ZS20 with Teleconverters, part 4


Magnification Factors

From measurements on the test images I calculated the magnification factors for the various TCs and stacked TCs versus the ZS20 at the same distance, as shown in the table below.  I have also included notes on vignetting.

As can be seen, there were only slight increases in magnification when the distance was increased from 30m to 200m.

Closest Focus Distances

I carried out tests to determine the closest distance from the ZS20 when set at maximum zoom (480mm equiv.) at which it was possible for the AF to achieve a sharp focus with the different TCs and stacked TCs.  What is notable is that for close distances with the single TCs and for all distances with the stacked TCs tested it was necessary to set the focus to Telemacro, as the AF did not achieve a focus in normal focus mode.

Wider Aperture with Longer Focal Length

The ZS20 has a widest available aperture at  maximum zoom (480mm equivalent) of f/6.4.  Although it seems a contradiction, it is possible to use the ZS20 at a wider aperture than f/6.4 and with a longer optical focal length than 480mm by using TCs. 

The SZ20’s widest available apertures change as the lens is zoomed.  I have tabulated the changes in widest available aperture at the 45 discrete steps in FL across the zoom range here.  It can be seen from that table that in the range from 280 to 385mm, the widest available aperture is f/5.9.  When a TC is attached to the ZS20 it is therefore possible, by setting the zoom to this range, to use an aperture of f/5.9 while also achieving an effective optical FL of 480mm or greater.

I have shown in the table below the effective focal lengths that can be achieved at f/5.9 with various TCs:

To show an example of this technique, below is a hand-held shot of the communications tower (distance 200m) taken with the ZS20 at 386mm FL and f/5.9, without any TC attached (click on an image for a larger view).  The full sized 14MP images can be downloaded from my DPR gallery here.

ZS20 without TC; 386mm, f/5.9, distance 200m

This is a shot from 200m taken hand-held at 386mm FL and f/5.9, with the E15ED attached:

ZS20 with E15ED; 386mm, f/5.9, distance 200m

The effective optical FL of the shot with E15ED attached is 578mm, at an aperture of f/5.9.

The following section gives some examples of shots of birds and the moon taken with the ZS20 using TCs.

Continue to Example Images with Teleconverters

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