filter

Band:

Started by Richard Patrick who was part of Nine Inch Nails and Brian Liesegang. Brain departed in 1997 in between Short Bus and the new album, Title of Record. They are called New Metal which Richard seems to be cool with.

Word:

1. removes something from whatever passes through it
2. alters whatever passes through it
3. pass through

See percolate, strain

Our brains have remarkable filtering capabilites. Everyday, we throw away huge amounts of information because we deem them irrelevant.

For example, when I was a child, I was facinated by everyday objects in the bathroom or the kitchen. I simply had to know what purpose every surface, handle, dial or switch held. Now, I can walk into one of those rooms and not give it a second thought.

However, the process of seperating relevant information from useless information is a boon to creativity. Take a guitar player playing a solo. With 6 strings across 24 frets, he has to choose 1 through 6 notes out of a possible 144 notes. But, due to knowledge, or even intuition, he can choose only from the notes that will sound pleasing to the ear.

A chess player might have over 30 possible moves. When looking moves ahead, the number of possible board configurations grows exponentially. For each of his 30 possible moves, his opponent might have 30 replies.. Then, for each of those, he could have another 20 or 30 replies. Luckily, the brain can discard the moves that would not be very beneficial. (Although, it can discard beneficial moves..)

When stuck in a rut, I have gone through days where my brain has deemed almost everything irrelevant.

In topology, a filter E on a set X is a collection of subsets of X satisfying the following axioms:

• ∅ (the empty set) ∉ E
• If B ∈ E, and A is a subset of X containing B (B ⊂ A ⊂ X), then also A ∈ E
• If A, B ∈ E, then A ∩ B ∈ E.

If X is a topological space, then a filter E is said to converge to a point p of X if E contains every neighborhood of p.

The concept was formulated by Henri Cartan as a response to the problem of convergence in general topological spaces. In spaces which are not as topologically nice as our familiar Euclidean space and the like, the sequence may not be a fine enough tool to describe all limit constructions: a point may be in the closure of a set and yet have no sequence from that set which converges to it. Describing convergence via filters solves this problem. A complementary approach uses objects called nets, which generalize sequences in a more obvious way.

In photography, a filter is something that you place in front of your lens (or, more rarely, between the lens and the film), in order to modify the light (and, consequently, the image projected on the film).

Filters can be made of glass, plastic or gel. There is about a million types of filters out there, and some of them produce really nasty effects. The most common (and useful) are

1. filters for black and white photography
2. polarizers
3. neutral density filters and graduated neutral density filters
4. color correction filters (also known as CC) filters, used in neutralizing color shifts
5. soft focus filters
6. protective, like UVs and skylight filters

It is a common misconception to believe that filters will improve your photography. Filters are only a tool for realizing a concept; you can buy the tool, but the concept must be in your head.

A filter is a system which processes some input signal f(x) into an output signal g(x). The output signal is often referred to as the response of the filter.

Mathematically, a filter is usually denoted as

f(x) -> g(x)

A filter can be a physical system, such as defraction of light. It can also be a purely mathematical formula, an electronic circuit, or a computer algorithm.

Filters are often classified by various criteria. For example, a null filter is such in which the output is exactly same as the input:

f(x) = g(x)

A filter is linear if a linear change in the input produces a linear change in the output, i.e.:

af(x) -> ag(x)
f1(x) + f2(x) -> g1(x) + g2(x)

Or, more generally,

a1f1(x) + a2f2(x) -> a1g1(x) + a2g2(x)

A filter is deemed shift invariant if a shift in the input produces an identical shift in the output:

f(x - a) -> g(x - a)

In reality, most physical filters (e.g., optical lenses) are never quite linear or shift variant (or null). Software generated digital filters can be, and often are, both linear and shift variant (though rarely null, as that would be just a waste of computing resources). They can also produce such g(x) that either does not normally occur in nature, or would be very hard if impossible to create.

Theoretically, any naturally occuring physical filter can be achieved through software. All you need to know is the f(x) and the g(x), though sometimes that is easier said than done.

That means that, at least in theory, a program such as Photoshop equipped with the right plug-ins can produce any effect that a photofilter can do, plus many effects that cannot be produced by purely photographic means. Similarly, a software sound mixer can, theoretically, produce any sound effect that occurs in nature, plus many more.

In practice this is not always the case simply because software filters tend to be linear and shift variant (which makes them much easier to implement and faster to run), while real-world filter tend not to. Even when that is not the case, software filters tend to be more ideal, i.e., more pure math than real-life filters. However, they can come very close to real life, and tend to be cheaper. They also have the advantage that they can be tried and discarded if the effect is not what is expected. They are also easier to modify (e.g., a filter you screw on the camera lens either is there or is not there, but a software filter can be adjusted for many subtle differences in its effectiveness).

film at 11 = F = Finagle's Law

filter n.

[very common; orig. Unix, now also in MS-DOS] A program that processes an input data stream into an output data stream in some well-defined way, and does no I/O to anywhere else except possibly on error conditions; one designed to be used as a stage in a `pipeline' (see plumbing). Compare sponge.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Fil"ter (?), n. [F. filtre, the same word as feutre felt, LL. filtrum, feltrum, felt, fulled wool, this being used for straining liquors. See Feuter.]

Any porous substance, as cloth, paper, sand, or charcoal, through which water or other liquid may passed to cleanse it from the solid or impure matter held in suspension; a chamber or device containing such substance; a strainer; also, a similar device for purifying air.

Filter bed, a pond, the bottom of which is a filter composed of sand gravel. -- Filter gallery, an underground gallery or tunnel, alongside of a stream, to collect the water that filters through the intervening sand and gravel; -- called also infiltration gallery.

 

© Webster 1913.

---

Fil"ter, v. t. [imp. & p. p. Filtered (?); p. pr. & vb. n. Filtering] [Cf. F. filter. See Filter, n., and cf. Filtrate.]

To purify or defecate, as water or other liquid, by causing it to pass through a filter.

Filtering paper, ∨ Filter paper, a porous unsized paper, for filtering.

 

© Webster 1913.

---

Fil"ter, v. i.

To pass through a filter; to percolate.

 

© Webster 1913.

---

Fil"ter, n.

Same as Philter.

 

© Webster 1913.