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Old Apr 2, 2011, 12:41 PM   #1
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Default quick teleconverter question

I plan on buying a 1.4x for my sigma 70-200 f2.8. I know it will change my fstop to f4... but will it change the amount the background is blown out? Im worried of that because i payed $800 specifically for the f2.8 and being able to easily blow out the backgrounds.... if i add the teleconverter, am i totally counteracting that? Does the bokeh look like f4, or does it just let the amount of light like f4?

If that made any sense... lol


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Old Apr 2, 2011, 2:33 PM   #2
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You can do your own test quite easily.

The lens will be a 98-280mm f4 with a 1.4x TC. So to see the difference shoot something at 70mm f2.8 then at 100mm f4 and you have one comparison. Then you could do 142mm at f2.8 and 200mm at f4. Obviously you can't try 200mm and 280mm but hopefully the first two tests will allow you to see the sort of difference you are looking at.

When you do the test also try moving the subject distance so rather than at f4 framing tighter, move the object further away so you frame the same then look at background. I say this as if you are shooting sports rarely do you shoot tighter (you usually want to fill a minimum of 2/3 of the frame) but just get the ability to shoot a little further out.

Be aware that you will find the lens getting quite soft, especially at 280mm f4 unless you have a good version (I honestly haven't played with the latest range but the older ones were pretty soft at the long end).

In a nut shell, at f4 you are still able to get shallow DOF shots, all of these shots were at f4.5 and admittedly the lens was a bit longer (from 168mm to 420mm but again it should give you an idea). http://www.marksmithphotography.co.uk/p690351225
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Old Apr 2, 2011, 3:57 PM   #3
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thanks.
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