beginner, pleae help....

[sarahleedavies]

Hi there, this is the most fantastic sight and as I am completely new to this I am reading everything I can. I have been looking at some of then assignemtns that people have done and see that they put a list after and was wondering about them and have pasted them below and was wondering if anyone could help me and explain focal length etc.
Exposure: 0.02 sec (1/50)
Aperture: f/1.8
Focal Length: 50 mm
Exposure: +1.67
ISO Speed: 200

was wondering why exposure is 1/50 means 0.02 secs? and focal length. thank you so much in advance....

[deltacsar665]

welcome, dont worry about the numbers at all, just remember that a smaller number (1/400)= short exposure, that means the sensor is only exposed for a very short time span. the focal length is just how far you will be able to focus with a designated lens, for example a 40mm gives you a wider picture while a 400mm focal length gives you a in-depth, zoomed pic. ISO is like a gauge for sensitivity for light, so a lower ISO (like 100 is for bright sunny days) while a high ISO is for dark gloomy day/night, but try to keep it low

i am not a teacher by any means, so if anyone who is more qualified, care to explain?

[Swisstony10]

ISO relates to the sensitivity of the camera's sensor. In the days before digital cameras (and nowadays for those who still use film) the ISO related to the sensitivity of the film - the lower the number, the less sensitive the film is to light. In terms of film, the more sensitive film (like an ISO 1600 film, for example) had larger grains of light-sensitive chemicals on them, so the image would have more "grain" to it when processed and printed - for digital cameras, this "graininess" takes the form of increased digital noise in the image. Different makes and models of camera deal with this noise with different levels of success, and there's plenty of software around to reduce noise in a high-ISO digital image.

The shutter speed (Exposure) is usually given on the camera in terms of fractions of a second. 1/30 (normally printed as just "30") for example, means that the shutter is open for one thirtieth of a second (fairly slow), whereas 1/500 (normally shown on the camera as "500") is one five-hundredth of a second (fairly fast). The difference between expressing the shutter speed as 1/50 and 0.02 secs is that the first one is a fraction (one fiftieth) and the second is the same figure in a decimal format. (Try entering 1/50 into the calculator on Windows and you'll see that the resultant value is 0.02).

The aperture value relates to the size of the little hole between the front of the lens and the camera's sensor that lets the light through. The smaller the number (also called an f-stop), the bigger the hole (and thus the more light gets through it). The size of the aperture directly affects the shutter speed which you can use, particularly if you're in a place with not much light, or in a place which is very bright. For example, if you're outdoors on a very bright day, and you want to use a very wide aperture, that'll let a lot of light in, so you'll have to use a very fast shutter speed to prevent the image from being over exposed. On the other hand, if you're indoors in a badly-lit room and you want to use a smaller aperture, then you'll have to use a very slow shutter to let enough light through to the sensor.

Russ.

[sarahleedavies]

thank you for your help and I now understand the 1/300 thing so thank you again Just one more ask if possible. So if the exposure is written as Focal Length 50mm that means they used a 50mm lense??? thank you

[Swisstony10]

Ah - they didn't necessarily use a 50mm lens. Most (if not all) DSLRs record the actual focal length that the lens was at when the photo was taken. So if I took a bunch of pictures using my 50mm prime lens, they'd all be recorded as being taken at 50mm, but if use the 18-200 lens, some of them might come out at 50mm, but in general they'd come out at whatever I had the lens zoomed to at the time.

My camera, for example, records the focal range of the lens I used (ie, 18-200mm, 35-80mm, 50mm etc) as well as the actual focal length the lens was at when I took it - I'm guessing it's a safe bet that pretty much all DSLRs do too.

Russ.

[sarahleedavies]

thank you for your guidance, it really helps.. thanks. s