Hyperfocal distance explained, and how to use all of your depth of field.

Discussion in 'Articles of Interest' started by stephensphotos, Dec 24, 2012.

  1. stephensphotos

    stephensphotos New Member

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    I have recently written an article that explains hyperfocal distance, and how to calculate what your hyperfocal distance would be for your situation. As well as a more useful use for this kind of information: I show you how to calculate what your focus distance and aperture should be in order to cover the entire object you're photographing with your depth of field.

    Ok.., right, sorry. Let me do some copying and pasting then, so that you can access the information the link would have led you to. I've skipped the hyperfocal distance story because you can find that info anywhere on the net, but I've included the part that I really struggled to find on the net, so I think this info would be the most interesting

    So sorry.

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    Finding the Right Focus Distance and Aperture to Render the Whole Object Sharp

    Getting to know and understand how and why you’d use the Hyperfocal distance to maximize the use of your DoF will naturally make you wonder about where else you could use this kind of technique. For example, if you were being paid by a magazine or any kind of client, to photograph something in a studio, and part of the client’s requirements is that the entire object be sharp. How would you go about making sure that the object in the picture is completely sharp, would you wing it? Or would you be a professional and make sure the job is done properly the first time? Below is a diagram explaining the situation in the studio, and its your aim to get the entire table sharp. In other words, you’re trying to fit the entire Depth of Field over the entire table. There is a way to calculate what the minimum Aperture and focus distance should be, to make your DoF just the right size for the object you’re photographing to be rendered sharp.


    $schematic.jpg This is the diagram explaining the hyperfocal situation in which the aim is to get the whole table acceptably sharp


    • The closest point to the camera that needs to be sharp is called the “near DoF limit’, and is designated with this symbol 'Dn'
    • The farthest point to the camera that needs to be sharp is called the ‘far DoF limit’, and is designated with this symbol 'Df'
    • The focus distance setting of the lens (subject distance) is designated with this symbol 's'
    • The Aperture that we need to use in order to get the whole object sharp will be designated with this symbol 'N'
    • In this situation I am using a 35mm format digital camera, which has a sensor dimension of 36mm X 24mm. This format has a circle of confusion size that is 0.03mm, and circle of confusion is designated with this symbol 'c'


    So you’re standing in the studio with this table in front of you, and you know that the closest point to the camera that needs to be sharp is 1.5metres away, and you know that the farthest point that needs to be sharp is 3.5 metres from the camera. You could ascertain this information by either measuring the distances yourself, or by focusing on each point and reading the distance off of your lens. The first thing you need to work out is what your focus setting should be, and you are able to calculate this with the information you already have. Use the following formula and solve for “s”
    $solve for S.jpg
    This is the formula to calculate the focus distance (subject distance), with the near and far DoF limits.
    s = subject distance
    All measurements were converted to millimetres, but in this format you could also just leave the measurements in metres.

    Now you know that with the camera at the distance from the closest and farthest part of the table, the lens focusing distance should be set to 2.1m. At this point you can guess where 2.1m is and just manually focus the lens to that point, or you could take out a measuring tape, your choice.

    Now to calculate what the aperture is that we need to use, we need to work out the following formula and solve for N.

    $solve for n.jpg
    This is the formula to calculate the Aperture needed
    N = the Aperture we need

    All measurements were converted to millimetres because the focal length (f) and circle of confusion (c) are always expressed in millimetres.

    And there you have it. With the aid of mathematics we have calculated that the focusing distance should be 2.1m, and what the Aperture should be using is f/16. Now you can go forth with confidence and fulfil the brief explained above, if you ever get one like that. On the other hand there are much easier methods to work out the information that we have just worked out. There are Depth of Field and Hyperfocal distance calculators online, and available to download to your cell phone or tablet device. These are much easier and time saving, but at least now you understand what these devices are doing.



     

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    Last edited: Dec 24, 2012
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  2. pgriz

    pgriz Well-Known Member

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    First post, and you want us to click a link? I'll pass. Sorry.

    Edit... Ok, now that you've pasted your article into the post, I'll read it.
     
    Last edited: Dec 24, 2012
  3. HughGuessWho

    HughGuessWho TPF Supporters

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    Ditto
     
  4. terri

    terri Administrator Staff Member

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    Hi there, and welcome to the forum. If you'd like to contribute an actual article, as a new member you might want to paste the whole thing in your thread. Linking to your website is not recommended, since as you can see it is not well received. Keep posting here and get to know your fellow members! :) Enjoy the forum.
     
  5. amolitor

    amolitor New Member

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    Did I reply to this? I swear I replied to this. Did I get moderated out or am I going insane?
     
  6. pgriz

    pgriz Well-Known Member

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    In one of the universe threads, you did reply to this. In the other one, in which you present find yourself, you didn't. Unfortunately the inter-universe communication seems to be a little flaky. So, in this universe, it appears that you are NOT insane. But I haven't been able to check up on the other universe instances to verify if that's the rule or the exception. :)
     
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  7. snowbear

    snowbear Well-Known Member

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    You replied. I believe you mentioned non-standard capitalization and inconsistency in defining terms. ;)
     
  8. nikT2i

    nikT2i New Member

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    great post, very helpful! now if only i enjoyed math :sillysmi:
     
  9. raaskohx10

    raaskohx10 New Member

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    You didn't mention which point on the table one should aim at for setting the focus? The start, middle, or the end?
     
  10. stephensphotos

    stephensphotos New Member

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    Wherever you are aiming your lens is irrelavent, having set your focus and aperture the whole table, and hence whatever you are photographing on the table, will be considered acceptably sharp on the final print. The important thing is to set your focus to the 2.1metres, to make sure your focus point is set to that distance, you can use the distance markings on your lens(which you probably wont have if you're using a modern lens) or use a measuring tape to find out what point of the table is that distance away and focus on that.
     
  11. nimendrum

    nimendrum New Member

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    While the article is interesting and useful, I never really bothered to do the math. I'm more of a trial and error kind of guy. Take a shot, zoom in, check the depth of field, take another shot if necessary. I think this is particularly useful for film rangefinders.
     
  12. stephensphotos

    stephensphotos New Member

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    I don't agree that this is only useful for rangefinder cameras. This principal is a mathematical concrete that can be applied to any optical system, and if you are someone who does high end studio photography such as advertising or the like, you will more than likely find information such as this useful if you need exact and predictable technical results. Imagine for example if your aim was to create a billboard meant for the side of a multi-story building, and only after printing the picture you created you are told the picture is useless because their are parts of the image that were not within the depth of field. Which is easier to discover the larger you print your picture. Trial and error is fine when you are shooting your own stuff, or in a wedding or news situation where you don't have time for long speculations, but when large amounts of money depend on you getting a job done correctly, its better to get it done correctly the first time than making mistakes and loosing a client.
     

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