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|Gary Wolstenholme takes a close look at the Spyder LensCal. A device aimed at those who wish to make accurate focus micro adjustments on SLR cameras with that feature included.|
With today's autofocus lenses, for most people's requirements it will not matter how sharp the lens is, if it can't focus accurately. Many a horror story can be found of people having to try two or three copies of a lens before a satisfactory copy can be found. In my own experience I have known lenses that were once great, have become less accurate to focus as the years advance. In response to this, many manufacturers have added focus calibration features to their high-end SLRs, so that accurate focusing can be obtained without having to send your lenses off to be calibrated.
The issue here is that without an accurate, repeatable test for focus accuracy, you could end up making matters worse than they already were, which is where Spyder's LensCal device comes in. Costing around £50, it is aimed at advanced photographers who are unwilling, or unable to put up with focus inaccuracies. This may seem a little steep for what is essentially a piece of plastic with spirit level and a tripod mount included, but if it does its job, it could potentially save money on getting lenses calibrated, especially if they are out of warranty.
To make the most of this product a digital SLR camera with some way to calibrate the focus system is required. Canon call their system 'Micro Focus Adjustment' and recent camera models from the 7D upwards have this feature. Nikon's version of this feature is called 'AF Fine Tune' and is present on recent cameras from the D300 upwards.
Datacolor Spyder LensCal: In Use
The device works by providing an AF target, which needs to be set up level to the sensor plane. When the camera is focused to this, a sloped ruler, which lies at roughly 45degrees, shows whether the lens is focusing accurately to the surface of the AF target. The idea is, that the sharpest point is ahead of the target, your lens has front-focused and vice-versa. Having this information should than allow you to make the adjustment necessary and re-check the lens.
In the box the LensCal device is packaged flat, and can quickly be set up by unclipping the ruler from the base and raising the AF target. A spirit level is provided to ensure that the LensCal is set up square. I found it necessary to use a hotshoe spirit level on the Nikon D700 used for testing to ensure the camera was set up square too. A brass threaded hole is included for mounting on a tripod, although I found it easy enough to set the LensCal on a flat level surface during testing.
|The LensCal folds flat for storage.||A spirit level bubble helps to ensure the device is set up properly.|
The testing process is simple. The camera needs to be focused on the AF target and a picture should be taken. Examining the image on the camera's screen at full magnification should show whether the lens is focusing in front or behind the AF target, allowing you to make the adjustments necessary.
Datacolor Spyder LensCal: Performance
To test the LensCal I used a variety of my own lenses in conjunction with a Nikon D700. To my surprise, only a couple of my lenses showed focusing errors (and I own some right old beaters!) so the reassurance alone was a pleasant bonus.
Two of my lenses that showed focus errors were my Sigma 24mm f/1.8 EX, which was front focusing by quite a noticeable margin, and my Nikon AF 135mm f/2 DC, which I have always suspected of being a bit off but have never got round to testing.
As both are wide aperture lenses, the depth of field is quite shallow, which should make it easy to see the point of focus. With the 135mm lens, this is certainly the case making the front focusing problem easy to diagnose and correct. An adjustment of +3 seemed to have the lens focusing much more satisfactorily.
With the Sigma, the transition from in focus to out of focus is more gradual, so I found it more difficult to ascertain exactly where the point of focus was. Still I managed to diagnose the front focusing issues with this lens, which required the maximum +20 adjustment to get the focus point as close to accurate as possible.
Datacolor Spyder LensCal: Verdict
Although £50 may seem a little steep for what is essentially a piece of plastic with a spirit level, it could potentially save a fortune in service charges for getting out-of-warranty lenses calibrated. If like me, you own more lenses than you have fingers, then the peace of mind alone of knowing all is well with your equipment may be worth its while also.
So long as care is taken to complete the testing process accurately, it is very straightforward, and easily repeatable, which is exactly what is required of a product like this. Still, I can't help thinking that this would be a much more appealing product if the price were just a little lower.
Datacolor Spyder LensCal: Pros
Easy enough to set up
Testing procedure easily repeatable
Accurate results are possible so long as care is taken
Datacolor Spyder LensCal: Cons
£50 is maybe a little pricey
Wide angle lenses are more difficult to test than telephoto lenses
|VALUE FOR MONEY|