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Thread: A simple tip for improving focus sharpness

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    A simple tip for improving focus sharpness

    About a year ago I attended one of the Leica M9 roadshow workshops and there were a few good tips shared. One of the tips in particular has helped me increase the number of sharp, in focus shots I take, which is always something we're striving to do with rangefinders.


    For this tip, think about depth of field and where your focus point lies within the in focus portion of your shot. As you can see in the diagram below, in front of your focus point, you only have 1/3 of your depth of field, whereas behind your focus point you have 2/3 of your depth of field. This is probably old news to many of you, but even after many years of a photography hobby, somehow I had never understood this concept.





    So here's where the tip comes....

    When focusing, you can approach your focus point from either direction; from the minimum focus distance, or from infinity. Go pull out your M camera and look at the top of the lens with the depth of field markers. You can either rotate it clockwise or counterclockwise to arrive at the point where your subject is in focus.

    Now, think about the diagram above. The trick is to always approach the point of focus from the rear, or from infinity, because you're more likely to have the portion of your subject in focus that you desire. If you're a little off, it's probably ok because you've got twice as much depth of field on that side of your focus point.

    Give it a try, and feel free to discuss this one. I'm open to hearing if any of you have similar tricks or a variation of this tip to share. Overall I've found that if I approach the focus from infinity rather than hunting back and forth for focus, I have a better chance of of a sharp in-focus subject. Obviously this is critical when shooting the lovely Leica glass wide open!

    Diagram credit and more about depth of field:
    http://www.dumetier.com/photography/depth.html

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    Re: A simple tip for improving focus sharpness

    To add to this, I've gotten in the habit of always throwing my lens focus to infinity after I'm done with a shot, or when setting it down. This way, when I go to pick up the camera or bring it to my eye, it's already in position. Then it's just extend finger, pull focus tab until subject is in focus, and click! This also helps eliminate much of the "hunting" for focus.

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    Re: A simple tip for improving focus sharpness

    OK, as for your first post, the 1/3 - 2/3 rule is approximately true for far enough distances, and can be useful to know. As for its application to RF focussing, I´m a bit doubtful. In fact, if the DOF is measured instead in terms of lens displacement (same as rotation angle of the focussing ring), it is perfectly symmetrical, as can indeed be seen from the DOF markers you mention; they´re all symmetrically placed around the index mark. So the demand on focussing in terms of turning the ring is just as ´tight´ from the infinity end as from the close end.

    As for your second post, I agree wholeheartedly; it makes life far easier, and most old Leica shooters have this habit since years. And that´s quite enough to make it a good tip....

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    Re: A simple tip for improving focus sharpness

    Per, you're certainly correct about the lens displacement distance going from either direction. Physically turning the lens from either directions gives no advantage.

    But I believe the advantage is achieved because of the human error we can all make when we *think* an object is in focus, but isn't quite. If I've erred by focusing slightly behind the subject, wouldn't this be more desirable than erring in front of the subject, because there's twice as much wiggle behind than in front?

    I'm still learning a lot about they physics of photography, so by all means educate me where I'm wrong.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by dannh View Post
    ... But I believe the advantage is achieved because of the human error we can all make when we *think* an object is in focus, but isn't quite. If I've erred by focusing slightly behind the subject, wouldn't this be more desirable than erring in front of the subject, because there's twice as much wiggle behind than in front? ...
    It doesn't really make any difference. If you want a particular plane of focus to be sharply focused, it is what needs to be in focus. The same amount of distance in front of and to the rear of that plane will be in focus no matter which way you approach it.

    If you are looking for which error in focus plane ("too close" or "too far") might be more tolerable, that will change depending upon what the scene you're shooting contains. For example, if there is a lot of significant detail behind the subject plane and you focus a little farther away than you ought, that detail will be better focused at the expense of the subject ... whether this is more or less distracting is up to the particular scene. Similarly, if there is significant detail in front of the subject which is out of focus, that might be more or less distracting depending on what's important in the scene.

    The important thing to realize is that whatever the focus zone might be, the sharpest plane of focus in that 'acceptably sharp' focus zone is approximately 1/3 of the way in from the near edge.*

    With that fact in mind, look carefully at your scenes and subjects to understand where, for a given scene, the best placement of the focus plane might be. Then use whatever means to achieve that works best for you.

    * a note on hyperfocal focusing: The hyperfocal distance setting is that point, for a given format, focal length and lens opening, for which the far edge of the acceptably sharp focus zone first reaches infinity. A lot of people seem to misconstrue this as saying that "everything from the near distance to infinity is sharp" where "sharp" implied "equally sharp". That's not true: If you're focused at the hyperfocal setting, THAT is the sharpest plane of focus, and things in the scene which lie at that distance are sharper than things further away or nearer. So when you're shooting landscape photos, you don't necessarily always want to use the hyperfocal setting if you're trying to get ultra sharp detailing of the trees in the distance. In this case, you'd be better off losing a bit of sharpness in the near field so that tree branches and such are better defined in the distance.

    Resetting the lens to infinity (or close to it) is one good habit, at least at the beginning, if you're typically shooting a relatively distant subject and want the camera to be as ready as possible for the next shot. I take this another step: when I'm out shooting and using manual focus, after I work on a particular subject, I always re-set the focus to be where I expect the next shot might be. The goal is always to have the camera ready ... re-set focus as close to the right point that you can make a quick capture without having to work to move the focus to the right point.

    When I'm walking and looking about, I'm constantly calibrating what focus zone and primary subject distance I think might pop up at any moment, so I don't set the camera to infinity, I set it to the right focus distance for the expected subject I am looking to capture.
    Last edited by Godfrey; 19th March 2011 at 15:52.

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    Re: A simple tip for improving focus sharpness

    Godfrey, you've helped clear up a few misunderstandings on my part, thank you. I enjoyed your website as well. I always enjoy learning from someone with many many more hours experience than I.

    I guess one of my struggles is that I always want to oversimplify photography. I look for simple rules and tips that I can apply during that small window of time when I'm about to take a shot, where time speeds way up because I don't want to miss that critical moment. I'm learning that instead of oversimplifying things with rules, the better approach is to spend a lot of time practicing and learning, as well as taking the time before the shot even presents itself to prepare myself and my gear.

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    Re: A simple tip for improving focus sharpness

    One important thing to remember is that in reality no one factor really makes or breaks a photograph being sharp or unsharp, rather it is a combination of factors. One might have a lens that slightly backfocuses and by taking that 1/3-2/3 principle into account more shots of acceptable critical focus could be achieved, but then on the other hand, a front focusing lens might end up with a very low keeper ratio because if your focusing slightly past your subject on purpose, with a lens that front focuses your then at or even out of the DOF for acceptable focus.

    On top of that sometimes the slightest lean in our out can also throw your focus off a bit. I know that as a habit, I find myself leaning back a little when I view the full viewfinder image after focusing on the center patch. Just a habit I do as I slightly recompose but with a fast lens, that 1" lean can sometimes be enough to shift my focus from eye to tip of nose.

    As such, I think the only good "rule" is that there are no rules and to each his own. Everyone is going to have some lens or a RF that is going to differ from another shooters, and also our own body mechanics and habits.

    In the end one really just needs to learn their camera and given focal lengths for a given subject distance and learn, for example, that if you've shooting a subject at 6 feet with your Zeiss 50 f1.5 at f.5 but which is calibrated for f2.8 where to focus.

    Nothing wrong with theory of course but there are just so many variables that trying to use any one size fits all rules of thumb that some lens/distances are going to be hindered as much as others are helped.

    But all and all, thats a little bit of the fun of RF photography. Its not an exact science nor a 100% assurance that all you have to do is press a button and get a perfectly exposed, perfectly focused photo. I've got cameras that darn near come close to giving me that and they are great for paid work but don't give me near the same satisfaction of getting a perfectly focused and exposed photo where I feel I can take the credit rather than the camera

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    Re: A simple tip for improving focus sharpness

    I've been using the "Back To Infinity" technique for 40 years ... a photojournalist taught me to do that for faster focusing in spontaneous street conditions. It served me well when I started shooting weddings with a M. It is a speed technique as much as anything, but can help with accuracy also ... like with the 50/0.95 and 75 Lux.

    Sorry, but I do not understand the statement: "... as can be seen by the DOF markers, they're all symmetrically placed around the index mark." Really? While the numbers are placed symmetrically, the actual indicators grow narrower and narrower as they approach the index mark don't they?

    1/3 to 2/3 DOF is only an approx. indicator, and an average rule of thumb mostly for average distance focusing: using a M35mm lens set to f/11 and critically focused at 8', the DOF distance covers from 5' to 30' ... so, approx. 25' total is in reasonable focus with 8' falling roughly 1/3 into that total plane of focus (25' X.33 =8.2'). Same lens set closer to 3.2' critical focus: f/11 provides DOF distance from 2.5' to 4', or 1.5' total plane of reasonable focus with 3.2' falling roughly 1/2 into that plane of focus ( 3.2' X.50 = 1.6'). So a more reasonable rough rule of thumb for DOF is 1/3 into a scene when at distance, and 1/2 in when closer.

    The following depends on how one tends to shoot ... consistently closer up, or at more normal distances:

    ... Using "infinity reset" as a speed technique can be attributed to the fact that greater distances can be covered with less focus throw from infinity. The amount of focus adjustment to go from infinity to 6' with a M35mm lens is less than from 2.5' to 6' ... and involves a more natural hand action (presupposing one holds the lens cradled in the left hand and uses the forefinger/thumb to drive the focus adjustment) ... the forefinger is already in position to do this from infinity, and is not in position if driving the focus preset to the closest focus distance.

    Presetting to an approximate distance is fine when there is time and things aren't in spontaneous flux ... where it can then lead to hunting. Resetting to infinity after a series of shots develops a natural muscle memory action of always moving in one direction.

    My 2˘

    -Marc

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    Re: A simple tip for improving focus sharpness

    The other easy tip to focus faster was taught to me by Guy and Jack. It works on all lenses with a focus tab. Having that tab at the bottom will always be at the same focus distance. I forget exactly what that distance is and can't check it (no longer have any lenses) but it is a good way to work quickly regardless of focal length.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TEBnewyork View Post
    The other easy tip to focus faster was taught to me by Guy and Jack. It works on all lenses with a focus tab. Having that tab at the bottom will always be at the same focus distance. I forget exactly what that distance is and can't check it (no longer have any lenses) but it is a good way to work quickly regardless of focal length.
    It's about 4' or 5' on the 35/1.4 ASPH ... which is a good distance. It's more on a 50mm.

    -Marc

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by fotografz View Post
    It's about 4' or 5' on the 35/1.4 ASPH ... which is a good distance. It's more on a 50mm.

    -Marc
    It should be the same on all of them

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TEBnewyork View Post
    It should be the same on all of them
    Yeah, You may be right there ... just checked and it's 4.5' on my tabbed 28/2 ASPH. Good info.

    -Marc

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    Re: A simple tip for improving focus sharpness

    My guess is that Per's reference to symmetry probably relates to the placement of indicators on either side of the index mark as they are evenly spaced left and right.
    Being able to accurately gauge close distances without the viewfinder seems key to either technique.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by johnnygoesdigital View Post
    My guess is that Per's reference to symmetry probably relates to the placement of indicators on either side of the index mark as they are evenly spaced left and right.
    Being able to accurately gauge close distances without the viewfinder seems key to either technique.
    Got it, thanks.

    It is the relationship of those evenly spaced indicators on either side of the center, to the uneven distance markers which grow wider apart as you approach the closest focusing distance, that determines DOF.

    -Marc

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    Senior Member Per Ofverbeck's Avatar
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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by johnnygoesdigital View Post
    My guess is that Per's reference to symmetry probably relates to the placement of indicators on either side of the index mark as they are evenly spaced left and right....
    Exactly what I meant....

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    Re: A simple tip for improving focus sharpness

    if you focus from the back and don't quite get there due to error, doesn't that place your object in front, and therefore in the 1/3 range, not the 2/3 range?

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TEBnewyork View Post
    It should be the same on all of them
    Well, I can't speak for all lenses with tabs, but my tabbed 35mm summaron f/2.8 is about 7' when tab is down. My 28 cron shows about 4.5'.
    Scott

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by dannh View Post
    Godfrey, you've helped clear up a few misunderstandings on my part, thank you. I enjoyed your website as well. I always enjoy learning from someone with many many more hours experience than I.
    You're welcome. And thanks for visiting and viewing my website! :-)

    Quote Originally Posted by dannh View Post
    ... I'm learning that instead of oversimplifying things with rules, the better approach is to spend a lot of time practicing and learning, as well as taking the time before the shot even presents itself to prepare myself and my gear.
    That sounds like you're on the right track! When you see well enough, and the muscle memory of what to do in various situations is there, and your equipment is all ready, you'll find that the hectic anxiety of the moment of shooting disappears. At that point the camera disappears and your attention is on the scene, you can calmly make decisions without conscious thought.

    It's a great place to get to.

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    Re: A simple tip for improving focus sharpness

    On a side note, starting from infinity is also a tip for manual focusing on a SLR as well. Ted Grant had mentioned this years ago in regards to focusing wide angles on Leica SLRs.

    Robert

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    Re: A simple tip for improving focus sharpness

    Very helpful thread, thx everyone. The best recent addition for me was an MS Optical 1.15 which allowed me to dial in a diopter adjustment so I no longer have to wear glasses while shooting. I've probably had a 100% increase in usable shots. Also now focusing from the direction of infinity per above

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    Re: A simple tip for improving focus sharpness

    Sharpness is a bourgeois concept. - Henri Cartier-Bresson

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by Chuck Jones View Post
    Sharpness is a bourgeois concept. - Henri Cartier-Bresson
    Maybe he meant slightly different? I have many photos, that are not in focus, and are great, I like their climate a lot. These are rather situations, when nothing is sharp, we see only contour of people, someting like this.

    But I hate when I try to focus eg. on eye, but got back or front focus. When I used Summarits - I had no problem.

    Since I use Lux'es - I put magnifier 1.4x, but only when used at 1.4 and from close distance (70-100cm).
    If distance is further or aperture is closed slightly - I have hit rate so high, that I can only blame myself.

    PS: me gear was once at Solms for calibration

    PPS: I try to remember unconsciously position of focusing tab as starting point.
    I mean I can set it to close position - before raising camera to the eye.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by Chuck Jones View Post
    Sharpness is a bourgeois concept. - Henri Cartier-Bresson
    I'm curious of the context around this quote. Was he targeting "film peepers" of his day? After recently visiting the Cartier-Bresson exhibit at the SF MOMA, I don't remember a lot of OOF shots, but then again, he was shooting film.

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    Re: A simple tip for improving focus sharpness

    Not to muddy the waters, but I could use some clarification on the business of depth of field with regards to the long-standing notion that it extends 1/3 in front of the focal point and 2/3 beyond it. I recently read an explanation on the site that sells those fancy focus checking devices and the guy who sells them claims that the 1/3-2/3 thing is a myth. That in fact, depth of field is actually spread almost equally before and behind the focal point.

    I have always operated on the assumption that the 1/3-2/3 rule was true. Is it fact or myth?

    Thanks!
    Tim

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by dannh View Post
    I'm curious of the context around this quote. Was he targeting "film peepers" of his day? After recently visiting the Cartier-Bresson exhibit at the SF MOMA, I don't remember a lot of OOF shots, but then again, he was shooting film.
    Don't know whether this is true or not, but it's a starting point:

    http://jimaustin.wordpress.com/2011/...on-vs-reality/

    This quote expands his thoughts on the subject nicely:

    http://vizualpoetry.com/Henri-Cartie...on-quotes.html

    I’m always amused by the idea that certain people have about technique, which translate into an immoderate taste for the sharpness of the image. It is a passion for detail, for perfection, or do they hope to get closer to reality with this trompe I’oeil? They are, by the way, as far away from the real issues as other generations of photographers were when they obscured their subject in soft-focus effects.

    -Henri Cartier-Bresson, on technique.
    "American Photo", September/October 1997, page: 76

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TRSmith View Post
    Not to muddy the waters, but I could use some clarification on the business of depth of field with regards to the long-standing notion that it extends 1/3 in front of the focal point and 2/3 beyond it. I recently read an explanation on the site that sells those fancy focus checking devices and the guy who sells them claims that the 1/3-2/3 thing is a myth. That in fact, depth of field is actually spread almost equally before and behind the focal point.

    I have always operated on the assumption that the 1/3-2/3 rule was true. Is it fact or myth?
    IMO, most of the people chasing autofocus accuracy with those laughable toys are as misguided as the HCB comment I just posted suggests.

    In this case, it's *very* easy to take out your camera and do a little first hand ground truth. I think you'll find that the "one-third front, two-thirds back" rule of thumb is pretty darn accurate most of the time.* The mathematics supports it too. ;-)

    * With the proviso that the set focus distance isn't beyond the hyperfocal for the given lens and aperture. Once you're focusing past the hyperfocal, you can indeed place the focused plane exactly such that DoF extends equally in front of and behind that plane, or you can move the focus plane around to get nearly any proportions of front/back in focus depth you want.

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    Re: A simple tip for improving focus sharpness

    I probably should have said this up front, but I'm not a pixel-peeper. I just think that my images look better when they are in focus. That's the only thing driving my curiosity about focus techniques.

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    Re: A simple tip for improving focus sharpness

    Just go and shoot eg. this:
    http://www.whibalhost.com/lensalign/
    of course you can build quickly something similar by yourself using ruler.

    And you will know the answer. Personally I found some lenses that follow 1/3 - 2/3, some that are closer to 50 - 50.

    But for sure it is myth that ALL have the same split.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by Jerry_R View Post
    Just go and shoot eg. this:
    http://www.whibalhost.com/lensalign/
    of course you can build quickly something similar by yourself using ruler.

    And you will know the answer. Personally I found some lenses that follow 1/3 - 2/3, some that are closer to 50 - 50.

    But for sure it is myth that ALL have the same split.
    The laws of optics and the mathematics of depth of field makes this notion impossible. I invite you to review the DoF equations posted on the DOFMaster site:

    http://www.dofmaster.com/equations.html

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    Re: A simple tip for improving focus sharpness

    So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TRSmith View Post
    So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?
    Terry - us simple folks use practice - knowing (in principle) how to get it in focus is very interesting, but it's not nearly as useful as knowing (in practice) how to get it in focus .. . . . . . . . and in my very humble opinion practice is where it's at.

    . . . and as a little irrelevant aside, I have more than one manual focus lens, and I've learned that whether to come from infinity or close up depends on the circumstances and the lens.

    I think it's a bit like reading books about how to do sex - it certainly can be useful, but practice and experience is probably a better tutor.

    Just this guy you know

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by Godfrey View Post
    makes this notion impossible. I invite you to review the DoF
    I did, I open:
    http://www.dofmaster.com/dofjs.html

    I select M9, 35mm at f/1.4, distance 70 cm. And see split: 49% - 51%.

    I change distance to 600 cm and receive 40% - 60%.

    Is this wrong?

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by Jerry_R View Post
    I did, I open:
    http://www.dofmaster.com/dofjs.html

    I select M9, 35mm at f/1.4, distance 70 cm. And see split: 49% - 51%.

    I change distance to 600 cm and receive 40% - 60%.

    Is this wrong?
    No, what you're seeing is the fact that at short focus distances, the curves are closer to 50-50. That's because the near and far 'acceptable focus' limits are not defined as a linear progression, they're a geometric progression. The same characteristic will be true of ALL lenses as you walk the DoF curves for near and far from close distance to far distance settings.

    The 1/3-2/3 rule of thumb is a first order DoF approximation for use when shooting at normal subject distances, e.g.: 5 to 20 feet and beyond. As you focus closer than that, the lines representing near and far converge to an asymptote.

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    Re: A simple tip for improving focus sharpness

    Quote Originally Posted by TRSmith View Post
    So, for us simple folk, what you're saying is that the notion of 1/3 in front and 2/3 in back is NOT a myth and that when shooting, it's a safe "rule of thumb" with which to work. True?
    Yes, for normal subject distances.
    For close up work, the rules change. :-)

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    Re: A simple tip for improving focus sharpness

    Makes sense. Thanks. Nice to have a long-held belief reinforced with a little math (as long as someone else is doing it).

    Tim

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