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"Why Focus-Recompose Sucks" - your solution?

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feinschmecker

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Hi,

After taking some casual portraits recently using the center AF, then recompose method I noticed that sometimes the eyes, which I focused on in the first place, were out of focus.

I had a look around the internet and found this very good explanation, suggesting using another focus point as best solution: http://visual-vacations.com/Photography/focus-recompose_sucks.htm

Do you have any other solution to this problem / a special technique to deal with this?

Many thanks!

Cheers,
Pablo
 
Nothing as reliable as shifting the AF point every time.

For kids you generally don't have that luxury so sometimes I'll focus, recompose and then try to move just a couple of inches back (depending on how close the subject is- sometimes all it takes is to lean back ever-so-slightly. I find that the viewfinder in the E-3 gives me a good guess as to whether I'm close or not but if I really want the shot I've been known to fire off a burst of 3 or 4 shots while leaning slowly back (I think that's called physically bracketed focus).

Whenever possible though I try to shift the AF point to cover the subject's eye.

Cheers.

--
breinholt.zenfolio.com
 
Gidday Pablo
feinschmecker said:
Hi,

After taking some casual portraits recently using the center AF, then recompose method I noticed that sometimes the eyes, which I focused on in the first place, were out of focus.
Click to expand...
You have to expect that many shots will be less than perfect. Then you need to ask yourself whether it is worth more to you for the subject than throwing it away because it is less than 'perfect' ...
feinschmecker said:
I had a look around the internet and found this very good explanation, suggesting using another focus point as best solution: http://visual-vacations.com/Photography/focus-recompose_sucks.htm

Do you have any other solution to this problem / a special technique to deal with this?
Click to expand...
Practice ... more practice ... :|

Try both methods. You will still need to practice ...

Being involved in this craft for over 50 years, I can assure you that any "technique" for capturing anything requires lots of practice, and lots of honest self-criticism ... A friend reckons I am too hard on myself in this regard; I replied that he was exactly the same on himself, lol. He agreed. This is the way to improvement.

Having said that, I have used focus and recompose for most of my photography, and still do. It does work! BUT, you need to practice ... ;).

Now I will go and have a look at the link you posted. I am not even supposed to be using my computer at the moment ... :(

--
Regards, john from Melbourne, Australia.
(see profile for current gear)
Please do not embed images from my web site without prior permission
I consider this to be a breach of my copyright.
-- -- --

The Camera doth not make the Man (or Woman) ...
Perhaps being kind to cats, dogs & children does ...

Gallery: http://canopuscomputing.com.au/gallery2/main.php



Bird Control Officers on active service.

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With the 11 point system on the E-3 I find that it's rare to have an AF point not be covering, if not very close to where I want to focus. I enable the arrow pad to select AF points after half-press (after all, C & N work similarly...).

With the old 3 point system, given that the outer two points aren't as reliable, you're pretty much stuck to focus-and-recompose. You can also enable AF+MF mode and tweak the focusing ring after autofocusing. Caveat: with the exception of the E-1, the viewfinder is not good enough to judge focus especially with lenses brighter than F3.5.

Finally, if your portraits are posed and considered, there is live view.
 
G'day again Pablo

I just read that link.

The author is completely correct ... focus and recompose will never work for him!

This is because he only thinks he understands what he is doing ...

In order to correct for the error he is explaining (and making ... ), you have to realise that the point you focus on has to be in exactly the same arc as the intended point of focus, not in the same plane .

In order for this technique to work, it is necessary that the focus and recompose point has to be the same distance from the lens/sensor as the intended point of focus. This requires it to be the same distance away. Another object that is in the same plane as the intended focus point is not the same distance from the lens/sensor ... The closer you are to the subject, the worse this error will become.

--
Regards, john from Melbourne, Australia.
(see profile for current gear)
Please do not embed images from my web site without prior permission
I consider this to be a breach of my copyright.
-- -- --

The Camera doth not make the Man (or Woman) ...
Perhaps being kind to cats, dogs & children does ...

Gallery: http://canopuscomputing.com.au/gallery2/main.php



Bird Control Officers on active service.

Member of UK (and abroad) Photo Safari Group
 
John King said:
Practice ... more practice ... :|
Click to expand...
However long you practice hitting yourself over the head, it still hurts.
John King said:
Try both methods. You will still need to practice ...
Click to expand...
Perhaps you could explain how his technique will develop with the practice. There is basic bit of trigonometry which explains why focus/recompose doesn't provide correct focus, how is practicing going to change that?
 
John King said:
G'day again Pablo

I just read that link.

The author is completely correct ... focus and recompose will never work for him!

This is because he only thinks he understands what he is doing ...

In order to correct for the error he is explaining (and making ... ), you have to realise that the point you focus on has to be in exactly the same arc as the intended point of focus, not in the same plane .

In order for this technique to work, it is necessary that the focus and recompose point has to be the same distance from the lens/sensor as the intended point of focus. This requires it to be the same distance away. Another object that is in the same plane as the intended focus point is not the same distance from the lens/sensor ... The closer you are to the subject, the worse this error will become.
Click to expand...
Lets get this right. To autofocus correctly using your technique you need to know the subject to camera distance before you focus? And you use focus/recompose by focusing on something different than the subject?
Sounds like a useful technique to learn.
 


Lol.

--
Regards, john from Melbourne, Australia.
 
Hi John,

I am not too much of a technical expert myself, but are you sure that the points in focus are on an arc? That's a genuine question - don't know myself...

Most of the internet resources are saying they are (at least with better lenses) on a plane. But that's just me searching the non-reliable internet, can't verify that with knowledge by myself unfortunately - was always rubbish in physics :(

E.g. this excerpt is from this website: http://photo.net/leica-rangefinders-forum/00LQNd

-snip-

...Visualize a flat plane at right angles to your lens's axis. The object you want to focus on, lies on that plane. Now when you focus a rangefinder (or SLR) by centering the finder on the point you focus on, then all objects in that flat plane should be in focus. (Note: this assumes your lens has a flat field. Some do not.)

But when you now move your camera through an arc to recompose, the point of exact focus now lies a bit closer to you than that flat plane. To visualize this, sketch out the lens axis and plane of focus; then sketch the new axis after recomposing, and a new plane at right angles to the new axis. Make the distance from camera to the second plane, the same as it was to the original one. You will see that the point of focus has shifted. It's closer to you now.

This error in focus caused by moving the camera through an arc, is called Cosine Error, because the error is proportional to the cosine of the angle through which you swung the camera.

I first noticed this when photographing impressionist paintings in a museum. There were no straight lines to focus the rangefinder on, in thoise fuzzy paintings! So I focused on the frame and swung the camera to center the picture, and shot. In my slides, the paintings were a little fuzzier than Degas intended!

So here's the solution: After focusing, don't swing the camera through an arc to recompose. Instead, slide the camera sideways in a plane parallel to the plane of focus, until you get the picture re-centered the way you want it.

-snip-

Cheers,
Stevo
 
You'll find that the dof on a 50mm f2 is small enough, especially at closer distances like head shots, to create this problem.
 
AF, lock focus, recompose move camera slightly fore and aft whilst watching focus on eyes. It is fast and works. Many people who do macro photography do this all the time. It matters more in macro photography.
--
Oll an gwella,
Jim
 
John King said:
...

In order to correct for the error he is explaining (and making ... ), you have to realise that the point you focus on has to be in exactly the same arc as the intended point of focus, not in the same plane .
...
Click to expand...
I don't think this is right. The point of focus has to be in the same plane as the point you want to have in focus. Focus on a wall that is exactly parallel to the sensor. The edges of the image will be in focus if the center is.

--
Jeff

'Yeah, well, you know, that's just, like, your opinion, man.' The Dude
 
Focus is nothing but distance between your lens and your subject. I have never had a a problem with my focus when recomposing while maintaining the same distance, and yes it does require some practice along with some knowledge, technique and talent.
--



http://www.pueblostudio.com
 
We get away with focus and recompose most of the time, because DOF is sufficient to hide the fact that the intended point of focus has been thrown slightly out of focus. The problem occurs at short distances and wide apertures.

Some possible solutions:
  • Use a focus point closer to the intended subject, rather than the center focus point.
  • Use manual focus.
  • Slide the camera sideways, instead of rotating it when you recompose. (I read this in a Contax G2 forum many years ago, but I haven't tried it. I suspect its not that easy to do well.)
--
Jeff

'Yeah, well, you know, that's just, like, your opinion, man.' The Dude
 
I see John's point, and he is right that these things need to be practised and I am grateful for him to provide some sensible answers.

Cheers now,
Pablo
 
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