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Thread: Focus & Re-Compose - not good idea?

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    Marty's Avatar
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    Focus & Re-Compose - not good idea?

    Hi folks,
    I found this article which challenges an established AF focusing technique many of us have been using for years. I realise that the amount of focusing 'failure' depends very much on depth of field, lens angle and focused distance etc., but for portraiture, it strikes me as potentially quite significant.

    In any case, I thought this article was worth sharing for your consideration.

    Your opinions folks?

    http://visual-vacations.com/Photogra...pose_sucks.htm

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    Re: Focus & Re-Compose - not good idea?

    Yep - been saying this for years.

    I always choose the AF point closest to the "area of interest" (usually an eye). More modern camera have better AF cross-type and diagonal-type AF sensors. Not so much of a problem of a 1D series camera

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    Re: Focus & Re-Compose - not good idea?

    Been aware of that for a while and yes I always 'walk' the AF points around the viewfinder instead of using the middle one and reframing.
    To be fair the better the DSLR the easier this is as they tend to have more AF points to play with. Mirrorless System Cameras and some of the higher-end compacts - like Bridge Cameras - can AF at ANY point on the screen. A modern DSLR will do this in Live View mode but the AF is then desperately slow. I use the Live View option when shooting static macro images as I can then use any point on the rear screen to focus and I can magnify that point to get a very accurate conformation of the focus.

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    Re: Focus & Re-Compose - not good idea?

    The technique works just fine if the distance focused at is very close to the recomposed focus distance, particularly at SMALL apertures. But herein lies the trick - who can estimate distances accurately? Trigonometry applies - the cosine of the angle through which the camera is "swung" after focusing makes the difference. For very small angles, the cosine is very close to unity and it will be negligible; for large angles one can get into serious trouble. The difference or the limitations are hard to ascertain.

    Glenn
    Last edited by Glenn NK; 1st March 2012 at 01:04 AM.

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    Quote Originally Posted by Glenn NK View Post
    The technique works just fine if the distance focused at is very close to the recomposed focus distance, particularly at wide apertures.
    Wide apertures?

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    Re: Focus & Re-Compose - not good idea?

    This comes up periodically. To my mind, it is much ado about nothing for most of us. If you've reached a level of craftsmanship where the thing that needs to be improved in your photography is detemined by this rotation, you've far surpassed anything I've ever achieved. And, for most cameras (including my D5000), the center focal point is vastly superior to the others (cross type versus a simple line) while most lenses are sharper in the center than on the periphera. Throw that into the mix, and this effect becomes even more of a yawn. Or so ISTM.

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    Re: Focus & Re-Compose - not good idea?

    Photography students are a lot like music students, those who could not play always blamed the instrument. A 2" dof will give you funny ears. So the solution stays the same as when I started many years ago. Back-up and stop-down. My p&s has tracking focus, set on the eyes and move to where ever you want. The new systems are great.
    Tim

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by Tim Bond View Post
    Photography students are a lot like music students, those who could not play always blamed the instrument. A 2" dof will give you funny ears. So the solution stays the same as when I started many years ago. Back-up and stop-down. My p&s has tracking focus, set on the eyes and move to where ever you want. The new systems are great.
    Tim
    I rather think you are missing the point of the post. There will be those around this forum who will be reading that information for the first time and may find it useful. It might also be thought provoking and interesting for some "old hands" too. I don't think that any part of the post or the article it links to suggests that anyone is blaming the equipment for self failure. Not sure why you felt the musical analogy was appropriate really. Oh well.... never mind!

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by Colin Southern View Post
    Wide apertures?
    I'm pretty sure he meant small ones! (or maybe wide lenses?)

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    Re: Focus & Re-Compose - not good idea?

    Am I naive in wondering why this solution ever came into common usage when manual focus is available? I mean is the camera's AF that much superior to manual focus that it is even better to use AF and move the camera rather than use MF?

    I've always had trouble understanding how people have pushed this idea... as Glenn points out, it is simply trigonometry... You change the angle, you change the distance; you change the distance, you change where the focal plane lands... and in all but a very *very* limited set of circumstances, that just isn't going to work the way you want.

    I think when Glenn said about 'wide apertures' he meant that the problem is exacerbated when you have a very narrow DoF. If you move the focal plane and your DoF is already razor thin, the chances of being able to move it from one spot to another are just as thin as the DoF.

    But I digress... and not to hijack a thread, but can someone tell me whether I am wrong to flip to MF when I feel AF isn't picking up on the point I want it to use? Should I get better about moving my AF points around instead?

    - Bill

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    Re: Focus & Re-Compose - not good idea?

    Am I naive in wondering why this solution ever came into common usage when manual focus is available? I mean is the camera's AF that much superior to manual focus that it is even better to use AF and move the camera rather than use MF?

    I've always had trouble understanding how people have pushed this idea... as Glenn points out, it is simply trigonometry... You change the angle, you change the distance; you change the distance, you change where the focal plane lands... and in all but a very *very* limited set of circumstances, that just isn't going to work the way you want.

    I think when Glenn said about 'wide apertures' he meant that the problem is exacerbated when you have a very narrow DoF. If you move the focal plane and your DoF is already razor thin, the chances of being able to move it from one spot to another are just as thin as the DoF.

    But I digress... and not to hijack a thread, but can someone tell me whether I am wrong to flip to MF when I feel AF isn't picking up on the point I want it to use? Should I get better about moving my AF points around instead?

    - Bill

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by ktuli View Post
    Am I naive in wondering why this solution ever came into common usage when manual focus is available? I mean is the camera's AF that much superior to manual focus that it is even better to use AF and move the camera rather than use MF?

    I've always had trouble understanding how people have pushed this idea... as Glenn points out, it is simply trigonometry... You change the angle, you change the distance; you change the distance, you change where the focal plane lands... and in all but a very *very* limited set of circumstances, that just isn't going to work the way you want.

    I think when Glenn said about 'wide apertures' he meant that the problem is exacerbated when you have a very narrow DoF. If you move the focal plane and your DoF is already razor thin, the chances of being able to move it from one spot to another are just as thin as the DoF.

    But I digress... and not to hijack a thread, but can someone tell me whether I am wrong to flip to MF when I feel AF isn't picking up on the point I want it to use? Should I get better about moving my AF points around instead?

    - Bill
    Hi Bill,
    I agree with you about manual focus. I revert to it quite often and sometimes just use AF to get me close to the plane of focus and then gently tweak the ring until I think it's at its best.

    However I think it's generally true to say that AF has made many photographers a bit lazy. It's all too easy to press the button and watch the world snap into sharpness. One other thing that makes manual focusing less attractive (at least for me) is that modern DSLRs don't have those lovely focusing aids we had on our film SLRs, such as the Fresnel ring and the split-screen circle. Without those, along with my increasing years, I'm not able to determine true focus nearly as well as I once could. Therefore I too am often guilty of that laziness that I mentioned above. These are just thoughts and ramblings of course... but in essence I agree with what you say.

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    Re: Focus & Re-Compose - not good idea?

    Marty, I too believe that many photographers I talk to from the digital age don't understand the basics well enough to easily drop into that "full manual mode" when they need to. Auto settings have bypassed the need in many people. Prior to digital for advanced photography you had to learn the basics before you could even take a photo so there was a real need to pay attention to details. No looking at a screen to see how you did and make adjustments on the spot. Now, you start out in auto taking fine photos and learn what you have to as you go along. Some never even get to manual. Not that that's a bad thing but they sure can't manage an unfamiliar situation.

    By the way, here's a couple of links for you to look at.

    http://www.katzeyeoptics.com/
    http://www.linkdelight.com/View-all-...d=focus+screen
    Last edited by Andrew1; 29th February 2012 at 03:18 PM.

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    Re: Focus & Re-Compose - not good idea?

    Hi Andrew,
    Thanks for the reply and also for those links. I see there's a major price difference between the two outlets! I was at the point of ordering a Katzeye screen for my D300 about 2 years back and then a friend de-stablised my thought process by saying that if it had no down-sides, then Nikon would have already have built it into the camera. I then read various threads about how these screens can confuse AF etc etc... Then there were people who were saying that the installation of the screen was difficult and that they damaged their screens doing so etc, etc...

    I'd still like to know more. do you happen to have one of these screens? I'd love to hear from somone who has really tried it and has used it. I could still be readily persuaded to go this route.

    BTW, I concur 100% with your sentiment about learning the basics and attention to detail. Sadly, automation has buried many of the basics to many photographers!

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by ktuli View Post
    Am I naive in wondering why this solution ever came into common usage when manual focus is available? I mean is the camera's AF that much superior to manual focus that it is even better to use AF and move the camera rather than use MF?
    I learned on a 4x5 Crown Graphic, which has ground glass that allows you to see a very good sized image, and the focus adjustment was excellent for manual adjustment. The lens quality (if not the brightness of the glass) was superb. However, the sharpness of focus that one could routinely obtain was not comparable to the routine sharpness of your average P&S IME. We have a tendency to romanticize the "good old days," especially if we were never subjected to them.

    Now, lenses are manufactured for AF. The "throw" on a typical lens today is very slight, and opitmized for computer control. You just can't get the same "feel" with a lens designed to move very little to achieve focus -- but, in auto, it will focus very quickly, and under computer control, spectacularly accurately.

    The camera itself is not intended to be used for manual focus. Not only was the Crown Graphic intended for manual focus, but so was my first Voigtlander VITO CLR 35mm. It had a split focus with a rocker control that made manual focusing quick (by the day's standards) and accurate (again, by the standard of the day.) If you really think those cameras were so usable, I would be quite happy to sell them to you. Compared to modern equipment, they were incredibly limited.

    Manual focus on a modern digital camera is a complete PITA and generally not nearly as accurate as the AF system. Throw in the desire to focus quickly, so you can focus on thngs more lively than a bowl of fruit, and the notion that manual focus is desirable just seems weird. Literally the only time I find manual focus either necessary or desirable is when shooting macro photography, where the AF focus region is just too big to be sure where it will focus, or to allow you to select the subregion you really want. And, when I shoot macro, the tediousness of getting the camera to focus reminds me of how much I am glad to no longer be stuck in the good old days...

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by ktuli View Post
    is the camera's AF that much superior to manual focus that it is even better to use AF and move the camera rather than use MF?
    That's the easiest question I've answered since I joined here. Yes.

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by Colin Southern View Post
    That's the easiest question I've answered since I joined here. Yes.
    So by that statement, the best focusing results will be achieved by (in order):

    1. Selecting the appropriate focus point and AF
    2. AF and recompose
    3. MF

    Is that correct?

    - Bill

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by ktuli View Post
    So by that statement, the best focusing results will be achieved by (in order):

    1. Selecting the appropriate focus point and AF
    2. AF and recompose
    3. MF

    Is that correct?




    - Bill

    Bill , the way i see it, modern lenses arn't designed to be manual focused. They go from 0 to infinity in less than a quarter of a turn. If you move the ring a 1/8 of an inch, you've changed the focus several feet. (focus motors are very precise and consistant) Now if you had a lens that was designed for manual focus, that would be a different story, but it's been my experience that autofocus is much more accurate than manual.

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    Re: Focus & Re-Compose - not good idea?

    Quote Originally Posted by ktuli View Post
    So by that statement, the best focusing results will be achieved by (in order):

    1. Selecting the appropriate focus point and AF
    2. AF and recompose
    3. MF

    Is that correct?

    - Bill
    Hi Bill,

    I'm not saying Manual focus can't or shouldn't ever be used, but (a) I've yet to see it focus more accurately the AF (assuming not an extreme situation where AF can't lock on) but the main reason is (b) speed - I just can't imagine for example trying to manually focus a lens for a 600 frame studio shoot - or with a moving target. In my mind it's a bit like buying a car and then pushing it instead of driving it. Personally, I like to use the automation - as I see it it's my assistant, not my master.

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    Re: Focus & Re-Compose - not good idea?

    Colin,

    Don't get me wrong - I'm not arguing with you at all. I'm just trying to make sure I understand. I want to make sure I'm learning the techniques that will help me get better photos. If learning how to quickly move my AF points around will produce better results than MF, then I will put energy into that. I was just under the assumption that MF would get me the same results.

    In my case, a lot of my work is done with macro - how does that change things (if at all)?

    Thanks for the info. I'll definitely be trying my own experiments with this in the near future to see how my results go.

    - Bill

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