Those of us who use a camcorder to take wildlife videos while travelling are often in a dilemma. A very small sensor can produce excess noise in low light while the image is subject to diffraction at all or just about all lens apertures; such cameras are though light in weight. A large-sensored (APS or full-frame) camera, by contrast, is much less liable to noise and diffraction but with a long lens is both heavy and bulky. To some extent the 1-inch sensor is a good compromise in terms of noise, diffraction and weight but choice in the market is very limited with new models appearing only very rarely. Those available have a useful if limited lens zoom range. Thus my Sony FDR-AX700, with which I have a continuing love-hate relationship, has an optical zoom range, in 35 mm equivalents, of 29-348 mm, which in some circumstances is not wide enough or long enough.
The option to use Sony’s ‘clear image zoom’ provides additional focal length at the long end, with a zoom range of 18x, i.e. 29-522 mm when using 4K. I really cannot see the stated small difference in resolution between optical and ‘clear image zoom’ when I shoot in 4K, edit in and output from a 1080 timeline in FCPX and then watch the video on a normal sitting-room sized 1920 x 1080 television.
I always shoot in 4K and edit on a 1080 timelines, giving me the option of cropping without loss of resolution up to 2x. That scaling effectively doubles the maximum focal length of the lens, in this case to 696 mm (optical zoom) and 1048 mm (clear image zoom).
Sometimes, though I need a greater focal length and have been working with two lens extenders, both of which will fit directly on to the filter thread of the AX700. Lens extenders in general have a terrible reputation with cheap and nasty versions available since the 1960s. However, Olympus made a tele-extender (‘Tele Extension Lens Pro’ TCON-14B) for its E-10 and E-20 cameras which went on sale in 2000-2001. That one multiplies the focal length by 1.4. They now sell for very little; I paid £13 for one in mint condition. Reviews from the time praised its high quality but the tests were made on a 4 MP camera. The TCON-14B is very heavy (465 g).
Raynox are highly praised for their converters—the Raynox DCR-2025Pro seemed ideal for my purpose. I have been deterred from buying one by the UK retail price—in excess of £220 and from some suppliers much higher. When I saw one advertised at £115 I ordered it. This one multiplies the focal length by 2.2, providing a very respectable increase in maximum focal length of the AX700 to 766 mm (35 mm equivalent) with optical zoom and to 1148 mm with clear image zoom. Multiply those figures by 2 for maximum cropping of 4K video in a 1080 timeline and we have 1532 (optical zoom) and 2296 (clear image zoom). With those sorts of focal lengths you really could not ask for more.
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| Raynox DCR-2025Pro mounted on the Sony AX700 |
The choice between optical zoom and clear image zoom isn’t just one of a small, imperceptible to my eyes when used in the field, difference in resolution. One of the annoying features of the AX700 is that some features that are available in optical zoom disappear when using clear image zoom. I find the central focus area option very useful subjects like perched birds or small mammals. However, the option for that is not available in the clear-image zoom range of x12 (348 mm) to x18 (522 mm). Therefore, it will sometimes be better to use manual focus with peaking.
Apart from the problem of heat distortion in the air between camera and subject that cannot be avoided with any very long lens, there are disadvantages of using a teleconverter. The first is having to operate at full zoom or very nearly full zoom; with any wider angle there is severe vignetting reaching the point of a central circular image. The second is having to screw it in position and then remove it when not needed—a fiddly, two-handed job. A friend lost a Raynox from a canopy hide in a rainforest; it fell while she was trying to screw it into position and was never seen again.
Turning to the Raynox DCR-2025Pro itself. I was delighted to find it is built of light plastic and for such a long and powerful extender weighs only 380 g. Mine came in its original box (I suspect it had never been used at all) and contained a Raynox brochure, dated 2018, which states:
The model Raynox DCR-2025 Pro high definition telephoto lens is made of high index optical glass elements, and it’s designed with new designing concept of two group/four element formula to obtain the maximum resolution power of 260-line/mm at center (MTF30%.
The lens hood (shade) is included as are caps and adapter rings for 43, 52, 55 and 58 mm filter ring lenses. I was confused when looking at the description of this lens by UK dealers since they did not included in their descriptions the fact that it fits a 62 mm lens ring—the AX700 size. In fact 62 mm is the native size with no adapter needed.
The combination of AX-700/Raynox DCR-2025Pro providing such long focal lengths does need a sturdy tripod even without pan/tilt movements while filming. And I soon discovered that shot against the light were a no-no; flare is too great even with the substantial hood on.
I have been testing the AX-700/Raynox DCR-2025Pro a little. To do so I have had the camera on a tripod with stabilisation off. I have put the 4K footage (clear image zoom on) on a 1080 timeline in FCPX and without further processing exported still image tiff files from a single frame. I looked at still images this way because the resolution of in-camera still images is different from that of video and I use this camera for video not stills.
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With the following series the flower is in a different position because there was a gentle breeze.
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The nest series is a similar illustration for comparison of the two extenders with the maximum focal length of the AX700. Below is added an image from the same position taken with a Panasonic Lumix DC-FZ82 at 1680 mm (35 mm equivalent) from 4K footage on a 1080 timeline. The difference in resolution is very clear but perhaps not surprising given the price difference between the cameras.
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| Panasonic Lumix DC-FZ82 'bridge'camera |
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I have also tried the Raynox extender in the field. I chose a dull day to prevent the effect of ‘heat shimmer’ affecting the image.
These two series are from two single frames at maximum camera focal length plus the 2.2x extender with clear image zoom on. The top is straight from the timeline; the next at 150% scale (i.e. 1.5x) and the bottom one scaled to 200% (i.e. 2x). Thus the bottom image is the equivalent of using a 2296 mm lens on a full-frame 35 mm camera, i.e. a lens 2.3 metres long in a non-telephoto design). The head shots are cropped stills from the exported tiff files.
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Finally, I made the footage I took into a short video. Except for the wide-angle shots all the rest was made using the Raynox extender on the AX-700.
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When I started the search for a tele-extender I suspected the Olympus version, although only 1.4x would be so optically superior that I would have to abandon the Raynox 2.2x. But no. When length matters the Raynox on the Sony AX-700 reigns supreme. I will be using it in other scenarios and will report if my initial verdict changes.
