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Mar 29, 2021 23:59:29   #
Rongnongno Loc: FL
Filter are at is most simple a piece of transparent material screwed onto the front of the lens...

The best system is one that allows the sliding of filters in and out. They are particularly efficient when using gradient filters. They allow a full X*Y positioning. There is one issue thought, they do not work all that well if a polarizing filter is needed unless you purchase a rather expensive system.

 ► Use only high quality filters i.e. Optical glass.
 ► Do not stack filters. Doing so will reduce the light quality.
 ► Filters can cause vignetting, especially if used with a wide angle.

Always upsize your filters and use a Step-up ring adapter. This will prevent vignetting due to the filter being too high and standardize your filters across most of your lenses - One size fits all -.

The most common filters are:
 Neutral density

Less common are those who create special effects such as prism, blurring, special effect...

Note: Almost all filters will create a color cast, even the more expensive ones so buyer beware.

dpullum contributed a couple of interesting links:
Glass vs resin filters
Distortion-free, optically flat surface
Short Wavepass Filters

Mar 30, 2021 01:22:31   #
Rongnongno Loc: FL

This filter is made to keep out Ultra Violet light from your sensor/film.

Trouble is: All lenses since the 1980s are UV coated.

Do not use a UV filter as a protection for your lens simply because they create a color cast. Use a clear glass filter instead.

Mar 30, 2021 01:33:58   #
Rongnongno Loc: FL

A clear filter is a made to let the light in a lens without interference. These can be used as 'protection' as in theory they do not create a color cast.

They are wrongly referred to as 'UV filter'. A true clear filter is a ND 0 filter.

If you purchase a clear filter make sure is a screw on and made out of optical glass. Avoid all others cheap versions made of plastic, resin or uncertified glass.

CPR Commented: My favorite special filter is a smear of Vaseline on the lens... While in jest this describes what can be done using a clear filter to achieve unlimited special effects, soft blur, colored blur...

Mar 30, 2021 08:59:52   #
dpullum Loc: Tampa Florida
Rongnongno, great subject. Your comment " Avoid all others cheap versions made of plastic, resin or uncertified glass." lead me on a knowledge search in defense of float glass. The study I recall said that modern float glass was, in a practical sense, equivalent to optical glass. Unfortunately, I did not find that study, but I did find some interesting info on glass and filters. Rongnongno, I know you to be a knowledge sponge, a lifelong learner so here the doors I opened and the rooms I glanced into.

When searching for a scientific comparison between modern float glass vs optical I came across a study and discussion of resin filters [yes, resin is plastic! ] As we expect, resin is not as good as optical glass, but, resin filters do have their rugged place in photography.. Lee and HiTech’s were tested. The study was scientific.

In a discussion of float glass the comment was made, "Distortion-free, optically flat surface":

This article ... Optical Material: Float Glass is the first article in this 5-part series of blog posts that aims to highlight the various optical materials used to design and manufacture optical components for the photonics industry.

I am not disputing the wonders of "optical glass" rather, I am saying that clear float glass lower-cost filters may be fine for many photographers... they are affordable.

Wandering around in Dynasil I found a discussion of filters for actually filtering out/selectively-transmit wavelengths of light ...

Mar 30, 2021 11:51:23   #
Rongnongno Loc: FL
Neutral density

Neutral density filters are used for special effects as well as reducing the amount of light when a scene is too bright.

Neutral filters are classified by the degree of their opacity from 1 to 24.
This is reflected in their generic names ND ###
The ranking is exponential as each number increases the previous filter opacity x2.

There are three exceptions:
 ► Clear filters
 ► Variable Neutral Density Filter (two layers that need to be twisted in order to adjust the opacity)
 ► Polarizing filters are sometime referred to as neutral filters because they will reduce highlights. Two polarizing filters stacked will basically behave like a Variable Neutral Density Filter.

Neutral density filters main use:
Solar photography
Landscape photography
Special effect (running water by example)
Brightly lit scenes that cannot be captured otherwise

Unless one purchase a high quality neutral filter that ONLY reduces the light a neutral filter will add an unwanted color cast.

Mar 30, 2021 23:48:33   #
Rongnongno Loc: FL
Color filters

Color filters do not receive a great review in the DSLR world. The reason is simple: The camera WB setting tries to correct the bias, especially if you shoot JPG.

Color filters have their use as despite what many folks say. They change the light quality introducing a bias before the sensor array registers the capture.

Once again folks claim the same result can be achieved using software and willfully ignore that the sensor array has recorded the bias. So where does the controversy lie? Ignorance.

Anything in front of a lens changes the light quality before it is recorded.

Mar 30, 2021 23:58:18   #
Rongnongno Loc: FL
B&W Filters

To understand how B&W filters work you need to be familiar with Complementary colors

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