Kenko extension tubes: Good with 100mm macro?

Can someone explain the benefits of Kenko tubes if you are already using a macro lens?

Will the tubes let you get even closer to the subject?
Will you be able to get the same zoom as the lens, yet be further away from the subject?
Will the photos have greater quality/detail, or will it not be as good as just using the lens by itself?

...also, if using the tubes with say, a 50mm f/1.8, does it improve the lens greatly?

...and finally, can they be used on non-prime lenses, such as the 55mm-250mm?

I guess the main question is...are they worth getting? Will they make that much of an improvement?

Thanks!

~Steve

The Kenkos will work on any EF lens. They will not improve your image quality, but they won't degrade it, either. All they do is allow you to get closer to the subject, nothing more. They have no glass elements, so they won't increase the telephoto power of any lens.

Will the tubes let you get even closer to the subject?
Yes, that is the advantage of an extension tube. It enables the lens to focus closer and therefore obtain a higher subject to image ratio...

Will you be able to get the same zoom as the lens, yet be further away from the subject?
NO, the extension tubes will only allow you to focus closer however, you will lose infinity focus.

Will the photos have greater quality/detail, or will it not be as good as just using the lens by itself?
No and no. the extension tube contains no glass elements it is simply a tube which allows the lens to focus closer than without the tube. It will allow a larger subject to image ratio but will not increase or decrease the image quality of the lens with which it is used.

...also, if using the tubes with say, a 50mm f/1.8, does it improve the lens greatly?
No, no quality dfference except that you can focus closer...

...and finally, can they be used on non-prime lenses, such as the 55mm-250mm?
Yes...

Note: when using an extension tube, exposure must be increased. How much increase is required depends on the lens and extension tube.

gibbit1 wrote in post #14836967
The Kenkos will work on any EF lens. They will not improve your image quality, but they won't degrade it, either. All they do is allow you to get closer to the subject, nothing more. They have no glass elements, so they won't increase the telephoto power of any lens.

Thanks! Ok, so with my 100mm macro, I need to be like 4.6" away from the subject...the Kenko's will let me get even closer? If so, then it magnifies more, correct?

OK, thanks RPCrowe!!