Talk:Neutral-density filter

message: The filter pictured as an "ND4" is, in fact, not an ND4.  An ND4 has an attenuating factor of about 10,000 for a 13-stop reduction (ND4 is 10^4 = 10,000 ~= 2^13 is 13 stops) and is impossible to see through with the naked eye.  It does look like a 4-stop filter, which would make it ND1.2.  If the author of the photo does not verify this assertion, I will make the edit myself.  Dmitriy.kostyuchenko (talk) 16:12, 8 January 2008 (UTC)
thread_title:  Incorrect photo 

message: Does anyone else think that the 2 photos of the filter in this article could be better? Perhaps a series of filteres lined up next to each other would better convey the difference between 2ND, 4ND etc.? —The preceding unsigned comment was added by Cnjackson (talk • contribs) 18:06, 2 May 2007 (UTC)
thread_title:  Photos in Article 

message: Any details about how NDFs are made? —Nahum Reduta 01:27, 19 May 2007 (UTC)
thread_title:  Construction 

message: The term shutter speed reflects the fact that a motion picture camera shutter is a continuously revolving disk with one or more apertures cut out of it. The speed with which the aperture sweeps across the film area determines the exposure length. Thus, a camera with a 180 degree aperture would be open one-half of the time, resulting in an exposure time of 1/48th of a second at 24 frames per second. Film speed refers to the sensitivity rating of the film, formerly assigned by the American Standards Association (ASA) and presently by the International Standards Organization (ISO). So the word "speed" may be used as a synonym for both exposure length and film sensitivity (not to mention the light-gathering ability of a lens). Typical of the mishmash of photographic and cinematographic terminology.Jim Stinson 03:13, 12 July 2007 (UTC)
thread_title:  shutter and film speeds 

message: Is it worth mentioning that neutral density filters are especially useful in digital imaging because the greater depth of field resulting from the small imaging area makes selective focus very difficult except at very wide apertures?Jim Stinson 03:19, 12 July 2007 (UTC)
thread_title:  ND filters in digital imaging 

message: Unlike Light balance filters (LB) (see wratten number), which are calibrated to color temperature, all the Color Compensation (CC) filters that I have come across are calibrated - like ND filters - by optical density. In this sense, it might be better to group CC filters with ND filters rather than LB filters? 
For example a CC30M : "CC" means "Color Compensation" (or Color Correction?), the "M" means that it looks "Magenta" because it attenuates (magenta's complementary color) green light. The 30 means it has an optical density of 30/100 = 0.3 (= 50% transmittance) at the peak of the green wavelength (around 550nm). Ideally it would allow 100% transmittance of Red (650nm) and Blue (450nm), and depending on the measured spectral bell curve of the filter, we might get something like 75% transmittance of Yellow (600nm) and Cyan (500nm).
Redbobblehat (talk) 18:58, 31 August 2008 (UTC)
thread_title:  Color Compensation (CC) filters 

message: Both optical density and exposure values (often called "F-stops" by photographers) are logarithmic scales, so converting one to the other is very simple : where D is the optical density (for given wavelenth, W) and EV- is the attenuation (of the same wavelength, W) as an exposure value adjustment. 
*DW = EV-W x 10/3
and 
*EV-W = DW x 0.3
or for the less mathematical of us:
* Optical Density of 0.1 =  EV-1/3 = EV-0.3 (1/3rd of a stop)
* Optical Density of 0.2 =  EV-2/3 = EV-0.6 (2/3rds of a stop)
* Optical Density of 0.3 =  EV-3/3 = EV-1.0 (1 stop)
* Optical Density of 1.0 = EV-10/3 = EV-3.3 (3 and 1/3rd stops)
Redbobblehat (talk) 18:58, 31 August 2008 (UTC)
thread_title:  Exposure Value & Optical Density 

message: Why use an ND filter with such a well-defined light source as a laser? Wouldn't even the most unlinear filter do well, provided it is defined at the required wavelength? europrobe (talk) 19:32, 5 June 2009 (UTC)
thread_title:  ND filers with lasers 

message: How are these filters made?
What material is used?
--Error (talk) 01:10, 23 October 2009 (UTC)
thread_title:  Material 

message: I'm not sure the numbers in this table are correct.  The early ones seem to be fine, but everywhere I've read has said that the f-stop reduction increases by one for every 0.3 increase in optical density.  The B+W 3.0 density filters are quoted by B+W as resulting in a 10 f-stop reduction (which fits with the other sources I've read), but this table implies a 32 f-stop reduction.  I don't have a definitive source, but I thought that it was worth highlighting as it might need checking.  —Preceding unsigned comment added by 195.171.105.102 (talk) 11:56, 7 June 2010 (UTC)
replies: text: I agree; no filtermaker's marketing info seems to correspond to this table. Hoya's marketing materials for the ND400 (which is advertised for photographing solar eclipses) advertises 9 stops of light reduction and 1/500th original intensity; this table suggests it should be 20-22 stops. B+W's "3.0" ND filter claims 10 stops reduction and 0.1% transmittance. The table in this article is poorly sourced, and it was only very recently by an IP, and the older version did correspond to the marketing info of these other filters. —/Mendaliv/2¢/Δ's/ 17:53, 26 June 2010 (UTC)
replies: text: According to a Cokin ND filter chart, the f-stop reduction is calculated as the density divided by \log_{10} 2. See this PDF. Not a scientific source, but it gives some hints as to what's right and what's wrong. By that formula, ND8192 should give roughly 13 stops, not 91. —/Mendaliv/2¢/Δ's/ 18:01, 26 June 2010 (UTC)

text: I agree as well. Seems that f-stops are somehow confused with f-numbers in the table. One f-stop decrease corresponds to a halving of the light. So if ND2 allows 1/2 of the light through, that should give a reduction of exactly 1 f-stop - not 1.4 as the table indicates. One can use \log_{2} for calculating the f-stop reduction from the lens area opening fraction. KMS (talk) 13:15, 3 July 2010 (UTC)
thread_title:  ND Filter table 

message: Near the top of the page, there was a link to 'blur' with a superscript note 'disambiguation needed'.  I resolved the ambiguity by changing the link to point to the 'motion blur' page, and removed the disambiguation request. InsertNameHere (talk) 22:04, 11 June 2011 (UTC)
thread_title:  Minor edit. 

message: cite:
(small aperture for maximum sharpness or large aperture for narrow depth of field (subject in focus and background out of focus)
shouldn' it be replaced? AFAIK small aperture (for example 2.8) means a big hole and causes minimal sharpness and otherwise. I'm not sure, I'm correct?  — Preceding unsigned comment added by Outslider (talk • contribs) 12:25, 3 October 2011 (UTC)
replies: text: You have the meanings of small and large aperture mixed up.  This is not uncommon due to the fact that a small F-stop number is a large aperture and a large F-stop number is a small aperture.  The aperture is the actual hole through which light passes.  A small aperture (e.g. F22) provides a large depth of field.  A large aperture (e.g. F2.8) gives in a narrow depth of field. The inverse relationship between F-stop number and aperture size results in a considerable amount of confusion for a lot of people.  It is something that has to be continuously clarified, usually by context, in most writing about photography.  One always has to be on the look out for the possibility that a slip up might have been made either in writing, or in conversation, as it is easy to talk/write about one when thinking about the other. Makyen (talk) 22:43, 3 October 2011 (UTC)
thread_title:  small/large aperture - good? 

message: Hello! This is a note to let the editors of this article know that :File:Neutral density filter demonstration.jpg will be appearing as picture of the day on May 18, 2014. You can view and edit the POTD blurb at Template:POTD/2014-05-18. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! The herald 14:18, 30 April 2014 (UTC)
thread_title:  [[:File:Neutral density filter demonstration.jpg]] to appear as POTD soon 

message: Even though they attenuate all colours by the same amount, ND filters will appear slightly green, rather than grey, as one would intuititively suspect. This is because of performance of the human eye-brain system. There might be an opportunity here to link to an existing article on he subject.
Another example of this is that moonlight appears bluish, whereas it is actually yellowish. The Purkinje Effect also comes into play.
60.229.56.94 (talk) 06:34, 18 May 2014 (UTC)
thread_title:  Appearance and colour of an ND filter.