Depth of Field Revisited

This topic comes up now and again in the forums because it is hard to grasp that the size of the sensor has a direct effect on the depth of field, which of course has a significant effect on subject isolation ...

Read an excellent explanation here of how crop factor affects the image. The bottom line is that, when you shoot at the same subject distance with the same magnification of the final image at the sensor, you get more depth of field as the sensor gets smaller. A simple relationship that is the primary reason why you can never really get that "dSLR look" from a small sensor ...

I shot a pair of examples tonight ... one with the ZS3, which has a very small sensor at 1/2.33" ... this has a crop factor of about 5.7 ... this causes a rather vast gulf in subject isolation between the ZS3 and, say, a D700 FF dSLR. In fact, at max zoom the ZS43 is at f/4.9 ... which translates in effective depth of field to approximately f/28. That's a pretty deep field of focus.

Two examples ...

ZS3 at f/4.9 at 300mm from about 6 feet with background about 4 feet behind.


You can see the hound's tooth pattern distinctly.

Then we have the D700 at 300mm and f5.6 (disadvantage) from about a foot further (disadvantage) and everything else the same ...


The cable hanging down is already a bit blurred and the pattern on the background is essentially blurred out ...

So there you have it ...

If the ZS3 wanted to be able to replicate that effect, it would require an f/0.98 aperture ... something that will clearly never happen ...