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07/13/2007 11:31:24 AM · #1 |
| I know that aperture priority affects DOF but here's my questions. On a Point and shoot like mine where I have some SLR features like control of exposure and some manual focus(on a side note: i hate my manual focus with arrow keys) do I get much control over DOF? Also which way do you have to go for DOF to increase or decrease? Bigger the aperture number the more DOF or less? I really like pictures where you get a blurry background and I can get that happening with my camera on some shots but not all of course. Boy I wish I had an SLR LOL. |
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07/13/2007 11:36:35 AM · #2 |
the higher the number the more area will be in focus, the lower the number the smaller the focused area. if you want a really sharp subject and really blurred background the best thing to do is get your aperature up high enough so that the whole subject is in focus and then move it as far away from the background as possible to get the background real blurry.
HTH
here are a couple examples:
 
Message edited by author 2007-07-13 11:40:12. |
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07/13/2007 11:41:51 AM · #3 |
With a P&S, getting the DOF you want can be tough. You don't get the same results at f2.8 as you would on an SLR at f2.8 with a similar focal length.
The most blur will happen when using the longest focal length the camera has with the lens wide open.
As has already been mentioned, subject to background distance will also be a factor in the amount of blur you get in the background. With a P&S you will need greater distances to achieve the same blur as can be achieved with an SLR with similar settings. |
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07/13/2007 11:47:47 AM · #4 |
Add to above: Also, a short camera to subject distance will give you a shallower DoF.
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07/13/2007 11:52:24 AM · #5 |
Originally posted by cpanaioti:
With a P&S, getting the DOF you want can be tough. You don't get the same results at f2.8 as you would on an SLR at f2.8 with a similar focal length.
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Reason being the very small sensor size compared to a DSLR.
There are even differences between DSLRs, a Canon 5D has shallower DOF than a 30D.
A MF digi (or film for that matter) like a Hassy has even shallower DOF at a given f/stop.
Rule of thumb, bigger the sensor/film plane the shallower the DOF at a given aperture. |
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07/13/2007 12:27:44 PM · #6 |
Quick lesson:
1. The larger the sensor, the longer the focal length for the same angular coverage. Example: on the 20D 10mm lens is the same angular coverage as 16mm on the 5D. The 20D has an APS-C sensor with a "1.6 crop factor" and the 5D has a full frame sensor.
2. In any lens, the DOF is a function of the physical size of the aperture; a 10mm aperture gives more DOF than a 20mm aperture. Makes no difference how long the lens is, all 10mm apertures have same DOF whether on a 50mm lens or on a 200mm lens.
3. F/stop is a ratio between the focal length of the lens and the physical diameter of the aperture. That is to say, a 25mm aperture on a 50mm lens is f/2, while a 25mm aperture on a 100mm lens is f/4. So to get the same DOF on a 100mm lens as the 50mm lens has at f/4, you need to stop down to f/8. The rule is, for same DOF you need to adjust by the ratio of focal lengths; a lens twice as long needs to be stopped down one more stop, a lens 4x as long needs to be stopped down 2 more stops, and so forth.
4. An easy way to remember which f/stop is "bigger" (lets in more light) is to visualize them as reciprocals, which is in fact what they are. So f/2 is an aperture of a diameter 1/2 the focal length, and f/22 is an aperture with a diameter 1/22 the focal length.
5. The compact point 'n shoot cameras have very small sensors, so their equivalent focal lengths for the same angular coverage are MUCH shorter than those on dSLR cameras. Therefore, all their apertures are correspondingly much smaller in diameter, and they tend to have tons of DOF for a given shot as compared to dSLR's.
Hope this helps.
R.
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07/13/2007 02:14:11 PM · #7 |
Here is a LONG write-up that should answer most any questions ...
//en.wikipedia.org/wiki/Depth_of_field
Message edited by author 2007-07-13 14:14:24. |
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07/13/2007 02:20:05 PM · #8 |
I've had some luck with getting shallow DOF on a P&S when I set it to macro mode and move closer to the subject. Try playing around with that and see what happens. |
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07/13/2007 03:52:15 PM · #9 |
Yep, that article helped me a lot.
You could also read the tutorial on DPC.
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07/13/2007 05:03:47 PM · #10 |
Originally posted by jhonan:
I've had some luck with getting shallow DOF on a P&S when I set it to macro mode and move closer to the subject. Try playing around with that and see what happens. |
Yes, this can work very well if you move the cam so the point of absolute focus is actually in FRONT of the subject, so the subject is "caught in the DOF" and everything else is off the chart.
R.
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