where to focus

This is a discussion on where to focus within the Composition forums, part of the Photography Tips category; I'm trying to take a scenery picture. The classic picture you've seen multiple times, from Brooklyn at night , take Manhattan and the Brooklyn Bridge ...


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Thread: where to focus

  1. #1
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    where to focus

    I'm trying to take a scenery picture. The classic picture you've seen multiple times, from Brooklyn at night , take Manhattan and the Brooklyn Bridge with all the lights. Obviously they are on the other side of the river so they are far. How do I focus? I was trying manual focus and at first I tought to put it straight on infinity, but it turned out that it'd get a little cleared if I did it just a little bit before infinity. Also, where should it set the focus on? If I "aim" at let's say the tower on the bridge is one thing but if I "aim" at 2 buildings behind it is another.

    Thanks,

    ps: I use a panasonic dmc-fz100 and the manual focus is not the typical "moving on the lens" but I do it digitally.


  • #2
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    Congratulations! You have, on your own, discovered an important tool in photography! Just in case it is not clear, I'm not being sarcastic, I am trying to praise the fact you are experimenting with your camera, a good thing. You can read this thread:
    Photoforum Photography Challenge 2011-12 - Long depth of field & hyper-focal distance

    Paolo

  • #3
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    This is the current "challenge" in the challenge forum... what you want to do is increase the depth of field so that the overall scene is in focus and not just objects at some specific distance.

    You increase the depth of field (depth-of-field, or DoF for short, is the range of distances at which objects will appear to be reasonably focused) by making the aperture diameter smaller (meaning you select a higher f-stop... such as f/16 as opposed to a low f-stop like f/4). When you do this, you reduce the amount of light the lens can collect, so you'll need to compensate by leaving the shutter open longer... and for a night photo you'll be wanting a tripod (otherwise your subtle body movement while trying to hand-hold the camera will blur the overall scene.)

    In theory, with this high f-stop value, if you focus at "infinity" then you'll have a lot in focus, but it turns out you can do even better. The general guideline (rule of thumb) is that from your focused distance, you'll noticed that whatever the depth of field, about 1/3 of the focused area will seem to be closer than your lens-to-subject focused distance and about 2/3 of the focused distance will seem to be beyond that distance (don't try to measure it out because it's not even close to accurate... it's really to help you visualize the fact that the depth of field isn't actually "centered" at your focused distance (with equal distance nearer and farther from that point) but rather favors the far side. That means you can cheat the focus forward from infinity, which improves sharpness on the nearer objects and yet the far objects will STILL seem to be pretty well focused.

    Basically you'll focus your camera on the nearer buildings of the skyline across the river, set a high depth of field (such as f/16... even f/11 will be good at these distances), set the shutter speed accordingly (since you're mostly exposing for the "lights" and not necessarily the buildings, this will probably be shorter than you might expect), use a tripod to make sure the camera doesn't move while the shutter is open, and take your shots.

    That's all there really is to it. You can stop reading here.

    BUT... if you really want to know how to maximize the depth of field, there is a theoretical distance known as the "hyper-focal distance". This is the distance (corresponding to the focal length and focal ratio you are using) at which the maximum possible range will be in focus. You used to be able to find this because cameras has "depth of field" markers on the lens... few lenses have these anymore (I have a few 'prime' lenses that still have them... none of my zoom lenses have them anymore.) So now there are tools and a website where you can look up the precise distance. Go to DOFmaster.com and they have tools (which are probably fairly handy for you since you get to digitally enter the focus distance into the camera.)

    1) Go to DOFmaster.com
    2) Pick the "Online Depth-of-field Calculator".
    3) In the pull-down menu, select your camera (it's in there... there are hundreds of cameras, but I just checked and your Panasonic FZ-100 is listed.)
    4) Once you've decided which focal length you'd prefer (by zooming until you're happy with the composition of the shot), enter that value. For example, I entered 50mm.
    5) Set a high focal ratio (f-stop) such as f/16
    6) Ignore the "subject distance" box... this is if you were focusing to a specific distance and were just curious to know how much depth-of-field you'd get... INSTEAD look in the box to the right for the value of "Hyperfocal distance". Using the example above, it came out to 102.7 feet (103 feet is close enough).

    If you were to then use your camera's manual focus menu to enter 103 feet, then your camera will shoot the shot with the maximum in-focus area possible (for that focal length and focal ratio... each DIFFERENT focal length or different focal ratio will compute a different value of hyper focal distance.

    Incidentally, if I then enter that 103 feet value back into the online tool, it tells me that those settings will cause everything from about 51 feet to "infinity" will appear to be acceptably sharp.

    Though you could use a smartphone and web browser to look all this up while trying to take the shot, they have tools you can download into a smartphone and I think they also let you generate a printed table that you can stuff in your camera bag.

    Good luck, and don't forget... we hope to see you post your results! :-)
    Tim Campbell

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    what can I say, THANK YOU!!! it makes much more sense now.

  • #5
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    This means selecting a small Aperture (remember the larger the number the smaller the actual Aperture) to ensure that you end up with a large depth of field. This will ensure that parts of the image that are both close and far away from you have a good chance of being somewhat in focus.

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    there are depth of field calculator apps


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