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On December 02 2011 04:40 MoonBear wrote:
As someone who knows nothing about cameras but is interested in learning about them, would someone mind explaining to me some of the things that came up? (Like F2.8, ISO+Number, 1/1.7 sensor, etc.) I tried reading wikipedia but I have a feeling I interpreted some of them wrong. This is what I think they mean:
F+Number: Shutter speed. The higher the number the better the quality of picture and depth of view?
ISO+Number: Format of picture, the bigger the number the better?
Number+Sensor: Determines whether the camera is better at close range pictures or long range pictures?
You have to talk about Aperture, ISO, and Shutter Speed all at once.
When you take a picture, you open a hole, light comes in and hits the film or sensor.
Let in too much light and it becomes bright, let in too little light and it becomes dark.
Aperture: The size of the hole. The bigger the hole the more light you can let in. The smaller the number the bigger the hole. If you have wider apertures, you don't need to open it for longer, so you can get faster shutter speeds. The light it gathers will be closer rather than farther, so you have narrower depth of field. You will see aperture being important for low-light/indoors pictures, or pictures where you want to control the depth of field.
Shutter Speed: How long you want the hole to be open.
ISO: The sensitivity of the sensor. If it's sensitive then you get more noise and you get a grainy picture; but it also operates on less light.
The number of the sensor is just the ratio of the size of the sensor compared to the size of film on a full-frame 35mm camera. 1.3x means that the ratio of the full-frame 35mm to the cropped sensor camera is 1.3:1, and the cropped sensor is smaller. This means you get less picture. Full-frames are technically better, but for typical, non-professional usage it's not gonna be an issue.
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I have a T1i with a 17-50mm f/2.8. That's been good for my uses, which is typically just pictures I take when traveling. Any other time that I need to take a picture, I use my cell phone.
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F-number: If you think back to how all cameras operate similarly to the principle of a pinhole camera, this number is how big the pinhole is, expressed as a ratio. What this really means is 'the pinhole has the diameter of X, where X is the focal length divided by this number'. The number is usually to the nearest tenth from multiples of the square root of two. A 50mm f/1.4 lens has a "pinhole" 35.3mm in diameter. With regard to what's listed on lenses, that number represents the widest aperture the lens can achieve, and in zoom lenses with two numbers, it typically represents the widest aperture on the wide end followed by the widest aperture at the longest end.
ISO rating: This is how sensitive the sensor is to light. (keyword: exposure value) The numbers were originally used for film, but their respective equivalents still carry over to digital without diving into the mess that is emission/absorption spectra differences and specific sensitivity to certain colors.
The best analogy I can think of is to think of a properly exposed photo containing the "light" equivalent to a gallon of rain. You can collect it with a shot glass and get fairly precise results (lower noise) at the price of trading speed to do so. You can also collect rain with a bucket, which might lead you to overflow or underfill, but takes quite a bit less time (faster shutter speeds allowed, but more noise).
Shutter speed: With regard to the analogy I used earlier, it's basically how long you want to collect "water" with the container of your choice. Optimally you collect a gallon of "water", but you can choose to collect more or less, depending on what you need the photo for.
Sensor size: With point and shoots, sensor sizes are expressed as diagonal lengths. A 1/1.7 sensor is 0.58 inches from corner to corner. A 1/2.5 (far more common size) sensor is 0.4 inches from corner to corner.
When dealing with typical DSLR that have smaller than a full (36mm x 24mm) 35mm frame sensor, they're expressed as crop factors. A 1.5 crop (Nikon APS-C) sensor is 24mm x 16mm, a 1.6 crop (Canon APS-C) is 22.2mm x 14.8mm, and a Canon 1.3 crop is 27.9mm x 18.6mm.
The larger the sensor, the easier it is to blur the background with the same size aperture. (keyword: circle of confusion),
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I think noise would just be better expressed as noise - imagine radio static. Imagine you have it at volume 2 and you can hear fine, but there's very little static in the background. Imagine the sound you are hearing drops so you have to bump the volume up to 6. Now you can hear the sound at normal levels again, but the static has increased with it.
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Well, that's actually the exact same type of noise -- electronic randomness that exhibits itself as noise; whether it's perceived visually as grain or audibly as white noise is immaterial.
That said, when you're primarily publishing for web, you can get away with a lot more than if you're publishing for print.
70-100 PPI is quite a bit more forgiving than the 300 DPI that goes into typical prints.
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On December 02 2011 07:01 silverfire wrote:
F-number: If you think back to how all cameras operate similarly to the principle of a pinhole camera, this number is how big the pinhole is, expressed as a ratio. What this really means is 'the pinhole has the diameter of X, where X is the focal length divided by this number'. The number is usually to the nearest tenth from multiples of the square root of two. A 50mm f/1.4 lens has a "pinhole" 35.3mm in diameter. With regard to what's listed on lenses, that number represents the widest aperture the lens can achieve, and in zoom lenses with two numbers, it typically represents the widest aperture on the wide end followed by the widest aperture at the longest end.
ISO rating: This is how sensitive the sensor is to light. (keyword: exposure value) The numbers were originally used for film, but their respective equivalents still carry over to digital without diving into the mess that is emission/absorption spectra differences and specific sensitivity to certain colors.
The best analogy I can think of is to think of a properly exposed photo containing the "light" equivalent to a gallon of rain. You can collect it with a shot glass and get fairly precise results (lower noise) at the price of trading speed to do so. You can also collect rain with a bucket, which might lead you to overflow or underfill, but takes quite a bit less time (faster shutter speeds allowed, but more noise).
Shutter speed: With regard to the analogy I used earlier, it's basically how long you want to collect "water" with the container of your choice. Optimally you collect a gallon of "water", but you can choose to collect more or less, depending on what you need the photo for.
Sensor size: With point and shoots, sensor sizes are expressed as diagonal lengths. A 1/1.7 sensor is 0.58 inches from corner to corner. A 1/2.5 (far more common size) sensor is 0.4 inches from corner to corner.
When dealing with typical DSLR that have smaller than a full (36mm x 24mm) 35mm frame sensor, they're expressed as crop factors. A 1.5 crop (Nikon APS-C) sensor is 24mm x 16mm, a 1.6 crop (Canon APS-C) is 22.2mm x 14.8mm, and a Canon 1.3 crop is 27.9mm x 18.6mm.
The larger the sensor, the easier it is to blur the background with the same size aperture. (keyword: circle of confusion),
Thanks for this! UPS just delivered my t2i tonight. :D The terms associated with photography can be overwhelming at first... (especially to a complete photo noob like myself)
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EPT
