Lens with smallest possible depth of field? 50mm?

Discussion in 'Nikon' started by james_tye|1, Feb 20, 2010.

  1. Would the 50mm 1.4 fit this description? Does it have significantly narrower DOF than the 50mm 1.8? If so is the 1.4D or 1.4G my best bet? Are there any other lenses I should consider?
    Many thanks
     
  2. 50mm f/1.2 or 55 mm f/1.2. The 55 will have slightly less DOF then the 50. Both of these lenses are manual focus and the 55 is a non AI lens. But you can find it AI modified easily enough
     
  3. Any of the f/1.2's have even less DOF wide open.
     
  4. I think it would help, James, if you mentioned what you're really up to. Are you shooting people? At portrait-ish distance (say, head-and-shoulders), a 50mm at f/1.4 (or f/1.8, for that matter) is going to have vanishingly small DoF. The sort that gets you one eye in focus, and not much else. If you're interested in very shallow DoF, then it's a fair bet that you're going to be intentionally having noticeably out-of-focus areas present in the image. If the rendering of those areas (the ol' "bokeh" topic) is important in the results, you need to consider more than just the DoF physics ... but also the way the lens was designed, and for what purpose.

    For example: though the 50/1.4 G will have exactly the same DoF behavior as Sigma's 50/1.4 HSM, the Sigma is built primarly to be used at very wide apertures, while the Nikon G is built a bit more around all-purpose use. There are very visible differences between those two lenses when you're using them wide open. And since you're asking about shallow DoF, it seems safe to think you'll be using the lens wide open, or close to it.

    Say a little more about what you'll be shooting, and you'll get some more directly useful info about which lenses are perhaps a better fit. You can use a DoF calculator like this one to help you form expectations about working distance, camera format, focal length, and aperture ... but the look of the results, in terms of bokeh, CA, distortion, contrast, etc., will depend a great deal on which lens you buy.
     
  5. I would imagine the DOF would be shallowest on their longest fast lenses - 600/4, 500/4, 400/2.8, 300/2.8 and 200/2.
     
  6. Of course we can talk about the crazy-shallow DoF of ever-longer focal lengths used in ever-closer shooting ... but until James mentions some practical things about what he's actually going to be shooting (elephants? computer parts? insects? brides?), it's probably not worth getting too far into the multi-thousand-dollar lenses and highly unusual uses of them.
     
  7. It has to be a 50 mm f/0.75 Rodenstock TV-Heligon...... http://www.naturfotograf.com/index2.html
     
  8. As Matt says, it depends on what your intentions are, and also by what you gauge as "significantly narrower DOF".
    At a head and shoulders portrait distance of 6ft on a DX format body for example, the DOF of a 50/1.8 @ f/1.8 is 0.30 ft (3.6 in). The DOF of a 50/1.4 @ f/1.4 at the same distance is 0.24 ft (2.9 in). So the difference in DOF is only 0.7 in.
     
  9. Shallow DOF was the question, not practicality. My 200/4 macro has shallower DOF than a fast 50. If you want to stay around 50mm, you best bet for shallow DOF might be the Voigtlander 58/1.4 at less than $400.
     
  10. I know in astronomy circles, they use a slightly different view of 'Effective Aperture'. By dividing focal length by f number, you get a number, ie 100mm f2 has a Value of 50. 50mm f0.75 would be errr...66.6. The rather expensive 600mm f4, does very well at 150. It has to do with light gathering rather than transmission I think. Is it safe to assume the bigger this Value the shallower the DOF?? These are wide open values only of course.
     
  11. With the 50 mm f/1.4 you get 0.19 feet at a 6 foot focus distance. The 55 f/1.2 gives you 0.16. That's skinny
     
  12. Canon made an EF50/1.0. That is a fast as you can go on a EOS body and still able to shoot distant subjects. If you're looking for the most (and lovely) blur on a portrait, check out the old 200/1.8 (or the new 2.0). Thats properly as thin DOF as you can get without going to the other side of the football field to get it :)
     
  13. Sorry in me previous post that should read 50 f/1.2 not 50 f/1.4
     
  14. If one sets ones 50mm lens at the same Fstop setting and focuses at the same distance; the DOF is the same. Thus if one shoots and image at F4 and focuses at 10 feet away; all the 50mm lenses on the planet; or type M planets will have the same DOF.
     
  15. If you mean with a 50mm lens, then the answer is the widest aperture made, practically for most makes that is going to be f/1.2 (although a few rare f/0.95 or f/1.0 have been made at times).
    Otherwise, your absolute practical limit of "shallowness" is going to be something like 500mm or longer telephoto "wide open" and used for close focus (think a Reflex-Nikkor 500mm f/8, for example). Then, you are talking a few millimeters DOF in most cases. Ditto for most macro work, wide open.
     
  16. On my Nikkor 1.4 50mm I get about 3 cm DOF at the "portrait distance", which is hardly enough to have the entire face in focus. It's also a bit soft fully open.
    I woud imagine the 1.2 will probably mean 2 cm or less. What's the point?
     
  17. Thanks all. The usage would be for small groups from which I'd like to isolate 1 individual. I can achieve this with my 50mm 1.8 or any 2.8 lens but I was hoping to achieve a greater degree of focus blur (client keeps asking for 'more blur'). I'm hoping for something approaching the dof I can achieve with medium format.
     
  18. By dividing focal length by f number, you get a number, ie 100mm f2 has a Value of 50. 50mm f0.75 would be errr...66.6.​
    When you divide the focal lenth by the f number (which is aperture / focal length), you're left with the diameter of the entrance pupil, which is the size of the aperture as seen from the front of the lens. So, yes, the larger the entrance pupil, the shallower the depth of field.
    Sometimes it's useful to imagine a cone with its base at the lens, its point at the subject (the point of focus), and a diameter at the base that's the same as the aperture of the lens. When you think about the thinness of the cone at the subject (or the thickness of it with a wide aperture and a subject that's up close), you can get a feeling for the depth of field at the subject, instead of thinking of it as misfocus at the film/sensor plane.
     
  19. Depth of field is "controlled" mainly by distance. The closer the subject is the lens, the shallower the DoF. Aperture and focal length of course also come into play. But subject distance is always critical.
     
  20. I'm hoping for something approaching the dof I can achieve with medium format.​
    Someone please correct me, if I am wrong, but I did not think sensor/film size affected DOF. The DOF of a 50mm f2.8 lens at a given focus distance is the same. Now, the angle of view will be different, but the DOF is not affected. Correct?
     
  21. Douglas, sensor/film format does affect the DOF. If you shoot a 100 mm lens with a 35 mm sensor, the depth of field at a given aperture shall be larger than with a corresponding lens (~200 mm) at 6x7 cm film. Try to experiment with this link, or try "depth of field calculator" in Google, you shall find many similar tools.
     
  22. Get a longer focal length if you really want to isolate.
     
  23. A little more on how sensor size affects DOF: because of the crop factor of DX sensors, you must back off from your subject to get the same image size (i.e. a person's face occupying the same portion of the frame) that you would see in FX, which results in a change in DOF. The equations can be seen at http://www.dofmaster.com/equations.html if you want to really dig in and see the contributing factors. In fact, you can use these equations to create a quick table in Excel and then plot the curves for the near and far distances (Dn and Df) for acceptable sharpness relative to subject distance (s), given values for the other independent variables.
     
  24. DOF is almost the same for different focal lengths if the object is framed the same way.
    From article in http://www.cambridgeincolour.com/tutorials/depth-of-field.htm :
    "Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to make the subject appear bigger when one is unable to get closer. If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length! This would of course require you to either get much closer with a wide angle lens or much further with a telephoto lens."
    A few examples:
    http://toothwalker.org/optics/dof.html
     
  25. DOF scenarios can be construed in so many different manners that you can "prove" almost anything.
    At the film plane, since the lens lacks any inherent intelligence, the format can't influence DOF. From that point on, the conclusions depend entirely on the conditions you specify for the entire chain up to and including the final print and the distance it is meant to be viewed from.
     
  26. With photoshop using layers, layer masking and gaussian blur, you can give some controlled blur to any part of an image. Just a suggestion.
     
  27. At the film plane, since the lens lacks any inherent intelligence, the format can't influence DOF. From that point on, the conclusions depend entirely on the conditions you specify for the entire chain up to and including the final print and the distance it is meant to be viewed from.​
    The DOF calculator seems like a handy tool. I did a little test to see whether full-frame or crop would make a difference on DOF Bjorn, and it tells me the D700 with 50mm, 1.8 at 10 feet = 2.93 feet, whereas the D300 at 75mm (ie same lens, crop equivalent), 1.8 at 15 feet= 0.38 feet. Someone please check my maths but if that's correct the cropped format offers far narrower dof than the full-frame. I would have guessed the reverse!
     
  28. Calculator has probably already considered the crop factor. So you should put 50 mm in both examples. On http://www.dofmaster.com/dofjs.html results are:
    D700 with 50mm at 1.8 at 10 feet = 1.29 ft
    D300 with 50 mm at 1.8 at 15 feet = 1.94 ft
    In both examples Circle of confusion is 0.02 mm
     
  29. Your math is OK, James, but the concept is wrong. A 50mm lens is a 50mm lens no matter what camera you put it on. If you're going to change the focal length of the lens when you do that math, you also have to change the distance at which you're shooting.

    In your example, a shot with a given framing (say, a standing person, taken with a 50mm lens from 10 feet away on an FX body like the D700) would require a shorter focal length lens on the cropped sensor. So, you'd want to look at at 30-35mm lens on the DX body in order to have that same person fill the frame in the same way, when shooting from the same distance at which you used a 50mm lens on the larger sensor camera.

    Put another way, your 10-foot shot with the 50mm lens on the FX body would have to be a 15-foot shot with the same 50mm lens on a DX body. And as the distance from the camera to the subject changes, so does the DoF (check with that calculator - you'll see). If you stand in the same place, using the same lens on an FX and then a DX camera, you will indeed get exactly the same DoF ... but you'll get a different looking image because you're seeing a smaller field of view when you use the cropped sensor. If the FX shot contains a standing person, the DX shot would chop of heads/feet unless you moved back.
     
  30. You're correct Matt but in my test I did vary the shooting distance (15 feet for the D300 vs 10 for the D700). I think Darko has nailed it, of course the calculator will assume that my 50mm will become 75mm on the DX body so no need to change the lens in the test.. So apparently the full frame does give a marginally narrower dof in identical situations. I wonder if anyone has noticed this in practice.
     
  31. The variety of responses in this thread gives ample testimony to the truth of Bjorn Rorslett statement.
     
  32. You probably do not want a small DOF, but a blurred background. That's not the same. The DOF is almost constant with focal length and the same subject covering the frame, and the same F-stop. But the blurriness at infinity is much better with a tele.
     
  33. I was hoping to achieve a greater degree of focus blur (client keeps asking for 'more blur')​
    If not going for another lens ( likethe 85mm 1.4 .. :) ) , and do not want to "Photoshop" the blur, there is also always the very old fashioned trick of a filter ( like an UV one) smeared with vaseline ( not totaly, but leave the center open for the not blurred part of course..), this method has been used from the early days on for "pictures with a blur" for more than a century.....
    The nice is that you control the blur, can shape it, can vary it towards the edges etc.
    The less nice part is, not all autofocus fields remain avalable, only the center ones ( or if you smear ofcenter , the ofcenter ones...).
     

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