Page 1 of 3 123 LastLast
Results 1 to 10 of 22

Thread: DOF, f-values & sharpness

Hybrid View

  1. #1

    Join Date
    Aug 2009
    Location
    Utrecht, Netherlands
    Posts
    12

    DOF, f-values & sharpness

    I've seen some massive, super sharp prints with a very narrow DOF (I might compare it to f2.8 when working with a 85mm 1.8D Nikkor lens on a Nikon D200 digital camera and the subject is about 2 to 3 meters away). He's a student and his equipment was under $1000,- he claimed, dunno what equipment though, might have been a Sinar. The effects and pastel-like unsharpness he achieved was far beyond anything I've ever seen (even compared to high end digital, like Nikon D3X digital camera's or Canon 5D mkII's!).

    I'm reading for hours now in the internet (including this forum and tons of articles by Ken Rockwell) to figure out ways to work with DOF.

    As far as I can figure out these are all variables:
    -Lenses (duhh) & f-stop set
    -Bellow extensions
    -Camera movements

    In theory I know how to calculate or review the 'plane of sharpness' (or whatever it's called ) and I know I should lean the lens a little bit forward to get a bit of extra sharpness. But what confuses me is that most of the lenses I find (like on e-bay) have a f-stop of 5.6 as the largest opening. I know there are some big differences between lensen on digital and LF, but can't seem to figure it all out..

    I guess my question would be: are there other ways of working with DOF, except from changing the f-stop? And... how?

    Hope the silly questions will get less silly soon!
    Fortunately I'm familiar with digital, but trying to figure out 4x5" LF, please be patient considering silly questions from my side :-)

  2. #2
    David Gainer
    Join Date
    Apr 2008
    Location
    Philadelphia, PA
    Posts
    88

    Re: DOF, f-values & sharpness

    The actual range that is sharp will not change, but you can use the camera movements to bring different aspects of the image into that range. Have you consulted the homepage of this forum? Lots of good articles there.

  3. #3

    Join Date
    Aug 2009
    Location
    Utrecht, Netherlands
    Posts
    12

    Re: DOF, f-values & sharpness

    Quote Originally Posted by DJGainer View Post
    The actual range that is sharp will not change, but you can use the camera movements to bring different aspects of the image into that range. Have you consulted the homepage of this forum? Lots of good articles there.
    It was actually my first step towards reading the articles, so yes I did. I found a very good article about sharpness and about DOF (though a bit theoretical with diagrams I couldn't make much out of). But I couldn't find an article about really controlling the DOF and make it as small as possible.

    Did I miss one of the articles maybe?

    Thanks
    Fortunately I'm familiar with digital, but trying to figure out 4x5" LF, please be patient considering silly questions from my side :-)

  4. #4

    Join Date
    Nov 2001
    Location
    IL
    Posts
    720

    Smile Re: DOF, f-values & sharpness

    Regarding the lenses, f/5.6 is a fast lens for LF. In fact, many common lenses have a max. aperture of f/9. You won't find lenses with wider apertures unless they are big, brass, probably heavy and 100 or so years old (okay, maybe this last is overdoing it a bit).

  5. #5
    David Gainer
    Join Date
    Apr 2008
    Location
    Philadelphia, PA
    Posts
    88

    Re: DOF, f-values & sharpness

    My fault! I misunderstood you. You're not likely to find a larger apeture on modern lenses. And most interested look to increase the area of the image in focus, so you seem to be attempting the opposite. Are you sure the student was using LF? If so, it's likely he had the bellows racked out and was focusing closer in; this would surely decrease the amount of the image in focus.

  6. #6

    Join Date
    Aug 2009
    Location
    Utrecht, Netherlands
    Posts
    12

    Re: DOF, f-values & sharpness

    Aha, bellow out & focus closer. Those are the tips I'm looking for.
    The guy was definately using LF, I might get a hold of his e-mail but I'm afraid it could get difficult.

    And another question, might be a bit on the wrong bit of forum though:
    Afaik in digital telephoto lenses tends to get smaller DOF. Does this also counts for LF? The "Introduction to large format lenses" doesn't say much about it.
    Fortunately I'm familiar with digital, but trying to figure out 4x5" LF, please be patient considering silly questions from my side :-)

  7. #7

    Join Date
    Feb 2009
    Location
    Chicago, IL
    Posts
    107

    Re: DOF, f-values & sharpness

    Quote Originally Posted by Anonomatos View Post
    <snip>
    And another question, might be a bit on the wrong bit of forum though:
    Afaik in digital telephoto lenses tends to get smaller DOF. Does this also counts for LF? The "Introduction to large format lenses" doesn't say much about it.
    To greatly oversimplify, telephoto lenses really don't have a smaller depth of field. The depth of field is related to the size of the image on the film, and the larger the image, the smaller the DOF. If you move in with a telephoto lens so that an object is 1:1 on the film, it will have the same DOF (for the same f-stop) as a wide angle lens when you have moved in so that the image is also 1:1.

  8. #8

    Join Date
    Aug 2006
    Location
    Boston
    Posts
    139

    Re: DOF, f-values & sharpness

    You might find that this DOF calculator useful:

    http://dofmaster.com/doftable.html

    Keep in mind that 210mm lens on 4x5 is a short telephoto and normal lenses are 135-150mm.

  9. #9

    Join Date
    Dec 1997
    Location
    Baraboo, Wisconsin
    Posts
    7,697

    Re: DOF, f-values & sharpness

    Only three things affect depth of field: aperture, focal length, and camera-to-subject distance. Tilt and swing affect the plane of focus. Shift, rise and fall have no effect on depth of field. Ansel Adams' book "The Camera" has an excellent discussion of depth of field. If you read it you'll know all you need to know about depth of field.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  10. #10

    Join Date
    Nov 2003
    Posts
    1,218

    Re: DOF, f-values & sharpness

    To reiterate the points made above.

    1) For distant subjects, with the subject at a fixed specified distance from the lens, the DOF is determined by the focal length, the f-stop, and the degree of enlargement of the image in the camera needed to produce the final print or other image. The wider the aperture, i.e., the smaller the f-number, the smaller the DOF. The longer the focal length, the smaller the DOF. The greater the degree of enlargement, the smaller the DOF. If you change more than one of these simultaneously, the answer can be a bit complicated, and you have to look at formulas (or a DOf calculator) to find out what happens.

    2) For relatively close subjects, it is often more appropriate to look at the scale of reproduction or magnification (taio of subject size to image sie in the film) than the distance of the subject to the lens. If you keep the scale of reproduction fixed, the DOF is essentially independent of the focal length.

    3) Tilt doesn't limit DOF significantly, it still depends on the f-stop as above. But it does change the exact plane in focus, with the DOf extending on either side of that plane. So, you may select by tilting some narrow section of a subject which lies in a plane parallel to the film plane. There will still be a lot in focus in front of and in back of that plane, but it may not contain anything visible in the photograph. The effect will be that you see only a narrow vertical slice of the subject in focus and nothing else.

Similar Threads

  1. Is it me ?
    By Stephen Lewis in forum Digital Hardware
    Replies: 37
    Last Post: 29-May-2009, 11:05
  2. Sharpness - an unnatural obsession
    By George Kara in forum On Photography
    Replies: 91
    Last Post: 28-Apr-2007, 21:21
  3. Lens Design For Maximum DOF
    By Scott Rosenberg in forum Lenses & Lens Accessories
    Replies: 24
    Last Post: 24-Jun-2006, 06:55
  4. Too many Zones?
    By Pete Andrews in forum Style & Technique
    Replies: 28
    Last Post: 6-Sep-2004, 15:49
  5. Questions about focus and DOF technique and aperture
    By Clark King in forum Style & Technique
    Replies: 5
    Last Post: 7-Aug-2001, 23:48

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
  •