 Katie Ward |
Appeture settings My Rokinon Auto Zoom Super Coated 1:4.5 f=80-200mm No. 909369 lens has appeture settings of (from left to right) 22, 16, 11, 8, 5.6, and 4.5 . I've just recently gotten into photography, so I just need a little clarification as to if I've got this straight: The higher the appeture setting (i.e. 22) the clearer the whole picture will be? And the lower it is (i.e. 4.5) the more out of focus the background will be? I know it's sort of confusing to understand that, but if someone could help me out, that'd be great! Katie
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Kerry L. Walker |
The higher the number, the smaller the opening of your aperature. The higher the number, the greater the depth of field. Therefore, given the same focal point, the higher number will give you more in focus in front and behind the focal point. So, to answer your question in a word - yes. Remember, however, that the higher the aperature number, the slower your shutter speed must be to achieve a proper exposure.
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Alan N. Marcus |
Hi Katie, It would be my pleasure to help you along. However, this might be more than you care to read. The camera lens mimics the human eye. In dim light conditions your iris (the aperture of your eye) dilates (opens wide) to allow more light to enter. In bright sunlight, the iris contracts forming a tiny opening that greatly restricts the amount of light allowed to enter. The light plays (is projected) on the retina (light sensitive membrane at back of the eye). The iris, the colored portion of the human eye and is named for the Greek god of the rainbow. The eye/brain combinations cause the iris to contract or expand based on the amount of ambient light. Camera makers follow this model. Should insufficient light reach the film in a conventional camera or a digital camera, under-exposure results. Should too much light enter over-exposure results. Thus modern cameras have an adjustable aperture called the iris diaphragm. This mechanical restriction inside the camera lens changes the working diameter of the lens by contracting or expanding, just like the human eye iris. In this way the camera regulates the amount of light that the film/chip will receive (exposure). Numerical values are assigned to indicate the size of the lens opening. Technically these numbers are known by the name “focal ratio”. For short we abbreviate using a lower case f. Because the number is technically a ratio, we follow the f with a forward slash /. Thus when writing one of these numbers we use this convention; f/22. Some folks call them f numbers, some call them f stops. “Stops” because the restriction passes some light and stops some light. A ratio must be used because there are two factors that must be taken into account. 1. The working diameter of the lens. 2. The focal length of the lens. The f number is derived by dividing the focal length by the working lens diameter. Your lens reads f/22 (smallest opening), f/16, f/11, f/8, f/5.6, and f/4.5 largest opening). Each indicates a change in aperture that doubles or halves the amount of light regulated. As an example: Taking a picture at say f/8 allows light to enter. Changing to f/5.6 doubles the light energy hitting the film/chip. Changing to f/11 halves the amount of light. On your camera, the largest opening is f/4.5, this value is a slight violation of the double haves rule. You see, the next number in this set should be f/4 which would allow twice as much light to enter as f/5.6. Your camera lens maker decided that they could give a little more than f/5.6 so they gave you an extra 1/3 more with f/4.5. The system with these strange numbers seems weird. Lens makers have had hundreds of years to think about the way lens speed is expressed. Many systems have been tried; perhaps you will come up with a better one. As to clarity and sharpness. It is true that your lens has a sweet spot that will produce the sharpest image, probably f/8. The difference between this sweet spot and all other f numbers is so tiny you will never see the difference unless you produce a giant print for over the fireplace. There is no difference in image size or uniformity between the various f numbers. You can freely choose any one that satisfies you picture taking situation. However tiny openings like f/16 have the greatest depth-of-field. Larger opening like f/5.6 have shallow depth-of-field. Depth-of-field is that zone that has acceptable detail (sharpness) in front of and behind the point (distance) focused upon. Non adjustable cameras are set to about f/16 and focused at about the 10 foot mark. This produces a depth-of-field of about 3 feet to as far as the eye can see (infinity). This allows the casual shooter to work without the need to focus his/her camera. When working in dim light, we open the lens up to say f/5.6. This allows more light to enter. However, this action results in a shallower depth-of-field. Now we are forced to carefully focus. Stated another way, an adjustable lens allows taking pictures under adverse conditions but now we must pay close attention to focus. Control of depth-of-field is one of the keys to success. You need to lean about this issue. In scenic photography we want a great expanse in focus, we use f/16. With portraiture, we want the eyes in focus and the background out of focus, we use f/5.6. Once upon a time, photographers needed to know all about f stops. Now days, it doesn’t hurt to know but, a modern camera with its wonderful chip logic does most of the settings for you. Today you need only a cursory understanding to be good, however to be great, I think you will need to take command and thus you must learn the whole story. Best of luck, have fun learning. Alan Marcus
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Katie Ward |
Thank you both for your help- it certainly cleared things up for me! Thanks,
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