Mar 14

What is ISO? What you should know about ISO setting in order to get good photo with your camera?

In photography, ISO stands for light sensitivity for the camera sensor. Lower ISO means lower light sensitivity. For low ISO, the camera sensor needs more time to receive enough light to frame a picture. At high ISO, the sensor needs a much shorter time. Therefore, lower ISO needs longer exposure time (slower shutter speed). And higher ISO needs shorter exposure time (faster shutter speed).

But if the subject is moving or your hand is not steady, low ISO (longer exposure time) tends to produce blurry photo. So you need to use higher ISO with shorter exposure time. But if higher ISO has the advantage of producing blur free photo, why don’t you just use high ISO all the time? Why bother with lower ISO?

Well, here’s the catch.

High ISO produces noisy image. That means the image details are not complete. Instead, some details are replaced with other scattered dots, or noise. On the other hand, lower ISO produces clearer image. For a simple analogy, a 20 minute car wash is much cleaner than a 2 minute car wash.

Here are some photos taken with my Nikon D60 at different ISO setting for comparison. All photos are taken at 2.5 Megapixel. Noise Reduction (NR) is turned on. Active D-Lightning is turned off.

The following bear photos are taken in a bright room and cropped at actual size. This is our baby’s first toy.

ISO100 - the best image

ISO100 F5.3 1/3s - the best image

ISO200 - still looks good

ISO200 F5.3 1/6s - still looks good

ISO400 - some details are washed out

ISO400 F5.3 1/13s - still acceptable with slight noise

ISO 800

ISO 800 F5.3 1/25s - some details are washed out due to Noise Reduction processing

ISO 1600

ISO 1600 F5.3 1/50s - washed out details and apparent noise


ISO HI1 F5.3 1/100s - lesser detail and very noisy

The following photos are taken in my toilet which is not very bright. It is also cropped at actual size.

ISO 100

ISO 100 F5 1/2s - best image quality

ISO 200

ISO 200 F5 1/5s - still looks good but slight noise starts to surface

ISO 400

ISO 400 F5 1/10s - noise is apparent at darker area

ISO 800

ISO 800 - NR controls the noise with some detail lost and color change

ISO 1600

ISO 1600 - unacceptable noise level


ISO HI1 - this is too much

As you can see, the Nikon D60 produces satisfactory image up to ISO 400. However, photo taken at low light condition has more noise. At ISO 800, the noise reduction (NR) function helps to control noise at the cost of some detail lost. You can turn off the NR function to preserve the details but you will have higher noise level.

I always switch on the NR since I prefer having less noisy image. Some minor detail lost is acceptable. Usually we don’t bother much whether a fur or two is lost. But we will notice high picture noise quickly.

All above photos are cropped at its actual size. So you can notice the picture noise easily. However, we don’t usually need a big image. For my notebook, a wallpaper is 1280 x 800 pixels, which is only 1 Megapixel. Photo for this blog is 600 x 400 pixels, which is only 0.2 Megapixel. That’s why I always use the minimum image size for my Nikon D60, which is 2.5 Megapixel, although it’s capable of 10 Megapixel.

So what if we resize the image to a smaller size? Can we still notice the noise level? Here are the same toilet pictures resized from 1936 x 1296 (2.5MP) to 600 x 400 (0.2MP).

ISO 100

ISO 100 - looks good

ISO 200

ISO 200 - looks good too


ISO400 - still okay


ISO800 - still looks okay but the color becomes lighter


ISO1600 - some noise and color fade


ISO HI1 - too noisy with more faded color

Here you can see the Nikon D60 produces virtually noise free image up to ISO800, if you resize the image. However, the color begins to fade at ISO 800 (compare the blue toothbrush container).

Therefore, I will set the ISO to 400 if I shoot photo in my dimly lit room. If necessary, I’ll set it to ISO 800.

In my living room, I’ll turn on all light bulbs for shooting. For static object, I’ll use a tripod and use ISO100. For moving object like baby, I’ll still use ISO 400 without flash. Since I mostly shoot baby photo, I haven’t started to use flash.

For clear and crisp image, you should always use lower ISO if possible. Only change to higher ISO if you have no other choice. To use low ISO, you need to:

  • have adequate lightning
  • have still object
  • have steady hand or use Vibration Reduction (VR) lens to reduce camera shake
  • use tripod if possible

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