Filters and lenses

7. What does the ø symbol on my lens mean?
After the focal and aperture ranges, the other measurement you'll see on most D SLR lenses is preceded by ø and describes the diameter of the screw mount on the front of lens barrel. Check this number each time you head out to buy a filter or hood as you can't guarantee that it will be the same for each lens in your collection, even if they are all designed to be used on the same camera.

8. If you only buy one filter...
...make it a circular polariser. This is the perfect beginner's filter, and one that will have the biggest effect on your day to day photography, giving holiday skies a vibrant blue tone and accentuating the contrast between the sky and passing clouds to afford your images greater texture. Although you can add blue to your images in Photoshop or a similar post-production editing tool, the effect is never as believable when done that way as it is when shot using a lens.

9. Don't confine it to skies
Polarising filters also cut through glare and reflection. Use it to shoot through windows and water.