I have outlined the steps in my logic which have lead me to this conclusion. I look forward to hear other peoples opinions. Please let us keep the posts in this thread focused to precisely the question outlined below. Let us assume we have two CCDs. One is by
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General options for PDF You can set the following options in the General section of the Save Adobe PDF dialog box: Description Displays the description from the selected preset, and provides a place for you to edit the description. You can paste a description from the clipboard.
Note: The Preserve Illustrator Editing Capabilities option counteracts aggressive compression and downsampling. If file size is a concern, deselect this option. Deselect this setting when users of Acrobat 5. This allows Adobe Acrobat 6, 7, and 8 users to generate multiple versions of the document from a single file. Compression and downsampling options for PDF When saving artwork in Adobe PDF, you can compress text and line art, and compress and downsample bitmap images.
Depending on the settings you choose, compression and downsampling can significantly reduce the size of a PDF file with little or no loss of detail and precision.
Each section provides the following options for compressing and resampling color, grayscale, or monochrome images in your artwork. Note: The Preserve Illustrator Editing Capabilities option in the General preferences area counteracts aggressive compression and downsampling. Downsampling If you plan to use the PDF file on the web, use downsampling to allow for higher compression.
If you plan to print the PDF file at high resolution, do not use downsampling. Deselect the option to disable all downsampling options. Downsampling refers to decreasing the number of pixels in an image.
To downsample color, grayscale, or monochrome images, choose an interpolation method—average downsampling, bicubic downsampling, or subsampling—and enter the desired resolution in pixels per inch. Then enter a resolution in the For Images Above text box.
All images with resolution above this threshold will be downsampled. The interpolation method you choose determines how pixels are deleted: Average Downsampling Averages the pixels in a sample area and replaces the entire area with the average pixel color at the specified resolution. Subsampling Chooses a pixel in the center of the sample area and replaces the entire area with that pixel color. Subsampling significantly reduces the conversion time compared with downsampling but results in images that are less smooth and continuous.
Bicubic Downsampling Uses a weighted average to determine pixel color, which usually yields better results than the simple averaging method of downsampling.
Bicubic is the slowest but most precise method, resulting in the smoothest gradations. Compression Determines the type of compression that is used.
The Automatic option automatically sets the best possible compression and quality for the artwork contained in the file. For most files, this option produces satisfactory results. ZIP compression Works well on images with large areas of single colors or repeating patterns, and for black-and-white images that contain repeating patterns.
ZIP compression can be lossless or lossy, depending on the Quality setting. JPEG compression Is suitable for grayscale or color images. JPEG compression is lossy, which means that it removes image data and may reduce image quality; however, it attempts to reduce file size with a minimal loss of information.
JPEG Is the new international standard for the compression and packaging of image data. It also provides additional advantages, such as progressive display. Group 4 is a general-purpose method that produces good compression for most monochrome images. Group 3, used by most fax machines, compresses monochrome bitmaps one row at a time. Image Quality Determines the amount of compression that is applied. The available options depend on the compression method.
It determines the size of the tiles for progressive display. This method results in no loss of detail or quality. You can include bleed in your artwork as a margin of error—to ensure that the ink extends all the way to the edge of the page after the page is trimmed or to ensure that an image can be stripped into a keyline in a document.
Trim Mark Weight Determines the stroke weight of the trim marks. Registration Marks Places marks outside the artboard for aligning the different separations in a color document.
The trim marks are at the edge of the space determined by the offset. Color Bars Adds a small square of color for each spot or process color. Spot colors converted to process colors are represented using process colors. Your service provider uses these marks to adjust ink density on the printing press. Page Information Places page information outside the artboard of the page. Page information includes the filename, page number, current date and time, and color separation name.
When the button is selected, these four values are proportional—editing one will update the values in the other three. Interactions between Output options change depending on whether Color Management is on or off and which PDF standard is selected. All spot color information is preserved during color conversion; only the process color equivalents convert to the designated color space. No Conversion Preserves color data as is. Convert To Destination Preserve Numbers Preserves color numbers for untagged content in the same color space as the destination profile by assigning the destination profile, not converting to it.
All other content is converted to the destination space. This option is not available if color management is turned off. Whether the profile is included or not is determined by the Profile Inclusion Policy. Convert To Destination Converts all colors to the profile selected for Destination. Profile Inclusion Policy Determines whether a color profile is included in the file.
Output Intent Profile Name Specifies the characterized printing condition for the document. The available options depend on whether color management is on or off. For example, if color management is off, the menu lists available printer profiles. If color management is on, the menu lists the same profile selected for Destination Profile provided it is a CMYK output device , in addition to other predefined printer profiles.
Output Condition Name Describes the intended printing condition. This entry can be useful for the intended receiver of the PDF document.
Output Condition Identifier A pointer to more information on the intended printing condition. The identifier is automatically entered for printing conditions that are included in the ICC registry. Registry Name Indicates the web address for more information on the registry. Mark as Trapped Indicates the state of trapping in the document.
For instance, if a font contains 1, characters but the document only uses 10 of those characters, you may decide that embedding the font is not worth the extra file size. Overprints Specifies how to save overlapping colors that are set to overprint. You can choose to preserve the overprinting or discard the overprinting. Alternately, click Custom to customize the flattener settings. Note: Acrobat 5 PDF 1. As a result, the Preset and Custom options are not available for these levels of compatibility.
Adding security to PDF files When saving as PDF, you can add password protection and security restrictions, limiting not only who can open the file, but also who can copy or extract contents, print the document, and more. A PDF file can require passwords to open a document document open password and to change security settings permissions password. If you set any security restrictions in your file, you should set both passwords; otherwise, anyone who opens the file could remove the restrictions.
If a file is opened with a permissions password, the security restrictions are temporarily disabled. Depending on the Compatibility setting in the General category , the encryption level will be high or low. Options vary depending on the Compatibility setting. Compatibility Sets the type of encryption for opening a password-protected document. Be aware that anyone using an earlier version of Acrobat cannot open a PDF document with a higher compatibility setting.
Require Password To Open The Document Select this option to require users to type the password you specify to open the document. Note: If you forget a password, there is no way to recover it from the document. If the file is opened in Illustrator, Photoshop, or InDesign, the user must enter the Permissions password, since it is not possible to open the file in a view-only mode.
Permissions Password Specify a password that is required to change the permissions settings. This option is available only if the previous option is selected. None Prevents users from printing the document. Printing may be slower because each page is printed as a bitmap image.
High Resolution Lets users print at any resolution, directing high-quality vector output to PostScript and other printers that support advanced high-quality printing features. None Prevents users from making any changes to the document that are listed in the Changes Allowed menu, such as filling in form fields and adding comments. Inserting, Deleting, And Rotating Pages Lets users insert, delete, and rotate pages, and create bookmarks and thumbnails.
Any Except Extracting Of Pages Lets users edit the document, create and fill in form fields, and add comments and digital signatures. This option is only available when Compatibility is set to Acrobat 6 or later. More like this.
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There are three options you can choose from that controls how these pixels are removed: Downsampling, Subsampling, and Average Downsampling. Downsampling will throw away that excess data. Resampling images in will analyze pixels in a given area and replace those pixels with their average value. Average Downsampling. Average downsampling averages pixels within a sample area. The average pixel value is then assigned to the entire pixel area.
Bicubic downsampling and quality
From an image processing POV, resizing algorithms for photography are probably best considered as data re-gridding algorithms that are optimized for several performance metrics. The performance metrics that the algorithm will be judged on include accuracy of estimation which is partially reflected in visual sharpness , immunity to noise in the original data, minimizing stair-stepping, minimizing ringing, etc.. For any given scene, or even different parts of a scene, the photographer will almost certainly want to weigh these factors differently. For example, an algorithm that re-grids natural textures eg, grass well ie, produces a nice, sharp, realistic downsized image , will most probably have unacceptable artifacts when used to downsize an image of sharp edged geometrical patterns e. Similarly, "nearest neighbor", an algorithm that perfectly preserves sharp edges at 0 and 90 degrees, is utterly horrible when applied to noisy input data. The above is a long way of saying that a good post-processing person should know the pros and cons of various resizing algorithms and apply them as appropriate for each image or different areas in an image.