Friends ... need your help and advice .

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Permalink Reply by CameraClicker on April 3, 2011 at 1:36pm

I thought that your question was excellent, and hard to answer, and took some test shots.  Then I read your question again, and the answer became clear, I also took an extra test shot. 

 

The first scan of your question, I did not notice the f/4, and was thinking about the f/2.8 lens.  With the f/2.8, it becomes a much harder question.  Here is the deal:

 

The 2X teleconverter eats 2 stops of light.  Light is required for auto-focus.  An f/2.8 lens with a 2X teleconverter will still auto-focus.  An f/4 lens with a 2X teleconverter will not auto-focus.  If you had the f/2.8 version of the lens, I would have said the teleconverter is a lot less expensive than the 100-400 zoom, and a lot lighter to carry around, assuming you would still be carrying the 70-200.  Since you have the f/4 version of the lens, I think you would be happier getting the 100-400 lens because then it will auto-focus.

 

These were just quick hand held shots using a Rebel T2i (same sensor as 7D) so you can see field of view with the various combinations.  If you want to see what a 2X teleconverter can do for you, look at this page:  http://cameraclicker.com/Compare/Teleconverters/Teleconverters.html

Here are some test shots:

 

70-200 f/4 L (non IS version) with 2X teleconverter -- does not auto-focus -- 1/3000, f/8, ISO 1600

 

100-400 f/4.5-5.6 L IS USM, auto-focus works -- 1/4000, f/5.6, ISO 1600

 

70-200 f/2.8 L IS USM + 2X teleconverter, auto-focus works -- 1/3000, f/5.6, ISO 1600

 

Of course, if you had the lens and the teleconverter, then you could do this:

100-400 f/4.5-5.6 L IS USM + 2x teleconverter, no auto-focus, 1/1000, f/11, ISO 1600

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Permalink Reply by Alan Ang on April 4, 2011 at 5:59am

A EF 100-400mm sound more relevant to your wild life shooting. for protrait you can get a cheap 50 f1.8mm and  for landscape a EF 10-22mm. Not sure why you get 28-135mm as this len is meant for full frame. 7D is a crop sensor so you should get 18-200mm so sell of the 28-135mm and get a 18-200mm or 18mm -270mm.

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Permalink Reply by Anil Patil on April 4, 2011 at 8:32am

Alan i think 28-135 is not meant for full frame. it works perfect on 7 D .. Am i right ?

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Permalink Reply by CameraClicker on April 4, 2011 at 8:37am

The 28-135 is a full frame lens, it is an EF lens, not an EF-S.  You can use a full frame lens with a crop sensor body.  You can not use a crop sensor lens on a full frame body because the image circle is too small.

 

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Permalink Reply by Alan Ang on April 5, 2011 at 6:07am

It is meant for full frame camera like 5DM2 just like 18-200 is meant for 7D

you still can use this len on your cam but it will not be 28-135 but 44 -216.

 

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Permalink Reply by CameraClicker on April 5, 2011 at 7:17am

The 100-400 mm is also a full frame lens, not EF-S, but you can use it with the 7D as well.

 

The 7D has an APS-C sized sensor, so images are mechanically cropped from what they would be if they were captured with a full sized sensor.  This does not magically change the focal length of the lens.  It does change the field of view, the same as if you used Photoshop to crop the image.  This is more of an issue at the wide angle focal lengths.  However, if you attach the Sigma 18-250 set at 28 mm and take a picture, then attach the 28-135, set at 28 mm and take the same scene, you will get the same picture.

 

The crop factor as a simple multiplier works fairly well if you are comparing most models of Nikon, it is more complex if you are using a Canon.  I put a full explanation with pictures here:  http://cameraclicker.com/Compare/Sensors/Sensors.html

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