Bokeh. Possibly one of the most misunderstood, yet most bandied-about terms in the world of photography today – right up there with dynamic range, resolution, A-is-noisier-than-B and other such myths.
The term is a derivative of the Japanese word boke, which doesn’t really have a good translation into English. The closest we can get is ‘the nature/ character of blur’. It’s certainly not quantitative in any way – what constitutes good bokeh and what is bad or ugly bokeh is very much up to the viewer. There are some who like ‘busy’ bokeh where out of focus areas take on double images, swirls or other patterns; some like the pentagons and other shapes on highlights. Yet others prefer a uniform wall of gaussian blur foreground-background.
What factors affect bokeh? Mechanically, the lens design plays a big part. The nature of the optical formula and placement and design of the diaphragm, specifically. In general, round diaphragms produce the best bokeh; though having said that, the Leica 50/1.4 Summilux-M ASPH has some of the nicest bokeh around, but that has a strange multi-pointed star-shaped diaphragm. Telecentric lens designs generally have better bokeh than conventional spherical designs; this is because you’re less likely to get crossing of rays after and before the nodal point within the lens, causing double images and the like. It’s also why most of the new Nikon f1.4 lens designs have beautiful, non-offensive, smooth bokeh; they’re all telecentric designs and optimized for digital sensors.
One important concept to explain up front is depth of field. For a given aperture and focal length, a certain percentage of the focus distance will be in acceptable focus. This percentage doesn’t change with the focus distance; the difference is the longer the focus distance, the wider the actual, physical range that comes into focus.
The rules of optics also play a big part. The degree of blur is related to:
1. Real focal length (not effective 35mm focal length; longer focal lengths have shallower depths of field and thus more pronounced blur)
2. Aperture (wider apertures have shallower depths of field and thus more pronounced blur)
3. Distance between camera and subject (shorter subject distance means shallower depth of field – remember the percentage explained above).
4. Distance between subject and background (the further away your background from your subject, the more the blur).
With that, let’s look at two examples.
A. Worst case: subject is far away from the camera and close to the background; very short real focal length and moderate aperture. What will happen? Everything will be in focus. This scenario is precisely why compact cameras are incapable of delivering any noticeable blur under most conditions.
B. Best case: subject is close to the camera, with a distant background; long real focal length and fast aperture. This is your typical telephoto shot: beautiful isolation and no hint of foreground or background. It’s why you can shoot through light foliage or fences with a telephoto and not even notice their presence in the final image.
Good and bad bokeh, generally?
Remembering that it’s down to personal preferences, most individuals prefer:
1. Good gaussian defocus in background areas: uniform blur all over, with no double imaging
2. No color fringing on highlights, either left-right (lateral) or background-foreground (longitudinal).
3. Round highlights with uniform luminance, smooth edges and no internal pattern (those circles you sometimes see in out of focus areas are interference patterns caused by imperfect lens grinding or minute surface imperfections in moulded plastic elements)
4. Similarly smooth uniform blur in foreground out of focus areas. The foreground is something that few people look at or consider when addressing bokeh; it’s important because distracting foreground bokeh means that you can’t shoot through or around things. Nice foreground bokeh dramatically increases your composition options.
Which lenses do I think deliver good bokeh?
There may be some surprises in this list.
1. Any of the fast-aperture super telephotos.
2. The new Nikon f1.4 AFS lenses; 24, 35, 85.
3. The Nikon 105/2 DC and 135/2 DC.
4. Most of the Leica M ASPH lenses; specifically the 35/1.4 ASPH FLE, 50/1.4 ASPH, 50/0.95 ASPH, 90/2 APO ASPH. I don’t personally like the swirly bokeh of the older f1.0 Noctiluxes – caused by uncorrected spherical aberration.
5. The Zeiss ZF 85/1.4 Planar, ZF 35/2 Distagon.
6. Special mention to the Zeiss ZF 2/28 ‘hollywood’ Distagon – its curved plane of focus increases the apparent bokeh at the border and edge zones because the plane of focus is brought even closer to the camera than the central zone. It’s a pretty unique optical formula, and delivers spectacular results.
7. The Ricoh GR-Digital III – what, a compact? Yes. Used close up and wide open, the bokeh is up there with the best of them.
8. The Canon 85/1.2 L II
9. The Olympus ZD 45/1.8
Parting shot: Light is much more important than bokeh. You can always isolate a subject by the way it’s lit regardless of your lens and camera; you can’t do it if you’re using a telephoto lens as a crutch. What happens when you can’t get far away enough to get the whole subject in the frame? MT
I’m going to start by defining shot discipline. There are two aspects: timing and technique.
Part one: Timing
Imagine having a revolver, and say four enemies that are going to come towards you in a short space of time – too short for you to reload. You’ve got six shots. If you’re good, you’ll only need four; if you miss three times, you’re screwed. How is this relevant to photography? What part of the workflow is limited to just a few shots? Your buffer, especially during fast paced action. (Why do you think pro cameras have huge buffers? Insurance.) Anticipation and waiting for the critical moment – that peak in action when everything comes together – is very important; more so if your camera doesn’t have a motor drive or a huge buffer.
The revolver analogy is a good one. I’d compare a D3/D4 class camera to a machine gun with a telescopic sight: it’s complicated, but you can spray and pray indefinitely and probably get something good – even if you have no skill or experience whatsoever, simply by the sheer weight of statistics. (If you take a thousand photographs, one or two will probably be okay – similarly, aim in the right general direction and you’ll probably hit the target once or twice). In experienced hands, it’s impossible NOT to get the shot.
Honestly, I found shooting with the D3 too easy. Same goes for the D700. The M9-P, on the other hand, is a completely different beast. It’s like a Magnum .44 or a Desert Eagle 50 Cal; utterly useless to a beginner, but a fantastic tool if you know how to use it. But, you pretty much only get six RAW shots when the barrel is hot. See why timing is important while shooting action?
Do I find it limiting? Yes, but only if I’m not paying attention. And guess what: that was the simple part to shot discipline.
Part two: Technique
The higher the pixel density of your camera, the more technique matters. For a fixed sensor size, small movement on a low-resolution camera matters less than on a high resolution one. Let’s say camera A has 4MP, and camera B has 16MP – that’s double the resolution, not quadruple (2x in each linear axis). If you move by a factor of half a pixel on camera A, the image is still pretty much aligned with the original pixel it was focused on; your edges might be a bit blur, but you could probably use unsharp masking to fix the perceived acuity. If you move by the same factor on camera B, you’re going to be out by a whole pixel. And that’s not fixable by unsharp masking. Increase the resolution further, and the effect is compounded. Those original 2.7MP APSC cameras were pretty forgiving, actually. The 24MP APSC ones will not be.
Technique actually covers several things.
1. Stability. This is the biggest one. If you don’t move, then your edges will stay where you focused them on the sensor plane. All will be sharp. So how do we achieve this? Several ways – the easiest is a sturdy tripod. Good shutter tripping technique – roll gently, don’t jab. And the last way is to reduce apparent movement by maintaining a high shutter speed, either by cranking the ISO, using faster lenses, or using a flash.
2. Lenses. Good lenses have better resolving power, right? Yes, but these days, the difference is mostly visible only when shot at maximum aperture. By f8 or f11, most lenses are capable of resolving identically to near as enough makes no difference at the sensor plane. And certainly not enough to be noticed in a moderately-sized print. Having said that, test your lenses carefully to determine what the optimal aperture is, and by what point resolution is ‘acceptable’. Look at the corners. It’s pretty important to do this before buying too, to avoid any issues or inconvenience later on. Just one of the reasons I’m still happy to go to a real retail store to buy stuff; I want to make sure the lens I’m going to use is going to perform the way I expect it.
Speake-Marin Immortal Dragon. The eternal fight between more DoF and diffraction limits. I cheated a little by using a wider focal length, which has more DOF for a given aperture. Nikon D700, Zeiss ZM 2.8/28 Biogon
3. Watch out for diffraction. Although all lenses have an optimal aperture, the smaller the pixels, the closer the diffraction limit will be to wide open. Most compact cameras – especially the 1/2.33″ kind – will resolve optimally wide open, and be noticeably softer if set to f5.6 or f8. (This is one reason most manufacturers use a switchable ND filter rather than a real aperture; also on a sensor that small, everything is in focus all the time.) For instance: I can use f45 to shoot macros on the 4.1MP D2H without noticing any diffraction softening; however, by f27 on the D700, I’m seeing a noticeable reduction in acuity. That limit becomes f16 on the 16MP APS-C cameras, and I suspect as low as f11 on 24MP APS-C. F8 is as far as I’d go with any lens on Micro Four Thirds.
4. Focusing. If you’re shooting a rangefinder, make sure the RF is properly calibrated for the lenses you normally use. Be aware of focus shift with aperture stop down. If you’re shooting an SLR, make sure your AF system is properly calibrated, especially for wide open lenses; use the AF fine tune function if you’ve got one. Shoot live view, wide open, manual focus and magnified to determine what the absolute best result you can obtain is, and then adjust your AF system until you achieve that consistently. AF accuracy matters most when shooting wide open – sadly these days SLR focus screens are optimized for brightness rather than focusing snap, which means it’s much harder to see when something is in focus or not. (Camera makers want to sell you the latest AF lenses, so they discourage you from focusing yourself.) It isn’t helped either by tiny viewfinders. If you’re going to use your SLR manual-focus, it’s worth adjusting your mirror zero position and focus screen shimming to ensure that what you see in the finder does in fact match what the sensor sees. And a coarser matte split prism or micro prism screen helps immensely, too. Don’t try to do this yourself, however – it’s difficult and there are a lot of fragile, easily scratched components inside the finder which can be irreparably damaged if you don’t know what you’re doing.
5. Maintenance. This also covers several things: make sure your lenses and mounts are clean, for one. Clean lenses are obvious. Clean mounts, less so: a little bit of misalignment between the lens/ mount/ sensor combination can cause noticeable softness on one side of the image. It mattered less in the days of film because the ‘sensor’ plane had some thickness to it; you could be off by a bit and the image would still be focused on the emulsion. A digital sensor is a perfectly flat single plane, with no forgiveness in the front-back direction.
Bottom line: if you don’t think you can handle that many pixels, shoot in a binned and downsized raw mode, or get a camera with fewer pixels. You’ll save yourself the hassle of handling enormous files, too. I know that under certain conditions – photojournalism and street, for example – it’s extremely unlikely that I’ll be able to fully achieve more than 12MP of resolution on a full frame camera. This isn’t because I’ve got poor technique, but simply because there are restrictions put on you by the shooting conditions – for instance, being jostled by people; having to shoot in extremely dark environments at high ISO; using a MF rangefinder with wide open shallow-DOF lenses on a moving subject. The list of excuses goes on. Bottom line: I know I’m the weak link in the imaging process here; I’ll try to improve, but I also recognize my limits and won’t fall into the trap of thinking more MP will make for a better image. It won’t. In the studio however, that’s a totally different matter. MT