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23rd March 2011
Datacolor Spyder LensCal lens calibration target reviewed
by Ian Burley
7926: Datacolor Spyder LensCal lens calibration target reviewed

Check and adjust the autofocus of advanced DSLRs with a Spyder LensCal

Price: UK: 59.26, USA: $57, via Datacolor Europe website: 49 (excluding VAT)

Check out the prices on Amazon at the bottom of this page.

Autofocus SLR traditionally cameras use range-finding sensor to focus the lens. As these sensors are not physically on the focal plane, or sensor plane, they need to be calibrated in the factory. If the calibration is out, the camera won't focus correctly. If the camera is calibrated in the factory, why would a photographer need to calibrate the camera again? There are several reasons: the camera may have been knocked, throwing the delicate AF sensors out of calibration, or the lens attached to the camera may not be calibrated. Each lens has its own opto-mechanical focusing characteristics and sometimes calibration is required to get accurate focus with a given camera body.

The Datacolor Spyder LensCal ready to go. Note the bubble level at the front and the tripod bush at the back. You can also use the LensCal on a table top.

Focus calibration in the factory is largely down to mechanical adjustments. The position of the reflex mirror, for example, is critical to both visual and auto focus accuracy. But for years photographers have occasionally been blighted by front and back focus problems. This is where the focus of a given lens falls in front or behind the required focus distance. It's particularly problematical with very fast (bright) lenses, and especially telephoto lenses, where open aperture depth of field is very shallow. Therefore camera manufacturers devised a solution that enables photographers to bias the autofocus, using a camera menu function, in order to compensate for any front or back focus issues. Most DSLR camera manufacturers now offer user-calibration in their higher end models. Calibrations are specific to a particular lens and the camera will know which calibration profile to use by interrogating the lens for its model type and serial number.

The Spyder LensCal is supplied in flat-pack form, which makes it convenient to store.

This is the lens calibration interface for an Olympus E-620 DSLR. Note that the lens serial number and lens model is recorded as the calibration is specific to that lens.

Cameras that can be AF calibrated by the photographer

  • Canon EOS 50D, 7D, 5D Mark II, 1D Mark III, 1DMark IV, 1Ds Mark III
  • Nikon D7000, D300, D300s, D700, D3, D3s, D3x
  • Olympus E-30, E-620, E-5
  • Pentax K20D, K7D
  • Sony A900, A850

(Above) Here is the LensCal mounted on a tripod. The large and small squares are targets to aim at with your camera's focus points. As you can see the scaled strip goes from -6.5 to +6.5, with zero representing accurate focus. The scale is in centimetres as measured in front of and behind the target.

(Above) Here is a side profile view of the Spyder LensCal. A brass tripod lens bush is built into the plastic base of the Lenscal, and the extra lump to the right is a bubble level.

(Above) And here is a look at the back of the LensCal. Construction quality is good, and should last well if handled with respect.

In use

Datacolor has made a good job of the physical design of the LensCal, but what is it like in use?

(Click on the image above for a larger view in a separate window)

If you have a fast lens, it's reasonably easy to see the precise focused position on the scale. Here we have used an Olympus Zuiko Digital 150mm f/2 telephoto lens. Depth of field is only about 12mm in this example.

(Click on the image above for a larger view in a separate window)

Above, the focus is about 2cm behind the target.

(Click on the image above for a larger view in a separate window)

Above, the focus is around 2.5cm in front of the target.

(Click on the image above for a larger view in a separate window)

In the above example we're using a 14-42mm kit zoom lens at 42mm. The maximum aperture is only f/5.6. Depth of field is now around 70mm, and so it's very difficult to judge where the precise focus is.

Conclusion

The Datacolor Spyder LensCal is a nicely designed and manufactured piece of kit. I'm sure professional photographers will be interested in a LensCal to ensure their investment in expensive glassware, especially telephoto lenses, safeguarded. Whether non-pros will want, or even need, a LensCal is less clear. If you are an enthusiast and you have managed to add some fast lenses to your arsenal, especially telephoto lenses, and your camera body supports AF calibration, and you have noticed focus problems, a LensCal may well be an attractive solution. But cost may be a decider and I have already seen quite a few home-made alternatives to a LensCal and by all accounts they work fine.

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