I've owned a Tamron 28-75 for about 6 months or so. I just purchased a 24-70 a few days ago and will probably sell the Tamron. Before I sell the Tamron I want to evaluate or compare the IQ between these two lenses. I own a 1D Mark IIN by the way.
So far, I've taken a few comparison shots at different focal distances and apertures inside the house since it's been dark by the time I get home from work now. I've shot bowls of fruit, people, calendars etc. It's very difficult to distinguish which lens is actually better. Both are very similar but the 24-70 seems to be a little sharper towards the edges of the images. The colors also seem a little better with the 24-70 but it's very subjective shooting these types of images.
This weekend I want to take some comparison shots between the two lenses outdoors in real conditions. I'm not sure the best way to go about this. Does anyone have any reccomendations for me? Any helpful advise would be appreciated.