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Posts: 4
Registered: ‎05-14-2016
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why canon lens 100-400mm not fucos well

why canon lens 100-400 f/4.5-5.6l is usm not fucos well when i taking wild birds,The  lens just in and out when i fucos to the subject and not take a photo, i try many setting but the problem still not solve, The lens is used from adorama tv ,the camera is canon70d brand new,my other two canon lens work fine with my camera,Thanks for any help.

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Posts: 8,340
Registered: ‎08-13-2015

Re: why canon lens 100-400mm not fucos well

Some setttings that could throw your shots off are:

 

  • Number of Focus Points - Manually selecting just the center point is easiest way to shoot
  • Shooting Mode  - "One Shot" mode is easiest to use, for most scenarios.
  • Lens Focusing Mode - Your lens should have settings to adjust for focusing distance to the subject.
  • Image Stabilization - Your lens should have settings to fine tune IS.

Any one, or all, of those settings could affect the focus in your images.  What settings are you using?  How far away is your subjecgt?  What focal length are you trying to use?  Are you using a tripod, or handheld?  What are your exposure settings?

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Respected Contributor
Posts: 1,117
Registered: ‎02-06-2013

Re: why canon lens 100-400mm not fucos well

There are a couple of things you might want to check:

 

1. You are not too close to the subject.  This lens minimum focus distance (MFD) is 6 feet (1.8m).  Closer than this the lens cannot focus.

 

2. Check on the lens and make sure the distance button is set to 1.8m - infinity and not 6.5m - infinity.  If this is set, you can't focus on anything closer than 20 feet.  This button helps speed up the focusing if your subjects are farther than 20 feet.

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Posts: 11,351
Registered: ‎12-07-2012

Re: why canon lens 100-400mm not fucos well

"The lens is used from adorama ..."

 

Although not a free ride ticket, Adorama tests all their used stuff before they sell it.  That in mind, it is something you are doing wrong.  It is possible it is faulty, but it wouldn't be top of the list.

 

Of the suggestions from above, too close to the subject is a likely one.  My second place to look is contrast. If you are trying to focus on the sky when you shoot BIF, it will never focus correctly.  Take it to a controlled place with good light and nice contrast and vertical lines and try to AF.  If it works there, it is fine.

 

EOS 1DX and 1D Mk IV and several lenses!
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Re: why canon lens 100-400mm not fucos well

[ Edited ]

@diverhank wrote:

There are a couple of things you might want to check:

 

1. You are not too close to the subject.  This lens minimum focus distance (MFD) is 6 feet (1.8m).  Closer than this the lens cannot focus.

 

2. Check on the lens and make sure the distance button is set to 1.8m - infinity and not 6.5m - infinity.  If this is set, you can't focus on anything closer than 20 feet.  This button helps speed up the focusing if your subjects are farther than 20 feet.


We don't know which version of the lens the OP is talking about. 

 

The original has a MFD of 1.80 meters, while version 2 has a MFD of  0.98 meters.  I find it less likely that the subject is too close, than the IS focusing range switch being set improperly.  It's easy to forget about the switch, if you're not accustomed to it.

 

In fact, I suspect the lens is most likely hunting when 400mm is dialed in, which I accept as normal.  Version 2 of the lens, like many long zooms, does tend to hunt when refocusing from a relatively near object to a distant object at maximum focal length zoom settings.  If benefits from a little bit of pre-focusing when making large changes in focusing distances.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
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Posts: 4
Registered: ‎05-14-2016

Re: why canon lens 100-400mm not fucos well

Thank you for your reply, sometimes I use infinity -6.5 and over 20 feet, but the lens just in and out not take photo,(camera setting :AV, SP1500, ISO350,)
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Registered: ‎08-13-2015

Re: why canon lens 100-400mm not fucos well


@Vincent72 wrote:
Thank you for your reply, sometimes I use infinity -6.5 and over 20 feet, but the lens just in and out not take photo,(camera setting :AV, SP1500, ISO350,)

Okay.  How far away is your subject?  What focal length are you using?

 

Do you think you have sufficient light?  If you pre-focus the lens some, can the lens lock focus?

 

It is not usual for a super telephoto lens to not be able to switch from focusing on a close object with its' shortest focal length, to focusing on a distant object at its' longest focal length.  Soimetimes the lens needs a little manual override help from the photographer, just to get the focus close, and the lens can usually do the job from there.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
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