Focussing speed.


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wong1979

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#1
Hi, I have just gotten a 70-300 lens. From the 70mm, and tried to zoom on a contrasty object, quite ok. But once I up to 300mm, it keeps on focussing. Is this normal?
TIA, wong
 

ynot

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#2
Sorry, but what lens are you using? Nikon? Canon? Minolta? 3rd party? different lens and different cam have different capability.
 

wong1979

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canon 70-300 IS USM. Also, i noticed the focussing is like very slow. I though USM should be almost instant? Can take more than 1 second to zoom from nearest to infinity. Is that too long???
 

n0d3

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#4
I don't think its the "true" ring type USM, should be the inferior micro USM.
 

ynot

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#5

wong1979

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ynot said:
here's a lens review
http://www.the-digital-picture.com/Reviews/Canon-EF-70-300mm-f-4.5-5.6-DO-IS-USM-Lens-Review.aspx

"The Canon EF 70-300mm f/4.5-5.6 DO IS USM Lens is not a fast lens to begin with, but stopping down to f/8 or so makes it very slow. Image Stabilization helps greatly, but not if you want to stop non-panning action. "

hope it helps
Nope it doesn't help. I think u misunderstood the meaning of fast in here. You also got my lens model wrong :bsmilie: But thanks anyway
 

wong1979

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n0d3 said:
I don't think its the "true" ring type USM, should be the inferior micro USM.
I think true ring or false ring, as long as is USM, ultra sonic, should be ultra focussing speed right? And not take 1.5 second to focus from 1 end to another?
 

wong1979

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#8
Nvm...disregard that I asked....maybe night time is not a good time to test. I'll try when day breaks. Thanks
 

Aug 16, 2005
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#9
ynot said:
here's a lens review
http://www.the-digital-picture.com/Reviews/Canon-EF-70-300mm-f-4.5-5.6-DO-IS-USM-Lens-Review.aspx

"The Canon EF 70-300mm f/4.5-5.6 DO IS USM Lens is not a fast lens to begin with, but stopping down to f/8 or so makes it very slow. Image Stabilization helps greatly, but not if you want to stop non-panning action. "

hope it helps
I dont think it his version of the lens.:think: coz this one has the Ring-USM.I think what the author meant with his 'very slow' is the apperture, and not focussing speed.
Night time is also not a good time to test focussing, it will tend to hunt.
And dosent mean USM mean ultra fast focussing.Hope you will do more research into this before you make a comment.Micro USM and Ring USM is different.IMO, micro USM is just a cheap excuse for Canon to increase the price of the lens.:)
 

n0d3

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#10
wong1979 said:
I think true ring or false ring, as long as is USM, ultra sonic, should be ultra focussing speed right? And not take 1.5 second to focus from 1 end to another?
Wrong. Only the true ring type USM will give you that silent/fast focusing speed.
 

#11
wong1979 said:
Hi, I have just gotten a 70-300 lens. From the 70mm, and tried to zoom on a contrasty object, quite ok. But once I up to 300mm, it keeps on focussing. Is this normal?
TIA, wong
Read through the posts.

Usually, focussing depends on the contrast and available light. the lens have difficulty focusing if they can't 'find' the spot to focus on.
 

solarii

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Oct 20, 2005
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#12
If you have problems focusing a night, hook up an external flash and use the AF-assist beam to help your camera focus. Has limited range but its useful.

And SLR lenses generally have difficulty focusing in low light situations as there's not enough contrast for AF to get a fix. Nothing to do with what kind of focusing motor it uses. If you want to test the speed, do it in broad daylight.
 

benedium

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Jun 19, 2004
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#13
Do you mean the focussing is slow as in it 'hunts' back and forth, or u mean it moves really slow like a toy car with weak batteries? You may want to take it to the shop to test another copy of the same lens. If shop don't let you change then worst case, bring to canon for checking/servicing.
 

wong1979

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#14
benedium said:
Do you mean the focussing is slow as in it 'hunts' back and forth, or u mean it moves really slow like a toy car with weak batteries? You may want to take it to the shop to test another copy of the same lens. If shop don't let you change then worst case, bring to canon for checking/servicing.
Yup, like ur toy car analogy. But I think it should be normal, I just got the impression that USM must focus from 1 end to another fast.

This is what I do with mine. I aim at someting of the same color, and it takes ruffly 1 sec ++ to reach to the other end. Normal?
 

drumma

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#15
n0d3 said:
Only the true ring type USM will give you that silent/fast focusing speed.
Yes. not all canon lenses with the word 'USM' means fast and silent focusing. the ring type one's faster. my 17-40 focuses quite fast. i think it's almost negligible. perhaps i'm exaggerating! :p but 1 sec++ is abit too long.

maybe u want to read this review?

http://www.the-digital-picture.com/Reviews/Canon-EF-70-300mm-f-4-5.6-IS-USM-Lens-Review.aspx

not too sure if urs is this model.

to quote a paragraph,

But, Ring USM (Ultrasonic Motor) is not part of the package. Improvements in the CPU and AF routines help in the focus performance increase according to Canon. Accuracy is often more important than speed. Good thing as actual performance of the Micro USM shows accuracy to be very good but speed is just OK - not as good as I had hoped.
 

wong1979

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Aug 16, 2005
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#16
perhaps I'm being too panicky. Daytime testing seems good enough :bsmilie:
 

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