Kelda 8mm f/3.5 Fisheye CS Lens Review

Kelda 8mm f/3.5 Fisheye CS Performance

The lens resolution tests were very impressive when we consider the design parameters of the lens. We have enormous amounts of barrel distortion and that is fully expected in a fisheye. It is, of course, one of the “creative” lenses, where we look for its wacky effects and strange apparent perspective on the world. I say apparent because it obeys the laws of optics like any other lens and its world-view is correct. To test this, we would need to see a print from a distance of maybe a few inches. If we could focus that close, the image would no longer look odd. From more normal distances it reverts to looking as we want a fisheye to look.

It is true to say that fisheye lenses are not designed for lens testing charts and the figures provided are interesting but the lens is probably far better than the results indicate. Sharpness is impressively good and resistance to flare is also very good, which is important with such a large front element.

Looking at the resolution figures, the lens performance is very good across the frame at f/5.6 and f/8 and good overall except at the widest and smallest apertures, where it drops to only fair at the centre (wide open) and fair at the edge (smallest aperture). Imatest refused to measure distortion, perhaps unsurprisingly, so we can summarise that as a large amount of barreling.

MTF
 

How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. 

The scale on the left side is an indication of actual image resolution as LW/PH. The taller the column, the better the lens performance. Simple.

For this review, the lens was tested on a Canon EOS 600D using Imatest.

 CA impressively low at the centre, and visible but at reasonable levels at the edges, especially considering the ultra wide angle.

CA
 

How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimise the problem, hence they usually cost more.

For this review, the lens was tested on a Canon EOS 600D using Imatest.

The field of view is very wide, so much care is needed to avoid anything unwanted creeping into the frame. If the lens is pointed downwards, do watch out for your own feet, something that I fell foul of whilst distracted by the texture I was trying to capture in a couple of shots. It's also worth noting that for landscapes, the image will look wide but quite normal if the horizon runs right through the centre and the camera back is absolutely vertical.

Focusing was the main issue, but part from that, subjectively the lens performed very well indeed and is a very usable fisheye with enormous creative potential. The key is probably to get in close to see the effects desired. If we stay back then all we have is a very wide and distorted shot. It is a lens for the bold.

A final thought on metering. Fisheye lenses, and this one is no exception, may well need some exposure compensation, depending upon the make of camera body. Centre weighted metering seems to work very well, in my case -1 EV is the norm for correct exposure, but once that is dialled in then exposures are generally accurate.

Value For Money

The Kelda 8mm f/3.5 Fisheye CS lens is available for £180, from Kauser International, which makes it excellent value for money. Also available from Kelda, is the 6.5mm f/3.5 Fisheye lens (£170). Other alternatives to consider include the manual Samyang 8mm f/3.5 UMC Fisheye CS II (£220), the auto-focus Sigma 10mm f/2.8 EX DC Fisheye lens (£559), and for Nikon the 10.5mm f/2.8G ED DX fisheye lens (£549).
 

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