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Old May 22, 2008, 10:07 AM   #1
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I have a Sony Alpha 100, and sometimes the photo takes really really slow to capture therefore causing most of them to end up blurry. I heard it's because of the shutter speed but I don't know how to adjust it!!
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Old May 22, 2008, 11:08 AM   #2
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If you try to use a shutter speed that's too fast for the widest available aperture (smaller f/stop numbers), lighting and ISO speed set, you'll get an underexposed (too dark) image.

You're probably trying to take photos in conditions too dark without using a flash or tripod (and the tripod won't help with blur from subject movement).

You can shoot in P (Programmed Auto) mode and increase your ISO speed to help out. Each time you double the ISO speed, the camera will use shutter speeds twice as fast in low light if you're not using a flash. But, increasing ISO speed will add noise (i.e., the grainy look you'll see). So, you don't want to increase more than necessary.

You probably need a brighter lens for the conditions you're trying to shoot in if you're trying to use something like the 18-70mm kit lens indoors without a flash (it's not really bright enough for that purpose if you have non-stationary subjects). You'll want a bright prime for best results (Minolta 28mm f/2, Sigma 30mm f/1.4, Sony or Minolta 35mm f/1.4, Minolta 50mm f/1.7, Minolta 50mm or Sony f/1.4 Autofocus lenses are good choices, depending on how much room you've got to shoot in).

Or, use a flash when light is too low. An external flash will provide best results (for example, a Sony HVL-36AM, HVL-42AM or HVL-56AM) so you can bounce it for more diffused lighting.

Although we have a lot of automation with newer camera models (both film and digital), the concepts of exposure still work the same way as they do with old manual only cameras.

You still have only 4 main variables to take into consideration for exposure (and I use the term "main" since there are a lot of nuances to how you measure the light (for example, your metering mode), as well as different film characteristics if shooting film, and camera settings if shooting digital for the desired tone/contrast curve within an image and more). Once you have a better idea of how these 4 variables work together to give you a properly exposed image, the other fancy features will make more sense. These variables are light, aperture, ISO speed and shutter speed.

Light is typically measured as EV for Exposure Value in Photography.

Aperture (which works similar to the pupils in your eyes, where you can open up the aperture iris wider to let in more light, or close it down to let in less light). If you let in more light with a wider aperture, you can expose the film or sensor faster. If you let in less light with a smaller opening, it takes longer to expose the film or sensor. Note that aperture is normally expressed as f/stop, which is a ratio between the focal length of the lens and the diameter of the aperture iris. So, smaller values represent a larger iris diameter.

With a prime (non zoom) lens, you will see one aperture listed (the widest available). But, you can still use smaller apertures (represented by higher f/stop numbers).

With a zoom lens, you usually see two apertures listed (the largest available aperture at wide angle zoom setting, and the largest available aperture at the full telephoto zoom position). When in between the widest and longest focal length of the lens, the largest available aperture will fall somewhere in between the apertures shown.

Many high quality zoom lenses can maintain a constant aperture throughout their zoom range (with f/2.8 being the most common). So, you'll only see one aperture listed for this type of lens (the widest available, since you have that aperture available at all focal lengths supported if desired). But, you can still set it to smaller apertures (higher f/stop numbers). For lower light, primes (fixed focal length versus zooms) can be found that are brighter (smaller f/stop numbers).

When you vary the aperture, you're controlling the iris in the lens (which like a pupil in your eye, can be opened up to let in more light or closed down to let less light in). So, this impacts the shutter speeds you'll need for proper exposure (since more or less light is getting through to the sensor). Aperture also impacts Depth of Field.

The aperture scale in one stop increments (with larger than f/1 apertures possible but very rare in lenses) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22... With each one stop move to a smaller aperture (represented by higher f/stop numbers), you will need shutter speeds twice as long for proper exposure for the same lighting and ISO speed (only half the light gets through compared to a one stop larger aperture).

ISO speed. This is how sensitive the film or sensor is to light and is the same thing as the older ASA rating for film. The higher the ISO speed, the faster you can expose it (each time you double the ISO speed, you can use shutter speeds twice as fast for the same lighting and aperture.

Shutter Speed is how long the camera's shutter stays open to expose the film or sensor).

IOW, it all boils down to how senstive the film or sensor is to light (which you control via the ISO or ASA speed of the film you use with film, or the ISO speed settings you use with digital), and how much light you need to let it see to "expose" the iimage (which you control via the aperture opening size and shutter speed).

So, you've got lots of fancy features on newer cameras to automate what settings it uses, and let you vary it's behavior to expose an image darker or brighter than the camera's metering would normally expose it. But, it really boils down to the camera changing the same things you had to worry about with a strictly manual camera without a fancy metering system, Automatic Exposure modes, etc. These exposure calculators and simulators may help you understand it better.



Note that aperture also influences depth of field. See this handy calculator for more information about it:


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