In cities, particularly large ones where millions of cars move daily, pollution can dramatically reduce contrast which easily results in dull images. Naturally, if you cannot beat them join them is a valid approach and one can create moody images under such conditions.
However, if you need the clean air look, there is no real substitute for clean air. So, if you know when the air is clean, shoot at those times, usually:
- Early morning before the air warms up and lifts particles.
- On colder days when air is denser and lifts less particles.
- After a downpour that washes out particles onto the ground.
Sometimes you just have to shoot around a specific time. In such cases, these adjustments may help:
- A polarizing filter. This works best at 60 to 120 degrees from the sun and not so much on overcast days. Remember to keep turning the polarizer to control the intensity of the effect.
- Avoid backlighting. This would light up particles and emphasize them. By having the sun more or less behind you, the particles should not appear as intensely.
- Sharp tone-curve. Most cameras can adjust the tone-curve. In the simplest models you have a single control for contrast, usually in 5 to 11 steps. The higher the contrast, the less dynamic-range is captured with the captured range spread out more which increased contrast. Some cameras have separate curves for shadows, highlights and mid-tones.
- Zoom with your feet. Prefer stepping closer over zooming in. There will be less air between up and the subject that way and thus less polution.