I just purchased a used 17-55 F2.8 EFS lens to use with my 7D. The lens will replace a Tamron 28-75 F2.8 that would hunt for focus in all but bright light. The 7D is set up for sports, so the back * button is configured to trigger focusing, and I am in AI Servo mode. On two occasions when trying to use the IS function the lens "jiggled" as the IS was in constant adjustment mode. Don't know how to describe it, but the lens was actually vibrating a little. I would immediately release my finger and if I turned IS off the problem went away. The first time was trying to shoot small stripped fish at the Long Beach Aquarium. The lens was around 35mm, ISO 1600 and I was in Av mode. The second time was trying to film video at an indoor basketball game. As the action moved up and down the court, I would press the * button to regain focus and the jiggling would happen.
FYI, I plan on buying a Carry Speed LCD Viewfinder to help with manual focusing during videos.
I spoke to the person who sold me the lens. He is not that familiar with the 7D, but said that I may not have my camera in the correct mode to use IS. He wasn't sure if I should be in Full Time AI Servo or another setting.
Can anyone with experience with this camera and lens tell me what settings I should use to have the IS work? If using it for small fish in an aquarium is bad, please let me know that too.
Thanks so much!