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

Reply
 
Thread Tools Search this Thread
Old Apr 27, 2005, 9:30 PM   #1
Senior Member
 
KM_krazy's Avatar
 
Join Date: Dec 2004
Posts: 292
Default

I will probably be getting the XT soon, so I am looking at my lens choices. I would love to have a "super tele" like a 500mm (then times 1.6) but they seem pretty pricey, and not the fastest or most practical (for something like a 200-500)
So, I decided I might give the TC idea a try. The lens that I was looking at was the 70-200 f/4L. with a 1.4x TC attached that gives me a 100-280mm f/5(?) lens (160-450 with 1.6 mag factor). This seems pretty good, and I have heard fairly good things about the 1.4x TCs from both canon and sigma. However, for the same price. . . what about the 2x TCs? the 70-200 f/4 would then be a 140-400 f/6.3(?) which would be really nice.
Is the optical quality REALLY going to suffer that much with a 2x TC?:?:
Thanks,
Max
KM_krazy is offline   Reply With Quote
Sponsored Links
Old Apr 27, 2005, 10:41 PM   #2
Senior Member
 
Join Date: Jul 2003
Posts: 3,396
Default

That 70-200 F4 L lens will work with the 1.4 converter as an F5.6 lens, the camera will be able to autofocus with it.

The lens itself will work with the 2x teleconverter, as a manual focus lens. But at an effective F8 the camera will not autofocus, and your viewfinder will be a bit on the dimish side.

I can't speak for image quality, as I have not tried that lens with a 2x teleconverter. The F2.8 version sharpness does suffer with a 2x TC but it still produces acceptable images.

Peter.

PeterP is offline   Reply With Quote
Old Apr 27, 2005, 10:56 PM   #3
Senior Member
 
KM_krazy's Avatar
 
Join Date: Dec 2004
Posts: 292
Default

PeterP wrote:
Quote:
That 70-200 F4 L lens will work with the 1.4 converter as an F5.6 lens, the camera will be able to autofocus with it.

The lens itself will work with the 2x teleconverter, as a manual focus lens. But at an effective F8 the camera will not autofocus, and your viewfinder will be a bit on the dimish side.
I was under the assumption that the 1.4x TC takes off one stop, and the 2x takes off two stops. . .why is an f/4 lens an f/8 lens with a 2x TC? (or is that the more technical side of the f-stop game :lol

Quote:
I can't speak for image quality, as I have not tried that lens with a 2x teleconverter. The F2.8 version sharpness does suffer with a 2x TC but it still produces acceptable images.

Peter.
Thanks
KM_krazy is offline   Reply With Quote
Old Apr 27, 2005, 11:01 PM   #4
Senior Member
 
Join Date: Jul 2003
Posts: 3,396
Default

:-)
F4 + 1 stop is F5.6
F4 + 2 stops (or F5.6 + 1 stop) is F8

These are all 1 stop away from their neighbour on either side.
F2.8 F4 F5.6 F8 F11 F16 F22 F32

Each larger F-stop (towards F2.8 ) doubles the amount of light entering the camera, and each smaller number (towards F32 ) halves the amount of light entering the camera.

(Same with the Shutter speed, each step up or down doubles/halves the amount of light that gets to the sensor, as does each step up or down in ISO speed).


Peter.
PeterP is offline   Reply With Quote
Old Apr 27, 2005, 11:26 PM   #5
Senior Member
 
KM_krazy's Avatar
 
Join Date: Dec 2004
Posts: 292
Default

PeterP wrote:
Quote:
:-)
F4 + 1 stop is F5.6
F4 + 2 stops (or F5.6 + 1 stop) is F8

These are all 1 stop away from their neighbour on either side.
F2.8 F4 F5.6 F8 F11 F16 F22 F32

Each larger F-stop (towards F2.8 ) doubles the amount of light entering the camera, and each smaller number (towards F32 ) halves the amount of light entering the camera.

(Same with the Shutter speed, each step up or down doubles/halves the amount of light that gets to the sensor, as does each step up or down in ISO speed).


Peter.
Lol, ok. I guess I knew that, I was just thinking 1 stop. . .
brain fart there:lol::G
KM_krazy is offline   Reply With Quote
Old Apr 28, 2005, 5:37 AM   #6
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,544
Default

A word of advice here:
How much is a 70-200 f/4L?
How much is a Canon 1.4x teleconverter?
-> Now add the two together - What is the total?

There's a much better option once everything is added up: http://www.stevesforums.com/forums/v...65&forum_id=65

Remember a lens + TC can never equal one without - especially one which is faster too :blah:
i.e. f/4 and not f/5.6 (1-stop) with a longer reach (300 vs 280)!!!

... now @ f/5.6 with a 1.4xTC you'll get 420mm instead
Here's some samples @ 420mm: http://morrobayphotos.com/Sigma/100-300/
NHL is online now   Reply With Quote
Old Apr 28, 2005, 4:51 PM   #7
Member
 
Join Date: Apr 2005
Posts: 52
Default

I have the 70-200 f/4 and the 1.4 TC. They work together much better than I expected. Actually the combo = ~448mm. There are certainly other options but the nice thing about this lens is the light weight (easy to carry all day).
Humrme is offline   Reply With Quote
Old Apr 28, 2005, 10:21 PM   #8
Senior Member
 
Join Date: Sep 2003
Posts: 229
Default

I just recently purchased the 70-200 4L for my 20d. Reasonably sharp lens but it is very fast and smooth focusing. My comment/question is: how can someone judge lens sharpness when Canon DSLRs (300D and 20D) have a tendency toward soft images when viewed at 100%? I usually sharpen a bit once I get the image to my PC, not portraits but still life and scenics get some sharpening. No complaints, just an observation.
Ctrack 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 10:03 AM.