Thank you for using Canon products.
We have confirmed that in certain camera settings and shooting conditions, the phenomenon described below may occur in images captured by the EOS 7D Digital SLR camera.
Canon is currently investigating and analyzing the cause of this phenomenon, and we are planning to release a firmware update to address this issue.
Once the support measures have been established, we will post the relevant information on our Web site.
We offer our most sincere apologies to customers using this product who have been inconvenienced by this issue. Going forward, we will spare no effort in our quality management to make sure our customers can use our products with confidence. We hope our efforts will earn your understanding.
In images captured by continuous shooting, and under certain conditions, barely noticeable traces of the immediately preceding frame may be visible. This phenomenon is not noticeable in an image with optimal exposure. The phenomenon may become more noticeable if a retouching process such as level compensation is applied to emphasize the image.
EOS 7D Digital SLR
Source : http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=139&modelid=19356&keycode=2112&id=60427
Merci à Paul Binocle