Kenko Ext Tubes on Zooms don't work!..

[mypoppy31]

Well, I just tried it and it don't work, except for VERY CLOSE UP shots.
I thought I had read that if you used the Kenko Tubes with a zoom telephoto lens that you could get REALLY CLOSE UP so as not to disturb the birds, etc...

My Kenko ext. tubes go from 12, 20 to 36mm's. And, I tried shooting with my Sigma 18-200 3.5 Zoom Telephoto Optical Stabilization lens and got blur!..except when I focused to about one or two inches, then it focused.

Am I doing something wrong?.... What I"m getting out of this is that using the Kenko ext tubes by themselves, my Macro shots come out pretty good, but attaching my Sigma lens, it simply's not working for me.

Where am I going wrong?
http://www.youtube.com/profile?user=SalPedi

[elysium]

Lens focal length is a factor here. Should try a close up lens up on your 18-200. I know a friend who tried it on his 70-200 with interesting results.

Raynox DCR250
http://images.channeladvisor.com/Sell/SSProfiles/22001023/Images/4/RAYNOX_DCR-250-1.jpg

[LordV]

You won't be able to use the ext tubes with the zoom at very short focal length - but they should work fine longer than about 40mm. The focus distance will vary from about 2" in front of the lens around 50mm to about 2 feet at 200mm at a guess.

Brian V.

[lance v]

To get 'closer' to the subject ie birds without actually getting closer i think u are wanting teleconverters instead of extension tubes.

On longer focal lengths extension tubes DECREASE the minimum FOCAL LENGTH so u can actually get the camera closer to the subject than the lens usually allows. for example with the 500mmf4 you cannot focus on anything closer than 4 meters! but with extension tubes you can focus closer that 4 meters but the focal length is still 500mm. However the downside of extention tubes is that it also decreases the MAXIMUM focusing distance so things far awa can no longer be focused on

Teleconverters however the minimum focusing distance stays the same but it INCREASES the FOCAL LENGTH itself. This means you get more reach and get "closer" to your subject without scaring them away


Hope this help!:D

[cricketboy75]

kenko has extension tubes and tele-converters. if you have the extension tubes, you can only that for macro. to get pictures of birds and things far away, you need to buy the tele-converter tubes...

[dpastern]

Well, Lance, sorta right, mostly wrong. Artie Morris frequently uses tubes and extenders (as do other birding photographers). The tubes let you work from a shorter distance, i.e. closer to the bird. When you're closer, you get more magnification ;-) 'nuff said.

Dave

To get 'closer' to the subject ie birds without actually getting closer i think u are wanting teleconverters instead of extension tubes.

On longer focal lengths extension tubes DECREASE the minimum FOCAL LENGTH so u can actually get the camera closer to the subject than the lens usually allows. for example with the 500mmf4 you cannot focus on anything closer than 4 meters! but with extension tubes you can focus closer that 4 meters but the focal length is still 500mm. However the downside of extention tubes is that it also decreases the MAXIMUM focusing distance so things far awa can no longer be focused on

Teleconverters however the minimum focusing distance stays the same but it INCREASES the FOCAL LENGTH itself. This means you get more reach and get "closer" to your subject without scaring them away


Hope this help!:D

[lance v]

Well, Lance, sorta right, mostly wrong. Artie Morris frequently uses tubes and extenders (as do other birding photographers). The tubes let you work from a shorter distance, i.e. closer to the bird. When you're closer, you get more magnification ;-) 'nuff said.

Dave

Haha thats what i tried to say?? guess i complicated it to much