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10/02/2003 07:15:31 PM · #1
Hi,

I've some questions about the ISO setting on digital cameras. For indoor and low light shot, lower ISO setting is needed. Higher setting is needed for bright situation such as snow.

In automatic mode and even for indoor pictures,(with or without flash), my camera (sony dsc-v1) always set the ISO to 100 (which doesn't seems as automatic as this).

When I manually swicth to higher ISO such as 400 or 800, and even for pictures in the night with no moon, visible noise appears for every shot. This noise is not visible if the camera is set either to automatic ISO or to ISO 100.

Some are maybe going to say that I shouldn't care about switching to others ISO than 100, since the quality is better for this setting. But maybe someone has some explaination about the noise and ISO with digital cameras.

Thanks!
10/02/2003 07:28:13 PM · #2
Noise will always be worse the higher you go. You need to find a balance between ISO, speed, and aperture. If you're using a tripod and can take longer exposures then keep your ISO as low as you can. If you need a quick shutter speed (for handheld or action) you sometimes need to raise the ISO.

Most digicams have pretty bad noise at 400 or above, but sometimes it's necessary to use them.
10/02/2003 07:30:01 PM · #3
I believe it's the other way around.

Lower ISO # = well lit or outdoor lighting.
Higher ISO # = lower lighting conditions.

The higher the ISO the more noise you may get.

Aperture Priority= F-Stop number and Shutterspeed.

F-Stop # lower = lets in more light. Large shutter opening. Example f2.8
F-Stop # higher= lets in less light. Small shutter opening .Example f22

Shutter Speed is how fast your your camera blinks and opens for a longer time or closes very quickly.

Shutter Speed higher = 1/1000 (of a sec) Ex. Stopping wings on a bird,sports shots, cars in motion (freezing them)
Shutter Speed lower = 4" (seconds)Ex. Cool pictures of car stoplight and those red steaks, moon shots.

Message edited by author 2003-10-02 19:40:53.
10/02/2003 07:35:52 PM · #4
Originally posted by faidoi:

I believe it's the other way around.

Lower ISO # = bright day outside lighting.
Higher ISO # = lower lighting conditions.

The higher the ISO the more noise you may get.


OOOPS!
Yes exactly, the contrary!
Thanks!
10/02/2003 07:41:55 PM · #5
Using all 3 methods Aperture, Shutter Speeds, and Iso correctly you will achieve a great photo.
10/02/2003 07:44:50 PM · #6
As the others said - higher ISO means the sensor is more sensitive to light. Since the sensor is more sensitive, light needs to touch the sensor for a shorter amount of time. So when there's not a lot of light, you can set the ISO high and take a picture without the shutter being open for quite as long. There's an interconnected relationship between shutter speed, apperature and ISO. When you double the ISO, you double the sensitivity, and so you need half as much light to get the same exposure. This allows you to either cut the shutter speed in half or use a smaller aperature (higher f-stop number). Here's a page that helped me come to grips with the relationship between these settings: The Ultimate Exposure Computer. It's technically written for film fotography, but the principles are basic to all photography and translate well.

As for noise, its the price you have to pay for using higher ISO. Getting some noise in your image is better than getting unwanted camera shake or motion blur in the image - noise can usually be fixed, but blur often (at least at my skill level) can't. The best solution for noise that I've worked with is a program called Neat Image. It does a good job on 80-90% of the shots I have with noise in them, and also has some pretty good sharpening capabilities. There's a free version that's pretty much fully functional. It's just missing a few convenience features like batch processing.

In general, if you can get a fast enough shutter speed (say above 1/120 sec.) with an ISO of 100, then keep the ISO there. If your shutter speed drops below that (especially below 1/60), and you either don't have a tripod or your subjects may move, then push the ISO up and use Neat Image to repair it later.
10/02/2003 08:00:02 PM · #7
Originally posted by ScottK:

As the others said - higher ISO means the sensor is more sensitive to light. Since the sensor is more sensitive, light needs to touch the sensor for a shorter amount of time. So when there's not a lot of light, you can set the ISO high and take a picture without the shutter being open for quite as long. There's an interconnected relationship between shutter speed, apperature and ISO. When you double the ISO, you double the sensitivity, and so you need half as much light to get the same exposure. This allows you to either cut the shutter speed in half or use a smaller aperature (higher f-stop number). Here's a page that helped me come to grips with the relationship between these settings: The Ultimate Exposure Computer. It's technically written for film fotography, but the principles are basic to all photography and translate well.

As for noise, its the price you have to pay for using higher ISO. Getting some noise in your image is better than getting unwanted camera shake or motion blur in the image - noise can usually be fixed, but blur often (at least at my skill level) can't. The best solution for noise that I've worked with is a program called Neat Image. It does a good job on 80-90% of the shots I have with noise in them, and also has some pretty good sharpening capabilities. There's a free version that's pretty much fully functional. It's just missing a few convenience features like batch processing.

In general, if you can get a fast enough shutter speed (say above 1/120 sec.) with an ISO of 100, then keep the ISO there. If your shutter speed drops below that (especially below 1/60), and you either don't have a tripod or your subjects may move, then push the ISO up and use Neat Image to repair it later.



Hey!

Thanks a lot Scott! Your post really helped me a lot!
10/03/2003 02:07:35 AM · #8
Glad to hear. Sometimes I start typing, and pretty soon it feels like I'm rambling. Glad I made some sense! :)
10/03/2003 05:17:50 AM · #9
Higher ISO values do not mean that the CCD or CMOS sensor is more sensitive to light, it simply means that the light received is amplified. noise is also amplified which is why there is more apparent noise in the image.
10/03/2003 11:35:07 AM · #10
Yep, Rob's right. Sorry. I had forgotten the specific mechanics of it.
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