Sigma Lenses For Canon Rebel Xti
Is the Sigma lens on a Canon body do you recommend?

Hello Friends, I have a Canon Rebel XTi, with two lenses: a Canon 28-85 IS and Sigma 18-200 f3.5-6.3. From my brief observation, when I try to shoot in automatic mode, the images of the Sigma lens are darker compared to the Canon lens. This If I use the manual mode for 99% of my shots. In fact, when I'm at the point of travel, I prefer to use my point and shoot during the day – and that captures the colors of right and immediately right exposure, whereas I have given in the Manual mode, you take some quiet time. So my question is – is this normal. Is this the reason why the lenses from the same manufacturer as the body of the camera are recommended.

Have you people ever heard of a gray scale? It can be used to "mark on their lenses" that can make the necessary compensation each time.Shoot a roll of film with half the picture frames Canon Lens with his half with his exhibitions sigma.Bracket 5-5 below, print and compare it with the Grey scale.Make sure to register your exposure time and diaphragm for each exposure.when to find two that match Grey scale factor will have its compensation for its lens sigma.