Filters

Hi can someone please explain the basics about filters to me. Which kinds there are, what each one does, what manufacturers/models to look for and which ones to avoid. How do they effect IQ? Any info will help. thanks

lasulax said:

How do they effect IQ? Any info will help.

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http://www.google.com/ - type in "basics photographic filters"

http://halley.cc/photo/filters.html

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[ e d @ h a l l e y . c c ] http://www.halley.cc/pix/

There are only three types of filter that you may "need" with a digital camera. Circular polarizers, which are used to cut reflections from glass and water, help prevent blown skies (in some cases), and produce more saturated colours; neutral density (ND) filters, which are used to block light and reduce shutter speeds; and graduated neutral density filters which are used to partially block light from part of image frame. Any other filtering effects are better done in PhotoShop.

Some people use UV and skylight filters to protect the front element of the lens, but adding any glass in front has the potential to degrade image quality.

Best manufactures are B&W, Hoya, and Heliopan. But Hoya makes a whole range of filters, some much better and more expensive than others. Look for multicoated filters,

If you don't know which filters you need, you probably don't need any.

Brian A.

It’s true that a lot of filter effects can be done digitally but that isn’t necessarily as good as using a filter on the lens. When a filter is used on the lens, typically the filter factor is taken into consideration when the exposure is determined. When a filter effect is applied digitally, that filter factor doesn’t magically go away. The image editing program must do a virtual sensitivity (“ISO”) increase in order to deal with the filter factor. That increases the visibility of noise in the image, especially in the darker areas (whether this is much of a problem depends on the particular circumstances). If a filter is used on the lens at the time of the exposure, there’s the possibility that the exposure can be increased by changing the lens aperture or the shutter speed rather than increasing the ISO setting.

Another limitation with digital filter effects has to do with the spectral information loss once the scene is reduced to the camera's 3 RGB channels. When the camera makes the picture, most of the scene's spectral information is permanently lost. There's no way to reclaim this data and then filter it. There are some filters that can’t be simulated digitally but many photo filters can be.

Filters can and do degrade image quality. This can be especially noticeable with poorly coated filters used in night photography. Ghost images can become visible.