When you work with drawings created in earlier versions, you should be aware of the following visual fidelity issues.
You can specify that "annotative" objects maintain visual fidelity when they are viewed in earlier versions, with the SAVEFIDELITY system variable.
If you work primarily in model space, we recommend that you turn off visual fidelity (set SAVEFIDELITY to 0). However, if you need to exchange drawings with other users, and layout fidelity is most important, then turn on visual fidelity (set SAVEFIDELITY to 1).
Annotative objects may have multiple scale representation. When visual fidelity is on, annotative objects are decomposed and scale representations are saved (in an anonymous block) to separate layers. These layers are named based on their original layer and appended with a number. If you explode the block in an earlier release, and then open the drawing in the current release, each scale representation becomes a separate annotative object, each with one annotation scale. It is recommended that you do not edit or create objects on these layers when working on such a drawing with an earlier release.
When visual fidelity for annotative objects is not selected, a single model space representation is displayed on the Model tab. Depending on the setting of the ANNOALLVISIBLE system variable, more annotation objects may be displayed on the Model tab, and more objects may be displayed in paper space viewports at different sizes when viewed in an earlier release.
In an AutoCAD LT 2008 drawing, when an annotative block does not have its paper orientation set to match the layout, and the block contains multiline attributes that are based on a text style that is not set to match the orientation of the layout, the attributes may shift positions if you open this drawing in an earlier release.
When you open an AutoCAD LT 2008 drawing containing layer property overrides, overrides are not visible. The property override settings are retained when the drawing is saved in a previous release, and are visible again when the drawing is opened in AutoCAD LT 2008.
If a viewport containing layer property overrides is deleted when the drawing is opened in a previous release, the override settings are not retained and are not available when the drawing is opened in the current release.
When the VISRETAIN system variable is set to 0 when the drawing is opened in a previous release, xref layers containing viewport property overrides are not retained.
If you open an AutoCAD LT 2008 drawing in a previous release, property overrides may display in a thumbnail image. When the drawing is saved with a layout tab, and then opened in the previous release, those property overrides do not display.
DGN underlays do not display in versions prior to AutoCAD LT 2008.
AutoCAD LT 2008 dimension enhancements are lost when they are edited in earlier versions. If you don’t change these dimensions, they are restored when you open the drawing in AutoCAD LT 2008.
The following dimension enhancements do not lose visual fidelity in previous versions if they are not edited:
Multileaders display as proxy objects in versions prior to AutoCAD LT 2008. The PROXYSHOW system variable controls the display of proxy objects in a drawing.
Some of the new paragraph spacing and paragraph line spacing options are not supported when an AutoCAD LT 2008 mtext object is opened in earlier versions.
The following mtext formatting features have no visual fidelity in previous versions:
The following mtext formatting features have some visual fidelity in previous versions (when it’s possible to add white spaces or replace text with white spaces):
Mtext with new formatting that is edited and saved in previous versions loses the new formatting when re-opened in AutoCAD LT 2008.
Editing AutoCAD LT 2008 tables in previous versions removes AutoCAD LT 2008 table formatting. Also, AutoCAD LT 2008 table cells with long block and text strings may extend outside of cell borders when opened in previous versions.
For tables that were created with the Data Extraction wizard in AutoCAD LT 2008, you can’t edit or update the extracted data in previous versions.
Drawing properties in AutoCAD LT 2008 are saved with Unicode characters. For instance, if you save the latest format drawing containing multiple language drawing properties to a 2004-format drawing, the drawing properties are converted to the native characters of the current Windows language. If text cannot be converted to the native characters, it is saved to CIF codes (U+nnnn) or MIF codes (M+nxxxx).
When saving the latest format drawing to a 2004-format drawing, any new symbol or dictionary names (for example, layout name, text style name, dimension style name) created in AutoCAD LT 2008 are saved in the language that was used when the symbol names were created.
In order to view and edit drawings with characters that are not included in the languages specified for your operating system, make sure supplemental language support is installed in your computer operating system. You can specify the language in the Regional and Language Options dialog box, available from the Windows Control Panel. (You may be able to view text that uses SHX fonts without specifying extra language support.)
Text styles for Asian languages that use SHX and Big Font can support characters only from the same code page. For example, text styles that use a Japanese Big Font cannot support German or Korean characters. (English characters, which are part of every code page, are supported.) Multiple-language support for non-Asian languages is supported for text styles that use SHX fonts with Big Fonts disabled. (The SHX font must define the required characters.)
Multiple-language support does not exist in some earlier versions of AutoCAD. For example, when you save a file to AutoCAD 2000 format, the contents of multiple-language multiline text may be corrupted. This problem is more likely to happen when you open and save a drawing on an operating system with a system language setting that differs from the system in which the drawing was last saved.
Drawings that include external references (xrefs) to drawing files saved in earlier versions also have the limitations described above.