exposure, apperation, shutter speed, etc

Discussion in 'Photography Beginners' Forum' started by stephras07, Apr 16, 2010.

  1. stephras07

    stephras07 TPF Noob!

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    I really don't understand how all of this works, and how to know when to adjust the settings. I also dont really understand metering. I know that I will learn some of this just by playing with stuff, but I can't really play unless I know what I'm playing with (minds out of the gutter, guys), and I wouldn't know how to tell the difference when I'm playing either. Can anyone help explain this stuff to me??
     
  2. ajkramer87

    ajkramer87 TPF Noob!

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    Get the book understanding exposure by bryan peterson. Its a really good book that will explain everything your asking about.
     
  3. stephras07

    stephras07 TPF Noob!

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    Cool, thanks! I'll look for that.
     
  4. Johnboy2978

    Johnboy2978 No longer a newbie, moving up!

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    You're really going to want to focus of ISO, aperture and shutter speed. Together they form the exposure value. Typically, you want the exposure value to be 0, that is not over exposed (too much light) or under exposed (too dark). Most of the time it should be right in the middle unless you intentionally want to over/under expose for artistic impression.

    ISO is similar to film speed and the higher the number the more sensitive to light. In digital, a lower ISO generally means less noise (in film it equates to less grain). You want more light sensitivity when you're in more demanding lighting situations. Such as, if you're shooting a wedding in a dark church, you may want an ISO of 800 because it allows more light to hit the sensor (or film). In situations where there is plenty of light (outside on sunny day or inside with good flash/strobe) you generally want less sensitivity to avoid the grain/noise, again unless you're going for that look.

    Aperture has to do with how wide the diaphram of the lens is open. The lens will have an aperture of f/1.4 to f/22 or more. The smaller the number, the wider open the diaphram and the more light is let in to expose the image. In addition, aperture also affects the Depth of Field (DoF). This is also determined by the distance between the lens and the subject and the background, but a wider aperture (smaller f number) tends to blur the background like you see in portraits while an aperture of say f/22 makes most everything in the picture in focus. As you go from an aperture of f/1.4 to f/22 the longer it takes to expose the image b/c you are making the diaphram smaller and thus, less light can get in. Imagine 2 hoses, 1 with a 3" diameter and 1 with a 1/4" diameter. The 3" diameter will let much more water in in a shorter time than will the one w/ 1/4" diameter, but both can fill a 5 gallon bucket given enough time.

    Shutter speed controls motion. You may want to capture an image of a drop of water that is frozen in mid air as it strikes a pond. To do this, you would want a faster shutter speed like 1/2000th of a second. On the other hand, you may want to take an image of a water fall where the water is all smooth and wispy. For that, you need a longer shutter speed, maybe as much as 1-2 seconds depending on the ambient light.

    The way these 3 things connect determines your exposure value. You can vary them to produce the effect you want. Metering has to do with measuring how much light is available in the scene (and how much you might introduce w/ flash). Your camera measures this to tell you how over or underexposed the image is so that you can make necessary adjustments either in the ISO, aperture, shutter speed or combination to make an appropriate exposure value. Typically, the camera will have a diagram like this: -2 -1 |0| 1 2 and a bar somewhere to tell you how far over/under exposed you currently are if you take the picture with those settings.

    Now, there's a very pedestrian explanation for you. Google these to get a better handle on it, then go buy the book, Understanding Exposure by Brian Peterson.
     
  5. myfotoguy

    myfotoguy TPF Noob!

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    Yep, a fantastic book! Also, check out "short courses" Using Your Digital Camera-Contents. I also have some info at the exposure series in my link below.
     
  6. AnneClaire

    AnneClaire TPF Noob!

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  7. stephras07

    stephras07 TPF Noob!

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    thank you everyone!
     
  8. Marmeduke

    Marmeduke TPF Noob!

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    One useful image to have in mind when starting out is of pouring water into a bucket. More water hits the bottom of the bucket the longer the tap is left on, just as more light hits the image sensor the longer the shutter speed is.

    Metering is just about how the camera detects the brightness of the light in front of it. There's normally 3 options: 1 takes in the whole of the scene through the viewfinder, shadows, bright areas etc. and averages them out to suggest an exposure value - often called multi-matrix; 1 gives a reading based on the middle area of the scene in the viewfinder, often called centre-weighted; 1 gives a reading of the exact spot that the centre of the view-finder is set on, often called spot metering. So spot metering is the most accurate when you need to get a specific point perfectly exposed. But they all have pro's and cons so play around with them.

    Here are two pages with clear introductions to using aperture and shutter speed -

    Aperture: What is Aperture?

    Shutter Speed: What is Shutter Speed?

    Best of luck, :D
     

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