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Jack Pfeiffer
03-07-2003, 03:18 PM
Hello..

Many people get confused as to the differences between the types of blur filters that are included with Combustion.

WHEN do you use WHICH, and WHY? So, to help differentiate and understand the differences between the blurs, I have collected below the precise definitions about the blur types, as well as how and when to use them.



regards,

Jack Pfeiffer

Denmark





Box Blur:

The Box Blur is a quick and easy way to create a blurring effect. The Box Blur changes the color value of each pixel based on the pixels next to it in the vertical and horizontal directions. It is fairly close to the look achieved using Gaussian Blur, but renders much faster. Use it when a faster rendering time is important, and the quality of the blur is less important. With Box Blur, you can adjust: Radius - Varies the strength, or reach, of the blur filter. The radius is measured in pixels. OR Resize Image - Blurs outward from the edges of the layer giving the layer a soft edge.



Channel Blur:

Use Channel Blur to blur each channel separately. You can blur the alpha channel, or create some unusual effects by adjusting the blur filter independently for each color channel. For example, blur the Blue channel to reduce grain, green to blur image detail, and red to reduce contrast. In Combustion, you can adjust the: Red, Green, Blue, and Alpha sliders - Each sets the blur radius, in pixels, for each color channel, as well as Undefined Areas - Which sets the color to use to blur pixels at the edge of the image, or where the color channel is black. And lastly, Resize Image - Extends the blur beyond the edge of the blurred layer.



Compound Blurs:

Channel blurs allow you to create a blur based on the pixels of another channel, either in the same layer or from a different layer. In fact, the compound blur can be based on the output of any operator in the work-space. If you apply a compound blur based on luminance, the image is blurred where the pixel luminance is high, and it is not blurred where pixels are black. With Combustion, you can also adjust: the Layer - Displays the Operator Picker. You use this to select the footage whose pixels are used to set the amount of blur applied, and Radius - Which sets the blur strength. The Radius is measured in pixels. The Channel - which determines which channel, in the source layer, is used to set the amount of blur applied. And lastly, the Blur Type - Determines whether the blur is a Box Blur or a Gaussian Blur.



Dolly Blurs:

Use Dolly Blurs to create a radial blur that increases outwards from a defined center point. By keyframing the blur radius, you can duplicate the effect of a blur created from a rapid camera dolly (camera moved towards or away from the subject). With Combustion, you can also adjust: The Amount- Sets the strength of the blur. The amount is measured as a percentage of the image. The Center - which determines the point from which the blur radiates. The center is not blurred. You can enter the X and Y values of the center, or
click the Pick button and pick a point in the active viewport. The Quality - Determines whether the effect is grainy or smooth. and Resize Image - Which blurs outward from the edges of the layer.



Gaussian Blurs:

Really cool, BUT: Gaussian Blur uses a MUCH more complex formula for calculating its blurring effect than Box Blur. The results are more realistic and approximate more closely the real-world effect of shooting a subject with an out-of-focus lens. The problem is that they take a LOT longer to render :-) With Combustion, you can adjust: Radius - Varies the amount of the blurring effect: The radius is measured in pixels. and Resize Image - which blurs outward from the edges of the layer.



Motion Blurs:

These are used to simulate the blur created by fast-moving objects. To create a Motion Blur, combustion takes samples of previous and subsequent frames and composites them over the current frame. Note: Combustion uses sub-frame sampling to create a smooth effect. You control the number of samples, the transparency (or weight) of the samples, and the duration over which the samples are taken. Side Note: You must nest a layer before you use Motion Blur on an entire layer. Motion Blur Controls allow for : Samples - Determines the quality of the Motion Blur. Increasing the number of samples improves the quality of the Motion Blur, creating a softer effect. Note: Increasing the Sample value causes the processing time to increase linearly. In many cases, you do not need anti-aliasing on a blurred layer, so to save processing time, you can turn it off. Phase - Specifies whether the Motion Blur is based on the movement before or after the current frame. A value of -100 places the Motion Blur before while a value of 100 places the Motion Blur after. A value of 0 is centered, which evenly distributes the Motion Blur. Shutter - Determines the size of the Motion Blur.



Pan Blurs:

Pan Blurs simulate a directional blur created by a fast-moving object. Use this filter to simulate the blur created from a fast-moving camera panning or craning. With Combustion, you can vary: the Amount - Varies the amount of the blurring effect. The amount is measured as a percentage of the image. The Angle - Sets the direction of the blur. A direction of 0 simulates camera craning (moving up and down). A direction of 90 simulates camera panning (moving left to right). The Quality - Determines whether the effect is grainy or smooth. And lastly, Resize Image - Blurs outward from the edges of the layer.



Roll Blurs:

Roll Blurs are used to simulate the blur created when a camera or object is spun on its own axis. Here, you can adjust such things as: The Amount - Varies the amount of the blurring effect. The amount is measured as a percentage of the image. The Center - Determines the point around which the blur swirls. The center is not blurred. You can enter the X and Y values of the center, or click the Pick button and pick a point in the active viewport. The Quality - Determines whether the effect is grainy or smooth. and lastly, Resize Image - which blurs outward from the edges of the layer.



Sharpen:

Sharpen, which is not really a "blur" is used to increase the clarity and sharpness of a layer. The filter works with object edges and areas where color differences occur. You adjust the Amount - Determines how much the image is sharpened. The amount is measured as a percentage of the image.



Unconstrained Box Blur:

Unconstrained Box Blur is similar to Box Blur BUT you can set the horizontal and vertical radii individually. In combustion, you can adjust: The Horizontal Radius - Sets the strength of the blur in the horizontal direction. The Vertical Radius - Sets the strength of the blur in the vertical direction. The radius is measured in pixels, and lastly Resize Image - Blurs outward from the edges of the layer.



Unconstrained Gaussian Blur:

Unconstrained Gaussian Blur is very similar to Gaussian Blur but you can set the horizontal and vertical radii individually. Here, you can adjust and set the: Horizontal Radius - Sets the strength of the blur in the horizontal direction. The Vertical Radius - Sets the strength of the blur in the vertical direction. The radius is measured in pixels. and lastly, Resize Image - Blurs outward from the edges of the layer.

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