Results 1 to 19 of 19

Thread: DOF - how to?

  1. #1
    Member
    Join Date
    May 2004
    Location
    my house
    Posts
    315

    Question DOF - how to?

    Hi Pro,

    How do you guys/gals get the blur blur background, sharp sharp foreground photo?
    what setting to use?
    i tried using f2.8 but stil very difficult to get.
    must i get those dslr (they got dof button) then i can control the dof?

    Thanks in advance.
    Nikon D5000, D70; Nikon 18-55, 18-70, 70-300; Sigma 18-250, 50-500.

  2. #2
    Senior Member
    Join Date
    Mar 2002
    Location
    Astin Studio
    Posts
    4,736

    Default

    You can try to move your main subject further away from the background, ie main subject nearer to your camera. But you must set the camera auto focus to the main subject.

  3. #3
    Member
    Join Date
    Nov 2003
    Location
    Northeast
    Posts
    1,226

    Default

    How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

    The longer the focal length, the less DOF you have.
    The larger the aperture, the less DOF you have.
    The closer you are to the subject, the less DOF you have.

    So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject.

  4. #4
    Moderator nightwolf75's Avatar
    Join Date
    Dec 2003
    Location
    really MORE diaper changes
    Posts
    17,867
    Blog Entries
    1

    Default

    Quote Originally Posted by justarius
    How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

    The longer the focal length, the less DOF you have.
    The larger the aperture, the less DOF you have.
    The closer you are to the subject, the less DOF you have.

    So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject.
    try reading up here! very helpful article.

    http://luminous-landscape.com/tutori...ries/dof.shtml
    If Life worked on auto mode then manual mode for photography would have never existed.” ― Deeksha Mittal

  5. #5
    Member
    Join Date
    Jan 2002
    Location
    Western SG
    Posts
    1,537

    Default

    Quote Originally Posted by justarius
    How much DOF you get is dependent upon 3 things: focal length, aperture, and distance from subject.

    The longer the focal length, the less DOF you have.
    The larger the aperture, the less DOF you have.
    The closer you are to the subject, the less DOF you have.

    So to get a picture with background blur and foreground sharp, use a longer lens at a large aperture while ensuring the background is far away from your main subject.
    and also on the size of your CCD/CMOS

  6. #6
    Member
    Join Date
    Aug 2004
    Location
    Malaysia
    Posts
    20

    Default

    Quote Originally Posted by coldman
    Hi Pro,

    How do you guys/gals get the blur blur background, sharp sharp foreground photo?
    what setting to use?
    i tried using f2.8 but stil very difficult to get.
    must i get those dslr (they got dof button) then i can control the dof?

    Thanks in advance.
    Saw u using Pana FZ10, f/2.8 at telephoto > 300mm should be produce a good background blur, if still not enough, PS CS it.

    - Select your subject (magnetic lasso + fine tuning using lasso)
    - Save selection as channel
    - Select the channel u just save an apply gaussian blur for 1 pixel
    - Select back the image and apply Lens blur using the channel u saved just now as mask.
    - Voila!

  7. #7

    Default

    Quote Originally Posted by Snowcrash
    and also on the size of your CCD/CMOS
    Not directly though. The size of the CCD/CMOS affects the focal length of the lens which can be used, which in turns affects the DOF.

  8. #8
    Senior Member
    Join Date
    Jan 2002
    Location
    Northwest
    Posts
    5,011

    Default

    Quote Originally Posted by Newman
    Not directly though. The size of the CCD/CMOS affects the focal length of the lens which can be used, which in turns affects the DOF.

    Actually quite directly....the size of the sensor versus the size of the final output affects the circle of confusion, which is in turn a direct factor determining the DOF, besides the focal length, aperture and subject distance.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  9. #9

    Default

    Quote Originally Posted by roygoh
    Actually quite directly....the size of the sensor versus the size of the final output affects the circle of confusion, which is in turn a direct factor determining the DOF, besides the focal length, aperture and subject distance.
    Sorry Roy, I'm a bit confused here. As quoted from Michael Reichmann:
    'There was a query in October, 2001 on my Discussion Forum as to whether Depth of Field was calculated any differently for digital Vs. film. The answer is, no. There is no difference whosesoever. DOF doesn't care about the recording media type or size, though a lower COF is used for medium and large format, since the amount of magnification to make a decent sized print is much less than for 35mm.'
    Isn't the CCD/CMOS the recording media?

    Or maybe I belong to the COF as jokingly defined by Michael:
    'Definition: "A group of photographers sitting around trying to understand Depth of Field". '

  10. #10
    Senior Member
    Join Date
    Jan 2002
    Location
    Northwest
    Posts
    5,011

    Default

    Quote Originally Posted by Newman
    Sorry Roy, I'm a bit confused here. As quoted from Michael Reichmann:
    'There was a query in October, 2001 on my Discussion Forum as to whether Depth of Field was calculated any differently for digital Vs. film. The answer is, no. There is no difference whosesoever. DOF doesn't care about the recording media type or size, though a lower COF is used for medium and large format, since the amount of magnification to make a decent sized print is much less than for 35mm.'
    Isn't the CCD/CMOS the recording media?

    Or maybe I belong to the COF as jokingly defined by Michael:
    'Definition: "A group of photographers sitting around trying to understand Depth of Field". '

    Your quote is correct, the DOF calculation remains the same regardless of the medium. What goes into the DOF equation are focal length, subject distance, aperture and COC, and the euqation does not care about the type of medium (film, CCD or CMOS).

    COC is affected by the sensor size and the magnification from sensor size to final output (screen or print size), as pointed out by the second half of your quote from Michael Reichmann. For the same sized print, COC_film is larger than COC_CCD (since most CCDs are smaller than film) to achieve the same DOF with everything alse being the same. As such the sensor size affects DOF directly, not just affecting the choice of focal length.

    Of course when you factor in the effect of CCD size on the choise of focal length (to achieve the same angle/field of view) the impact of sensor size is reduced, however, the net effect is that smaller sensor size actually results in higher DOF as compared to film if field of view, aperture and subject distance are kept constant. That's why the "blur background" effect is less on a digicam compared to a DSLR even if the equivalent focal length and aperture are the same.

    I was responding to your statement that sensor size does not affect DOF directly.

    Last edited by roygoh; 30th September 2004 at 07:46 AM.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  11. #11
    Moderator
    Join Date
    May 2002
    Location
    Melbourne, Australia
    Posts
    4,026

    Default Hoe this woudl give you a better picture...

    Quote Originally Posted by coldman
    Hi Pro,

    How do you guys/gals get the blur blur background, sharp sharp foreground photo?
    what setting to use?
    i tried using f2.8 but stil very difficult to get.
    must i get those dslr (they got dof button) then i can control the dof?

    Thanks in advance.
    The distance B should be greater than the distance A + try the longest focal length (better if the camera minimum focus distance is very short)



    rgds,
    sulhan

  12. #12
    Senior Member
    Join Date
    Sep 2004
    Location
    Cons digger.
    Posts
    3,924

    Default DOF disc

    Actually for beginners like me, I normally set my camera zoom to half of the maximum to achieve some longer focal length and go round shooting pics.

    I just have to stand a further from my target.

    Try using this program from DOF Master . It is a disc/calculator some sort which does the same thing for the dSLR's lens like the one below


    Picture taken from DOF Master.

    Best thing it's FREE.

    Just input your camera's COC (can be found on the website itself) and focal length range.

    Print out and assembly the discs and walla!
    It's quite a useful tool to have around for beginners.

    Else if you bring a palm around there also the Palm OS version.

    After some time I sort of gotten the hang of acheiving my DOF without the disc.

    Hope it helps
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  13. #13
    Senior Member
    Join Date
    Mar 2002
    Location
    Astin Studio
    Posts
    4,736

    Default

    Sometimes I admire sulhan's effort, he would draw a diagram and explain things in details.

  14. #14

    Arrow

    This is very helpful for newbies like me Keep the tips coming....

  15. #15

    Default

    Quote Originally Posted by roygoh
    Your quote is correct, the DOF calculation remains the same regardless of the medium. What goes into the DOF equation are focal length, subject distance, aperture and COC, and the euqation does not care about the type of medium (film, CCD or CMOS).

    COC is affected by the sensor size and the magnification from sensor size to final output (screen or print size), as pointed out by the second half of your quote from Michael Reichmann. For the same sized print, COC_film is larger than COC_CCD (since most CCDs are smaller than film) to achieve the same DOF with everything alse being the same. As such the sensor size affects DOF directly, not just affecting the choice of focal length.

    Of course when you factor in the effect of CCD size on the choise of focal length (to achieve the same angle/field of view) the impact of sensor size is reduced, however, the net effect is that smaller sensor size actually results in higher DOF as compared to film if field of view, aperture and subject distance are kept constant. That's why the "blur background" effect is less on a digicam compared to a DSLR even if the equivalent focal length and aperture are the same.

    I was responding to your statement that sensor size does not affect DOF directly.

    Thanks Roy for your explanation. My mind is still not taking it in yet. Perhaps it's because my mind is still 'recovering' from ICT syndrome . Just finished today and I'll come back to this after my head is clear.

    Cheers!

  16. #16
    Member
    Join Date
    Sep 2004
    Location
    eastern part of singapore
    Posts
    99

    Default Canon A80

    hi folks ..

    so armed with a Canon A80, is it possible to do DOF ? or at least .. a simple DOF ? thanks

  17. #17
    Member
    Join Date
    Nov 2003
    Location
    Northeast
    Posts
    1,226

    Default

    Quote Originally Posted by dfbread
    hi folks ..

    so armed with a Canon A80, is it possible to do DOF ? or at least .. a simple DOF ? thanks
    I don't think you do DOF. What is a complicated or simple DOF? DOF is simply the area of sharpness in your picture.

  18. #18
    Senior Member
    Join Date
    Sep 2004
    Location
    Cons digger.
    Posts
    3,924

    Default

    hahah whether it is "simple" or "complicated" DOF it is possible with the A80 although it is slightly harder because the manual focusing is only from 0.5 -5m then infinity (not too user friendly but still good to have some form of manual focusing).

    -Using only optical zoom, set to full telephoto (or whatever focal length)
    -use a relative big aperture (f2.8 or 3.2) for limited DOF
    -if you know the distance to the object then it'll be good to use manual focus otherwise you have to try to autofocus on the object correctly.

    example:
    at full telephoto (with f2.8) and you are standing 3m away from your object, only things that fall between 2.8m and 3.3m remains relatively sharp. All others will start to become blur. Probably you can focus at 2.8 to enhance the blur background effect.

    but if you set to full wideangle (with f2.8)at 3m, the range now becomes 1.6m - 18m. So you'll have to focus further (2m maybe) to get that "blur background" effect.

    Because you're not focusing AT the object but slightly in front of it all the time.. your intended object may not be at it's best sharpness...

    The above is valid only for the A80 because different cameras have different COC and range of focal lengths. There are many online DOF calculators to find the above info.

    There is also a mathematical equation to get the above values.. but that's another story..
    Last edited by yanyewkay; 1st October 2004 at 01:03 PM.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  19. #19
    Member
    Join Date
    Sep 2004
    Location
    eastern part of singapore
    Posts
    99

    Default

    Quote Originally Posted by yanyewkay
    hahah whether it is "simple" or "complicated" DOF it is possible with the A80 although it is slightly harder because the manual focusing is only from 0.5 -5m then infinity (not too user friendly but still good to have some form of manual focusing).

    -Using only optical zoom, set to full telephoto (or whatever focal length)
    -use a relative big aperture (f2.8 or 3.2) for limited DOF
    -if you know the distance to the object then it'll be good to use manual focus otherwise you have to try to autofocus on the object correctly.

    example:
    at full telephoto (with f2.8) and you are standing 3m away from your object, only things that fall between 2.8m and 3.3m remains relatively sharp. All others will start to become blur. Probably you can focus at 2.8 to enhance the blur background effect.

    but if you set to full wideangle (with f2.8)at 3m, the range now becomes 1.6m - 18m. So you'll have to focus further (2m maybe) to get that "blur background" effect.

    Because you're not focusing AT the object but slightly in front of it all the time.. your intended object may not be at it's best sharpness...

    The above is valid only for the A80 because different cameras have different COC and range of focal lengths. There are many online DOF calculators to find the above info.

    There is also a mathematical equation to get the above values.. but that's another story..
    thanks thanks yanyewkay... though it needs time to digest

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •