7D viewfinder DOF doesn't match image DOF?

The DoF that Chuck talks about here is the DoF you would expect when viewing the (LiveView) image at LCD size from arm's length (or however you hold your camera when chimping ) If you use 5x or 10x the DoF is then the same as for an image 5x or 10x LCD size, again viewed at arm's length. How these relate to viewing an 8x10-ish print at ~12" is an exercise left to the reader. For bonus points, also calculate the DoF for a 16x20 viewed from the same distance

I don't think it's limited to or a problem with the 7D, in particular.

It's all 1.6X crop cameras. They have smaller image areas, and the design just does not demonstrate DOF well even when preview is used. I do not have time to do DOF preview and Live View checks at 10X, so I just am in the habit of stopping down one additional stop than what the image appears to need in the viewfinder.

This is despite the fact that effective DOF with lenses on a crop camera is greater than it is on full frame. The reason for this is that with any given focal length you step back to get the same angle of view you would on full frame. So, you are farther from the subject and effective DOF is greater. There is approx. one stop difference here, too, but in the opposite direction. I.e., given the same focal length but standing farther away to compensate, f2.8 on the cropper renders about the same as f4 on full frame. (This is no different than with film cameras... 35mm vs medium format... f4 is fast and on MF offers about the same effective DOF performance as f2.8 on 35mm film... Or large format, where you might use f5.6 for similar DOF effects).

So, in effect, the crop sensor DSLR viewfinder is "off" by about the equivalent of two full stops, but one of those stops is "nullified" or offset by the difference noted.

It's not really that any thing is "off".... just that it's hard to see and evaluate, due to the smaller size of the viewfinder, the optics needed to make it usable, and the type of modern focus screens being used.

I have seen these effects on every 1.6X crop camera I've used - 10D, 30D and 50D mostly, in addition to 7D - and it's a key reason I prefer and recommend a full frame camera for portraiture or other uses where DOF control needs to be at it's greatest.

You can potentially improve the matter a little with an alternate focus screen.... But I don't know how much that might help, or what the trade offs might be. There are now some third party focus screens for 7D, although I think mostly just to assist with manual focsusing. Check out katzeyeoptic.com