The engineers I have worked with at various companies seem to be of one mind, in that they believe it's most useful to their clients if every field available in a given dataset is displayed in a datagrid. This can result in datagrids with gigantic widths, and lead to column-width issues, which I as a designer am assigned to fix. Looking at the glut of data presented in these tables, which somethimes even need to scroll offscreen, I cannot see how presenting this much information at once in such a manner can possibly be useful. Furthermore, it ties many of our tables to a fullscreen width, as the amounts of data cannot possibly be displayed in a useful manner in anything less. My question is this: how much data is too much to display, before the user feels overwhelmed, overloaded, and disinterested?
The amount of data (both in terms of the types of data that are presented, and the amount of information presented for each type of data) presented in a table becomes too much when your users are unable to complete their goals, or are able to complete their goals with a lot of difficulty and overhead. Which is to say, the amount of data that is presented is too much when your users tell you (directly or indirectly) whether it's too much.
You can quickly gather some information about whether you're presenting too much data by either interviewing current users about what they do with your product and how they go about doing it (if you have any; it's unclear whether this is a new product (or new feature in an existing product), or by conducting a usability study against your most important use cases with your current or potential users to see if they are able to accomplish their goals.
There are two aspects to this question:
- Amount of data - this really depends on your audiance. For example if you are working with financial planners they would be comfortable dealing with more data in the same spreadsheet. Other way to think about it is that if the user needs access to data, then what's easier - scrolling or some other mechanism
- Second aspect is how do they comprehend this large amount of data. This is where there are many techniques that can be applied - color coding values/cells based on a certain scale - e.g. all numbers greater than 100 are in green, between 50-100 are orange etc. You can add charts, allow filters, expand/collapse some data elements etc.
The point at which a user sees information that they don't want/need is the point where there is too much data in the table. Some users will need to see a lot others might not need to see all of this data. If you have many different audiences that have different needs then you should have a way for each user to adjust the presentation to suit their needs.
I am currently working on a project that has a datagrid with upwards of one hundred possible columns. This would be unmanageable so we allow users to hide/display columns and save the "layout". Users can create many layouts that have different column combinations that suit specific tasks.