I have a number of lenses that I use with my Panasonic GX1:
- Olympus 9-18mm
- Panasonic 14-45mm
- Panasonic 45-200mm
- Panasonic 20mm
- Olympus 45mm (a recent addition and a stunning lens)
When you look at scientific test results to understand which is the sharpest lens, the 20mm stands out as being in a class of its own. I should say that the 45mm is probably in a similar class but I haven’t seen any data on this.
The question I have then is why the images shot with the 20mm lens don’t appear quite as sharp as the 18-45mm lens which was actually a kit lens from my GF1.
A little bit of experimentation allowed me to identify that I wasn’t quite holding the camera steady enough when shooting with the 20mm lens. The lens is incredibly sharp and able to resolve a huge amount of detail. Unfortunately it also reveals the slightest movement leading to the image appearing not quite as sharp as I expected. There isn’t however sufficient movement to detect this as blur.
There is an old rule of thumb in Photography to say the slowest shutter speed you should use is the inverse of a lenses focal length. If the lens is a 20mm (effectively a 40mm) then 1/40 second is the slowest shutter speed that should be used hand held. What I was finding with this lens is that I really needed to use a shutter speed twice as fast as this (1/80 second) to be sure of having a steady, really sharp image.
I suspect the reason for my 18-45 appearing sharper is that it has an Image Stabiliser (unlike the Olympus cameras that have these built into the camera). If I switched this off it reveals a similar performance problem.
This was helpful but not quite the full story. I also found out that I was stopping the lens down a little too far. The 20mm lens appears to hit its sharpest level as around f/4.0. When I looked at some of the landscape scenes I was shooting I realised that f/4.0 was more than sufficient given I was typically focussing on a point that the camera often considered to be infinity. A greater depth of field from a smaller aperture would not therefore give me any sharper results. An f/4.0 aperture would however give me a faster shutter speed and keep me in the area where the sharpest results could be achieved.
It’s interesting how we get “locked in” to using our equipment in certain ways that might not give the best performance.
The Lightweight Photographer 