igma 70-200mm f2.8 IS
I recently purchased a new zoom lens 70-200mm f2.8. After saving for 18 months and reading lots of reviews I took the plunge.
Initial results were fantastic and I was thrilled. All these images were taken in good light at an aperture above 4. Now that I think about it the first test shoots I took in low light and wide aperture settings where also sharp and crisp. Things seem to have changed along the way.
Then I started doing some indoor line dance competition shoots. Low light, high ISO, low shutter speeds and apertures below 4.
I was not happy and kept questioning myself. Camera settings, camera shake (Even though the lens had good image stabilisation) I was very frustrated and could not figure out what I was doing wrong.
I did a family shoot on the beach this week in overcast weather so, similar camera settings. Again I was not happy. All the images were slightly out of focus or camera shake. Then I noticed that there was good sharp focus just in front of my subject and it was the same for all the images.
Huge big sigh of relief. It was not my error but the lens... frustrating but definitely the lens! First time this has happened to me.
After a lot of research and chatting to other professionals I was interested to find out that quite a few lenses (Even very expensive lenses) have a manufactures error in the exact focusing point of the lens especially at large aperture settings where the DoF is critical. They all recommended that I do an in camera lens calibration.
I was relieved to find out that this is a relatively easy fix and it is very quick and easy to check before or even on a shoot. Something else to remember while shooting.
How I calibrated my lens and will do so on a regular basis from now on.
I found the easiest way was to space a whole lot of clothes pegs on the clothes line about 100mm apart with a coloured peg in the middle and about ten pegs on each side. Using the widest aperture and pin point focus I then focused on the coloured peg in the middle shooting almost parallel to the clothes line. By doing this I was able to accurately see the focus range and where it fell as opposed to where I actually focused. From there it was easy to calibrate the lens by moving the focus point forward or backwards to suite my shooting style. This was all done on the camera. (Canon 5D Mk III)
So to finish off, when you purchase or use a lens you have not used before, even top of the range lenses it is a very good idea to do a focus point check first and check your lens calibration on a regular basis.
I hope this helps some of you out there.
Cheers Ken.