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Old Jan 11, 2007, 2:08 PM   #1
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I have read reviews that say the auto focus on this lens is real slow....They must of up-graded the motor in this one as my Tamron 200-500 is very quick on auto focus..
What are others findings on this lens...I think it's great even at 500mm
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Old Jan 11, 2007, 5:16 PM   #2
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wrams wrote:
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I have read reviews that say the auto focus on this lens is real slow....They must of up-graded the motor in this one as my Tamron 200-500 is very quick on auto focus..
What are others findings on this lens...I think it's great even at 500mm
IMO what they are refering to are the ultrasonic (USM/HSM) drives against the micro motors used in most other lenses - In some of the write-up, I noticed the time-out period of 200ms (USM/HSM) vs 250ms(non-USM) for the AF programmed in the cameras. This 200ms translate to 5fps (which you can overide at the expense of accurate focus on the 1DmrkII to get 8fps)

Also many L lenses have focus limit switches which limit the searching range of a lens making them focus faster - for example on the 500mm f/4 prime, if this lens has to focus from 10m to infinity, I don't find it to be any faster than my 120-300 Sigma; However, if you narrow the range to a more limited search then of course it's much faster than if another lens has to span the entire focus distances

-> If you already pre-focus then most lenses will focus quite fast if the motors do not have to step as far... try from something very far to very up close, and then back and forth!
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Old Jan 11, 2007, 5:36 PM   #3
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Thanks for explaining it to me...

I will go and try it soon but our weather is gale force at the moment so 80mph winds are'nt ideal tripod or handheld weather...
I'll do as you suggest though as soon as i can...

Regards

Andrew


P.S What is IMO...???
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Old Jan 11, 2007, 5:43 PM   #4
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In My Opinion the Tamron 200-500 is one of the best buy zoom in this range at the moment...
-> It's one of the sharpest - If not the sharpest!

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Old Jan 11, 2007, 5:47 PM   #5
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I was going to get the Sigma 50-500 but decided on getting the 200-500...Do you think i made the right choice...???

I also looked at your homepage and really liked the pictures...Best being England...Lol...Bath is only 20 minutes drive from me i live in Bristol...
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Old Jan 11, 2007, 6:14 PM   #6
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Can anyone tell me why the Tamron has a removable ring at the front of the lens..??

With the ring on it's 86mm thread and when i remove it it's also 86mm thread...Whats the reason..???

In the manual it say's FEC and FEC attaching ring what is this..???

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Old Jan 11, 2007, 6:25 PM   #7
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It's ok i just read it..It's for CPL's and other filter for when you want to turn them with the hood on....
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