URGENT Question on Depth of Field w. Point & Shoots

Discussion in 'Mirrorless Digital Cameras' started by rebecca_soto, Sep 19, 2010.

  1. Hi,
    Im a college student taking a beginner photography class. Most of the class, including myself, uses a point and shoot digital camera. I personally have a Nikon Coolpix s210. I am having incredible difficulty trying to create a photo that demonstrates the concept of "depth of field". If someone could give me some tips or give me a way to complete this assignment please help me out and respond. Thank You.
    B.
     
  2. Point and shoots would make it difficult to obtain a shallow depth of field because of the incredibly small sensor.
    Set the ISO to as low as you could get. Put the camera on portrait mode and zoom to the fullest extent. Now ensure that your subject is at least 20 metres in front of whatever you are using as a backdrop.
     
  3. With a small sensor camera (S210) it is little harder to show. You still can do it with close up subjects. Set the camera to macro focus mode. Take a picture including both close up and far away images.
     
  4. As it has been said already, DoF is one of the greatest drawbacks to point and shoots. Get as close as possible to the subject, and have your background as far away as possible.
     
  5. The simple answers given above are leading your astray and as a student I would hope you would be given correct answers.
    The sensor size has absolutely nothing to do with depth of field except with regard to the amount of magnification required for a print of a given size. In which case the P&S because of its small sensor requires greater magnification for a print of a given size so therefore has LESS Dof.
    What affects depth of field in the focal length of the lens in use. In this case the P&S has a very short focal length so it inherently has a lot of depth of field. You can demonstrate this by taking a photo with objects quite close to the camera along with objects a fair way away from the camera. Done properly all will be in focus ... you may need to take several shots until you find my experimentation the depth of field your camera has given the conditions.
    Most people seem to be pre-occupied with very little depth of field and credit the DSLR and slam the P&S on the basis that because the P&S usually has a lot of DoF it is no good. Forgetting that if you are truly competent with your editing program is is very eay to simulate lack of DoF.
    Whatever to demonstrate a lack of of DoF you should take a extreme close-up of a fly or perhaps a flower. Most of the subject will be out of focus demonstrating the lack of DoF. The LCD of you camera should enable you to find the most interesting point of focus ...perhaps several shots to illustrate the effect of focusing at different points of the subject. You could also experiment holding a magnifying glass in front of your P&S which enables your lens when at full zoom to focus closer than without it .. this need not be more than a cheap plastic lens to demonstrate what it can do for you. Mine cost me 50c at a discount store :)
     
  6. It depends on aperture n lens. In P&S becasuse the focal length is small and aperture starts around 3.5 making it a bit difficult. But it is very much achievable. try flowers. easiest.
    1. Make sure that the subject is very very close in ~ 20 cms.
    2. Make sure that there is enough distance between the subject and the background~ 2 mts.
     
  7. Jc... I don't understand your logic that sensor size does not effect dof. While
    you are correct that sensor size alone does not effect dof it does play a large
    part in it. a small sensor causes your imaging area from the lens to be
    smaller (in th case of point and shoots anyway). Which allows smaller lenses
    (a good thing for p&s users).

    Anyway I really am too tired to get anymore into this tonight but please do not
    say that sensor size has no effect on dof. But, it is one of the factors along
    with focal length, aperture, distance to subject, and distance to background.
     
  8. Rebecca, I am a bit unclear on the exact assignment...You state the project is to "…create a photo that demonstrates the concept of 'depth of field'." You probably already know that depth of field is the amount of content that is in focus relative to the main object being focused on. So you can have a very small amount in focus or a large amount in focus--as well as in between. Is it up to you which you attempt?

    Most comments above have stated that images from a small sensor P&S inherently cannot have shallow depth of field--this is true (NOTE: There is an exception with macro mode--more on that later.)
    Apertures control Depth of field
    Large aperture values (e.g. f/1.2, f/2.0) produce the least depth of field and small aperture values (f/8.0) produce images with the most content in focus (greater depth of field). The problem is that most P&S cameras don't allow you to set the aperture yourself. There are ways to trick it of course. If the camera thinks there is very little light it will make the aperture open wide (a small aperture number). Conversely if the camera meter sees lots of light it will reduce the aperture size.

    So, with your P&S without manual controls, if you are trying to either:

    a) Show minimum depth of field. In general…
    • Image capture should not be in bright environment (lots of light makes the camera use smaller aperture producing the opposite effect)
    • Put your camera in Macro Mode (Tulip/Flower icon)
    • Position the camera closer to the image subject than the subject is to the background.
    • Set the ISO as low as possible(helps keep the aperture down)
    NOTE: Macro mode typically won't work for a person because the wide angle needed for Macro mode caused extreme distortion. Small objects are best.

    b) Show a maximum depth of field, in general:
    • I suggest shooting your image in a well lit environment. This allows a small aperture to be set by the camera. Dark environments cause the aperture to be large (resulting in less depth of field)
    • Optional: there may be a landscape mode, which will set the aperture in to a
    • ISO settings can vary but a slightly higher ISO number will help keep the aperture

    Sorry but JC's comment about the lack of a relationship between sensor size and depth of field is incorrect. It's physics and it's a complicated relationship which I can't explain. But I have personally taken photos with two different P&S with a f/2.0 lens and the images did not look anything like a DSLR with a f2.0 lens. These technicalities are easily searchable online.
    Good luck and have fun.
     
  9. IMHO, since the OP was talking about a beginner photography class, so a simple advice of move the subject closer and the back ground further (ie: Use macro mode) make sense. It will help see DOF effect easier.
    Here is a more complicated version for a more advanced class. The formula for DOF described in magnification is as follow:
    DOF = 2Na2C (M+1)/ (M2a2 - C2) = 2NC (M+1)/ (M2 - (CN / f )2)
    where M = magnification.
    This read, in a some what simplified language, if everything else are the same, for the same DOF look, the magnification will also be the same. Since lens to sensor distant are typically less on a small sensor camera, meaning to maintain the same magnification and DOF look of a larger sensor, one need to move the subject closer and leave the back ground the same distant (ie: Far away) for the smaller sensor.
    BTW: C = Circle of confusion, not running around circle in confusion :) DOF is one of the more confusing topic in photography. Don't get discourage.
     
  10. The sensor size has absolutely nothing to do with depth of field except with regard to the amount of magnification required for a print of a given size. In which case the P&S because of its small sensor requires greater magnification for a print of a given size so therefore has LESS Dof.
    This statement is false or misleading. The smaller the sensor, the greater the depth of field for the same field of view, even though more magnification is required for the same print size. Assuming the focal length of the lens is proportional to the size of the sensor, you get the same FOV at the same distance for any sensor/film size. You can get the complete skinny on Bob Atkins' website (www.bobatkins.com).
     
  11. As others have said, in practical terms, the typical compact digitals have 4 or 5 stops more depth of field than the old standard student camera, the 35mm. So, for example, a typical compact digital will have as much depth of field at f/2.8 as a 35mm has at about f/11 or f/16, as long as the camera and the subject (or more technically, plane of focus) are in the same positions, the lens captures the same field of view, and the prints are the same size.
    Again as others have said, as a practical matter, the only ways to achieve a strong depth-of-field effect with a compact digital is to have some objects (or people) in the frame very close to the camera, and other objects (or people) in the frame very far from the camera. Often this will mean that the main subject is very close and there are visible objects (or people) very far away. (Note that this does not usually work well with a flash, given the inverse square law, so available light is usually needed for such pictures.) But you can also do the reverse: you can focus on something far away and include something very close. Here is a picture creatively using depth of field to put the main subject out of focus and the background in focus: http://www.myspace.com/julianahatfield.
    By the way, JC is way off base. I'm about 95% sure he has made these claims before, and been corrected, but he persists. He wants to consider one factor affecting depth of field and ignore or give too little effect to others.
     
  12. >>>By the way, JC is way off base. I'm about 95% sure he has made these claims before, and been corrected, but he persists. He wants to consider one factor affecting depth of field and ignore or give too little effect to others.<<<
    You are 100% correct in that I have said this before and sadly peoople have persisted in their mis-information in reply ... if they comprehended the complete sentance rather than part of it ... a common fault of contributors to blogs ... they would begin to understand hopefully why the small sensor decreases DoF by virtue of the extra enlargement for a given print size.
    The original source of my information is to be found in the Ilford manual of Photography,my copy was printed in 1948 shortly before I started my training at Guildford School of Art under Ivor Thomas and his tutors.
    The degree of magnification is a equal factor in DoF and the greater the magnification the less DoF possible. This is basic optics which every student should be aware of. Naturally there are other factors, aperture, focal length, [plus a fourth which evades my memory at the moment] which are the commonly known factors.
    So I feel that a student should be given the correct answer rather than popular mythology ... in this case the erroneous idea that the small sensor is the cause of great DoF. It is obvious to me that the large enlargement results in less DoF not more ..... but of course this is overcome by the short focal length being used, which also counteracts the large apertures found in these cameras also decreasing DoF.
    All up I fear some of you experts need to go back to school and learn the basics. :)
     
  13. All up I fear some of you experts need to go back to school and learn the basics. :)
    For the same field of view, the depth of field is inversely proportional to the square of the focal length, and decreases linearily with respect to the size of the media. Thus the shorter focal lengh more than offsets the magnification required for the same sized print.

    Is that basic enough?
     
  14. [T]he small sensor decreases DoF by virtue of the extra enlargement for a given print size.
    JC, it is true that the smaller sensor requires more magnification, and all else being equal, more magnification results in less apparent depth of field, but manifestly, all else is not remotely equal here. With the smaller sensors, you are using much shorter focal lengths to get the same field of view / angle of view. As Edward said, the other factors involved with the smaller sensor more than offset the increase magnification.
    Have you shot much with compact digitals? Did you ever notice that their pictures shot at f/2.8 have a lot more apparent depth of field than a 35mm or DSLR picture shot at f/2.8? It's pretty obvious. In fact, if we can agree on some neutral expert arbiter and somebody to escrow the money, do you want to bet $1,000 on this?
     
  15. I'm glad that you finally agree with me ... remember that I was merely questioning the statement that the cause of the great increase in DoF of a P&S compared to other cameras was the small sensor .. it is obvious that the focal length is the dominant factor which overrides others.
    I would have thought it obvious from my numerous comments here that I use a P&S [small sized sensor camera], not that I call it that, in preference to my DSLR.
    I subsequently remembered that a most common illustration of DoF is to set up some sticks, or trees, or newsprint at intervals from the camera. Some around the point of focus will be sharp while those closer and further away will be less so .. thus illustrating DoF. Bearing in mind that true sharpness, focus, is at one point only and apparent sharp focus depends on the human eye to accept a degree of blur* as sharp ... this often depends on the persons knowledge with the skilled worker more critical than the lay person.
    *Circle of Confusion .... can be demonstrated by using a lens to focus a light source, the Sun?, on a piece of paper. as you approach true sharp focus there is a circle of confused light rays on the paper. This is similar to what is happening inside the camera as light reflected from out of focus subject material is directed at the sensor.
     
  16. Poor Rebecca, she was only looking for tips how to complete her "Depth of Field" project, not driven to the circle of confusion!
    I hope you were successful Rebecca.
     
  17. One day hopefully Rebecca will be like the rest of us and know too much for our own good :)
     

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