Talk:Unsharp masking

message: The article mentions the first use in Germany in the 1930's.  Curiously, the unsharp mask operation is just a single step of the more general iterative deconvolution algorithm described by P. H. van Cittert in 1931.  Is this a coincidence?  mdf 22:56, 10 January 2006 (UTC)
thread_title:  History 

message: The intro reads: 'creating the illusion that the resulting image is sharper than the original.'. I was wondering if this is actually correct. Shouldn't it be 'resulting in a sharper image than the original but without increase of information'? 
This clearly depends on the definition of 'sharper', which is in my opinion 'a more clear distinction between objects', which is exactly what the unsharpen mask does. It does not mean 'more information' I think.
71.206.215.239 01:16, 13 February 2007 (UTC)
replies: text: I agree. This also answers the question above on the use of "apparent sharpness". Sharpness is given by the strength of the slope between dark and light: the less space an edge occupies, the sharper it is. This is not the same as resolution, which can be interpreted as "the amount of information." Though both concepts are related: the lower the resolution, the lower the sharpness. crisluengo (talk) 14:38, 3 December 2009 (UTC)

text: I agree too. —Ben FrantzDale (talk) 02:45, 4 December 2009 (UTC)
thread_title:  Unsharp Mask Creates Illusion? 

message: I think this article would be improved by adding at least before and after images, maybe with intermediate steps.--Jwwalker 03:19, 1 November 2007 (UTC)
thread_title:  How about an example?  

message: As a series of convolutions, isn't an unsharp mask a linear filter? As such, can't we describe it in the frequency domain by a transfer function? If so, is it a bandpass filter?  Since it is usually constructed from Gaussian blurs, its transfer function should be nonzero almost everywhere... —Ben FrantzDale (talk) 22:50, 21 January 2008 (UTC)
replies: text: Duah... the FFT of a Gaussian is a Gaussian, so the transfer function should also be a Difference of Gaussians. Sound right? —Ben FrantzDale (talk) 01:36, 22 January 2008 (UTC)
replies: text: Well, no.  Or yes, sort of.  The filters used are not necessarily linear (that is, they can use the "threshold" or other nonlinear mechanisms).  But a linear analysis is certainly a useful part of it.  They're also not usually Gaussian, because a filter that falls less rapidly in the frequency domain will make a better looking result.  The article says Gaussian blur, and that may be true in some cases, but it's unsourced and I wouldn't trust it.  And overall it's not a series of convolutions, it's a convolution and a difference and an add, but still there's an equivalent linear filter; it's usually applied in a nonlinear (gamma compressed) domain. Dicklyon (talk) 01:47, 22 January 2008 (UTC)
thread_title:  Frequency response 

message: I just added the "dubious" tag. Here's the thing: As a linear filter with, unsharp mask doesn't add any new information to an image. It makes the image look sharper by enhancing the high-frequency components, but it doesn't add any missing data. Deconvolution in its simplest form can't either, although it is often done in a more sophisticated way than just an edge-enhancing algorithm. I may just trim that section... —Ben FrantzDale (talk) 01:41, 22 January 2008 (UTC)
replies: text: I think what that section says seems true, as far as it goes.  It would be better if it were sourced.  What are thinking is worth removing?  Why not add a fact tag if you're not sure? Dicklyon (talk) 01:47, 22 January 2008 (UTC)

text: Here is a good place to start. Dicklyon (talk) 01:49, 22 January 2008 (UTC)
thread_title:  Dubious 

message: Does Wikipedia's version of the English language permit nouns to be 'verbed' at random ?)
I would let 'bolded' text pass, though - 'emboldened' is an ugly word, and tends to mean 'encouraged' ...
--195.137.93.171 (talk) 01:25, 7 March 2008 (UTC)
thread_title:  Sharped ? Or Sharpened ? 

message: I'm having trouble visualizing the analog process with the glass plates. It would be neat to have a side-view illustration showing the light from the enlarger passing through the original negative and the blurred positive, and the resulting brightness level striking the final print.
In my head, it feels like all this should do is make dark areas lighter because the dark areas of the positive are blocking the light which (because enlarging is working with a negative) would darken regions of the print. I'm failing to visualize the process, so if someone who understands it could sketch out a diagram rather than just before/after pictures (which any of us can see in our paint program, thank you), it would be very helpful. Myself248 (talk)  —Preceding comment was added at 01:12, 13 May 2008 (UTC)
replies: text: Presumably one using this process would increase the exposure to compensate for this problem. If you had a low-frequency sine wave, it would look almost exactly like a Gaussian-blurred version of itself, so if you make a positive of it and project its negative on it, you'll get a uniform brightness out the other side. If you have a high-frequency sine wave and blur it, you get medium gray. Project the original negative through that medium gray and you just have to compensate for exposure but will still get the same high-frequency pattern. Does that help? —Ben FrantzDale (talk) 02:06, 13 May 2008 (UTC)
thread_title:  A schematic illustration would help 

message: In computer vision and image processing there is an algorithm that, based on an input parameter--i have no idea which parameter matches with the photoshop description here--turns unsharp masking into high boost filtering. there is no article on high boost filtering or any mention of it on this page. there is also no algorithm for unsharp masking here on the page. addressing this would also solve the problem of citations for this page: any textbook on IP can give you that algorithm. Albert Cruz 02:38, 14 July 2009 (UTC)
replies: text: Not sure what you mean by "turns it into"; unsharp masking is just a form of high-boost filter.  Although some do distinguish the two.  I agree that it would be good to cite such sources for the their algorithms and terminology; I think you'll find that i t varies.  Dicklyon (talk) 02:54, 14 July 2009 (UTC)
thread_title: digital: high boost filtering

message: The article mentions using the unsharp mask to for creative effect. What does this mean? It seems like it needs a reference or example.
However, it is easy to create unwanted and conspicuous edge effects. On the other hand, these effects can be used creatively, especially if a single channel of an RGB or Lab image is sharpened. 
Sjf (talk) 14:20, 22 March 2010 (UTC)
thread_title: 'Creative Effects'

message: In the 11/2010 issue of Electronic House, there's an article about one Paul Darbee, who claims to have invented an image-enhancement system -- Visual Presence -- which, to anyone knowledgeable, is obviously unsharp masking. Perhaps I'll find time later today to contribute... WilliamSommerwerck (talk) 15:00, 10 November 2010 (UTC)
thread_title: pretender to the throne

message: Only the first paragraph of the "Comparison with Deconvolution" section is actually a comparison.  The remaining paragraphs simply explain deconvolution.  As such, that content should be relocated to the main deconvolution article.  If they have no content that isn't already present in the deconvolution article, they can be removed.  — Preceding unsigned comment added by Superbatfish (talk • contribs) 14:24, 15 June 2012 (UTC)
thread_title:  Comparison with Deconvolution section needs revising