Canon 100mm f2.8 Focus Issues?

[chinmaya]

<p>Hi,<br>

attaching a macro shot taken with Canon 100mm f2.8 lens.<br>

Looking at the auto-focus points and focus in the image, do you think<br>

there is a problem with the lens?<br>

Shot was taken: at F6.3, 1/320s, AI AutoFocus<br>

Attachment on the way ...</p>

<p>Thanks<br>

chinmaya</p>

<p> </p><div></div>

[carnagex_carnagex]

<p>Tripod or not ? Was the object free moving in nature, or was it "held" via grips or shot in a studio ? </p>

[carnagex_carnagex]

<p>Tripod or not ? Was the object free moving in nature, or was it "held" via grips or shot in a studio ? </p>

[mbkissel]

<p>I believe it may be a technique issue. At this distance, the DOF is going to be pretty thin at f/6.3. And the camera is trying to set focus for multiple points. Try this, One-Shot AF, center focus point only, f8.0. If necessary, increase ISO to keep shutter speed high enough to stop camera shake.</p>

[PuppyDigs]

<p>When all AF points are active they often locks on multiple points and average the diff between the points, usually not where you want it. This AF mode is okay for general snapshots but not for selecting precise points of focus. Instead, select a single AF point and place at your intended point of focus. And take a bunch of shots if you're hand holding as your body usually sways and throws off focus. Not a big deal at normal distances but a slight forward and back sway is enough to drift out of DOF for macro distance.</p>

[sattler123]

<p>Operator error.</p>

[ronhartman]

<p>To check focusing accuracy, you really need to use a focus chart like this:<br>

http://www.focustestchart.com/chart.html<br>

The camera needs to be set on center focus point, f/2.8 and on a tripod.</p>

[alan_green4]

poor technique.

 

1) you selected a middle-of-the-road f-stop

2) this resulted in a middle-of-the-road shutter speed

3) there is subject motion

4) there is poor dof

5) you auto-focused

 

fixes:

 

go with either shallow dof or lots of dof -- that is, select a really big f-stop or a really small one. don't pick one in between. for classical macro f-stops between 5.6 and 8 aren't very useful. f 6.3 is neither/nor. try f 9-16, possibly higher (although diffraction becomes an issue).

 

secure the subject. there is a tiny amount of subject motion in your shot. clamping the subject will help prevent this.

 

focus manually, unless that's not feasible. split the focus point between nearest and farthest areas and rely on dof to capture both in focus. also, use timer shutter release, mirror lock.

 

if you're going to hand hold and catch macro shots on the fly use high iso and motor through several frames hoping one is good. in such situations it might be better to go for the bokeh look and open the lens up -- selectively focus, shoot at highest shutter speed feasible, motor through several frames.

[kerry_grim]

<p>You need to use as single focus point or manual. If you are still out of focus it is because you moved back or forth.</p>

<p>If you still do not get an accurate focus, shoot a fine ruler at an angle with a SINGLE FOCUS POINT and the camera on a TRIPOD. When you find it is very likley in perfect focus, you can forever forget anything you heard about front or back focus and get on with taking photographs but with the correct technique.</p>

[ben_goren]

<p>Chinmaya,</p>

 

<p>The words, “macro,” and “focus,” should generally always be

accompanied by the words, “manual,” “tripod,” and “small

aperture.” For critical work, the word, “rail,” should also be used.</p>

 

<p>Along, of course, with the technique or tools each word represents….</p>

 

<p>Cheers,</p>

 

<p>b&</p>

[chinmaya]

<p>Interesting thoughts. Thanks a lot folks<br>

Ron thanks for Focus chart link.</p>