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05/03/2003 04:40:34 PM · #1 |
I noticed on the challenge entry form you had to enter the 'Aperture'
of the photo and I was just wondering what it meant or stood for.Thanks! |
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05/03/2003 04:48:19 PM · #2 |
Ok I'm not totaly positive I'm going to explain this right, but aperture is the size of the iris of the camera's lens while taking the picture. The lower the aperture number the more light enters the camera. The smaller the number the wider open the iris.
Also the smaller the aperture number the more narrow depth of field. So a wider open iris (aperture number lower) Will yield a shorter depth of field (less will be in focus) where a high number will let in less light and more will be in focus.
To learn how to get the aperture, shutter speed, etc from your photograph read the exif section of the faq on dpc
//www.dpchallenge.com/help_faq.php#exif
This will explain it a lot better than I could, and it gives you some links to files you can download for free to view this data on your pictures.
Here's a site that explain aperture a lot better than I just did *should have thought of this before posting*
//www.photocourse.com/03/03-03.htm
Message edited by author 2003-05-03 16:49:56. |
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05/03/2003 04:59:11 PM · #3 |
The aperture refers to the mechanism in the lens of a camera which controls the amount of light getting through to the sensor (or film, for traditional cameras). In your camera, I believe it is fixed, so 'fixed' would probably suffice :)
In other lenses and cameras, it is rated in 'F-stops', from a small value like F1, through to a large value like F32 and beyond. The F-stop indicates the size of the hole letting in the light, which opens and closes similarly to the iris in the eye. Paradoxically, the small values indicate a large opening, while the large values a small opening.
The aperture is also used to control the amount of the photo which is in focus, known as the 'depth-of-field'. This is covered in the tutorials section here - Depth of field tutorial written by magnetic9999.
I hope this answered your question!
Cheers :) |
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05/03/2003 05:04:32 PM · #4 |
| I understand what it means now,thanks guys! :D |
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05/03/2003 05:25:52 PM · #5 |
| I was going to add that it's the little hole in the center of the blue ribbon in the DPC logo, but that might not be helpful... |
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05/03/2003 06:23:55 PM · #6 |
Just to add to what's already been said, the reason that the f-stop number goes up as the aperture gets smaller is because the aperture's diameter is expressed as a fraction of the focal length of the lens (hence the standard notation f/8, f/4 etc - where f represents the lens's focal length).
So if you have a lens with a focal length of 48mm, an aperture of f/4 would mean the diameter of the aperture is 12mm, while an aperture of f/8 would mean your aperture is 6mm in diameter.
It's also worth noting that in the 'standard' f-stop sequence (f/2, f/2.8, f/4, f/5.6, f/8, f/11 etc.) each stop allows 1/2 as much light through as the stop before it.
Message edited by author 2003-05-03 18:24:55.
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05/03/2003 07:07:21 PM · #7 |
I wrote this to explain to a friend recently.
What is Aperture?
Inside a camera lens is a mechanism called a diaphragm, consisting of a set of curved blades. The blades form a rounded hole called the aperture. This is like the pupil in your eye, which expands or contracts when the light changes. So too can the aperture expand or contract at your command.
This is done to vary the amount of light that gets through the lens and onto your film.
The other way of varying the amount of light that hits your film is shutter speed - a 1/30th of a second exposure obviously lets in a lot more light than a 1/400th of a second exposure.
Together, the combination of shutter speed and aperture control your exposure.
As any given film type requires a certain amount of light to accurately record the scene the actual aperture and shutter speed settings used vary hugely depending on the ambient or man-made light of the scene being photographed.
When using the camera in fully automatic mode the exposure needed is calculated by the on-board light meter and the camera selects an appropriate combination of aperture and shutter speed. You can also use it in manual or priority modes to select these yourself.
For example, let's say my camera suggests an aperture of f11 and a shutter speed of 1/125th of a second.
I can change it manually to half the aperture and double the shutter speed the overall exposure will be the same - but there will be a difference in my finished photograph.
What you need to know in order to make aperture and shutter speed decisions
High shutter speeds will freeze motion - using these tends to mean you have to go for wider apertures (f2.8, f4) to let in more light.
Slower shutter speeds will allow you to capture motion – popular when photographing waterfalls for example – you’d need a narrow aperture (f22 etc), to compensate.
Wider apertures result in shallow depth of field – see below for DOF explanation – great when you want, say, an animal in sharp focus, but the grasses and bushes in front of and behind it out of focus.
Narrow apertures result in greater depth of field – where more of the picture from front to back is in focus.
Camera modes
Most modern SLRs have 4 modes – fully manual, fully automatic and then Aperture priority and Shutter priority. Aperture priority means you select an aperture and the camera works out, using the light meter, what shutter speed it needs to use in order to expose correctly. It will alert you when you’ve selected an aperture which it simply can’t use because there is just too much or too little light. Make sure to be aware of what shutter speed it selects if you use this – a speed of slower than 1/30th cannot easily be hand held without camera shake.
What is DOF?
A lens can only bring objects at a single distance from the camera into critically sharp focus (at a time). But if you look at photographs, you can see a considerable area of the scene (from near to far) that appears sharp. Even though theoretically only one narrow plane is critically sharp, other parts of the scene in front of and behind that plane appear acceptably sharp to the human eye. Objects become less and less sharp the farther they are from the plane of critical focus. Eventually they become so out of focus that they no longer appear sharp at all. The area in which everything looks sharp is called the depth of field. Where this is only a small area infront of and behind the focal plane it is said that the depth of field is shallow. Where this area is larger it is said that the depth of field is deep/ great.
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