Canon Digital Photography Forums  

Go Back   Canon Digital Photography Forums > 'Equipment Talk' section > Canon EF and EF-S Lenses
Register Rules FAQ Members List Search Today's Posts Mark Forums Read



Reply
 
Thread Tools Display Modes
Old 22nd of August 2009 (Sat)   #1
MikeMcGowan
Member
 
MikeMcGowan's Avatar
 
Join Date: May 2009
Location: Bensalem, PA
Posts: 238
Default Teleconverters on a crop sensor

I'm going to be picking up a Canon 70-200mm f/4 L(non IS)this week, and I have a 50D. I was planning on getting either a 1.4x or 2x teleconverter later on for extra reach. Since I already have 1.6x crop factor, that makes the lens 112-320 already right? Now if I add either one of the teleconverters does it add onto the already stretched focal length? And what brand of teleconverters do you suggest? I would just go Canon, but I'm sure there's one that's just as good for a smaller amount of money.

Also, if I used the 1.4x converter on this lens, it would make me one stop down to f/6.3. Now does that mean I can't shoot at f/4, or that I can but the amount of light coming in will be equivalent to what it is at f/6.3?
__________________
Canon 50D | Sigma 30mm f/1.4 | Tamron 17-50mm f/2.8 VC | Tokina 11-16mm f/2.8 | Tamron 90mm f/2.8 | Peleng 8mm f/3.5 | Canon 580ex | Vivitar 285hv(3) | PW Plus II Transceiver(4)

flickr

Last edited by MikeMcGowan : 22nd of August 2009 (Sat) at 14:57.
MikeMcGowan is offline   Reply With Quote
This ad block will go away when you log in as member
Old 22nd of August 2009 (Sat)   #2
joedlh
Goldmember
 
joedlh's Avatar
 
Join Date: Dec 2007
Location: Long Island, NY, North America, Sol III, Orion Spur of the Milky Way galaxy.
Posts: 4,564
Default Re: Teleconverters on a crop sensor

The crop factor would be assigned to the lens-teleconverter combination. A 1.4 would make it a 280. Multiply that by 1.6.

Be aware that you will lose two stops with the 2x converter.

Can't help you with other brands.
__________________
Joe

Gear: Kodak Instamatic, Polaroid Swinger. Oh you meant gear now.
http://photo.joedlh.net
joedlh is offline   Reply With Quote
Old 22nd of August 2009 (Sat)   #3
SCOTTinNJ
Member
 
SCOTTinNJ's Avatar
 
Join Date: Oct 2007
Posts: 491
Default Re: Teleconverters on a crop sensor

If you use a 2x on the 70-200 f/4 it will be a minimum of f/8 and you will lose autofocus on the 50D. Better to go with the 1.4x. Reportedly the Tamron/Kenko Pro are just as good as the Canon, and will work with lenses that the Canon version will not.
__________________
6D | 30D
17-40 | 24-105 | 70-200
8 | 14 | 35 | 50 | 100 | 1.4x
SCOTTinNJ is offline   Reply With Quote
This ad block will go away when you log in as member
Old 22nd of August 2009 (Sat)   #4
District_History_Fan
Goldmember
 
Join Date: Dec 2008
Posts: 2,286
Default Re: Teleconverters on a crop sensor

a 1.4 teleconverter would net you a 35mm eqivalent of 448mm, f5.6.
District_History_Fan is offline   Reply With Quote
Old 22nd of August 2009 (Sat)   #5
DreDaze
Cream of the Crop
 
DreDaze's Avatar
 
Join Date: Mar 2006
Location: S.F. Bay Area
Posts: 14,813
Default Re: Teleconverters on a crop sensor

if you've never used a FF camera, then you don't really need to do the whole 1.6X to figure anything out...it's just going to cause people to come in here and tell you that your lens really isn't a 112-320mm...it's just the equivalent FOV...and all that...

the kenko 1.4 is a good TC and can be used on other lenses, while the canon can only be used on a few L's i believe...also you do lose 1 stop which as mentioned above is actually 5.6...using a 2x loses two stops so it becomes f/8, and no autofocus...

you don't even have the lens yet right?...i'd wait to see if you even do need the extra reach...
__________________
Andre or Dre
gear list
flickr
DreDaze is offline   Reply With Quote
Old 22nd of August 2009 (Sat)   #6
MikeMcGowan
Member
 
MikeMcGowan's Avatar
 
Join Date: May 2009
Location: Bensalem, PA
Posts: 238
Default Re: Teleconverters on a crop sensor

So me losing one stop means the biggest aperture I can shoot with is f/5.6? As in the camera won't let me go lower, or that I can shoot at f/4 but it's as dark as f/5.6. I'm not too sure, and I am going to wait until after I get the lens to see if I need the extra reach.
__________________
Canon 50D | Sigma 30mm f/1.4 | Tamron 17-50mm f/2.8 VC | Tokina 11-16mm f/2.8 | Tamron 90mm f/2.8 | Peleng 8mm f/3.5 | Canon 580ex | Vivitar 285hv(3) | PW Plus II Transceiver(4)

flickr
MikeMcGowan is offline   Reply With Quote
Old 22nd of August 2009 (Sat)   #7
pwm2
"Sorry for being a noob"
 
pwm2's Avatar
 
Join Date: May 2007
Location: Sweden
Posts: 8,626
Default Re: Teleconverters on a crop sensor

Quote:
Originally Posted by MikeMcGowan View Post
So me losing one stop means the biggest aperture I can shoot with is f/5.6? As in the camera won't let me go lower, or that I can shoot at f/4 but it's as dark as f/5.6. I'm not too sure, and I am going to wait until after I get the lens to see if I need the extra reach.
Note the expression f/4.

There is a mathematical relation between the focal length and the aperture.

When you use a 1.4x extender, you will both multiply the focal length from 200 to 280 and at the same time multiply the possible aperture from 4 to 5.6.

With the 1.4x extender, the camera will not allow you to select any aperture past 5.6. If you tape the extra connectors on the extender, you may fool the camera. It will show a focal length of 200 and a aperture of 4, but in reality you will still have a focal length of 280 and an aperture of 5.6.

Taping the extra contacts on a 2x extender would allow you to autofocus even at f/8, but it will not always work. In low-light situations, then it may hunt which will result in extra wear on the lens. Letting the lens hunt for for a longer time could potentially overheat it.
__________________
5DMk2 + BG-E6 | 40D + BG-E2N | 350D + BG-E3 + RC-1 | Elan 7E | Minolta Dimage 7U | (Gear thread)
10-22 | 16-35/2.8 L II | 20-35 | 24-105 L IS | 28-135 IS | 40/2.8 | 50/1.8 II | 70-200/2.8 L IS | 100/2.8 L IS | 100-400 L IS | Sigma 18-200DC
Speedlite 420EZ | Speedlite 580EX | EF 1.4x II | EF 2x II

Last edited by pwm2 : 22nd of August 2009 (Sat) at 17:05.
pwm2 is offline   Reply With Quote
Old 22nd of August 2009 (Sat)   #8
SkipD
Cream of the Crop
 
SkipD's Avatar
 
Join Date: Dec 2002
Location: Southeastern WI, USA
Posts: 19,778
Default Re: Teleconverters on a crop sensor

Quote:
Originally Posted by MikeMcGowan View Post
I'm going to be picking up a Canon 70-200mm f/4 L(non IS)this week, and I have a 50D. I was planning on getting either a 1.4x or 2x teleconverter later on for extra reach. Since I already have 1.6x crop factor, that makes the lens 112-320 already right? Now if I add either one of the teleconverters does it add onto the already stretched focal length? And what brand of teleconverters do you suggest? I would just go Canon, but I'm sure there's one that's just as good for a smaller amount of money.

Also, if I used the 1.4x converter on this lens, it would make me one stop down to f/6.3. Now does that mean I can't shoot at f/4, or that I can but the amount of light coming in will be equivalent to what it is at f/6.3?
Mike, the part I put in bold in the quote above is NOT correct. A 70-200mm lens is, and always will be, a 70-200mm lens. Nothing can change that.

If you add a 1.4x extender to the 70-200 f/4 lens, then the combination becomes a 98-280mm lens. The maximum aperture becomes one stop smaller (higher f-stop number) with the 1.4x extender. Thus, the maximum aperture of the 70-200 f/4 with a 1.4x extender mounted would be f/5.6.

To the "crop factor" issue... Please read this "sticky" covering the "crop factor". The one thing to understand is that the focal length of a lens DOES NOT CHANGE when putting it on different format camera bodies. Note that "Format" refers to the size of the film frame or digital sensor in a camera. The "crop factor" essentially has one purpose in life. That is to compare the field (angle) of view provided by a particular focal length on two different format cameras, one of which is considered the reference format for the comparison.

The camera manufacturers have decided to use the 35mm film format as the reference format for DSLRs. However, the 35mm film format is not, never has been, and never will be the "master" format against which all other formats are measured. Thus, the current Canon marketing lingo for a 50D reads thusly: "35mm-equivalent focal length is approx. 1.6x the lens focal length". This language is far better than the old "magnification factor" that Canon used to use or even the very common "crop factor" term that you see/hear a lot today.
__________________
Skip Douglas
A few cameras and almost 50 years behind them .....
..... but still learning all the time.
SkipD is online now   Reply With Quote
Old 23rd of August 2009 (Sun)   #9
MikeMcGowan
Member
 
MikeMcGowan's Avatar
 
Join Date: May 2009
Location: Bensalem, PA
Posts: 238
Default Re: Teleconverters on a crop sensor

That explains everything, thanks a lot.
__________________
Canon 50D | Sigma 30mm f/1.4 | Tamron 17-50mm f/2.8 VC | Tokina 11-16mm f/2.8 | Tamron 90mm f/2.8 | Peleng 8mm f/3.5 | Canon 580ex | Vivitar 285hv(3) | PW Plus II Transceiver(4)

flickr
MikeMcGowan is offline   Reply With Quote
Old 23rd of August 2009 (Sun)   #10
yogestee
"hangs around male genitalia"
 
yogestee's Avatar
 
Join Date: Dec 2007
Location: Aussie living in Laos
Posts: 13,545
Default Re: Teleconverters on a crop sensor

Quote:
Originally Posted by MikeMcGowan View Post
I'm going to be picking up a Canon 70-200mm f/4 L(non IS)this week, and I have a 50D. I was planning on getting either a 1.4x or 2x teleconverter later on for extra reach. Since I already have 1.6x crop factor, that makes the lens 112-320 already right? Now if I add either one of the teleconverters does it add onto the already stretched focal length? And what brand of teleconverters do you suggest? I would just go Canon, but I'm sure there's one that's just as good for a smaller amount of money.

Also, if I used the 1.4x converter on this lens, it would make me one stop down to f/6.3. Now does that mean I can't shoot at f/4, or that I can but the amount of light coming in will be equivalent to what it is at f/6.3?
Mike,,your Canon 70-200mm F/4 will become a 98-280mm F/5.6 with a 1.4x TC

and a 140-400mm F/8 with a 2x TC.. Skip has explained so eloquently what happens with Field of View when comparing APS-C sensors and 35mm..

With either TC your auto focus will suffer and so will some image quality especially with a 2x TC.. With a 1.4x TC it's not too bad..

I have a Tamron SP AF 1.4x TC (the white model) which I team up with my Sigma EX 50-150mm F/2.8 APO with good results if I need that extra reach.. There is a little image degradation but nothing too severe and because the Sigma is a F/2.8 lens auto focus isn't affected too much..
__________________
Jurgen
50D~20D~700D~EOS M~S95

http://www.pbase.com/jurgentreue
The Title Fairy,, off with her head!!
yogestee is offline   Reply With Quote
Reply


Thread Tools
Display Modes

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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Future of the Crop Sensor? glbtrekker Canon EOS Digital Cameras 34 16th of January 2009 (Fri) 18:29
Sensor Size, Full-Frame, Crop Sensor - Link to a nice discussion RodneyCyr Canon EOS Digital Cameras 0 2nd of October 2008 (Thu) 14:13
Ef on crop sensor ,are they less sharp mantra Canon EF and EF-S Lenses 44 21st of January 2008 (Mon) 06:17
Teleconverters vs. Crop Factor mrkeenan0 Accessories & Storage 10 12th of August 2007 (Sun) 23:20
Hood with crop sensor Rey General Photography Talk 8 2nd of January 2007 (Tue) 22:24


All times are GMT -5. The time now is 00:32.


Powered by vBulletin® Version 3.6.12
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
This forum is not affiliated with Canon in any way and is run as a free user helpsite by Pekka Saarinen, Helsinki Finland. You will need to register in order to be able to post messages. Cookies are required for registering and posting. HTML in messages is not allowed, plain website addresses are automatically made active by the board.