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Old Oct 15, 2005, 6:44 AM   #1
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What is the iso setting about ?? i have a Sony DSC P120(same as P100), the review for the P100 said that iso was set to 100. Is it better to have it at 100 ? rather than auto,200 or 400. The manuel said that 100 will give high quality image but for dark areas and moving objects to set it high and that a image tends to become noisier at higher iso levels.

Does'nt explain what the iso level actually is.
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Old Oct 15, 2005, 7:22 AM   #2
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ISO speed is a standard for expressingthe sensitivity of the film or sensor to light.

You'll also see this expressed as film speed (or sometimes ASA) The higher the number, the more sensitive or faster the film.


ISOstands for International Standards Organization

If you look at almost any basic photography book, you'll see some information on how exposure works.

The shutter speed a camera can use for proper exposure depends on the lighting, the film speed (a.k.a ISO speed) and the Aperture (which is the ratio between the focal length and the diameter of the aperture iris opening).

With a digital camera, when you increase ISO speed, you amplify the signal from the sensor. Each time you double the ISO speed, the camera can use shutter speeds twice as fast for proper exposure in the same lighting, at the same aperture setting.

This amplification can cause noise (similar to film grain). When the light is low, not as many photons hit each photosite on the sensor (allowing the photosites for each pixel to generate a stronger signal before being read),So,when you try toincrease ISO speed, it can be like trying to turn up the volume on a weak radio station, only instead of hum, static and hiss, you get image noise.

But, you may need higher ISO speed to get shutter speeds fast enough to prevent blur from camera shake or subject movement in many conditions. So, it's often preferrable to have a little noise in the images, versus blur.

When light is good (and/or you don't need faster shutter speeds), it's preferrable to keep ISO speeds set lower for a cleaner image. Most subcompact digital cameras are limited to a maxiumum ISO speed of 400. Most DSLR models can go to ISO 1600 or higher (their larger sensors can gathermore light, since the photosites for each pixel are larger). But, you can't really go by sensor/photosite size alone, as each sensor may have slightly different characteristics.

Here is a handy online exposure calculator that can give you a better idea of how exposure works. Film speed is the same thing as ISO speed. Note that your Sony camera has a largest available aperture of f/2.8 (at the widest zoom setting only), dropping off to a largest available aperture of f/5.2 at your longest zoom setting. The more zoom you use, the lower the light isgetting through to the sensor with your model (and most other smaller cameras).

http://www.robert-barrett.com/photo/...alculator.html




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Old Oct 15, 2005, 8:04 AM   #3
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WOW... thanks for the info.
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Old Oct 15, 2005, 8:34 AM   #4
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I keep my Konica KD-510z pocket camera set to ISO 200 almost all the time anymore. Like your Sony DSC-P120, this model also uses a Sony 5MP 1/1.8" CCD. Using ISO 200 (versus this cameras default of ISO 50 without flash) allows faster shutter speeds and helps to reduce the number of photos I've get with motion blur from subject movement or camera shake.

It will have a little more noise this way, but it cleans up easily with popular tools like Noiseware or Neat Image (and they have free versions of these products, too).

Depending on the viewing size needed you may not want/need to clean up any noise (since it tends to be less noticeable at smaller viewing and print sizes).

This one was taken at ISO 200, with the camera using a shutter speed of 1/15 second at f/2.8. Even at ISO 200, this shutter speed is too slow to prevent motion blur from camera shake (unless you can hold a camera very steady), much less blur from subject movement). The "rule of thumb" is shutter speeds of 1/focal length or faster. So, if you're shooting at 50mm, you'll want shutter speeds of 1/50 second or faster. Or, if you're shooting at 100mm, you'll want shutter speeds of 1/100 second or faster (camera shake is magnified at longer focal lengths).

So, a tripod or monopod is often needed in lower light to prevent blur from camera shake (and that won't help blur from subject movement).

So, if you are in conditions when flash is not allowed in lower light, take lots of photos to increase your number of keepers (and you may need to go ISO 400, instead). I try to avoid ISO 400 unless absolutely necessary (due to higher noise levels in a small camera like this).

So, I sometimes try to shoot at slower shutter speeds compared to the "rule of thumb" for camera shake (carefully controlling my breathing and slowly squeezing the shutter button), trying to catch subjects when they are relatively stationary in low light when I can't use a flash (since much faster shutter speeds may be needed to freeze a moving subject).

Konica Revio KD-510z, ISO 200, f/2.8, 1/15 second, at a 35mm equivalent focal length of 39mm, hand held with no flash. Cropped for a 4x6" print, and downsized for posting here. No corrections to color, contrast, brightness, sharpness, saturation, noise, etc. were made.

I've got plenty more that didn't come out this well, due to blur from camera shake or subject movement. So, much higher ISO speeds would have been desirable in these conditions.



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Old Oct 16, 2005, 8:20 AM   #5
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Thanks for the info, that picture came out very well. I may invest in a tripod or monopod so its there if i need it. I'll do some testing and messing about of my own with the flash turned off. When the flash is on auto and theres enough light the flash does'nt go off the pictures are normally fine, i can never get a photo thats not blurred when i turn the flash off unless i use my mini desktop tripod.
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Old Oct 16, 2005, 8:41 AM   #6
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Jedi Master wrote:
Quote:
Thanks for the info, that picture came out very well. I may invest in a tripod or monopod so its there if i need it. I'll do some testing and messing about of my own with the flash turned off. When the flash is on auto and theres enough light the flash does'nt go off the pictures are normally fine, i can never get a photo thats not blurred when i turn the flash off unless i use my mini desktop tripod.
Trust me, I needed a tripod or monopod for the shots I took at this Dance Recital (as most were ruined from either motion blur from camera shake or subject movement). A tripod or monopod would have helped with the camera shake problem.

It was a "spur of the moment" decision to go to it (a friend's daughter was in it, and he asked if I wanted to ride along). I was already at his home at the time.

So, I rode along and took some photoswhile I was there using my little Konica Pocket camera I always have with me (kneeling under the edge of the stage on one side as not to block anyone's view). I needed to be closer soI wouldn't have to use any optical zoom from further way, since longer focal lengths cause too much loss of light with a subcompact model like this (not to mention that motion blur from camera shake is amplified at longer focal lengths).

For these kinds of conditions (indoors without a flash), a DSLR with a bright lens is the way to go, since these models can shoot at higher ISO speeds compared to subcompact cameras (although more subcompacts seem to be coming out now that can shoot at higher ISO speeds, they still lag behind DSLR models with larger sensors from a noise perspective).

For indoor use, photographingmoving subjects with small cameras like these, you're usuallybetter off using the flash and staying within the flash range.



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Old Oct 16, 2005, 11:59 AM   #7
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I see. I think i will get a trypod of monopod, but i dont think i will be buying a DSLR camera anytime soon, im not really a hobbiest or into photography but i am one of those people that if im going to do something i like to do it as best i can. I proberly will get a DSLR some time in the furture but for now i'll stick with this P120. Has given me some really good photos so far, but that was on the auto mode, now i'll learning and finding out more if i will start try the program mode and the manual modes.
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