Manual and Autofocus

[Ken MT]

Reading the specifications for my Canon 70-200/f4 and 100-400/f4.5-5.6 they both give minimum focus distance at 1200mm and 1800mm respectively. However both lenses on autofocus will not focus down to the specified distance, but will on manual focus. Is this typical for all lenses?. On autofocus the distances are about 2000 and 3000mm respectively. It doesn't appear to make any difference with full frame or cropped sensor.

[rpcrowe]

Have you assured that the focus range is not restricted... One range of the 70-200mm f/4L IS is about 3000 mm to infinity and the other range is about 1200 mm to infinity...

However, I have noticed in shooting my dog portraits that the AF of the 70-200mm f/4L is faster and seems slightly more accurate on my Canon 7D than on my 5D2...

[inkista]

As Richard says, how are your focus limit switches set? The focus limit switch lets you change the distance range through which you want the lens to search for AF lock. Limiting the near range speeds up AF lock on distant subjects--it's useful for wildlife and sports shooting, when you don't need the lens to hunt through its full range.

See page 6 of the EF 100-400L II's manual.

[Ken MT]

Thank you, they were set to the higher limits.

[compasiune11]

Thank you, i didn't knew that.

[rpcrowe]

Oh heck, I have been fooled by this on several occasions. Having the lens set to the farther restriction, I tried shooting a subject closer to the lens - nothing happened. It took a few seconds to realize that the lens was restricted in focus.

I try to remember to set the focus restriction to the entire range when I put the lens away. I can always set it back to the restricted focus range when I start to use the lens but, I will never miss an image (like a puppy in a cute position) if I have the lens in its unrestricted focus mode...

I like to store my cameras/lenses in a mode that I can just grab the gear and shoot if I am in a rush to get the image...