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08/07/2007 05:38:13 PM · #1 |
I have always had difficulty controlling my depth of field. It's always a tradeoff of getting enough blur in the background, without losing too much focus on the subject.
I would rarely want less than half a foot worth of focus and I often try to blur the background. I know that increasing zoom and increasing the aperture (smaller numbers) reduce the DOF, but I'm never really sure how much blur I'm likely to get, nor how little DOF I'm creating.
I'm just wondering if anyone has any rules of thumb that help them out. Does anyone have any tips for controlling this? Is it possible to get a reasonable amount of DOF and then have the focus drop off dramatically?
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08/07/2007 05:43:08 PM · #2 |
I use depth of field preview.
However, there is such a thing as a DOF calculator. Hopefully someone will pipe in with the link. |
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08/07/2007 05:45:01 PM · #3 |
The D70 has a DOF preview button on the lower right side of the lens. This will let you check the DOF and adjust accordingly.
See Front of Camera Controls HERE
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08/07/2007 05:46:06 PM · #4 |
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08/07/2007 05:51:24 PM · #5 |
This reminds me of how my understanding of how to land a plane evolved during my training. Initially, I asked for exact power settings, angle of bank, etc. Eventually, I realized I needed to use whatever power and angle would put the plane on the runway safely.
Same goes here. If it helps you understand the basic principles, or if you want to be very particular, use a DOF calculator. But If you're shooting something that lets you take a bunch of shots, just try it at different apertures and look in the LCD to see whether you're getting what you want. I find the DOF preview to be pretty dark through the viewfinder.
For most stuff I shoot these days, F/2.8 gives me what I want, and I work from there using the LCD review after I've taken the shot.
There's also a photojournalism tip of "F/8 and be there" meaning that if it's a moment in time that won't be repeated, you're better off with too much DOF than too little. You can always blur things in processing, even in advanced rules here.
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08/07/2007 06:24:46 PM · #6 |
Rule of thumb: at any given aperture and any given focal length, a lens has "x" amount of DOF, and 1/3x is in front of the plane of focus while 2/3 x is behind the plane of focus.
What does this mean to you? If you need MORE of the DOF on your subject and LESS of the DOF behind your subject, then "front focus": being the plane of focus in front of your subject by such an amount that the DOF ends at the limit of your subject.
In other words, if f/2.8 is not enough DOF for all your subject to be sharp, but f/5.6 makes BG too sharp, then use f/5.6 and focus towards the front of, or even *in* front of, your subject.
R.
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08/07/2007 07:48:11 PM · #7 |
Awesome! Thanks for all the replies.
I do recall playing with the lens DOF button when I first got my camera but had forgotten it was there. I'll have to have another go at that.
I agree with the idea about landing a plane. Being an engineer I like to learn the principles I need to get a job done. I don't care too much about theory for the sake of theory. All shortcuts are welcome... ;-)
I will also try playing around with a 2.8 aperture and see what I get.
I find the LCD on a D70 to be a little too small to be able to determine the focus of what I'm shooting and usually only check it for someone blinking and to check the exposure of the shot. I find out whether it's oin focus when I get it to the PC.
Thanks also for the tip, Bear, about focusing ahead of your subject to take advantage of where the actual DOF lies. |
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08/07/2007 07:59:39 PM · #8 |
There's another way you can accomplish the same thing Bear is talking about. We think about controlling our aperture and the plane of where we focus, but it many shots we can control the ratio of camera-to-subject and camera-to-background. That is, if you are really looking for background blur with sharp subject, aim to have a picture at close to the shortest focal distance the lens will allow and have the background be many multiples of that away.
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08/07/2007 10:08:14 PM · #9 |
Originally posted by isonaj:
I find the LCD on a D70 to be a little too small to be able to determine the focus of what I'm shooting and usually only check it for someone blinking and to check the exposure of the shot. |
Can the D70 zoom in the LCD? If so, you can zoom way in to see how things look in detail.
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08/07/2007 10:29:00 PM · #10 |
| Yep. It can. I was thinking that as I was replying earlier that I should actually use the zoom more to check focus. :-) |
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