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01/31/2006 01:49:40 AM · #1 |
| Most digital cameras have a smallest aperture of f8 only (like my Canon S1). Why not f22 as in conventional cameras? |
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01/31/2006 01:52:19 AM · #2 |
I read some place that a f8 on a p/s camera is different then a f8 on a dSLR.
Message edited by author 2006-01-31 01:52:30.
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01/31/2006 01:58:32 AM · #3 |
| The lenses on most p/s digital cameras are so small that it isn't physically possible to get an aperture much smaller than f/8... |
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01/31/2006 01:59:29 AM · #4 |
| You have to consider the cost involved. A Point&Shoot will not have as many features as a dSLR. One such loss of features is reduced range of fstops. |
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01/31/2006 02:03:50 AM · #5 |
Originally posted by TooCool:
The lenses on most p/s digital cameras are so small that it isn't physically possible to get an aperture much smaller than f/8... |
Not to mention the lens focal length is so short, an aperture smaller than f/8 isn't needed. P&S cameras have deep DoFs, so f/8 is pretty much all you need.
Message edited by author 2006-01-31 02:04:24.
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01/31/2006 02:18:47 AM · #6 |
| I had a Panasonic FZ10 with f8 as maximum aperture, but it has nothing to do with de dslr. There is much more DOF in a P&S at f8 than in a dslr at the same f stop. |
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01/31/2006 02:53:40 AM · #7 |
Beyond f8 you run into diffraction problems with these lenses and size of sensors and that means that your image will only look worse beyond f8.
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01/31/2006 05:11:47 AM · #8 |
F/stop is a ratio, not a fixed size. It's the ratio between the physical diameter of the aperture and the focal length of the lens. A 25mm aperture on a 50mm lens is f/2.0; the same aperture size on a 200mm lens would be f/8.0.
There's an optical phenomenon called "circle of confusion" that comes into play when the physical size of the aperture gets too small, and diffraction begins to occur, robbing the image of sharpness and contrast. Even in dSLR cameras this is a real problem; when I use my Canon 10-22mm lens zoomed out at 10mm I notice a falloff in image quality if I go smaller than f/11 or so, even though it will stop down much further than that if I ask it to. On the other hand, my 70-200mm lens is perfectly happy at f/32.
Your powershot has a much smaller sensor and therefore lenses of a given angular coverage are much shorter. You have oodles of DOF even at f/8.0; indeed, one of the great advantages of a P&S camera is that it very forgiving of focusing errors because the DOF is so great. DOF also is a function of the physical diameter of the aperture, you see.
Robt.
Message edited by author 2006-01-31 05:12:39. |
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01/31/2006 07:56:48 AM · #9 |
About half a kilometre of dof at F6.3 on my Canon Powershot A95 P&S in this shot. The one time it's huge dof served me well. Drove me nuts most other times.
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01/31/2006 10:53:38 AM · #10 |
| Does a camera with a limited range of apertures also mean a decrease in dynamic range? Let's say I'm using the zone system to figure exposure setting. When I meter the white of a wedding dress I get f5.6, 1/60th at ISO 100. If I figure that the wedding dress is 2 stops above mid grey (V), do I open up my aperture two stops to f2.8 or do I use a more compressed version of the zone system and maybe only open up by one stop? When I've tried this in the past I have always blown out the highlights. |
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