55-250mm lens - trouble shooting

vinarum

Husband bought this lens so that we can take better pictures while on vacation in Europe. Silly me, I didn't really take the time to learn how to use it, so our pictures did no turn out so well. I was not able to focus on the subject and background, so I'm sure it had to do with the settings, but I'm not sure what was wrong. It would either be the subject that is focus or the background. The intentions were to take focused pictures of the subject and background.

Thanks in advance.

PBked

Hi,
The autofocus on the T2i is extremely good, however there are 9 focus points and the camera does not know what you are looking at so it focuses on anything it can. For example, you are standing a few feet in front of a post and you want to snap your toddler kicking a ball a few feet beyond the post. In this example, your camera will most likely focus on the post as it is the nearest thing to you.
The way round this is
a) turn off the automatic selection of focus points and use the thumbwheel near the shutter button to select the focus point you choose.
b) choose the center point only as your focus point - the quick way to do this is to press the AF button and then set. Repeating this procedure will return you to automatic selection.
c) turn your mode dial to A-Dep. In this mode the camera tries to make sure that everything near and far stays in focus.

The other thing to consider is that the 55-250mm has a minimum focus distance of about 1 meter, so anything closer than that is likely to be blurred. For distance shots you need to zoom in and that makes your lens physically longer, so make sure you have IS on the lens switched on. Remember the general rule of using a shutter speed the same as or more than the focal length of the lens which on the 55-250mm with the T2i is 1/400 or more.

Hope this helps,
PBked

bruto

It sounds as if your problem is one of depth of field.

A lens will only focus on what it is focused on, and depending on several factors, this range will extend to some distance behind and to the front. The tolerance is called "depth of field."

Three factors govern depth of field: aperture, distance, and focal length.

The more wide open the lens is, the shallower the depth of field will be. This is why people who want blurry backgrounds in portraits seek out lenses with very wide (small number F stop) apertures. If you want more depth of field, you must close the lens down

The further away something is, the more depth of field you will have. You can focus anywhere near the horizon in a scenic shot, and everything far away will be in focus. But if you take the same lens, at the same setting, and use it at its closest setting, only a very small amount will be in focus. Depth of field in macro work is very very shallow.

And finally, the longer the focal length of the lens, the shallower the depth of field. A super-wide-angle fisheye lens may need almost no focusing at all. Taking a scenic shot with the 18 mm. kit lens at 18 requires very little care in focusing. If you take a close portrait with a 50 mm. lens wide open, and focus on a person's eyes, the nose and ears may be a little blurry. By the time you get to 250 mm., depth of field will be quite shallow at anything but a long distance and a small aperture.

As PBKEd mentions, if you are using a lens with limited depth of field you also need to make sure that you are using a single focus point, or else you can not be entirely sure what the camera will choose.