DEPTH OF FIELD QUESTION

Discussion in 'General Discussion' started by NANCY, Mar 27, 2005.

  1. NANCY

    NANCY

    134
    Mar 14, 2005
    FLORIDA
    I am reading Bryan Peterson's book Understanding Exposure. On page 38 and 39 of the book, he shows two pictures, both shot with a zoom 20-35 set at 20, f/22 for 1/30 sec. One is much sharper than the other in the foreground and far background. He said one could get maximum depth of field byaligning the distance above the distance-setting mark on the lens. (quoted from the top right hand side of page 39). I am wondering what setting he is talking about and what do I set it at? The difference in the two pictures is amazing.
     
  2. dkapp

    dkapp

    122
    Mar 18, 2005
    San Francisco
    Without having the book, I'm going to guess here. I bet he is talking about Hyperfocal Distance.

    There is a lot of info out there, so I won't make a huge post out of this.

    Google Search Results

    Hope this helps. If you have questions on it, let me know.

    Dave
     
  3. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Maximum depth of field is with the lens focused at hyperfocal distance.

    For example, if you focus 20mm lens on Nikon dSLR at 0.9m, at f/22 you will have sharpness from 0.5m to infinity. 0.9m is hyperfocal distance for 20mm lens at f/22.

    Online calculator:
    http://www.dofmaster.com/dofjs.html

    For printing scales of Depth of Field, you can try
    http://dfleming.ameranet.com/custom.html
     
  4. nfoto

    nfoto Guest

    Look at the aperture collar of your lens to see whether it has hyperfocal markings on it. They often carry small f-stop numbers on them as well, and you will find symmetric designations on either side of the focus indicator on the lens.

    The principle is very simple. say you want to maximize depth of field at f/16. Turn the focusing collar of the lens so that the infinity mark of the lens is above one of the DOF lines corresponding to f/16. Then, read the front focus limit from the other DOF line. Everything between these lines is in reasonably sharp focus.

    You can of course apply the same method to say a 3 to 8 m range, by aligning the end points to the DOF markers. In this case, you can read off the lens barrel which aperture you need to stop down to, to get DOF sufficient to cover the 3-8 m range.

    A very handy technique in theory, but with the common lack of the DOF markers on modern AF lenses, unfortunately not as useful as it once was.
     
  5. NANCY

    NANCY

    134
    Mar 14, 2005
    FLORIDA
    Thanks to all of you. Do you know if the D70 kit lens has this ability? What about the 70-200 zoom VR lens? or the 12-24? I am almost hoping you say no. so I can put myself out of my misery and just except that sometimes not everything will be sharply in focus.

    The difference between those two pictures was like a drug for me. I am now obsessed with sharpness. Have you found that if you focus 1/3 of the way into the picture, you usually get total sharp focus from front to back if you close the aperture down enough?

    I'm new to all this so I am not even sure if I am asking my questions correctly, but, I am hanging on every word that you are all kind enough to share with me.
     
  6. nfoto

    nfoto Guest

    People tend to stop down the lens way too much. True, you do get a bigger depth of feild, but concurrently, much fine detail is lost. So, in the end you won't get a sharper landscape view with a 20 mm lens set to f/22 than you get from f/11, even though DOF is much bigger in the first case.

    I think you will get a better feeling of the issue just by shutting off AF and do the focusing in the old-fashioned, manual way. Simultaneously, engage the depth-of-field preview on your camera and see how the background comes into focus (or the foreground going out of focus).

    Focusing 1/3 into the subject will very often not be optimal because you lose too much background detail this way.
     
  7. NANCY

    NANCY

    134
    Mar 14, 2005
    FLORIDA
    How can I tell if my lens has hyperfocal markings on it?
     
  8. Nancy,

    Your 18-70mm DX kit lens does not have hyperfocal markings -- actually, they are aperture markings. The markings usually run along the distance scale of the lens as aperture settings, ie. f-stops.

    Here's an example of a Nikon lens (ie. 35mm f/2) w/ the aperture markings being talked about:

    [​IMG]

    Here is your kit lens, which is missing the aperture markings:

    [​IMG]

    In the first pic of the 35 f/2, if you match the infinity distance w/ an f-stop number on either side of the middle marker, which tells you the focus distance, you will have the info for the hyperfocal distance (at the middle marker) and the f-stop (matching infinity) needed to achieve a DOF that stretches from 1/2 that focus distance to infinity for that particular focal length, ie. 35mm in this case.

    That's right. DOF depends on focal length, aperture and focus distance. There are also other factors involved, but those are the main ones you have control over for a given camera (or camera type).

    As Bjorn(?) pointed out, the distance scales and DOF markings on most modern lenses are not very helpful/useful. Some people solve the problem by carrying around their own DOF calculator (of sorts) to help out. Check out this site to read more about DOF calculations, if you're interested. There's an online calculator there as well as one written for the Palm Pilot and also a simple cut-out DOF scale you can print and carry w/ you.

    http://www.dofmaster.com/dofjs.html

    Be careful though if you have a certain aversion for math. :D You don't really need to understand all the math stuff there -- and there are some reasonably simple and intuitive helps there also. Do some experimenting as Bjorn suggested. And then also try plugging in some numbers to see how things work.

    Here's another online DOF calculator w/ perhaps easier/layman explanation that might help:

    http://bobatkins.com/photography/technical/dofcalc.html

    This one may be particularly helpful for understanding since it shows you a range of DOF values for range of settings simultaneously so you can compare at a glance.

    _Man_
     
  9. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    Hi Nancy, Most of Nikon's lenses that are new designs (like all of the DX and G lenses) do not have DOF markings on them. Although I am halfway good at math, I HATE to have to do it while I'm taking pictures. I think the left-brain concentration distracts my right brain that just wants to see the photo. So I use a much simpler method - I guess.

    If I'm wanting to capture detail in both distant and close objects, I'll focus somewhere in between - the rule of thumb is to put about one third of the distance in front of the place you focus and two thirds behind it - but again, I don't measure, I guess. Then set the aperture to something small. F/8 to f/16 is small. I reserve anything smaller than f/16 to macro shots where maximizing depth is critical.

    So, for example, in the photo below, I focused on the closest ranch just below the middle of the picture and shot it at f/8. At this magnification, both the plants and rocks up close and the mountains in the distance look ok to me:

    http://homepage.mac.com/cheilman1/images/photos/land/blackmountainnorth(bw).jpg

    Having a digital camera also helps, since I can shoot a lot more than I ever did with film, and the camera remembers my settings. Over time, I've had some experience with my various lenses, that I'm getting to know what f-stop will be needed for a particular depth of focus.
     
  10. Nancy. The Depth of Field requirements by a natural history photographer of small subjects is equally, if not more important than a correct exposure, at least with a D70. However, although everything that has been said above is good information YOU have the attachment on the D70 to see for yourself.
    It is called THE DEPTH OF FIELD PREVIEW BUTTON

    I am not going to go into a long explanation about this function, but suffice it to say that I use it MORE than the shutter button.

    So read about it and try it out. Put some small objects on a table in line astern and then focus from a slight angle at the side on the 2nd or third object. Use you kit lens at 18mm at THE LARGEST f-STOP and press this button. NOW, whilst holding the D. of F. preview button in, move the aperture ring towards f22 The picture will get darker and darker but you should notice the objects before and behind the original point of focus getting sharper and sharper.

    PLEASE NOTE. The objects behind get sharper quicker then the objects in front of the original point of focus. This is called the one third to two third rule.

    Let me give you a specific example. I am photographing an orchid in the French Alps and want the orchid plus the valley plus snow capped mountains in the background. I use the D70 and kit lens on the camera and focus on the orchid, which is very close to the camera. I push in the D of F preview button and watch as the Orchid remains in focus as I stop down towards f22 AND the mountains become sharper and sharper, until I can just about see them as being sharp. I THEN KNOW that I have got the orchid and the mountain sharp and the picture of the orchid in it's habitat is achieved.

    Hope this helps.

    Bob F.
     
  11. NANCY

    NANCY

    134
    Mar 14, 2005
    FLORIDA
    Oh, my gosh! I am jumping up and down for joy!!!! Thank you all so much. I am so excited.

    Man, you put me out of my misery. No wonder I couldn't find those numbers on my lens; they weren't there. It really helped to visually see that. Thank you so much for taking the time to send those two picutres.

    Chris, Thank you for your awesome picture. I loved knowing what you chose as your vocal point.

    Spiderman, thanks for the advice about the focal point button. I had actually discovered it on my own so you helped me to realize that I am slowly starting to learn about my camera. Also, your example helped me to realize that some of this is about trial and error.

    I love math and details. One of the reasons I want to pursue photography is to force myself out of the left side of my brain. I have to laugh at myself for immediately getting attached to numbers and wallowing around back in the left side. Thank you all for releasing me so that I am in fact in possession of a right side of my brain too!

    OK. One last question. I just tried to print out this discussion so I can have it as a reference and I can't get the whole text at one time. Is there anyway I can print it so all the text prints without the right hand part of each line being cut off?
     
  12. RE: the suggestion to use DOF Preview, maybe my eyes just aren't good enough (which is probably true in itself), but I don't find DOF Preview through the tiny viewfinder on the D70 all that useful myself -- one more reason to consider an upgrade although one could buy a viewfinder magnifier attachment to help this.

    Anyway, one other thing to note (as Bjorn and others also suggested) is that each lens also has a sweetspot where it yields sharpest results, so even though a smaller aperture will theoretically yield larger DOF, you don't necessarily want to go that way everytime. Most lenses' sweetspot seem to hover somewhere between f/8 and f/11, so that's something to consider. Many zooms also vary in sharpness depending on focal length, and some lenses also seem to vary depending on focus distance -- the 85 f/1.4 vs 85 f/1.8 seems to be a prime example of this from what I can gather (per Ron Reznick's reviews).

    As for printing, not sure what's easiest. Since the thread is not really that big, you might just try copy-and-pasting the individual posts into MS Word and then print from there. Seems like the extra wide formatting is just coming from the forum's page formatting. I tried a quick copy-and-paste of my reply, and it looks ok in Word.

    _Man_

    PS: Maybe the moderators would like to move this thread (and others like it) over to the Tech Discussion section instead. Just a suggestion since this thread could prove useful to other folks in need of such info.
     
  13. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    My fault Nancy for posting such a wide photo. I've edited my reply above so you should be able to format it for printing now.
     
  14. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    My eyes too, Man. On a D100, the viewfinder is pretty small already and then it gets DARK when you stop down to f/8 or more. The good thing is that it's digital - you can just look on a computer to examine the focus within minutes of taking a photo. Then you will know that those particular (focal length, focus point and f-stop) will work in the field. The 10X chimp magnifier also helps, but 10X seems like not quite enough if your gonna be really precise.
     
  15. Chris,

    Does the D100 actually provide 10x zoom in review mode? That should be close enough me thinks. The D70 doesn't zoom in that much though -- maybe more like 5x, which is not that useful for examining such things. It's something I missed from my Canon G3.

    _Man_
     
  16. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    Well that burst my bubble. I've been blissfully believing it was 10X. Now I measured it and I know the horrid truth - it IS only 5.5X. Bummer.
     
  17. NANCY

    NANCY

    134
    Mar 14, 2005
    FLORIDA
    Thank you, Chris, for removing the picture. I am printing out the entire topic now. It is like gold for me as I am just learning about all of this. I loved your picture and am so happy I can still see it by going to your site. Thanks, again.

    Thanks to everyone. I feel like I just took a course in photography. I am blown away by the generosity of sharing that goes on on this site.
     
  18. Gale

    Gale

    978
    Jan 26, 2005
    Viera Fl
    This is a teriffic thread. Good info. I sure do appreciate it.

    Nancy, I have the same book.. I think it is great. The trick is to read it. Go back and practice each step for awhile as he suggests.

    I need to do this:
    Go spend a couple hours or more at the park. For several practice sessions on each step.

    Happy shootin and learnin

    Gale
     
  19. Hi again.

    I'm not familiar w/ that book, but if you want some alternatives for basic tutorial, you might also want to check out:

    http://www.shortcourses.com/using/index.htm

    I bought their tutorial book a long time ago when I bought my ancient Nikon CP800. Didn't actually read it until a few years later when I bought my Canon G3. :D That's pretty much how I got started w/ learning photography -- that plus a bunch of other online resources I came across on the general Canon forum on DPR, which I keep listed in my profile section there. :D

    If you want to check them out, here's a short list of certain essential ones I came across besides the DOF ones:

    http://www.photo.net/learn/

    http://www.luminous-landscape.com

    http://www.chem.helsinki.fi/~toomas/photo/

    http://epaperpress.com/psphoto/ (for Photoshop essentials)

    This one is actually its own list of resources (includes some of what I already listed):

    http://forums.dpreview.com/forums/read.asp?forum=1010&message=3697387

    For the D70 (and D100), you might also find this one of interest after going through the above:

    http://fotogenetic.dearingfilm.com/index.html

    _Man_
     
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