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Old Nov 9, 2006, 11:34 AM   #1
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can someone please explain what the different ISO settings mean, or at least direct me to a link that has a good explanation of the term. This is my first camera (S5100) that I have owned that has allowed me to change this setting, so I'm not really sure what i'm dealing with.

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Old Nov 9, 2006, 12:01 PM   #2
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ISO is a term that is related to the sensitivity of the sensor to light. The term is a carryover (in a way) from the days of film sensitivity. ISO 200 is twice as sensitive to light than ISO 100. So it would seem that you would want to use the highest ISO setting possible. But, as in the days of film, as the ISO is increased so does the graininess or the noise in the image. Consequently, it becomes a process of choosing the proper ISO to produce the kind of the image that we want.

In the days of film a basic rule of thumb was a standard daylight shutter speed/aperture combination would be 1/ISO at f/11. Following that rule you would see exposure settings like:
ISO 100 - 1/100 @ f/11
ISO 200 - 1/200 @ f/11

When I use my 5100 I try to use the lowest practical ISO setting so that I can get pictures that are as noise free as possible. I would suggest that you try using different ISO settings and compare the results. The 5100 does quite well throughout the range of the ISO settings possible, but you will definitely see some noise or graininess at the higher settings. Also, be aware that when shooting in the RAW mode, you will be limited to a maximum ISO setting of 200.
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Old Nov 9, 2006, 12:32 PM   #3
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ok, let me see if i got this right, so the higher the iso setting, the more light it will capture, or something to that effect?
I have an example for you. 2 months ago I went to a chinese lantern festival, and of course it only really looks good to the eye at night when everything was lit up. Now I was having crazy problems getting pictures to come out good cause it was night time and the lights from the lanterns were so bloody bright, that the colors didn't seem right. now just last weekn when I was browsing around the settings of the camera, I noticed that the ISO setting was set at 100. I'm guessing that the pictures didn't turn out as well as I wanted because the camera wasn't allowing enough light in?

I hope i'm right on this, cause if i got that all wrong i'll be even more confused than when i first started...lol
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Old Nov 9, 2006, 2:03 PM   #4
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As the ISO is increased the camera multiplies the signals received back from the sensor.

This acts rather like turning up the volume on a radio station that has poor reception.

The sound gets louder, but so does the crackles and hisses, which in digital terms is the noise you will see in your images.

A better way to get more light would be to either open up the aperture or leave open the shutter for longer.

If thats not possible (larger aperture less depth of field, longer shutter, more potential camera shake and movement in the pic will show as blurs) and ISO has to be increased, you have to balance your need to take the picture and the intended print size vs the noise the higher ISOs will introduce into the picture.

Typically the smaller you print the higher ISO you can use since noise will be less noticable, but if you want to print larger, then the noise would show up worse.

Add into that mix the various noise reduction programs and your ability to get the best out of them.

Personally I would find a night scene and take the same picture at various ISOs, process them , print them out and then decide what you can get away or are willing to accept.

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Old Nov 9, 2006, 2:55 PM   #5
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badliquid,

You understand the concept, but ISO isn't the only controlling factor. The aperture and the shutter speed have a big effect as well. Perhaps part of the problem with the lantern festival is that there was very high contrast between the lanterns and the rest of the picture. The camera's metering system may be trying to balance everything and in the process the lanterns are being overexposed. A lot of cameras today allow you to switch how the metering works. You can switch between average, area, and spot metering. And you have to know enough about what you are trying to do to know which metering scheme to use. In other words, just take a lot of pictures.

I have been doing some photography of a restored courthouse. The building and the courtyard are nicely lit at night and I have been trying to capture the mood as well as the beauty of the scene. For my style of photography, I have found that I get the most pleasing results if I photograph early in the evening while there is still some light in the sky, but yet it is dark enough to show the effect of the lighting. The overall contrast isn't quite as great and it makes it easier to balance everything using Photoshop. If I wait until the sky is dark the contrast is much greater and the differences in the lighting are much more harsh and therefore more difficult to work with.
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Old Nov 10, 2006, 8:54 AM   #6
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Thanks guys,

just one more question if I may, at the beginning of your last post jphess, you mentioned aperture and shutter speed. I'm not quite sure what aperture is either.
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Old Nov 10, 2006, 11:59 AM   #7
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The lens in your camera has a diaphragm behind it that can be adjusted to let more light pass through to the sensor, or to restrict the amount of light. This is technically called the aperture. It is a process of adjusting the aperture and the shutter speed so that the combination of the two adjustments will provide a properly exposed picture. Depending on your subject, and the effect you want, you would want to use different shutter speeds or aperture settings. These settings are referred to as f-stops, f/8, f/5.6, f/4, etc.. As the number gets lower the aperture gets bigger, thus allowing more light to pass through to the sensor.

So why would you want to adjust the aperture? A wide aperture (lower number) will have less of the picture in focus from the front to the back of the picture. So if you are taking a picture of a flower, for instance, and you want the background to be out of focus, you would want to use a wide aperture. Wide aperture settings are often used in portraits for the same reason. On the other hand, if you are taking a scenic photograph, you would probably want everything in focus, including the foreground. In such a case you would want to use a small aperture (a higher number).

If you use the A mode on your camera you adjust the aperture and the camera chooses a shutter speed that will provide the correct exposure for the ISO setting that you have chosen. If you use the P mode the camera will choose both the shutter speed and the aperture, but you can use the controls to shift the program to get other combinations that will provide a proper exposure. In the Auto mode, the camera just automatically sets both and you have no other control over the setting.

As you can see, there is quite a bit to consider when preparing to take a picture. Unfortunately, the manual provided by Fuji isn't going to teach you very much about these things. I would suggest that you check with a community college to see if they offer a basic photography course and you could take. They also might be able to recommend some good books to help you. I'm afraid all the books that I read were back in my film photography days, and have little relevance to today.
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Old Nov 17, 2006, 2:35 PM   #8
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Thak You all for all these helpful informations.
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