Need some help with DOF and Bokeh

[steve_munoz]

I am having abit of a problem trying to understand exactly how DOF and

bokeh are controlled. I know that using F1.8 instead of F8 would

yield alot less DOF and much better bokeh, but what else comes into

play? Distance between the lens and the subject, the subject and the

background, the focal length of the lens, other things? I am trying

to understand what things affect it, and how to properly gauge bokeh

and dof. I have a dof preview button on my Elan 7, but it gets quite

dark and hard to determine what is in focus and what isnt. I may just

have to get better at trying to see what is and isnt in focus on it.

Any info would be greatly appreciated.

 

Thanks

[idoy]

Read <a href="http://www.vanwalree.com/optics/dof.html">here</a>.

[jonas_gustavsson]

Or here: <a href="http://www.photo.net/learn/optics/lensTutorial">Lens Tutorial</a>

[steve_munoz]

Well I read through alot of that, but still find it difficult to know exactly what f-stop to use. If I want to take a portrait of a person with a 85mm lens and a 200mm lens what f-stop do I need to dial in to get the person (from nose/eyes to hair completely in focus). Alot of it was discussed, but is it still just trial and error? Is there a chart that tells you how much dof you have at x focal length and y F-stop. Let say at 200mm at F4 youd have a 10in DOF. Something you can refrence to to make sure that what you are shooting will be completely focused without stepping down more than you need to.

 

I will be shooting some portraits of my family when my brother and his wife have their first child. I will mostly be using a 50 1.8 and a 70-200 4L, but I am confused as to how much to stop down the aperture inorder to get a person infocus. Is this something you just learn with time, or is their some chart that most people refer too? When doing landscape photography, I always carry around my Hyperfocal Chart and use it religiously instead of trying to calcuate and do it manually. Is their an equivalent for portrait work aswell?

[byronlawrence]

there are DOF calculator charts available many places on the web.

 

the way I have always done it is just experience and rough guestimate after you have experienced the results for a while. but also a great helper is on some lenses. many lenses if you look at the distance scale (most all nicer lenses will have this as part of the focus) there are corresponding marks on the lens that indicates a range at a given f stop. Marks like 22 ll and 8; the marks will indicate the near and far distances within your focal range/dof. this is of course based on a standardized circle of confusion for a 35mm frame so if you are shooting dslr with a smaller sensor, just remember to be a little more conservative.

[KenPapai]

The BEST WAY is to SIMPLY DO IT and experiment and gain PRACTICAL KNOWLEDGE rather than trying to read it here. If you have a DSLR then it is a piece of cake -- practice on your wife, girlfriend, neighbor; shoot portraits from wide open to f/5.6 and see what you think. Also play with lighting variables -- sun at the back, at an angle, shooting in the shade, indoors, bounce flash; lots of good books available -- search Amazon. If your Elan 7 film SLR is your only tool then read up in a book and shoot a test roll of 100 speed film -- record in a notebook your aperture and shutter speed settings on EVERY shot.

[jim r]

Each lens comes with a depth of field chart that you can study, but as others have said you need to shoot. And then shoot a bunch more and learn what you like and don't like with each lens.

[steve_dunn2]

<p>Yup, what others have said. A DOF calculator will tell you the answer, but if you can get some practical experience at it, that will serve you well. You'll develop more of a feel for it and will be able to make a good guesstimate in the field when you don't have time to get out a measuring tape and calculator!</p>

 

<p>I have the same issue you do with DOF preview; in a dark, smallish viewfinder, it's hard to tell precisely what is or is not in focus. Just wait until you go digital with a 20D or similar, with its even smaller viewfinder, and the problem gets worse.</p>

[haunting_your_thoughts]

If you want quality baby-pictures with excellent bokeh, you can use your 50 f1.8 with the f-stop of f1.8. Now... here's the trick... The best way to focus is by using the eyes. If the eye is in good focus, the face will look slightly off-focus giving the portrait a soft look. There are lenses that are specifically meant to achieve the soft-look.<br><br>If you are taking the picture of more than one person, you are going to need the f-stop to be anywhere from f5.6 to f8.0 and you should be able to get everyone in the picture if they are posing. FOr children who are playing around, you can change to f12.0 or even f16.0 to allow greater depth of field. If you think that there is a guide to the Depth of Field and Bokeh required for each portraits, there isn't because it all depends on one's shooting style. The best way is to experiment, like someone else mentioned in here.

[athinkle]

For portrait work, you'll probably only be working with various wide apertures. This should make confirming DOF with the preview button possible, because the wider apertures should still be allowing enough light by which to compose. Worst case scenario: Ere on the side of too much DOF. You can always gaussian blur the background for some "made in the lab" bokeh, but you really can't sharpen a face that was accidentally shot out of focus through the use of too wide an aperture and the wrong focusing area.

[digitmstr]

With a 200mm you can use f/2.8-f/3.5 and get a nice background blur.

 

With an 85mm I wouldn't go past f/2.8. But, a lot depends on your camera to subject distance as well as the subject to background distance.