Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon Lenses

Reply
 
Thread Tools Search this Thread
Old Jun 9, 2006, 10:10 PM   #1
Senior Member
 
Striderxl's Avatar
 
Join Date: Aug 2004
Posts: 300
Default

if I use a 100-300 F4 Sigma EX and a Sigma 1.4 Teleconverter?This should work out to a 672mm lens.Would the converter also work on a 24-70mm Sigma EX lens?



Thanks

Charlie
Striderxl is offline   Reply With Quote
Sponsored Links
Old Jun 10, 2006, 12:48 AM   #2
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Striderxl wrote:
Quote:
... Would the converter also work on a 24-70mm Sigma EX lens?
A generic Kenko might work...

The Sigma won't: http://sigmaphoto.com/lenses/lenses_tele.asp
-> they are designed to match the longer tele lenses only!

NHL is offline   Reply With Quote
Old Jun 10, 2006, 7:14 AM   #3
Member
 
Join Date: May 2006
Posts: 31
Default

Striderxl wrote:
Quote:
if I use a 100-300 F4 Sigma EX and a Sigma 1.4 Teleconverter?This should work out to a 672mm lens.
I figure 140-420mm.
jjonsalt is offline   Reply With Quote
Old Jun 10, 2006, 10:22 AM   #4
Senior Member
 
Striderxl's Avatar
 
Join Date: Aug 2004
Posts: 300
Default

jjonsalt wrote:
Quote:
Striderxl wrote:
Quote:
if I use a 100-300 F4 Sigma EX and a Sigma 1.4 Teleconverter?This should work out to a 672mm lens.
I figure 140-420mm.

Sorry I have a 20d with a 1.6 crop factor.
Striderxl is offline   Reply With Quote
Old Jun 10, 2006, 7:37 PM   #5
Member
 
Join Date: May 2006
Posts: 31
Default

Striderxl wrote:
Quote:
jjonsalt wrote:
Quote:
Striderxl wrote:
Quote:
if I use a 100-300 F4 Sigma EX and a Sigma 1.4 Teleconverter?This should work out to a 672mm lens.
I figure 140-420mm.
*

Sorry I have a 20d with a 1.6 crop factor.
Regardless, the focal length of a lens does not change due to the format being used.
jjonsalt is offline   Reply With Quote
Old Jun 10, 2006, 8:23 PM   #6
Senior Member
 
Striderxl's Avatar
 
Join Date: Aug 2004
Posts: 300
Default

Thats what I was asking.Is this a 300mm lens even thought the 20D and the 1.4 converter?



Thanks for the help.
Striderxl is offline   Reply With Quote
Old Jun 11, 2006, 12:05 AM   #7
Member
 
Join Date: May 2006
Posts: 31
Default

The crop factor is to give those used to 35mm film cameras a reference point that they are used to. The format size does not change the focal length of a lens but does have an inpact on the angle of view one gets from a lens. The angle of view of a 420mm lens on your (by the way, I also use the 20D) 20D would be the same as a 672mm lens on a 35mm film camera.
jjonsalt is offline   Reply With Quote
Old Jun 11, 2006, 1:40 AM   #8
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

To adjust for the 1/focal length 35mm rule for shutter speed, then yes think of it as a 672mm lens.

This is one of those examples where you're better off ignoring the pendantically asserted fact that it's still really only a 300mm lens.

So if you can keep your shutterspeed at 1/1000 you might get away hand-holding. If you have a very steady hand 1/500 or even 1/250 might do.

But I think most people would fancy a tripod or monopod for that combo.
peripatetic is offline   Reply With Quote
Old Jul 10, 2006, 3:31 AM   #9
Senior Member
 
Join Date: May 2005
Posts: 429
Default

I have a 20D and a Canon 75-300 1:4-5.6 lens. Is there a good teleconverter setup that would work for me to reach out there a little farther? Will it mount on the camera or screw on the end of the lens?
RP33 is offline   Reply With Quote
Old Jul 10, 2006, 7:02 AM   #10
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

FYI - http://www.pbase.com/lightrules/14xtctest

-> It'll go between the camera and the lens, but the AF will be greatly affected because the resulting aperture will exceed the camera capability (i.e. f/5.6 lens or slower), hence read the comments on masking out the pins...
NHL is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 11:31 AM.