Following on from their presentation at a club night, a dozen members went along to Lehman’s on Saturday morning. This was to see what goes into checking and calibrating lenses and digital camera sensors. Once we were assembled we first saw the Canon DIA calibration process that matches cameras and lenses together by rewriting data within the equipment. The process is done for the horizontal, vertical and diagonal orientations of the Auto focus sensors. It isn’t uncommon for the camera to decide to use different focus point orientations on successive images even if the framing hasn’t changed at all.
Next it was upstairs to a long room, long enough to check 500mm focal length lenses with the same accuracy as 18mm focal lengths. First it was to see how the sensor is tested for its position and how parallel it is to the required position. During this there was a discussion about wet weather and camera gear. The advice was basically don’t get it wet, if fail on that then make sure it has time to dry as soon as possible. If travelling by car, get the gear out of the bag and let it start to very. Once home, keep the gear out of the bag and let it dry in a centrally heated room but not too close to the heat source. When it came to use b the sea and sea spray one bit of advice was to use someone else’s camera. It is possible for lenses to have hidden problems with circuit boards getting corroded in addition to the visible fungal growth and dust spots.
After that it was on to the lens checking, centring and resolution. The process was again clearly explained and demonstrated. Then came the moment some of us had been fearful of, some of our own lenses being tested. One of these was a ‘first edition’ model of a Canon 100-400 zoom. Earlier the better quality of the newer version had been extolled which made the pressure even greater. However, the owner was able to be delighted since the resolution check showed it to be up with the newer version. Another lens that was checked was found to not quite be centred at the 300mm end, although with good resolution. At the 28mm end it gave a very good showing. Their advice was to not get it adjusted since it still performed well and getting it centred at one end of the range might put it out at the other end. When a ‘dropped’ lens was checked it was found to be up with the standard expected of Canon’s L lenses despite not being one of those.
One of the lenses I had with me was from pre-digital days and not designed for the requirements of digital sensors and suffering from distinct fringing wide open and reflection of light from the sensor onto the rear element distinctly reducing contrast in portraits on a blown white background. Wide open at F2 my 135DC gives a lot of fringing and the resolution appears to be poor. I expected to be told something was out of alignment but instead it excelled on the resolution check. I think that I just have to accept that I cannot use it with blown white backgrounds and it needs to be stopped down to F4+ to negate the fringing and enjoy its quality. I also had a 50mm F1.4 that I’d become less satisfied with checked. It is the main one that I use for the cage fighting events and it has had a few knocks. It quickly became clear that I had nothing to worry about, even with a UV filter on it, admittedly a Hoya HD, it was deemed to be somewhat better than the Canon equivalent.
For me I now have to decide if it is worth my getting a camera checked for sensor alignment. I now have that nagging ‘am I getting the utmost quality from my gear’. There is only one way to find out, get my main body and a key lens checked as a pair.
Thanks go to Nick, Rob and Jeff from Lehmann’s for their clear and detailed explanations and their time.
Vice-chairman and ‘Webmaster’ with a preference for photography involving drama, stories and people.