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"Why Focus-Recompose Sucks" - your solution?

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Possibly.

I tend to like soft skin and bright eyes on people. I also don't mind out of focus areas on an animal shot as long as the eyes are sharp.
--
Oll an gwella,
Jim
 
I sometimes resort to manually focusing no matter how advanced the E-3 AF system may be. The only digital I have shot has been Olympus starting with the E-10 and CZ2000 so I can't compare it against any other camera. I sometimes have the urge to rent another brand just to see how the AF works. I hesitate because I am sure that I will want to change, and I can't see myself letting go of my HG lenses.
--

Quote by Robert Roaldi: I often take pictures at less than optimum apertures and shutter speeds. At 1-to-1 on my monitor I can often see the blur that is the result of too low a shutter speed and too much coffee. But I can often fix those pictures by just reducing the magnification and printing them anyway and pretending that I never saw them at 100%. It seems to eliminate the problem.
 
John King said:
...

Thanks for providing the diagram, mate. It also explains why the photographer in the OP's original link will never get it right ...
...
Click to expand...
Not sure how that can be, since the link and the diagram say the same thing.

--
Jeff

'Yeah, well, you know, that's just, like, your opinion, man.' The Dude
 
Gidday Jeff
Jeff Charles said:
John King said:
...

Thanks for providing the diagram, mate. It also explains why the photographer in the OP's original link will never get it right ...
...
Click to expand...
Not sure how that can be, since the link and the diagram say the same thing.
Click to expand...
No. Same diagram, different procedure, and conclusions ...

As I read the link, it shows the photographer focusing on a point in the same plane as the subject. As Rikke's diagram shows, this will always be further away from the camera than the subject. This will result in the subject being OoF ...

[EDIT]
I just re-read the link.
It clearly shows the photographer's misuse of focus and re-compose.

He is taking a focus point that is in the same plane of focus as the subject point of focus, then moving the camera so that the point focused on is now at a different distance from the lens/sensor ...

He has merely demonstrated his (mis-)understanding of why what he is doing won't work, lol.

It is because he does not understand the fundamental basis of the focus and recompose technique ...
The points must be equidistant from the lens/sensor.
[end edit]

Focus and recompose always requires (doh!) that the focusing point and the subject are at the same distance. Nothing in the same plane of focus as the subject will be, except when that point is very close to the subject itself, and a small distance from the subject relative to the camera-subject distance (angular displacement is small ... ).

Unlike Styrofoam, I am redefining nothing.

This technique has been successfully used and understood longer than I have been alive ...

Now, I really must stop typing. My arm is hurting like fury to such an extent that I will now have to take some painkillers. I do not like to do this during the day, as it is all too easy to continue damaging the very thing one is trying to allow to mend ... This is why I am avoiding the forum. I cannot respond properly. I made an exception to try to assist Pablo, and my friendly personal stalker has turned an uncontentious, well-known subject and technique into something else.

--
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
 
stevo2 said:
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
Click to expand...
Try rotating the camera around the nodal point.
 
Tyrone Wellhung said:
Absolutely. Everyone can follow photography just as they choose. So long as they find individual satisfaction form their hobby or profession, I have no argument whatsoever. However, they're better off if properly informed.
Click to expand...
I'll raise my glass to that.

This is what I have appreciated so much about this forum over the past couple of years - there is a broad cross-section of various cultures, careers, interests, interest levels, ages and proficiencies represented here which comprises a massive body of experience, information and insights to be gleaned/assimilated.

I learned about DPReview forums back when I purchased an Oly C-8080. I knew very little of photographic technique, had an incidental knowledge of optics and very little understanding of applications in real life.

Good people here have patiently answered numerous newbie questions and pointed me to many fantastic ideas, resources and explained things to me. I do appreciate the ones who saved me loads of unnecessary effort by offering "suggested" approaches and extra tips.

Hopefully, we can keep this forum flooded with constructive and useful dialog.

Cheers.

--
breinholt.zenfolio.com
 
kernow said:
I was simply pointing out that manual focus would eliminate this problem entirely.
Click to expand...
Only if it is possible to focus reliably on the ground glass (the AF equivalent would be having AF points where they happen to be needed for the composition - contrast AF may have an advantage here). Otherwise the situation is the exact same: using the AF center point or using the center split prism or the center spot of a range finder all introduce the cosine theta error if the photographer turns to recompose.

--
Rikke
 
John King said:
Jeff Charles said:
John King said:
...

Thanks for providing the diagram, mate. It also explains why the photographer in the OP's original link will never get it right ...
...
Click to expand...
Not sure how that can be, since the link and the diagram say the same thing.
Click to expand...
No. Same diagram, different procedure, and conclusions ...

As I read the link, it shows the photographer focusing on a point in the same plane as the subject. As Rikke's diagram shows, this will always be further away from the camera than the subject. This will result in the subject being OoF ...

[EDIT]
I just re-read the link.
It clearly shows the photographer's misuse of focus and re-compose.

He is taking a focus point that is in the same plane of focus as the subject point of focus, then moving the camera so that the point focused on is now at a different distance from the lens/sensor ...

He has merely demonstrated his (mis-)understanding of why what he is doing won't work, lol.

It is because he does not understand the fundamental basis of the focus and recompose technique ...
The points must be equidistant from the lens/sensor.
[end edit]

Focus and recompose always requires (doh!) that the focusing point and the subject are at the same distance. Nothing in the same plane of focus as the subject will be, except when that point is very close to the subject itself, and a small distance from the subject relative to the camera-subject distance (angular displacement is small ... ).
Click to expand...
If you focus on a point the same distance from the camera as the subject (is that not what equidistant means) then the focus gets set the same as if you focussed on the subject itself, and when you swing the camera, it's wrong again.
Why not focus on the subject?
Or is that not what you meant?
 
RoyGBiv said:
I kid, I kid. :D :D
Click to expand...
Why do you say that?

Live view with face detection, the camera keeping the AF point on the face (or even the eyes) whilst the photog recomposes freely is an excellent solution. I don't know if Oly DSLRs can do this, but users of µ43 report very good results and 4/3 lenses can be mounted and AF (though slower) in many cases.

EDIT: Okay, smile detection seems over the top. :-)

--
Just my two öre,
Erik from Sweden
 
There is a big hole in the technology when it comes to focusing outside the focus points. The last thing you want to do is have the focus points tell you where to put the subject.

My recent strategy has been
  • use manual focus lenses in some cases; every photographer should know how to fast-focus manually and nail it; a large viewfinder is a must though
  • let the autofocus focus on the placket of the shirt, which is often close enough to the plane the that subject's eyes are in, that it will be very very close, especially in half or full length shot
  • use the continuous single point 3D tracking function in my Nikon; acquire focus with the center focus point, then recompose and watch the focus point follow the subject
  • I keep the thumb button assigned as an AF-lock; you can use this to lock in a very close setting, and then use the following:
  • train your neck to lean slightly in for acquisition, and lean back just slightly as you recompose, so that the point of focus remains on the same part of the subject exactly
  • use AF-s or equivalent lenses and tweak the focus manually
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.

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
Click to expand...
 
Luke Kaven said:
There is a big hole in the technology when it comes to focusing outside the focus points. The last thing you want to do is have the focus points tell you where to put the subject.
...
Click to expand...
The idea is to use a focus point that is close to where you want to put the subject. That way, you only need to rotate the camera a short distance if you choose to focus and recompose from that point. That will minimize the focus error.
--
Jeff

'Yeah, well, you know, that's just, like, your opinion, man.' The Dude
 
Ehrik said:
...
EDIT: Okay, smile detection seems over the top. :-)
...
Click to expand...
And often inappropriate. Would we want smile detection at a funeral? Manufacturers need to do better:
  • For funerals: grief detection
  • For weddings: bliss detection
  • For natural disasters: dispair detection
  • For people who have just read an entire Oly forum equivalence thread: blank stare detection
;)
--
Jeff

'Yeah, well, you know, that's just, like, your opinion, man.' The Dude
 
Rikke Rask said:
digital ed said:
Photographers who properly take multi-photo panoramic do it all the time. Look it up.
Click to expand...
Don't be rude. I repeat my question.

--
Rikke
Click to expand...
Here are a few sources that will complete your knowledge about using the nodal point of a camera/lens combination.

http://en.wikipedia.org/wiki/Nodal_point#Nodal_points
http://reallyrightstuff.com/pano/05.html
http://archive.bigben.id.au/tutorials/360/photo/nodal.html
http://www.kingpano.com/nodal_tut.htm

http://www.vrphotography.com/data/pages/techtutorials/technotes/nodalptalign-tn.html
 
The nodal point of any given lens is typically its focal length away from the sensor. We know the plane the sensor lies in, it's denoted with a Ø symbol on the camera body.

Panoramic photographers use very expensive fancypants tripod heads that change the center of rotation from the tripod post to whatever the nodal point is. This permits panoramics with no parallax shift. I doubt it's realistically possible to put into practice when handholding. I'm not sure how it helps the focus and recompose problem however.

I think it would just reduce the actual focus and recompose problem to exactly distance/cos theta, rather than something more complex when using your head as the center of rotation. And as I've established in one of my other posts, the actual shift when given distance/cos theta and realistic angular shifts is pretty negligible.
--
http://www.photoklarno.com
 
It seems to me that in most of her posts, Rikke seems to know her stuff, therefore I would guess that it's a reasonably safe bet that she knows a little optics, and was not asking what a nodal point was . Rather, I suspect that the question was to do with the practical method for, maybe,
i) discovering where the entrance pupil of a particular lens is

ii) providing a good way of physically performing an accurate rotation of the camera lens around this point.
digital ed said:
Rikke Rask said:
digital ed said:
Photographers who properly take multi-photo panoramic do it all the time. Look it up.
Click to expand...
Don't be rude. I repeat my question.

--
Rikke
Click to expand...
Here are a few sources that will complete your knowledge about using the nodal point of a camera/lens combination.

http://en.wikipedia.org/wiki/Nodal_point#Nodal_points
http://reallyrightstuff.com/pano/05.html
http://archive.bigben.id.au/tutorials/360/photo/nodal.html
http://www.kingpano.com/nodal_tut.htm

http://www.vrphotography.com/data/pages/techtutorials/technotes/nodalptalign-tn.html
Click to expand...
Now, I see that these do indeed give some tutorials as to how to find the entrance pupil. So presumably a devotee of focus-recompose needs to do this for each of her lenses, maybe marking it somewhere on the barrel with a pain spot (if a control ring wasn't in the way), so yes, there is an answer to (i) if you're prepared to take the time and trouble.

Then, there's how to arrange to turn the camera around this point. Again, the web sites you cite suggest various specialised pano mounts to do just this. So, the aforesaid devotee can get one of these, and happily recompose assured that the camera is turning around the nodal point. Still, I have two questions on this:

i) is it not just a little cumbersome? Would not multi point AF be simpler? Or a tape measure.

ii) Even if you do swing the camera round the entrance pupil, it doesn't actually solve the D/cos θ problem. What it does is ensure that D/cos θ is an accurate measure of the actual focussed distance. If θ is subtended somewhere else than the entrance pupil, there is another small error term that creeps in, but it's so small that no-one had bothered with it. Probably not big enough to necessitate the bother of finding the entrance pupil position for all your lenses, investing in a pano head and tripod and using such a long winded and laborious focussing technique.
 
Tyrone Wellhung wrote:
Still, I have two questions on this:
Tyrone Wellhung said:
i) is it not just a little cumbersome? Would not multi point AF be simpler? Or a tape measure.

ii) Even if you do swing the camera round the entrance pupil, it doesn't actually solve the D/cos θ problem. What it does is ensure that D/cos θ is an accurate measure of the actual focussed distance. If θ is subtended somewhere else than the entrance pupil, there is another small error term that creeps in, but it's so small that no-one had bothered with it. Probably not big enough to necessitate the bother of finding the entrance pupil position for all your lenses, investing in a pano head and tripod and using such a long winded and laborious focussing technique.
Click to expand...
The points of foci are an arc not a plane. Therefore, as the camera is properly rotated so the arc remains on the eyes, the eyes will stay in focus.

The real discussion here (reading between the posts) is whether one is taking snapshots or portraiture photography. Snapshots are easy. Portraiture photography is extremely difficult to get all parameters in artistic balance. Thousands of books are written on this subject as well as college and private courses. If snapshots are the desire then snap away. If proper portraiture is the goal then there are no quick solutions.
 
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