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11-02-2013, 08:19 AM   #1
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a good TC (not too light-hungry)?

Is there any TC that wouldn't stop down my 85 from f/1.4 to more than 2 or 2.2 or so but would still give me more reach (100mm+ ) and that doesn't destroy the IQ? or is this a pipe dream / does it cost more than buying the equivalent lens?

11-02-2013, 08:37 AM   #2
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You probably want a 1.4x teleconverter, which would give you an f/2 119mm lens. Expect to spend $150 on one new.

A 1.7x teleconverter would get you an f/2.8 145mm lens and set you back about the same amount.

Good luck!
Bob :-)
11-02-2013, 08:45 AM   #3
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The amount of exposure correction that a TC requires is a matter of physics, not brand, quality, etc. A 2x TC spreads the incoming light over an area 4x the size that the lens it is being used with spreads it, so it needs 4x the light to support the same shutter speed/iso setting. I suppose there are things a manufacturer could to to make the situation worse (e.g. poor coatings or lousy glass), but a 2x converter is going to need 2 stops additional, and a 1.4 will need 1(ish) stop. a 1.4 would make your 85/f1.4 effectively a 127.5/f2. every additional piece of glass that you put between a subject and the sensor is going to degrade image quality to some extent.
11-02-2013, 08:45 AM   #4
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No such thing really. A 1.4x costs you about one stop of light and gives about 120mm focal length. 2x costs even more light. At that focal length it's just better to get a longer lens.

11-02-2013, 09:14 AM   #5
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You can find reasonably priced 100+ mm lenses that would do a better job for you. Check the lens databases for one that is in your price range and look through the market place and/or put in a wanted entry.
11-02-2013, 11:25 AM   #6
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QuoteOriginally posted by Parallax Quote
The amount of exposure correction that a TC requires is a matter of physics, not brand, quality, etc. A 2x TC spreads the incoming light over an area 4x the size that the lens it is being used with spreads it, so it needs 4x the light to support the same shutter speed/iso setting. I suppose there are things a manufacturer could to to make the situation worse (e.g. poor coatings or lousy glass), but a 2x converter is going to need 2 stops additional, and a 1.4 will need 1(ish) stop. a 1.4 would make your 85/f1.4 effectively a 127.5/f2. every additional piece of glass that you put between a subject and the sensor is going to degrade image quality to some extent.
QuoteOriginally posted by Canada_Rockies Quote
You can find reasonably priced 100+ mm lenses that would do a better job for you. Check the lens databases for one that is in your price range and look through the market place and/or put in a wanted entry.
Thank you both for your answers.
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