67 mm Circular Camera Lens Filters
The one thing both digital and film cameras have in common is that neither is a perfect match for the human eye. People process images long before they get to the brain, so in order to create natural-looking images you often have to process the light before it hits your lens. If you put a 67 mm lens filter over the front of your lens, you can often get a more natural looking image than you would unfiltered.Filter Sizes
The first thing to do when looking for camera filters is to check the size. While step-up rings mean that you can adapt 77 mm circular camera lens filters to fit on a 67 mm lens you cannot effectively adapt a 62 mm filter to fit. It's always better to err on the side of a larger filter than a smaller one.Filter Usage
While you may not want to use filters for indoor photography, they are a must for many outdoor shots. UV filters are great for removing that atmospheric haze you get at high altitudes or perhaps near the water. They really make the colours pop. Another thing filters do is provide an extra layer of protection for your lens. Put a filter over the lens and any airborne dust or particles have to get through the filter to hit the glass.Circular Polarizing Filters
Although designed for use with autofocus lenses, camera lens filters with a circular polarizer effect can be used with manual focus lenses as well. You can adjust the level of polarization by rotating the filter, so it's easy to get exactly the colours you want. This is something Photoshop can't duplicate, because it's changing the information in the image, not just manipulating it.Mounting and Using Filters
The easiest filters to add are screw-in designs that just screw into the lens. Other filters may come in slot mounts so you can change the filter more easily. You can even use colour filters for black and white pictures. They change the intensity of different colours so the contrast stands out.