High ISO - who needs it

With the release of the Leica M9, I came across some discussion threads debating the performace of the said camera and its nominal weakness in maintaining good image quality when shooting in low light (at least as compared to the Nikon D3/D700 sensor). Someone was making the point that the benefit of low light high IQ is not for everybody. After all, people went a long time shooting comparatively slow film for all these years and still created good images.

My take on this is that everybody needs a camera with the highest low light performance they can afford. Sensor light sensitivity (also know as ISO, after the organization that used to rate film 'speed') is just another lever to pull for a photographer. Everybody will encounter some low light at some point or another. Why? Because that's just the nature of available light. Having good low light performance equipment will make you pull the camera and shoot in situations that you would not have considered suitable for capturing before. Even in 'good' light, long telephoto focal lengths and optimal lens apertures usually require longer exposures, so having the ability to change the ISO to shorten the exposure time with no significant hit to image quality is very desirable.

Digital photography is all about controlling the way the light hits the sensor. The more levers we have at our disposal to accomplish that control, the more artistic freedom we have to do more with our equipment. There are tradeoffs with good low light performance - usually camera bulk, which in itself is a compelling argument for giving up some low light ability. However, with today's technology, a take everywhere, shoot in every light condition camera is not available (pocket cameras just can't gather enough light in less than perfect light). Which side of the tradeoff one takes is a matter of personal preference and shooting habit.

The image attached to this post was shot at ISO 3200 with a Nikon D700 camera. The choice of ISO was part of a decision making process that allowed me to handhold the shot (ultra wide angle of view helped as well). The quality of the image is not perfect (there's some noise, especially in the darker areas), but it is much better than what could have been accomplished by pushing film.

Composition and focal length

This post deals with the use of focal length choice as a compositional tool. I will talk about shooting wide angle (short focal length), normal and shooting in the telephoto range.

The obvious effect of a wide angle lens (short focal length) is that you 'get everything in'. In other words, because the angle of view is wide, more of the environment is going to show up in your image. This helps when framing the element of interest with the surroundings is important. Care should be taken, especially at extreme wide angles, to maintain a satisfactory aspect ratio between your subject of interest and the environment. Often enough, the subject will appear too small as related to the rest of the elements depicted. To correct, get closer to that element of interest. Your perspective is not going to change, but the relative size will be corrected. Another compositional advantage of shooting wide is perspective exaggeration. You want this in a two dimensional depiction of a 3D world (unless of course, depicting is not your goal. I use a telephoto lens for most of my abstract work). At wide angles, near elements will look larger in relation to far objects as compared to 'normal'. This creates the illusion of depth and makes it easier to ompose a complex image, with multiple planes of interest. Another benefit of shooting wide, albeit a subjective one, is that the depth of field is larger (everything else being constant - eg the lens' light gathering abilities and chosen aperture). This is great if your aesthetic allegiance is ligned with the likes of the f64 group. I personally think that out of focus areas are more of an accident or necessary evil rather than something that should be used in composition.

Let's now turn to compositional uses for a 'normal' focal length - that is, 50mm for a 35mm camera or the digital equivalent. At this focal length, perspective is about what the human eye perceives. When would you use a normal angle of view for composition? When you want your viewer to concentrate on something else than perspective or lack thereof. I don't see any distinct advantages, from a composition point of view, for choosing this focal length. The viewer will be easily swayed by other compositional elements There are a lot of technical advantages fo shooting 'normal' - such as the availability of low cost, sharp and fast lenses with no or little distortion.

Moving on to telephoto lenses - the main thing to remember about those is that they have the opposite effect on perspective - they compress it. This comes in handy when your intention is to abstract or subtract. Abstracting means to downplay the representational cues in a scene. Long focal lengths help abstraction by flatening composition and by putting everything in the same plane. Subtracting means excluding spurious elements from the scene. Because the angle of view is so narrow at telephoto focal lengths, subtraction becomes somewhat easier - the clutter goes away. Going back to perspective compression - this is a great compositional tool when the ntention is to 'crowd' the element of interest. Perspective compression is perfect for conceptual portraits where the mood conveyed is negative (pensive, melancholic, entrapped, etc.). It also works great for shooting large but far away objects - such as the moon or sun against smaller (but a lot closer) terrestrial landmarks. Last and for me, least, long focal lengths can be used to isolate the subject of interest through use of selective focus, eg by making your in focus subject stand out against the blurred background. This takes advantage of the shallow depth of field typical for telephoto even when the lens is stopped down.

Part two of this article will present a few examples on how to apply
the information above in practice.