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05/24/2005 01:00:11 PM · #1 |
Hi all. This a basic "newbie" Q. (Since I am one)
I have a Sony DSC-P200. In its manual mode it has 2 aperture settings f/2.80 and f/5.60. I took some pictures and loaded them into PhotoShop Elelments 3 and looking at the "Exif" info, it has to point of info that I'm wondering about:
For a particular photo, it says,:
"F-stop: f/5.2
"MAX-Aperature: f/2.80"
How did it set the f-stop to 5.2 if I can't manualy set that? Isn't "f-stop" and "aperture" the same thing, or do I have that wrong and the camera is making some adjustments? Does shutter speed change the "f-stop" value?
Thanks! |
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05/24/2005 01:02:50 PM · #2 |
| f-stop and aperature are the same thing. The smaller the number the larger the opening. Yes there is a relationship between shutter speed and aperature. |
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05/24/2005 01:14:23 PM · #3 |
I am confused on this subject too. I keep trying to create a shallower DOF and the Higher F-stop # is supposed to help. But it doesn't. I can adjust my Aperature from 2.8 to 8. Limited I suppose, but does zoom have anything to do with it???
Message edited by author 2005-05-24 13:14:43.
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05/24/2005 01:20:23 PM · #4 |
DOF is affected by the focal length as well. More zoom will help with achieving a shallower DOF, however shallow DOF is hard with P & S cameras. Using closeup filters and/or macro mode will help.
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05/24/2005 01:22:11 PM · #5 |
| The larger the aperature (opening) the smaller the f-stop (number) will assist in creating a shallow DOF. |
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05/24/2005 01:31:56 PM · #6 |
The smaller the f-stop number, the larger the opening in the lens (lets in more light). small f-stop numbers give you a shallower depth of field (what is in focus, from near to far). conversely, the larger the f-stop, the smaller the opening, the greater the depth of field.
If you have a small f-stop, the opening in the lens is letting in alot of light, so you can shoot at faster shutter speeds. How you set them depends on what youre shooting. If you are shooting an action shot, you want to set you're shutter speed fast, like 1/500 or faster, youre aperature setting will be a small number, like f3.5. If youre shooting a landscape where you want everything to be in focus, set your aperature at the highest number you can and still maintain a shutterspeed fast enough where you won't get any motion blur. I can shoot hand held at 1/125 sec, occasionally 1/60 if I have something to lean against and use my strap as a sling, Like a rifle sling. Most people won't attempt hand held at under 1/250.
You're film speed (ASA) also plays a part. The larger number the film speed, the less light it takes to expose, but very large asa settings can become noisy and grainy. REally long shutter speeds can also get noisy.
Play with it. Set your camera on a tripod, lets say with with your subject being a line of parking meters. Change your shutter speed/and aperature settings one stop at a time, and you will see how youre depth of field changes.
I'm starting to ramble. Hope this helped
David
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05/24/2005 01:33:25 PM · #7 |
The wider the F stop, the longer the lens, and The closer your focus, the narrower the DOF. Also Crop facter has something to do with it as well.
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05/24/2005 01:53:25 PM · #8 |
Alot of the basic cameras are made so they can only have a wide dof.(no way to blurr the background) The F-stop number doesn't always compair to a SLR camera. On one I had I think 2.8 would be about 11 on a slr. If you can add a close up lens to your lens then you can have more control or at least blurr a background.
Tim |
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05/24/2005 03:10:16 PM · #9 |
DOF is a function of the physical diameter of the aperture. "f-stop" is a ratio of the diameter of the aperture to the focal length of the lens. A 25mm aperture in a 50mm lens = f:2.0, while a 25mm aperture in a 200mm lens = f:8.0... The DOF in these shots would be identical; a 50mm lens at f:2.0 has the exact same DOF as a 200mm lens at f:8.0...
On a camera with a small sensor, a shorter lens offers the same angular coverage as a longer lens does on a larger sensor. So effectively, on small p&s cameras the working focal lengths are very short, and even on a dSLR the working focal lengths are significantly shorter than they are on a 35mm camera. In film equivalences, the angle of coverage of a 28mm lens on a 35mm film camera is roughly the same as a 90mm lens on a 4x5 inch large format camera. In other words, what's a moderate telephoto for a 35mm camera is a true wide angle on a 4x5 camera.
So, to get back on topic, at a given f-stop physical apertures are smaller on smaller cameras, and thus they tend to have much deeper DOF. The plus side is they are a LOT more forgiving in focusing. The negative side is it's very difficult to control DOF when taking the shot, if you want to throw some elements out of focus. This is why God gave us Photoshop, selection tools, and Gaussian blur :-)
Robt.
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