Focus recompose of sharp eyes?

Discussion in 'Beginner Questions' started by dylan_park, Jan 14, 2017.

  1. I am quite new to photography and have only just realised that the centre focusing point makes quite a difference when aquiring sharper pictures, which in my circumstance is full body of people, and specifically being sharp on the eyes. Initially i have been shooting in portrait mode, taking the focus point up to the top of the camera so it focuses on the eyes and so i can get the rest of the body in shot to. Not something i could do with the centre point as it wouldn't get the body in shot (more so head and shoulders).
    With focus recompose supposedly the aperture is better at 2.8 and up (i have a 1.4 lense) but how low is to low to have a higher chance of keeping my subject in focus when recomposing? Also if i do have the centre point on the eyes, hold down back button focus so the focus is kept for sharp eyes, and then recompose so i can get the whole body in, should this work ok, or am i doing it wrong? Would appreciate any advice
     
  2. It's not entirely clear whether you're using full back button focus, or using the back button for focus holding only.
    There are three ways to focus and recompose (terminology differs with camera, but principle is the same)
    The first is to use single servo AF and single point focus. This will focus once, and as long as the shutter button is depressed, it will not track or refocus. You can recompose as long as you keep the shutter button halfway down, then fire. You don't need the back button at all for this.
    The second is to use the back button for focus holding. Focus where you want, hold the back button down, and hold it down while you recompose and shoot. This should work either with single servo or continuous servo (tracking) focus. You must keep your finger on the button until you shoot, or (on Nikons at least) you can go to the menu and change the operation of the button so that it toggles - hold on first push, release on second. If there's a chance anyone has been into your menu, double check to be sure that the back button is assigned to AF hold, because there may be options for it not to be.
    The third, and ultimately the easiest once you're used to it, is back button focus. Select BBF (in Nikons, it's a menu option in which you reassign the AE/AF lock button to "AF ON"). Now the shutter button does not operate focus at all. Only the back button does. Focus on what you want, and then let go of the button. AF will cease to operate, and focus will remain set as you set it. As long as you don't change the camera's distance to the subject or move it out of the picture, you can recompose at will and what you focused on first will remain in focus. On most Nikons once the button is released, you're automatically in "release priority," which means the camera will fire whether or not it thinks it's in focus.
    If you use back button focus, it's a good idea to check the menu and make sure that you have assigned AE lock to the shutter button. If you don't there will be no AE lock available at all. Where this occurs in the menu will vary, and may require more than one entry. On some cameras (Nikon D7xxx for example) you may also need two separate entries to fully disable shutter button focusing and send it only the back button.
    As to what aperture works best to get the whole subject in focus and give you the look you want, it will depend not only on aperture but also focal length and distance, so your best bet is to try it out different ways and see what works best for what you're using.
     
  3. I really wouldn't waste much thought and energy about whether to focus or recompose or not.
    For all intent and purpose, it IMO is a discussion/consideration with its roots in the film shooting days, and hardly of any relevance in the present, high megapixel camera. digital age.
    Back in the film days, it was, disregarding the 'artistic' performance of taking the 'perfectly composed' image with just one shot, especially when you shot 35mm on 'high sensitivity' film like Tri-X, indeed of major importance to 'fill' the negative as optimal as possible.
    Simply because a crop would inevitably show a lot of grain (although I personally had no problems with that, and actually loved shooting Trix-X as my first b/w film choice just because of that) compared to low sensitivity film like Panatomix-X, or medium and large format shots
    Also when using manual focus (which was the standard untill the Minolta 7000 in 1985 the first affordable AF SLR; the Nikon F3AF was earlier, but even by the standard of those days very expensive, and with a very limited range of AF lenses) focusing on an area outside of the center was not much of an issue even without eg the splitscreen aid in the A type focusing screen simply by using the rest of the focusing screen (which had a kind of 'matte' surface which still allowed easy focusing, of course in combination with a good eye/hand reflex)
    It however became an issue when using AF camera's, as the early models (I skipped the Nikon f501, started with the F801) only had one, although pretty large' AF point in the center, and lacked the 'matte' area in the rest of the focusing screen.
    Since film was still used that, for the above mentioned reason (grain) was more or less the time when 'focus and recompose' was 'invented'.
    Early DSLR's basically had both the problem of much centered AF points (my 2,7 megapixel D1H only has 5) and, due to the low resolution and lesser 'high ISO'performance (much similar to film the upper limit was ISO 800, much like film, on eg my D2X) , grain.
    However IMO and experience, especially with modern high megapixel DSLR's the whole grain thing is no much of an issue any longer (unless you're a 100% crop pixel peeper), and of course the much wider spread, and higher count AF modules in those camera's a a far cry from e.g. the single and five AF points in the F801 and D1H.
    From a practical, shooting point of view, also keep in mind that 'focus and recompose' also means slowing down your shooting process, in particular when shooting a living/moving subject(even a person standing still/posed is slightly moving all the time so needs refocusing all the time)
    When shooting a.g.landscapes or buildings, using AF IMO is more of a convenience then a necessity, and manual focus would IMO be a 'better' choice
    Imagine you're e.g. trying to shoot a more spontaneous portrait, so rather then force/freeze your 'model' in a static pose, allow them move somewhat, talk, laugh.
    I assume I don't have to mention that, unless you 'freeze' your model in the pose that struck your eye (and inevitably make it forced and unnatural) you will miss the shot if you focus and then have to recompose the shot, as the moment it 'clicked' will, by the time you have focused on the eye and recomposed, have gone away.
    I personally shoot in a very simply way, no matter what subject (portrait, beauty, fashion, catwalk) in particular since I started using high(er) megapixel DSLR's like the D3, DF and D800.
    I frame somewhat too wide, allowing space for cropping afterwards, and focus by basically/mainly always keeping one AF point on the eye/face of the subject/person I'm shooting
    When shooting people/with people as the main subject in a picture I think that's the point an observer looking at the picture is always first drawn to, and there inevitably 'needs' to be the sharpest in the picture.
    Even when a picture is completely out of focus, like e.g. Robert Capa's famous image of Omaha Beach 1944
    http://www.nearbycafe.com/artandphoto/photocritic/wp-content/uploads/2014/07/Capa-detail-CS-frame-9-neg-37-Pfc.-Huston-Riley-Landing-on-Omaha-Beach-Large-file.jpg
    I shoot a lot in portrait mode, but despite all the internet buzz never had issues when using the outer AF points of the camera's I use even when shooting under bad light (I a.o.shoot a fair bit of catwalk)
    Sure, on the DF the outer AF points don't work as good as those of the D3 and D800 under bad light, but as I have a number of camera's to choose from when gearing up for a job (and the DF isn't my first pick for shooting catwalk) that isn't much of an issue for me
    I hardly if ever use the AF-On button, only used it in my surf shooting days for 'prefocusing', to have my camera already focusing/prefocusing on a subject before actually taking the shot, especially when using long glass like my 600mm AF-I with a TC14II (still kept both AF and release on the release button)
    Back then I used it that way to, on one hand avoid the complication of having to concentrate on the action, while at the same time twiddling the AF-On button, and also having to take the shot (which would come if I took away AF activation from the release button),, and on the other hand the delay trying to get things 'in focus' that can come when the AF is coupled with, and acitvated by the release button
    With my D800 I can easily take a three quarter shot, to later, if desired (eg to have some variety in the type of shots) just take a, still high quality, more 'portrait' like crop.
    Admittedly I still shoot as if I shoot film (36 shots per roll) so I don't take hundreds of shots for e.g. a close up, just concentrate on getting a 'click with the model, and trying to capture the mood of the moment with only a few dozen, or sometimes even less, shots
    Sure, not the 'purist' way of doing things, but as long as I get/shoot the image I'm after (not 'photoshop till I get the image I'm after :) ) OK for me
    E..g. works out like this
    (original crop) http://www.pbase.com/paul_k/image/162085884
    (headshot crop) http://www.pbase.com/paul_k/image/162085886
    or
    (original crop) http://www.pbase.com/paul_k/image/162085896
    (headshot crop) http://www.pbase.com/paul_k/image/162085895
     
  4. I would agree that if you're shooting stills especially the outer focus points ought to work fine. My main reason for wanting to focus and recompose with BBF is for speed and convenience in travel and other non-studio sorts of photography, in which my hope at least is that the image will be complete as shot, and not cropped. Cropping is not always even an option. In this case, if you want to focus on something or someone that is not centered in the image, it is quicker to use the fast and accurate center point and move the camera than it is to move the focus point. I've found in some situations where the light is also difficult, it's very handy to have focus on one button, and AE lock separate, allowing me to choose an off center focus point and also a selected spot metering point, independently of the final composition. On lower end cameras without a separate AF ON button, this means assigning AF to the AE/AF lock button, and AE lock to the shutter button. AE lock is thus available but not required.
     
  5. William Michael

    William Michael Moderator Staff Member

    With focus recompose supposedly the aperture is better at 2.8 and up (i have a 1.4 [lens]) but how low is [too] low to have a higher chance of keeping my subject in focus when recomposing?​
    Given other variables are constant - the larger the Aperture used, then, the smaller the DEPTH OF FIELD. But the farther away from your Subject the larger the DoF, so there is not one definitive answer to your question, but there are guidelines and those guidelines will depend on the FRAMING of your Subject.
    In the first example let’s assume you use F/1.4 and you FRAME you Subject as a Full Length Shot: if you focus on the eyes and lock focus and then tilt the camera down slightly to recompose the shot to get the Subject from head to toe in the FRAME, then there will be little chance of the PLANE OF SHARP FOCUS changing enough for you to detect any focus error.
    On the other hand, if you FRAME a TIGHT HEAD SHOT (like this one: http://www.photo.net/photo/18031428&size=lg EOS 5D Series; EF 85F/1.8 at F/1.8) and use the centre point AF Point and then twist the camera to recompose the shot, then it is likely that you will get a soft eye because the Plane of Sharp Focus will change enough and because of the very short Subject Distance, the Depth of Field is very shallow - so on "recompose" (i.e. twisting the camera) the eye on which you focussed could move out of an acceptable Depth of Field and be slightly out of focus.
    However there is a technique to use when using ‘Focus and Recompose’, for very tight shots and that is NOT to twist nor tilt the camera for recoposition, but to move the camera parallel to the Subject Plane (Plane of Sharp Focus) – and that technique was employed for the sample image above.
    Note also that using a Lens close to or at the MAXIMUM APERTURE, the EGDE SHARPNESS will suffer degradation – so be aware that if you recompose a Full Length Shot, or an Half Shot and you ue F/1.4 or F/2, whilst the eyes might be in acceptable focus, but they still might be soft (the whole head might be softer than the body), because the head (and the feet) are at the outer edges of the lens. The amount of degradation will depend on the particular Lens and also on the CAMERA FORMAT being used.
    ***

    ‘Shot wide and crop in post-production’ is not a technique new to Digital Capture nor was it invented because of Digital Capture – the technique was common and typical amongst Wedding Professionals- for two main reasons – the necessity of a speedy shoot at various times and also the option of supplying different APSECT RATIOS of Prints to the Client.
    Whilst ‘shooting wide and cropping in post-production’ is a worthwhile technique to consider and also a worthwhile skill to have: it is not necessarily the answer to every shooting situation: just in the context of this discussion, it might not be a suitable technique for the OP to employ, considering only these two points which spring to mind:
    1. The OP is using a PRIME LENS, therefore the only option to create lose FRAMING for later cropping is to STEP BACK from the Subject – which in turn changes the PERSPECTIVE of the shot – this might be undesirable.
    2. The OP might be using AVAILABLE LIGHT and be using a camera with medium to poor HIGH ISO capacity – if the Ambient Light Level is low, then aggressive cropping might be an unsuitable or a less desired technique than using Focus and Recompose.
    *
    So I think that it is worthwhile understanding both techniques and practicing both and then employing the best technique to suit the circumstances and to attain the desired outcomes.
    WW
     

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