Stacked Teleconverters with a

Closeup Lens

 

In this section:

Stacked Teleconverters with a +1D Closeup lens

Stacked Teleconverters with a +0.75D Closeup lens

Stacked Teleconverters with a +0.5D Closeup lens

Stacked Teleconverters with a +0.25D Closeup lens



Stacked Teleconverters with a +1D Closeup Lens


Introduction


A useful technique that was brought to my attention by DPR Forum member “alxnv” is to use stacked teleconverters with a low power closeup lens attached to the cam lens.  This enables the stacked TCs to be focused at a much closer distance than is possible without the closeup lens.


Using this technique with the Panasonic FZ30, alxnv has obtained some remarkable shots of birds, as he reported in 2007 on the DPR Panasonic forum:

http://forums.dpreview.com/forums/read.asp?forum=1033&message=22897803


I tried this technique using my FZ38 with stacked shortened E15ED plus E17ED, with a 46mm Hoya coated +1D closeup lens attached to the front element of the FZ38 cam lens, and the results are shown below.


FZ38 plus stacked Nikon E15ED plus E17ED TCs plus +1D closeup lens


Using a tripod and the test chart I used for the resolution testing, I took shots with the FZ38 at maximum zoom (486mm) at the minimum and maximum focus distances and I measured the distance from cam to chart with a tape measure.  I calculated the magnification obtained by comparing the length of the 65mm bar on the resolution chart image with the bar length on an image taken from the same distance with the cam alone. 


Normally with the stacked Nikons on the FZ38 it is necessary to use the “Telemacro” (AF Macro) focus setting so as to obtain a focus, but with the +1D closeup lens attached, it was possible to obtain a focus in both the normal AF mode and the telemacro mode.  However, the different focus modes gave different closest focus distances, as shown in the table below.  Also included in the table are results for the stacked Nikons without any closeup lens attached.


Results


The images with the closeup lens were very sharp, with only a small amount of CA visible when viewed at 100%.  There was only slight vignetting in the extreme corners.


Images taken with background vegetation present

Below is an image of a Banskia serrata  tree taken at max zoom with the stacked Nikons plus closeup lens, using a tripod:



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As can be seen, there is a circular alignment of the distant out-of-focus background vegetation which presumably is caused by the single element closeup lens.  However, the area of focus is very sharp and the image otherwise shows very good IQ.  Below is a 100% crop of the central area (no PP):



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If the background is bright and the distortion appears distracting, as in full image shown above, then just a small amount of PP using “Gaussian blur” can remedy the situation, as shown in the slightly cropped image below:


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In situations where there is a dark background, the bokeh distortion does not tend to be noticeable.  This is shown in the following image of Gloriosa lilies taken at about 7-8m away under the same conditions as above.  The flowers are about 8cm in diameter:



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Conclusion


This technique can yield images of high IQ with an effective FL of more than 1,000mm with the cam as close as 14ft or as far as 45ft.   It therefore seems very suitable for obtaining highly detailed closeup shots of subjects such as birds or other animals which can’t be approached very closely.


Further Testing


Since doing the above tests I obtained a +0.75D achromat closeup lens, which promised to be more useful for this technique, and which I’ve used to do some further testing, as detailed on the following page.



Continue to Teleconverters with a +0.75D closeup lens


Continue to Testing of a 0.5D Closeup Lens


Continue to Testing of a 0.25D Closeup Lens


Continue to Graphs for Focus Range and Magnification


Return to Stacked Teleconverters


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