High pass filter sweeps

Dear all,
First I should say that I am relatively new to electronic music and mostly make rock. I do like to put synths in my music, and I am now getting more and more of a taste for adding more electronic effects too in to my recordings. What I am wondering is how to get a high pass sweep without losing volume when I cut those highs. When I automate it in the channel EQ, the volume starts off lower and gets higher. Now this is obviously going to happen, as I am cutting frequencies, so lowering the levels. How do people get a sweep that doesn't do that? I want the volume levels the same during the sweep, and I hear it done so often. Is it just a matter of automation with the volume too to get the levels even, or is there a plugin or a cheeky trick that does it? I have tried auto filter, but cannot get the effect I want. Thanks a lot in advance, all the best, Fred

Try using a unfiltered version of the string (or sound) which remains constant and couple this with a high version which "sweeps" the eq. Play them together - try with a lo-pass filter on the unfiltered version to get the sound of the "doubled-up" version right with the hi-passed string on top. Layering is probably the answer I think. Try using some compression on the hi-swept sound too.
Or alternatively, try using bandpass filters if you find a hi-pass filter too extreme and you still need more body. Use resonance too - this will make the sound frequencies which are currently at the "filter cutoff" point louder - as you sweep the cutoff up, the effect of increased resonance should be quite noticeable.
Best,
Mickey.

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High pass filter don't work

i used the following setting for the testing;
input signal 1: 2khz sinewave, amplitude 1V
input signal 2: 50Hz sinewave, amplitude 10V
the above 2 signals are added together and fed into a filter. my objective is to remove signal 1(1V sinewave). i've tried some filter but it don't seem to work. for the attached vi, i used high pass filter. the filter don't work.
i tried to view the frequency component of the signal before and after the filter and found out that both signals pass through the filter.
1. why isn't the 50Hz signal being filtered off?
i had the following values:
before filter after filter
50Hz ==> 3Hz
2kHz ==> 120Hz
the filter seem to scaled down the frequency compon
ent instead of filtering off the 50Hz.
2. why is this so, how can i solve this problem?
3. what should i take note when setting the parameters of the filter?
Attachments:
time2freq_domain.vi ‏573 KB

You might try increasing the number of FIR filter taps. Also, would an IIR filter work for you? I recoded your example using the waveform filtering VIs that were developed for LabVIEW 6i. Please look at the number of taps for the FIR filter, and the PassBand and StopBand frequencies. Also, notice the IIR filter's superior suppression of the low frequency sinusoid.
Attachments:
time2freq_domain2.vi ‏107 KB

Use a High Pass Filter for multiple connections

Hello, you can check this site: http://www.cableboxfilters.com
You can find the best filter and these are newly designed and is a super mini size high pass filters. They have excellent specifications, dimensions of only 13mm x 40.5mm and a weight of only 18g. These filters are best suitable for use in many communications applications, such as CATV, Cable Internet and other RF systems. Hope that this info can help your problem.
With too many connections as you mentioned, you must install a High Pass Filter. These are newly designed and is a super mini size high pass filters. They have excellent specifications, dimensions of only 13mm x 40.5mm and a weight of only 18g. These filters are best suitable for use in many communications applications, such as CATV, Cable Internet and other RF systems.

Hi, Graham,
You wrote: "...There is a Lowpass filter writen within LabVIEW (IMAQ LowPass) this has been optimized for multicore prosessing and runs pretty efficiently..."
Sorry, but I can't recognize any advantages of IMAQ LowPass on the DualCore system. See attachment. When this VI running, then I have approx. 50% CPU load, and no any effect when I set 2 cores with IMAQ Multi-Core Options. This take always approx. 60 - 70 ms for 5x5 low pass on 1024x1024 8 bit image.
I'm missing something?
Upd:
Sorry, forgot technical data:
LabVIEW 8.6f1; Vision 8.6.1; WinXP Prof SP3; Intel Core2 6700 CPU
Andrey.
Message Edited by Andrey Dmitriev on 11-19-2008 02:21 PM
Attachments:
Benchmark.vi ‏16 KB

High Pass Filter

I am trying to do a High Pass filter and I press CTRL I and go to use on subject an it is painting subject grey .........don't know what I am doing wrong? Pease help

Filter > Other > High Pass is where High Pass is.
Ctrl + I (as in, "India") simply inverts (at least by default).

How does high pass filter determine frequency

I Am having a hard time understanding how the high pass filter determines high vs low frequency. What value is it measuring. ? Change in RGB values or Contrast ? I see the words sharpness or blur , but what values determine amount of blurriness or sharpness? Is there and actual frequency being measures or is that just a metaphor To compare it to the audio high pass filter ?
Any insight into the inner workings of this filter is appreciated.

Some further explanations:
Audio signals:
frequency = cycles per second
This is the frequency in the time domain.
An arbitrary signal can be represented by a bundle of harmonic signals (sine, cosine)
plus a DC-part (direct current, non periodical component).
A typical high-pass filter for audio signals:
The cut-off frequency fc is found at the transition between increasing gain
(low frequency) and fixed gain 1.0 (high frequency).
frequency   gain (attenuation)
0.01 fc   0.01
0.10 fc   0.1
1.00 fc   0.707
10.0 fc   1.0
100 fc   1.0
A typical high-pass filter for digital images:
frequency = cycles per unit length or (better) cycles per pixel
This is the frequency in the spatial domain.
The highest frequency is 0.5 cycles per pixel (alternating black and white pixels)
An arbitray row in a digital image can be represented by a bundle of harmonic signals
plus a DC-part.
Each channel R,G,B is filtered individually, one after the other.
Frequency and gain are as above.
A high-pass filter applies an attenuation <<1 to low frequency signal components
and removes the DC-component entirely. This would result in a black background.
Therefore the background is shifted to R=G=B=128 (8bit per channel) or
R=G=B=0.5 (normalized).
Sharp edges contain stronger high frequency components. These are retained.
http://en.wikipedia.org/wiki/High-pass_filter
In this doc we find a simple implementation:
y[0] := x[0]
   for i from 1 to n
     y[i] := a * y[i-1] + a * (x[i] - x[i-1])
   return y
x[i] are values R (or G or B) in a row at column i in the original image
y[i] are values R (or G or B) in the same row at column i after filtering.
Factor (a) contains indirectly the cut-off frequency.
This example does not yet apply the shift to R=G=B=128.
The implementation can be different (non-recursive filter instead of recursive, as above,
higher order instead of first order, using a filter kernel 3*3 or 5*5 pixels instead of working
in each row independently).
I'm not trying to explain how Photoshop works! There are so many alternatives.
Best regards --Gernot Hoffmann

How can i disable the high pass filter on the headset mic on the iphone 4?

i would like to use my iphone for recording and frequency measurement apps. i have an adapter that allows me to use the headset mic input https://www.petersontuners.com/index.cfm?category=135&action=itemView&itemID=39 however, there is a high pass filter up to about 200Hz on both the headset mic input and the external mic. one app apparently has a work around in ios6 http://blog.faberacoustical.com/2012/ios/iphone/finally-ios-6-kills-the-filter-o n-headset-and-mic-inputs/ but is there an iphone setting that could temporarily bypass the filter? if not in ios6, if i upgrade to ios7 will i be able to do this?

There is no setting on any iPhone to disable/by-pass this.

Low Pass + High Pass Filter

I've just updated from logic 7 to Logic 8. I can't seem to load up some of the filters that I've been accustomed to in Logic 7 - namely the Low Pass Filter, High Pass Filter and the Low Cut Filter. When I load sessions arranged in Logic 7 into Logic 8, I can clearly use them but they are not present in the Filters panel? Any ideas?
Zav

zav wrote:
I've just updated from logic 7 to Logic 8. I can't seem to load up some of the filters that I've been accustomed to in Logic 7 - namely the Low Pass Filter, High Pass Filter and the Low Cut Filter. When I load sessions arranged in Logic 7 into Logic 8, I can clearly use them but they are not present in the Filters panel? Any ideas?
Zav
That's because they are in the EQ section. EQ > Single Band >

When, why, and how the high pass filter

i have a good grasp of the arcane nuances of unsharp mask,
but nothing on high pass filter, So can someone offer just a
summary of the thinking of when we select that tool, and
what parameters to consider to what end. Thanks a lot
best,
Steve z

The high pass filter is a tool for finding edges...from that, you can adjust the edge width to increase or decrease the radius of the edges. Everything that is not an "edge" turns into a middle grays. Depending on the blending, this give an opportunity to modify edge or non-edge values. Overlay lightens the lights while darkening the darks and does nothing at 50% grays In the case of high pass, this means the light side of the edges gets lighter and the dark edges darker. This can have a sharpening effect similar to USM without the threashold control.
If the HP radius is small, the effect is sharpening...if the radius is larger, it's more of a tone /contrast control. If you constrain the effects using Blend If adjustments, you can impact midtone contrast as mentioned by Robert.

Sharpening with High Pass Filter

I am using PS6 and Elements 11.
1. I import the image from LR
2. I duplicate the layer
3. I go to Filter....High Pass
4. I adjust the gray image to the amount I want to sharpen
5. I then go to hard light in the blend modes to change the gray to the image and nothing happens
6. The image stays gray and will not change..
7. None of the blend modes change the gray image.
8. ?
9. This happens in both programs.
Thanks Jean

If you want to understand how the highpass sharpening works, you should consider the highpass layer copy as a kind of 'adjustment layer'. By itself it only shows middle gray : no correction needed; lighter gray : the pixels should be lightened; darker gray : the pixels should be darkened. In itself, the highpass transformation shows the 'contours' of the image, where sharpening is needed.
When mixed with the underlying layer, you get the right effect. Changing blend mode is there is no underlying layer with wich to 'blend' does nothing.

Using high pass filter

I have a general question on using HPF in labview.
If I apply a hpf on 10 sets of data, 20 points each, is the results the same as applying the filter on all 200 points(the same values of course) at once?
I tried it and the results seem to be differenet....

Thanks! I will post a sample tomorrow but in the meantime this is what I am trying to do: It is a Butterworth filter, high pass, third order, sampling rate at 20 Hz. I have a version of the program which uses all 200 points and applies the hpf.
Now I would like to have another program that does the same thing, but this time works on smaller data sets. ..so as I mentioned 10 sets of 20 points each. These data point would be provided continously. Ideally I would like to achieve the same results, but it seems that it may not be possible. Another solution would be to save the data until I have enough points ( to get a valid result) )and then apply the hpf.
But how many points would I need to achieve similar results?
Hope this explains what I am trying to do.

Buggy action - 'the command "high pass" is not currently available'

Hi, I've recently been speedtesting a couple of mac minis with different RAM and scratch configurations. To speedtest I'm running a Photoshop action.
Today, I added 16Gb RAM (2 x 8Gb) to a 2011 i7 2.7 ghz mac mini and discovered that my previously well functioning speedtest action gets stuck at the High Pass filter step. It pops up a warning - 'the command "high pass" is not currently available'. If I then highlight the high pass stage in the action palette and click play, the filter works and the action continues.
I googled and found a suggestion to reinstall Photoshop. I did this and the action completed properly - but only once. When I tried to run it again it got stuck as before, at the high pass filter stage.
Any ideas?
(The steps in the action prior to this problem: background layer duplicated (layer via copy), image mode from 16bit to 8 bit, unsharp mask on copied layer... then i'm wanting to run the high pass on the same layer, but it stops...)

Boilerplate-text:
Are Photoshop and OS fully updated?
As with all unexplainable Photoshop-problems you might try trashing the prefs (after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved and making a note of the Preferences you’ve changed) by keeping command-alt-shift pressed on starting the program or starting from a new user-account.
System Maintenance (repairing permissions, purging PRAM, running cron-scripts, cleaning caches, etc.) might also be beneficial, Onyx has been recommended for such tasks.
http://www.apple.com/downloads/macosx/system_disk_utilities/onyx.html
Weeding out bad fonts never seems to be a bad idea, either. (Validate your fonts in Font Book and remove the bad ones.)
If 3rd party plug-ins are installed try disabling them to verify if one of those may be responsible for the problem.

High pass effect on color

Does the "high pass sharpening" subdue color saturation of the images?
I was creating a photo collage type of art in InDesign. I also used Photoshop to sharpen and resize each individual images. I used High Pass sharpening with Edge Masks. After readjusting the images in photoshop I saved them with new names and relinked the new file to the InDesign. When I relinked the new image, there was a noticeable degradation of color saturation. The images looked sharper but a lot more grayer or muddish. In photoshop, I didn't change the color space. So I wondered if the High Pass filter alters the color saturation.
Here is the link to my photoshop actions that I used to create the sharpening effect. If any one knows what caused the color shift in my file, I would like to solve the problem. This is very important for my future works. Thanks a lot.
http://www.4shared.com/file/VnawQ90N/High_Pass_Sharpening.html

I tried to sync the color space in Bridge. But when I click the Color Settings in Bridge, it freezes and stops responding. I don't know what is wrong. There is a problem details in a window. Can anyone help me?
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Fault Module Timestamp:          00000000
Exception Offset:          0012f878
Exception Code:          c0000005
Exception Data:          00000008
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High pass with color?

Hello.
Is there a way to achieve the same effect of high pass without desaturating the image?
Thanks in advance

Two ways I can think of:
1. Immediately after running the High Pass filter, Edit > Fade, and play with the blening mode in the dialog. Various modes will give different effects, so experiment.
— or —
2.Run the High Pass filter on a duplicate layer, and then change its blending mode.

Getting High Pass effect in AE.

Is there an After Effects equivalent to Photoshop's High Pass plug-in?

A search of PS-CS3 ehlp systems turned up 5 references to "high pass" in PS but the term actually appears only one place:
High Pass Retains edge details in the specified radius where sharp color transitions occur and suppresses the rest of the image. (A radius of 0.1 pixel keeps only edge pixels.) The filter removes low-frequency detail from an image and has an effect opposite to that of the Gaussian Blur filter.
It is helpful to apply the High Pass filter to a continuous-tone image before using the Threshold command or converting the image to Bitmap mode. The filter is useful for extracting line art and large black-and-white areas from scanned images.
Searching in AE's help system I get 8 hits but the term never actually shows up anywhere except as an audio filter.
So, umm, I think this can be faked with many filters. Depends on what you're trying to accomplish in AE. Sounds like Unsharp Mask but I'm sure you already know how to use that one.
The Unsharp Mask effect increases the contrast between colors that define an edge.
bogiesan

Simple low pass filter

Yo Guys,
quick question:
I got this sh*t pile of data that I just want to observe quick with a filter. So I don't need an advanced low-pass/high-pass filter in a program. I tried the filter in signal analyses in the plain LabView 7.1 version. But I can't read the array with data and analyze it. I keep on getting the error:
"The following conditions must be met: 0 < f_low <= f_high <= fs/2"
Anyone ideas of building a quick (live) filter into labview to filter the signal and see the results straight away on graphs?
Cheers to all!

this is the VI btw... might be helpfull in looking into what i'm doing...
who can help me out on this one?
Attachments:
filter prog.vi ‏427 KB

High pass filter sweeps

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