View Full Version : Apeture...Tell me about your lens'
09-01-2006, 09:57 AM
I have the Canon Rebel 350 blah blah blah...
I purchased the Tamron AF 18-200 and the Tamron AF 70-300. Met an individual on vacation who was talking to me about Apeture and he had lens that had less range but more apeture/wider lens.
Please tell me about this and what you own and anything I need to know about apeture from your experience...TIA :?:
09-01-2006, 12:35 PM
Well, here's what I understand about it--
The aperature is described by the "f number"--ie F2.8, F4.0, etc. I am not sure of the smallest numbers and largest numbers that exist, but basically speaking, the smaller the number, the bigger the opening when the shutter is released. The bigger the F number, the smaller the opening.
Sooooo, lenses are generally listed by their lowest "F number"--like my 50mm lens is called 50 mm 1.8. Meaning the lens will open pretty wide if I want/need it. I often hear lenses with smaller F numbers being called "faster" lenses--I imagine this is the case since you can use a faster shutter speed since you get more light with the wider aperature--bigger opening allows more light.
I also know that using a bigger F number will create that neat-o "star" effect with lights. You pretty much have to use a tripod or at least have the camera sit on a table (and use the timer too) so you don't get camera shake, since you also have to use a really slow shutter speed. But you can see the effect I got with F2.8 and I think a one second exopsure (not the best pic though)
09-02-2006, 02:26 PM
Aperature is the size of the hole that the lens opening makes. The smaller the number, the bigger the opening (think of fractions how 1/2 is bigger than 1/4.. even though 4 is bigger than 2). The bigger the opening, the more light it lets in... which in turn allows you to set your shutter at a fast speed. Or vice versa, if you have a smaller aperature, you'll have to slow down your shutter to get in the light. That's why the bigger aperature lenses (smaller numbers, remember) are popular and sought after... got to get that light in the lens!
Hope I wasn't too confusing... for me, it clicked by understanding how aperature and shutters work together.. and then remember smaller number = bigger opening.
Also, to throw in, the aperature is also one of the components to depth of field... or how much is in focus. Smaller aperatures will provide you with (in conjuction with focal length and distance) the smaller area of focus and things not on that plane fading out of focus, KWIM?
09-07-2006, 09:59 PM
clear as mud?
09-08-2006, 04:50 AM
I am copying my aperature explanation from the photo forum at DigiScrapDivas.....
Many of you may have point & shoot cameras which automatically adjust the aperature setting for you. But if you have a regular SLR camera, or even a SLR digital camera like the Canon Digital Rebel, you do have the option to adjust these settings. If you have one of these cameras, you should get it out and hold it while reading through this so that you can get a visual. Otherwise, this could get rather monotonous to try to follow.
First letís talk about what the aperture is. Think of the aperture of your camera as if it were the pupil of your eye. The aperture is the opening within the lens that allows light to expose the film. It is commonly referred to as the F-Stop. You can adjust the size of this opening by turning the aperture dial on your cameraís lens. Most lens aperture settings range from 2.8 to 22, with some lenses having a larger range than that. The smaller the number, the larger the opening. So an aperture setting of 2.8 will have your lens wide open, whereas a setting of 16 will be fairly small.
This opening in the lens not only allows a certain amount of light into your camera, but it also controls your depth of field. A smaller number F-stop (such as F2.8) will cause only your focal point and one foot in front and one foot behind your subject to be in focus. The foreground and background beyond one foot of your subject will be blurred. This is especially nice to use when you have a distracting background. On the flip side, a large number F-stop (such as 22) will cause pretty much everything within 5-20 feet of your focal point to be in focus.
Now letís talk about the shutter speed. The shutter controls the amount of light by length of time in seconds. Shutter speed ranges from bulb setting to 1/4000 of a second. Bulb setting is where you determine how long to leave the shutter open by pressing down your shutter release button and keeping it pressed down until you have elapsed the amount of time necessary for your shot. An example of when you may want to use the bulb setting would be capturing a time-lapsed view of the stars at night. From there, the shutter speed settings decrease the amount of time in increments of 1 second Ė 1 second, 1/2 second, 1/4 second, 1/8 second, 1/15 second, 1/30 second and so on. The more light you are dealing with, the faster your shutter speed will be. On a typical sunny day, you may find yourself shooting at 1/250 of a second.
Using your shutter speed settings to control the amount of light will also control motion. For instance, the slower shutter speeds (those under 1/60th of a second) will cause blurred images, whereas faster speeds (such as those over 1/500th) will cause a moving object to appear crisp and clear.
Both your shutter speed and aperture setting will affect the amount of light that enters the camera. To get a correctly exposed negative, you have to find the right combination of both of these settings. Most cameras have an internal light meter to help you with your decision making process. My suggestion would be to choose to work with one setting and let your camera choose the other based on your selection. For instance, letís say you are at a baseball game and you want to capture the pitcher without blurring his arm when he throws the ball. You know that you need a faster shutter speed to achieve this So set your shutter speed to around 1/250th of a second and let your camera automatically choose the aperture setting. If you find that it chooses a small number, like F 2.8, youíll need to get fairly close to the pitcher because of the depth of field being limited with the smaller aperture size. Or, you can slow down your shutter speed to 1/125th of a second and your camera will automatically open up your aperture setting to about F 5.6.
Another example Ė letís assume you are taking a portrait of someone on a slightly overcast day. You know that you want a short depth of field because the background is distracting. So you can set your aperture setting to F 5.6 to allow for a clear view of your subject while the background and immediate foreground will be blurred. Your camera will then automatically adjust the shutter speed accordingly. Now, the only time this will not work well is if you choose to use a dedicated flash that needs to be synched at 1/60th of a second. If this is the case for you, you will have to meter your F-Stop according to your distance from your subject as well as how much depth of field you want to achieve, but also set your shutter speed to 1/60th so that the flash will be properly synchronized and give you a properly exposed negative.
Okay, well, thatís the basics of aperture and shutter speed adjustments. If you want more detailed information, I would recommend checking your library for a book titled Photography by Barbara London Upton and John Upton. I think itís into the 8th edition by now and runs about $80. This book has everything you need to know to learn how to use your SLR camera.
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