recomposing?

Tilting the camera the minuscule amount it takes to recompose the shot has little to no effect on the focus....

With a wide angle lens, the DoF a LOT less shallow so this negates the effect of REALLY ACTUALLY losing enough focus by recomposing to REALLY notice...

With a telephoto lens even with the much more shallow DoF, you are usually zoomed in on the subject enough that you hardly have to move the camera to recompose as far as actual physical movement is concerned...

habenero wrote in post #7426461
thanks for the quick replies1 I was thinking about this with a zoom lens as opposed to stepping forward or backward - does it change things?

I think it's safe to say that no Canon zoom lenses are truly parfocal (able to maintain critical focus while changing focal length).

I have three of Canon's "L" zoom lenses (16-35 f/2.8L original, 24-70 f/2.8L, and 70-200 f/2.8L IS) and none of these will maintain focus if you make a significant change in focal length after focusing. They all definitely need a focus touch-up after changing from maximum to minimum focal length, for example.

My guess is that lens manufacturers felt that the cost involved in a truly parfocal design was not necessary with autofocus.

AlphaChicken wrote in post #7431312
Tilting the camera the minuscule amount it takes to recompose the shot has little to no effect on the focus....

With a wide angle lens, the DoF a LOT less shallow so this negates the effect of REALLY ACTUALLY losing enough focus by recomposing to REALLY notice...

With a telephoto lens even with the much more shallow DoF, you are usually zoomed in on the subject enough that you hardly have to move the camera to recompose as far as actual physical movement is concerned...

I disagree. I believe that it is very easy to loose focus while recomposing, especially at narrow DOF's. Doing the math, one can see that even mild recomposing can move the plane of focus quite a bit. People mistaking think that if the distance between the camera and subject does not change during recomposing, then the subject will remain in focus. Is is not the distance change of recomposing that is the problem, it is the entire shift of the focal plane. The focal plane is a plane (basically) not an arc around the camera. Of course you can use recomposing, but the user should know that some OOF shots are not back focusing but rather the camera doing exactly as instructed.

More info here for those who want read about it.

http://visual-vacations.com …focus-recompose_sucks.htm

single_track wrote in post #7431388
I disagree. I believe that it is very easy to loose focus while recomposing, especially at narrow DOF's. Doing the math, one can see that even mild recomposing can move the plane of focus quite a bit. People mistaking think that if the distance between the camera and subject does not change during recomposing, then the subject will remain in focus. Is is not the distance change of recomposing that is the problem, it is the entire shift of the focal plane. The focal plane is a plane (basically) not an arc around the camera. Of course you can use recomposing, but the user should know that some OOF shots are not back focusing but rather the camera doing exactly as instructed.

In the "olden days" of manual-focus-only 35mm SLR cameras, it was quite common to have a focus aid (usually a split prism, microprism, or a combination of both) smack-dab in the middle of the focusing screen. It was extremely common for photographers to move the aiming point of the camera a little to get an edge of the primary subject into the center of the focusing screen so that the focus aid would work for them. Very seldom did anyone have any problems with out-of-focus images as a result. I know that I cannot remember ever having such a problem.

In many cases, I would (and still do, by the way) focus on an object which is at a distance that I estimated to be roughly the same distance as it would be for my subject (racing cars, for example) and then pan the subject to the position I had focused on and pressed the shutter release.

When working with macro photography, focusing can be more touchy, of course. However, a minor shift in the aiming point for focusing a portrait image or something like that rarely would be problematic unless one was really attempting to use a super-short depth of field.

Shooting a head/shoulder shot at 75mm/f2.8... focus on the eyes and tilt the camera back down. I guarantee you that the only thing in true focus will be the nose and not the eyes.

I got so fed up with this that I use one of the outer focus points now, in portrait mode.

SkipD wrote in post #7431461
In the "olden days" of manual-focus-only 35mm SLR cameras, it was quite common to have a focus aid (usually a split prism, microprism, or a combination of both) smack-dab in the middle of the focusing screen. It was extremely common for photographers to move the aiming point of the camera a little to get an edge of the primary subject into the center of the focusing screen so that the focus aid would work for them. Very seldom did anyone have any problems with out-of-focus images as a result. I know that I cannot remember ever having such a problem.

In many cases, I would (and still do, by the way) focus on an object which is at a distance that I estimated to be roughly the same distance as it would be for my subject (racing cars, for example) and then pan the subject to the position I had focused on and pressed the shutter release.

When working with macro photography, focusing can be more touchy, of course. However, a minor shift in the aiming point for focusing a portrait image or something like that rarely would be problematic unless one was really attempting to use a super-short depth of field.

+1 I used to use a camera with a split prism focus aid. So far I and Skip can say from real world experience that it does not hardly ever have an effect on our shots' focus.

So if it really does affect the focus that much, then why do our shots seem to be in focus? I personally focus and recompose all the time. As the center point of my 5D mk II is A LOT more reliable than my outer points...this to me seems like a fair trade-off...accurate focus and an almost un-noticeable amount of focus change from the re-composition, OR inaccurate focus with the outer points...

Here is what I do.. When shooting in vertical orientation I choose the focus point near the eye/eyes.. I only ever have one focus point activated at any one time.. Focusing and recomposing is very problematic especially when using wide apertures, long lenses and close focus distances..

When focus is critical I manually focus ignoring the focus point.. I rotate the focus ring back and forwards to allow the subject to pop in and out of focus..This way I can tell if the subject is sharp or not.. It takes some practice but I've was shooting with manual focus lenses way before auto focus.. Don't let anyone tell you you can't focus a DSLR especially the xxxD series.. Focusing is one of the basic skillis along with exposure control and compostion.. It apperas many people ingore this skill and rely too heavily on technology..

AlphaChicken wrote in post #7434743
+1 I used to use a camera with a split prism focus aid. So far I and Skip can say from real world experience that it does not hardly ever have an effect on our shots' focus.

So if it really does affect the focus that much, then why do our shots seem to be in focus? I personally focus and recompose all the time. As the center point of my 5D mk II is A LOT more reliable than my outer points...this to me seems like a fair trade-off...accurate focus and an almost un-noticeable amount of focus change from the re-composition, OR inaccurate focus with the outer points...

It depends on what aperture you are using, what focal length, and how close you are to the subject. These three things determine depth of field for your given format. Since much portrait work is done close and with wide apertures, these are the situations where you tend to see things thrown of with focus/recompose.

tonylong wrote in post #7435511
It depends on what aperture you are using, what focal length, and how close you are to the subject. These three things determine depth of field for your given format. Since much portrait work is done close and with wide apertures, these are the situations where you tend to see things thrown of with focus/recompose.

+1 on that at 5ft-10ft f8 with 50mm on ff (5d) focus and recompose might not matter with the 2ft-6ft of DOF yo have. As you open the lens or get closer....it will matter a lot. Also shooting landscape it does not affect things a bit, since DOF most likely is infinite.

silvex wrote in post #7435970
+1 on that at 5ft-10ft f8 with 50mm on ff (5d) focus and recompose might not matter with the 2ft-6ft of DOF yo have. As you open the lens or get closer....it will matter a lot. Also shooting landscape it does not affect things a bit, since DOF most likely is infinite.

That's right, it depends on what you're shooting -- you have to be aware of what you're doing! Saying depth of field doesn't matter can apply to narrow apertures, but can wreak havoc on wide apertures!

tonylong wrote in post #7435980
That's right, it depends on what you're shooting -- you have to be aware of what you're doing! Saying depth of field doesn't matter can apply to narrow apertures, but can wreak havoc on wide apertures!

About two years a go I took some night shots at F22!!! Now that I got the hang of manual exposure...I took shots of the same pier at nite...this time F5.6 ISO100 w/various shutter speed...the results...pretty amazing!!!

Since my DOF is infinite I don't even need to focus. I just swith to manual focus and dial infinity...which I can re-compose all nite long...as long as my subject is 60feet+

silvex wrote in post #7436234
About two years a go I took some night shots at F22!!! Now that I got the hang of manual exposure...I took shots of the same pier at nite...this time F5.6 ISO100 w/various shutter speed...the results...pretty amazing!!!

Since my DOF is infinite I don't even need to focus. I just swith to manual focus and dial infinity...which I can re-compose all nite long...as long as my subject is 60feet+

This is true Ed but if your subject is 6' away you can have problems..

AlphaChicken wrote in post #7434743
+1 I used to use a camera with a split prism focus aid. So far I and Skip can say from real world experience that it does not hardly ever have an effect on our shots' focus.

So if it really does affect the focus that much, then why do our shots seem to be in focus? I personally focus and recompose all the time. As the center point of my 5D mk II is A LOT more reliable than my outer points...this to me seems like a fair trade-off...accurate focus and an almost un-noticeable amount of focus change from the re-composition, OR inaccurate focus with the outer points...

I would only use matte screens in my Nikon film cameras.. When I ordered or bought a new camera I'd get a matte screen straight away.. I never liked the split screens and how the lower portion would black out when using slower lenses or depth of field preview.. I found split screens distracting..

yogestee wrote in post #7441231
This is true Ed but if your subject is 6' away you can have problems..

Agree...and mine subject was about 100ft+ away...it is just the people hear about shooting wide open, recompose etc etc and they failed to analize the shooting situation. So just because they hear about these buzzwords...they think it applies to EVERY shooting situation.

Also peep study their photos at their pixel level and forget to study their lenses to see what makes the tick or not.

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