Olympus E-1 has a
5.0MP Four Thirds (17.3 x 13 mm ) sized CCD sensor . On the other hand, Panasonic L1 has a
7.0MP Four Thirds (17.3 x 13 mm ) sized CMOS sensor .
Below you can see the E-1 and L1 sensor size comparison.
Sensor Size and Resolution Comparison image of Olympus E-1 and Panasonic L1 Cameras
Olympus E-1 and Panasonic L1 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Olympus E-1 has 50% larger pixel area compared to Panasonic L1, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Olympus E-1
or the
Panasonic L1 ,
including hyperfocal distance.