Excel spreadsheets do not: redact/export/image/produce (or some variation thereof) as I expect them to. Why is that?
As a matter of routine, we will suggest native review and redaction with respect to these multi-dimensional doc types. There are simply too many ways that potentially relevant data can be obfuscated that, were developers to try to code these views into the review platform, they would eventually (re)create the native application.
Summation utilizes two viewers: Standard (an Adobe based viewer) and Alternate (OutsideIn). These are sufficient to view most document types including Excel. They lack however most of the features that native applications provide and this can hinder review and redaction. For example; If a reviewer were to search for a cell formula, Summation wouldn't return any result. That's because the viewers don't include the ability to search in formulas AND the processing engine in Summation (any review platform) doesn't extract this formula to text. Rather, it extracts the value the formula produces.
For example: If the formula: =10266619477369800/(1024*1024*1024) is present in a cell, a search for the formula (in Summation) would not return a result. If you searched for the product of that formula: 9561534.484 you would get a hit. Granted this may not be a common search, but it does come up from time to time.
Redactions can also become very problematic when done in the review platform. Truncated cell views, hidden fields, macros, filters and formulas can cause data to be viewed differently and the fact that these conditions exist are not all that obvious. The observant will probably notice that the columns skip a letter or the rows skip a number. In Summation, the reviewer can resize these hidden rows and columns in the viewer in the same way as they would in the native app. They wouldn't be able to turn word wrap on or off however.
Immediate work-arounds for truncated text is to select the "Text" sub-tab in Summation. It turns the spreadsheet into a flat text file, and all the text (including truncated text) is displayed. It's even highlighted in the text view if it's responsive to search.
For redactions in spreadsheets - We suggest exporting the spreadsheet to native, redacting in Excel (replacing the contents of a cell with "REDACTED" or some other common flag for example) and then adding this redacted spreadsheet back into the case. Once indexed, it can then be included as a native file in the standard production/export (including extracted text) without the need to image it. Imaging spreadsheets presents a whole new set of issues for review platforms... When done this way, we retain the original in its unaltered state for later comparison if that's necessary.