Can someone explain

[quat]

how to use these kenko tubes correctly. I may be using them right, or I may be using them wrong. I have them attached to my 50mm 1.8 lens and it simply seems that in order to control focus I have to move the camera instead of the focusing ring.

If I use my 55-250mm lens then I can control the focus with the focal length ring. but still have to be super close to take anything decent.

Do they really narrow the depth of field that much?

And would that change if I got a dedicated macro lens?

Some samples
http://farm4.static.flickr.com/3577/3825312306_21b170a032.jpg
http://farm3.static.flickr.com/2670/3825312038_3d7798cf07.jpg

so...amidoingitrite?

[Lester Wareham]

That is exactly how tubes work, same with a dedicated macro lens.
Depth of field will get smaller as magnification increases andcan be down below a mm.

[quat]

ok, so when you get a lens that is dedicated for macro does it have a greater focusing ability? I'm just wondering since it's hard to focus with the 50mm.

And my last question for now would be if the DoF is always right at the end of the lens?

[LordV]

ok, so when you get a lens that is dedicated for macro does it have a greater focusing ability? I'm just wondering since it's hard to focus with the 50mm.

And my last question for now would be if the DoF is always right at the end of the lens?

1. In some ways yes- you can still focus on distant objects with a macro lens but the maximum magnification is still pretty close to the end of the lens. It's fairly normal in macro to turn off AF and focus by moving the camera.

2. As explained above the DOF reduces as magnification increases so is always pretty thin in macro. A dedicated macro lens around 100mm will have a minimum focus distance about 5" in front of the lens. This gets longer with the longer focal length macro lenses but the maximum magnification is the same.
Brian V.

[quat]

1. In some ways yes- you can still focus on distant objects with a macro lens but the maximum magnification is still pretty close to the end of the lens. It's fairly normal in macro to turn off AF and focus by moving the camera.

2. As explained above the DOF reduces as magnification increases so is always pretty thin in macro. A dedicated macro lens around 100mm will have a minimum focus distance about 5" in front of the lens. This gets longer with the longer focal length macro lenses but the maximum magnification is the same.
Brian V.

thanks! now this begs the question...how do photographers get these awesome bug shots with out scaring the bugs away?

[LordV]

thanks! now this begs the question...how do photographers get these awesome bug shots with out scaring the bugs away?

With some luck and a lot of practice you learn how not to scare off bugs :)
some hints here http://www.flickr.com/groups/macroviewers/discuss/72057594073223102/

Brian V.