OM System OM-1 has a
20.0MP Four Thirds (17.4 x 13 mm ) sized Stacked BSI Live MOS Sensor sensor . On the other hand, Pentax K-500 has a
16.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor and features PRIME M processor.
Another difference between these two cameras is that OM System OM-1's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the OM-1 and K-500 sensor size comparison.
Sensor Size and Resolution Comparison image of OM System OM-1 and Pentax K-500 Cameras
As seen above, Pentax K-500 has a 1.6x Larger sensor area than OM System OM-1. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.
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
OM System OM-1
or the
Pentax K-500 ,
including hyperfocal distance.
One thing to watch when comparing these two: they have different sensor sizes
(Four Thirds versus APS-C),
so compare them at the same framing rather than the same focal length.
Put the same focal length on the smaller sensor and it will show less depth of
field, not more, because it also crops tighter. The calculator shows the
full frame equivalent focal length for each body so you can match the framing.
