In addition to the other mentioned important ergonomic concerns for capturing infants and toddlers - and assuming that you
are able to focus and shoot before they shift in physical position (yet) again ...
... the LX3/LX5 allows you a Depth of Field that works well with telephoto zoom (even at the relatively wider apertures).
I calculate that for a 1080 pixel-height display viewed up-close, with a LX5 at full telephoto zoom (90mm, 3.75x),
at a distance of 6.0 Feet between camera and subject (with an apparent distance relative to full wide-angle of 1.6 Feet between camera and subject), a conservative estimate of the Depth of Field for the following range of F-Numbers is:
F=2.0 --- DOF = 7.33 Inches
F=2.8 --- DOF = 10.40 Inches
F=4.0 --- DOF = 1.23 Feet
So, at full telephoto zoom, the LX5 would allow one to remain 6.0 Feet from the young subject (which I have often found be an advantage, and/or a necessity for spontaneous captures), have the effect of shooting at a very close 1.6 Feet, and (still) pull-of DOF of the (approximately 1.0 Foot) depth that is desirable to have in such situations. Very desirable, and something that larger image-sensors (more precisely the larger base focal-lengths that must accompany a larger image-sensor) cannot easily provide.
DOF is an important concern to resolve little heads - and higher telephoto zoom-factors (despite somewhat smaller-sized image-sensors) will only serve to further degrade DOF (by the
square of the ratio of the increase). This
square-law relationship rapidly trumps the DOF improvements that smaller image-sensors (in actuality, their smaller base focal-length lens-systems) are able to provide.
Note : While the above results are just ranging around 1.0 Foot DOF, the above results will improve in direct proportion to the
square of the ratio of 3.75 divided by any (lower) zoom-factor . The LX5 "Step-Zoom" adjust-ability allows users to determine zoom-factor to input into such calculations ...
... (whereas the LX3 user is largely left "in the dark" as to knowing an accurate estimate of focal-length at the time of shooting. Sadly, Panasonic (unlike Sony) has never provided a single digit of readout-precision to the LCD-displayed "Zoom Factor", and rounds the value to integer values only. Go figure ...
Note that at
70mm stepped (a zoom-factor of 2.92), where the subject is at
5.0 Feet , but still appears at an (apparent) 1.71 Feet, the DOF is improved:
F=2.0 --- DOF = 8.42 Inches
F=2.8 --- DOF = 1.0 Foot
F=4.0 --- DOF = 1.42 Feet
At
50mm stepped (a zoom-factor of 2.08), where the subject is at
4.0 Feet , but still appears at an (apparent) 1.92 Feet, the DOF is improved substantially:
F=2.0 --- DOF = 10.71 Inches
F=2.8 --- DOF = 1.28 Feet
F=4.0 --- DOF = 1.85 Feet