# Focus/Recompose Rule Of Thumb



## amolitor (Oct 13, 2013)

At some point pretty early you'll learn to use single point focus, to do that, and then to recompose the picture after you've locked focus. This works fine, a lot of the time. Geometry tells us that whatever you focused on isn't _quite_ the same distance away after you recompose, though. So your focus isn't _quite_ perfect when you recompose. The more radically you move the camera to recompose, the worse it gets. How can you tell how much you can get away with?

First you need to know, or remember, that your f-stop determines how much depth of field you have which is, roughly, how wrong your focus can be before it starts to look all unsharp and bad. You can look up more about Depth of Field elsewhere. What you need to know here is that the bigger your f-number, the more you can get away with.

Second, hold your hand out at arm's length, and see how wide your thumb appears to you. It should be about 2 degrees unless you're somewhat non-standard. That doesn't matter. Yes, this rule of thumb uses actual thumbs!

Here's the rule: You can recompose by one thumb-width per f-number. At f/2.0 you can move the camera's view from one side of your thumb to the other. Here's an example:

Let's say you focus on the model's eyes. Then you recompose so that same focus point has moved to the middle of her chest. Hold your thumb out at arm's length and estimate how many thumbwidths would cover the distance from her eyes to her mid-chest. Let's say it's 5 thumb widths. Then you better be "stopped down" to about f/5.6 or so.

CAVEATS AND WARNINGS:

- this rule falls apart for closer distances, under about 6 feet, or with lenses longer than about 100mm. It is useless for macro work.
- with closer distances and longer lenses, be more conservative
- with longer distances and wider lenses (say 50mm lens at 30 feet) this rule is pretty generous you can push it a fair bit
- don't use it for more than about 8 thumbs, that's a lotta recomposing there, find a better way to focus on what you want
- if you have multiple focus points, use the closest one to minimize the amount you have to recompose
- it's always possible i have botched the math, so, use with caution


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## cgipson1 (Oct 13, 2013)

amolitor said:


> - it's always possible i have botched the math, so, use with caution



LOL!


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## Designer (Oct 13, 2013)

amolitor said:


> - it's always possible i have botched the math, so, use with caution



!


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## table1349 (Oct 13, 2013)

I have always applied the K.I.S.S. principal with focusing.  Use the single focus point that lands on the area of the subject you most want in focus.  Especially when shooting portraits.


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## amolitor (Oct 13, 2013)

I am of course pretty confident that I have the math right. Presumably someone will check my work shortly, and then you can all be that much more confident.


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## table1349 (Oct 13, 2013)

Why Focus-Recompose Sucks

The Problem With The Focus-Recompose Method - Digital Photography School

For Sharp Photos, Should You Be Using the Focus-Recompose Method? at PhotoWhoa Blog | Discover how you can be a better photographer


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## cgipson1 (Oct 13, 2013)

With modern DSLR's and movable focus points... I think that people should seldom if even, have to focus / recompose. It can be done successfully, if you know your gear, and have a basic understanding of DOF. I usually recommend that those with little experience DON"T focus and recompose, because I have seen too many shots that were OOF from doing it.

If you can't find a composition where you can use the focus point adjustment.. then you need to recompose, and then Focus... (except in rare cases)


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## cgipson1 (Oct 13, 2013)

gryphonslair99 said:


> Why Focus-Recompose Sucks
> 
> The Problem With The Focus-Recompose Method - Digital Photography School
> 
> For Sharp Photos, Should You Be Using the Focus-Recompose Method? at PhotoWhoa Blog | Discover how you can be a better photographer



Exactly!


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## Derrel (Oct 13, 2013)

One of the strengths of the pro Nikon bodies that I like is that they can focus extremely well using the off-center AF points, so I use the giant, oversized multi-controller on the back of the camera to move the AF point to the spot I want to focus on. I never use focus and recompose, since the equipment itself is so good these days that there's no need to do it.

If the camera can use a small group focus, like 9 out of the 51 AF points in a tight cluster, it makes it easy to select a "top" group [camera is being held vertically, naturally], and that allows the camera to track a person as they do an activity, so that sequences can be shot, and the camera keeps continually focusing as the subject moves and goes about his or her activity. In social photography situations, this allows the photographer to use the camera in a very fluid way, focusing on-the-go, as opposed to stop-let me focus-okay-I'll-shoot-a-sngle-frame-now. Using a multi-point AF cluster also allows active, moving subjects to be photographed on the go, like people walking or running, kids engaged in play, and so on. Focus and recompose is mostly for static subjects, and is pretty much useless on subjects that are moving.

Different cameras have different specific focus system controls and focusing protocols. Newer cameras have the AF-A option, whereas old models do not.


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## hopdaddy (Oct 13, 2013)

Why would anyone want " how wrong your focus can be before it starts to look all unsharp and bad."? I thought one would want the best possible sharpness ? NO?


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## amolitor (Oct 13, 2013)

hopdaddy said:


> Why would anyone want " how wrong your focus can be before it starts to look all unsharp and bad."? I thought one would want the best possible sharpness ? NO?



Photography, like so much else in life, is a series of compromises. Lots of people recompose and focus, and now anyone who cares has the tools to quantify how much recomposition is acceptable when, where 'acceptable' uses pretty universally defined standards of acceptable sharpness from DoF tables. The same DoF tables the naysayers in this very thread are rather fond of chirping about, when they're not busy mumbling 'oh, it's Molitor, quick, I need to get my penis out and piss on him, because that's a thing I just have to do'


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## Josh66 (Oct 13, 2013)

amolitor said:


> I am of course pretty confident that I have the math right. Presumably someone will check my work shortly, and then you can all be that much more confident.


My right thumb is 1 inch wide (wow - didn't think it would be that big!), at arms length, it is 27.5 inches from my eye.

You said it should be about 2°...  At 27.5", 2° would cover 0.95975" of my field of view - that's pretty much dead on.

I was bored.  

But, hey!  At least now I have a handy way of measuring angles!  My thumb at arms length covers 2°, almost exactly.


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## Josh66 (Oct 13, 2013)

Derrel said:


> One of the strengths of the pro Nikon bodies that I like is that they can focus extremely well using the off-center AF points, so I use the giant, oversized multi-controller on the back of the camera to move the AF point to the spot I want to focus on. I never use focus and recompose, since the equipment itself is so good these days that there's no need to do it.



I always select the closest focus point to where I actually want to focus, to keep the recomposition to minimal levels.  None of my cameras have a ton of focus points though, so there is almost always going to be 'some' recomposition.  Even on a camera with only 3 focus points though, one of them is almost always surprisingly close to the spot I want to focus on.

With rangefinders though, I think I'm stuck with focus/recompose.  Unless I break out a tape measure...


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## usayit (Oct 13, 2013)

I shoot with a 50mm f/1 on FF on many occasions.  Its a real concern but not as bad as most would expect.  Do the math to give you an idea....







For the most part, I simply lean back during recomposition.  Takes a bit of practice but its not that bad and its true to KISS.  Once you start shooting at smaller apertures f/2.8 and on, its really not that much of a concern IMO.  Other's have told me they dial in a little front focus by "feel"... didn't work well for me but I'm sure it depends on the person.

Here's one of my test shots during practice as my way of getting a feel for the lens:


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## amolitor (Oct 13, 2013)

If you stick to a single thumb-width, the change in target distance is something like 6/100ths of a percent, which is probably a lot less than the focusing error of whatever system you're using.

The trouble with "leaning back" is that the amount you have to lean back depends on the target distance. On the other hand, at greater target distances it matters less. I expect you can get used to it, and kind of feel the right amount, especially if you have a good viewfinder.


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## Derrel (Oct 13, 2013)

Derrel on one side, A. Molitor on the other side.


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## amolitor (Oct 13, 2013)

But how many thumbs apart are we, man? I feel like.. I feel like we're growing apart. I feel a dozen thumbs away, man


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## usayit (Oct 13, 2013)

amolitor said:


> If you stick to a single thumb-width, the change in target distance is something like 6/100ths of a percent, which is probably a lot less than the focusing error of whatever system you're using.
> 
> The trouble with "leaning back" is that the amount you have to lean back depends on the target distance. On the other hand, at greater target distances it matters less. I expect you can get used to it, and kind of feel the right amount, especially if you have a good viewfinder.



* As the subject distance increases, it matters less.  DOF increases.
* As the focal length increases, angle (t) becomes significantly less.   Focus Error "E" decreases.
* As the focal length decreases, DOF also increases.
* As you stop down, it matters less very quickly.  DOF increases quickly.

My point is, other than at very fast apertures at close focus distances with normal focal lengths, recomposition error becomes almost a non issue when calculated against DOF and FOV calculators.  In most cases, the recomposition error falls within the DOF.

DOF calculator:
Online Depth of Field Calculator

FOV calculator:
Field of View Calculator - Rectilinear and Fisheye lenses - Bob Atkins Photography

I practiced with a 50mm f/1 at the lens's 1 meter close focus range which covers the worst case scenario.  Once subject distance is about 8-10 feet away, the error falls within DOF.  Do the calculations and see for yourself.  Don't forget that most spreadsheets assume angles are in randians not degrees.  

Again... this is just my experience based on calculations and practice with the 50mm f/1 with putting things into perspective.   My conclusion was that I was obsessing over a perceived larger margin of error that really didn't exist.  If the "thumb" method works better.. all the more power to you.


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## Joves (Oct 21, 2013)

I am in the F&R sucks crowd. I had to do it for too many years when all you had was the prism in the middle days. Now I only do it when I am using a manual focus lens, but I use the moving focus point to confirm I am still where I want to be with the Green Dot method. Got to love the technology.


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## StandingBear1983 (Nov 25, 2013)

I would gladly give up F&R...but i have a D5100 so its a bit tricky to count on the relatively small viewfinder and 11 focus points to nail exact focus...and i like the best to shoot portraits at 1.8 so its quite hard to nail focus. also the center focus point has vertical and horizontal focus which the other focus points around it don't have (or something groovy like that, from what i understood).

The bigger the viewfinder and the more  focus points you have to be able not to recompose and choose which focus point to pick does all the difference. also i have glasses so its hard for me sometimes to view exact focus (and yes i adjusted the diopter), i guess personally i have a reason to buy a better body now...


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## kchoi (Nov 29, 2013)

I think this is too complicated for me.
What I do is to put the focus point on where I'd like to focus. I normally do not care about if it is cross type of what. They just work fine in most cases.
If the focus point cannot reach the place where I want to focus, I will step back a little bit and put the subject on the focus point. Then go home and crop.


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## o hey tyler (Nov 29, 2013)

For everyone that's under the impression that focus and recompose doesn't work is apparently doing it wrong. I've used it for the past five years and have had zero issues.


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## robbins.photo (Nov 29, 2013)

O|||||||O said:


> amolitor said:
> 
> 
> > I am of course pretty confident that I have the math right. Presumably someone will check my work shortly, and then you can all be that much more confident.
> ...



My rule of thumb is, stop putting it in front of the lens.  It's distracting and I've got enough photos of my thumb already.  Other than that I use the focus points on the camera and just pick the one that I need.  Haven't done a lot of high end math or division, no in depth research on the topic.  Just noticed my camera had the feature and figured, oh, that's what that does.  So far so good.


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## amolitor (Nov 29, 2013)

I am fascinated by these systems that apparently have a focus point every place you'd want to focus. Maybe it's just me, but while mine always has a focus point that is "pretty close" it's almost never exactly on it.


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## usayit (Nov 29, 2013)

o hey tyler said:


> For everyone that's under the impression that focus and recompose doesn't work is apparently doing it wrong. I've used it for the past five years and have had zero issues.



Yup!  This is exactly my impression.  I simply did the math to see how much "error" is involved.   I then realized people are getting all worked up over a relatively small error within a small corner case situation.



kchoi said:


> I think this is too complicated for me.
> What I do is to put the focus point on where I'd like to focus. I normally do not care about if it is cross type of what. They just work fine in most cases.
> If the focus point cannot reach the place where I want to focus, I will step back a little bit and put the subject on the focus point. Then go home and crop.



Yup&#8230; whatever works for you.   Modern cameras are great that the focus can be assigned.  I personally found that futzing with the focus points can slow me down at times but my most recent camera is neat that it has a touch screen.  I can simply touch where I want the point to be.  So quick and no more multiple button pushes.


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## Blasthoff (Dec 29, 2013)

Just think, back in the "old days" street and press photographers all used a moderate wide angle, stopped the lens down, set the hyperfocal to that f-stop distance scale and just shot everything beyond the minimum distance or within wide zones without having to think or fuss, that WAS focusing. Just point and shoot and it never failed. I remember trying to teach that to newbe's back in the day of manual focus slr's, I'd make it easy using a wider 28mm at f11 where everything just beyond arms length would be in focus, Invariably, they just couldn't ignore the focus screen and just had to fidget with the focus ring. My point being, it helps to gain a "sense" of what the depth of field zone is in any particular situation as to gauge how much latitude there is to work with.


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## Rick58 (Dec 29, 2013)

Yep, Simpler times for sure!


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## FocusTester (Dec 30, 2013)

If in doubt (or close to wide open), put the subject on a focus point and crop later. It doesn't even have to be a rectangular crop, if you are using a decent image editor. Why are people so afraid to crop? Focus and recompose is fine if the two points are really really close. Otherwise, just focus and don't recompose, crop! Your other option is to position yourself in such a way that after you recompose, the new point of focus is the same distance from you as the original point of focus. People often forget that this option exists.

Remember, simple geometric distortion can easily be corrected after the fact. Framing can be corrected after the fact. Blurry pictures because you focused and recomposed at f/1.4, not so much.


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## nickzou (Dec 30, 2013)

I've never had a problem with focus recompose as long as I remembered that rotating the camera is what changes the distance between lens and the target of focus. Strafing side to side and up and down has worked fine for me. It's why there's always a level somewhere on my camera. It's like your dads have never made you memorize trig tables when you were 11 or something.


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## imagemaker46 (Dec 31, 2013)

I've just focused and shot without thinking any further than that. As my Dad has always said "it's just point and click"  It's that simple.


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## Rosshole (Jan 2, 2014)

gryphonslair99 said:


> Why Focus-Recompose Sucks
> 
> The Problem With The Focus-Recompose Method - Digital Photography School
> 
> For Sharp Photos, Should You Be Using the Focus-Recompose Method? at PhotoWhoa Blog | Discover how you can be a better photographer



I am confused... do people actually focus, lock, walk around, and then shoot?

because the links supplied show straight lines for the focus point... that can't be right. Once you set the focus @ 6' from the lens, no matter what direction you point the camera, 6' from the lens will always be in focus. I will almost always pick my focus point (like the eyes), focus on that, then do a slight recompose, and shoot. how is this wrong?

so modern cameras broke physics?


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## Josh66 (Jan 2, 2014)

Rosshole said:


> gryphonslair99 said:
> 
> 
> > Why Focus-Recompose Sucks
> ...


Did you even read the links?


---

First of all, the distance is measured from the film/sensor plane, not the lens.  And it's a plane, not a sphere, so "everything 6' away" will NOT be in focus.  This is all covered in those links...


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## Rosshole (Jan 2, 2014)

Josh66 said:


> Did you even read the links?
> 
> 
> ---
> ...



Yes, I did read the links... and I am confued because I have NEVER experienced this in any practical application...

It must be because I don't take portraits of people looking up at them...  I shoot from eye level to my subject...


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## Josh66 (Jan 2, 2014)

Rosshole said:


> Josh66 said:
> 
> 
> > Did you even read the links?
> ...


I think it will really only be an issue at larger apertures, like f/2.8 and larger.  The larger the aperture, and the closer you are, the more noticeable it is.  It would also be more noticeable in larger formats, so it would be harder to see on a crop sensor than full frame.

At, say, headshot distances around f/2, it's enough to notice.


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## table1349 (Jan 2, 2014)

It is basic Geometry 101.  Straight lines do not equate to equal distance.  Thin DOF leaves little or no room for error.


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## Derrel (Jan 2, 2014)

gryphonslair99 said:


> It is basic Geometry 101.  Straight lines do not equate to equal distance.  Thin DOF leaves little or no room for error.



A few keys in gryponslair99's brief post. "Geometry". "thin DOF". "Little or no" room for error.

Working backward, let's say we are close to our subject; that means the depth of field is MUCH more-limited than if we were say, five to 20 meters distant.

Let's say we have a 100mm lens, and the aperture value is f/3.2, for super-sharp optical performance and also for wonderfully soft background blurring.

The depth of field from *1)* close-range and * 2) *long focal length lens and *3)* wide aperture means that there is little to no room for error in placement of the focus.

Focus and recompose does not work very well in situations like that. But even #2 is not without a caveat; if you're at 10 feet and using a SHORT focal length lens, the edges of the frame are VERY MUCH FARTHER away than the center of the frame!!! it's actually very easy to envision the geometry...the wide-angle lens's field of view is wide, so you have a very much longer *diagonally-oriented line of sight* out to the edges of the frame. At f/stops where the DOF is shallow, the margin of error EXCEEDS the depth of field...and blows the shot...

A telephoto lens, since it has a narrower angle of view, is actually an EASIER tool to use focus and recompose on than is say, a 35mm f/1.4 lens, buuuut....when the magnification is very high, even slight focusing errors become apparent at wider f/stops.

Where the problems start to creep in in my experience are when using fast lenses, like 50/1.4 or 85mm f/1.4, at close ranges, at wide apertures...there's just soooooo little room for error when the actual DOF band is like 1.5 to 2 inches deep...either you hit focus, or you miss it. For that reason, I usually prefer to shoot stopped down somewhat, to cover my proverbial ass. You see, the real world also has issues like focusing accuracy, subject movement, and so on. There's often a _compounding of issues principle_ at work in real shooting scenarios...I often want to give myself a little of what I call "DOF cushion", so I can come back with usable shots, not excuses. There are situations where focus and recompose will work, sure. LOTS of them! And there are also situations in which it will ***k you up.


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