing and be ready to override when necessary. Modern metering, exposure modes and focusing systems are very sophisticated. Just by leaving everything on auto a reasonably well exposed and focused image can be achieved much of the time. But we can do better than that. We can ensure every last pixel of precious highlight and shadow detail is recorded. That will enable us to make big, bold beautiful prints with lovely noiseless gradation of tone and colour and crisp detail. And to do that we need to use and understand the histogram display.
Here on a hill looking at the camera back I need to know what the histogram is telling me, as I do when I come to convert the RAW image, and finally when I work on it in Photoshop. The histogram shows the brightness levels in the exposure, from a pure black on the left to a clear white on the right. An underexposed image will have all the levels clustered to the left; an overexposed will be bunched to the right. The actual shape of the display is determined by the subject matter; a dazzle of zebra would be represented by peaks of black and white left and right with nothing in-between, and a meeting of health and safety inspectors would show a peek of mid tone grey with nothing at the extremes.
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In practise we don’t need to worry about the shape of the graph, just the black and white points. I use the histogram display to judge the exposure and determine if I’m recording all the tonal information I possibly can, with no clipping of highlight or shadow detail. By using aperture priority exposure mode with evaluative metering and dialling in + or - exposure compensation accordingly to move the histogram display right or left I can fine tune the exposure of a test frame to perfection. It is a very quick and easy way of working. Using the highlight alerts also helps me to double check I’m not clipping crucial highlights. I think of the resultant RAW file like I used to a negative; it’s just a medium for recording information. When I expose a frame I’m not striving for the prettiest display on the camera’s monitor, that’s just an indication. In a nutshell I’m striving to give the maximum exposure possible without clipping highlights. That will maximise the shadow detail and signal to noise ratio, but I must keep an eye on the highlights. If the histogram is showing a complete tonal range I’m not too worried about a bright looking image on the camera back; that can be fine tuned in post if all the precious highlight and shadow detail is there.
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The village of Preci in the Valnerina in winter appearing through the morning mist with the mountains of Monti Sibillini National Park beyond, Umbria, Italy. Canon 1Ds mkIII, 70-200mm f2.8 L lens @ 125mm, 1/250 sec @ f8. For virtually all my landscape work I switch the AF system off and focus manually. |
Squatting amongst the purple jobbies in Umbria I’ve done a test exposure and dialled in +2/3 stop compensation. Now I need to consider my focus point and depth of field. Strong blocks of yellow, purple and green diagonals intersect and lead into the frame. With the nearest purple sainfoin just centimetres from the front lens element I need maximum depth of field. I don’t like using the minimum aperture of f22 unless I have to, diffraction caused by the almost pinhole sized diaphragm degrades the lens’ performance, softening the image slightly. But depth of field considerations outweighs such deliberations every time, so f22 it is.The focus point is critical to achieve maximum depth of field; auto focus is useless here. The AF system would just focus on the nearest object; I need to manually set the hyperfocal distance; that’s the closest distance at which a lens can be focused while keeping objects at infinity sharp. In a nutshell it’s the focus distance with the maximum depth of field for a given combination of focal length and aperture. When the lens is focused at this distance, all objects at distances from half the hyper focal distance out to infinity will be acceptably sharp. Squatting in amongst the vegetation sneezing with hay fever I know that with a focal length of 16mm and an aperture of f22 if I focus on an object at the hyper focal distance of 40 cm away everything from 20cm to infinite, or in this case Preci on the hillside beyond, will be sharp. How do I know this? I carry a tiny laminated depth of field scale in my bag. You can download one from my website; http://www.davidnoton.com/hyperfocal.htm. You would think this sort of calculation could be incorporated into the camera’s firmware, wouldn’t you? But no, an old fashioned chart and tape measure are the order of the day here. Even with my trusty depth of field scale getting the focus point right is tricky; a slightly fuzzy background will kill a picture. Using Live View or a test exposure to zoom in and check depth of field is a handy way of double checking. The depth of field preview button is pretty useless at minimum aperture; the viewfinder just goes too dark.
With my focus point set and exposure deliberations complete I’m ready to go. So I wait, and check all my settings again. Photography is all about momentary blinding flashes of opportunity, inspiration and creativity combined with painstaking preparation and attention to detail. It’s the difference between the taking and making of a photograph.
