Does ISO number really matter? Is 2000 ISO really better than 1600?

Question

I like a Casio camera but it has less ISO of 1600 and a Nikon camera I also want (I have 3 cams I'm choosing from.) has 2000. Does it make a really big difference??

Answer 1

No because they're pretty much unusable. High ISO is a marketing tactic to upsell point & shoot cameras. Nearly all P&S cameras are only good or ok up to ISO 400 at which point heavy post-processing is required recover the pictures, if at all possible. There are some exceptions, mostly from Fujifilm, that'll produce usable results up to ISO 800/1600. You can squeeze a 4x6, maybe a 5x7, out of these.

ISO is a measure of medium (CCD sensor in this case) sensitivity. The higher the ISO the higher the sensitivity. Using the higher ISOs will allow you to use a faster shutter speed when the lighting isn't adequate. You may choose to do so to reduce blur or freeze motion. It's also ideal when you don't want to or can't use flash in dim environments and you don't have a means of stabilizing the camera. However, as you increase the ISO you'll also be increasing the ammount of noise and noise reduction artifacts that will appear on your images. It's generally a good idea to keep the ISO as low as possible.

Answer 2

Unless you are choosing between full-frame DSLR cameras (Nikon D3, D700, Canon EOS 1Ds Mark III, 5D) ignore high ISO settings. This is especially true if you're looking at "point & shoot" digicams.

DSLR cameras that aren't full-frame (Sony A300, Pentax K200D, Nikon D60, Canon XSi) will still out perform any digicam at higher ISO settings.

The tiny sensor in a digicam simply cannot support very high ISO settings. This is exacerbated by the current trend of stuffing ever more pixels into their tiny sensors. In-camera noise reduction programs and editing programs like Noise Ninja can only do so much. Their best results cause a loss of detail that may be unacceptable.

Answer 3

The lower the number the better. 80 ISO or 100 ISO is great. But if you do not have enough light or want to shoot at faster shutter speed, increase your ISO setting as the situation dictates. With a point & shoot I'd almost never go above 400 ISO.

Answer 4

ISO matters to some extent.

The ISO number at any given time is a relative measure of light sensitivity versus noise. So on the same camera, an ISO of 100 is shaper, but 1/4 as sensitive as an ISO setting of 400. Higher ISO numbers are important to allow shooting in the dark, particularly when zoomed.

Now, all things being equal, there's not a huge difference between ISO 1600 and ISO 2000. In the days of film, you could pretty much be sure that the 1600 would be a bit less grainy than the 2000. But these days, sensor technology has been rapidly evolving, and the size of the sensor is also a factor. So there's no guarantee between different cameras that ISO 800 on one camera will be less grainy than ISO 1600 on another.

In the days of film, larger silver halide grains gave way to more sensitive emulsions, but with correspondingly more visible grain. In digital, the factors are a bit more complex. In every sensor, there's an analog pixel sensing element, usually a silicon photodiode, that's routed in some way to an analog to digital converter, which allows the camera to record the 12 or 14 bit for that specific pixel. To deliver the same effect as ISO setting in digital, there's a programmable gain amplifier in-between the photodiode and the ADC.

All electronic systems have some sort of random noise inherent in the system. When some of that noise is loud enough to be sampled by the DAC, you get noise visible in the picture. So in a camera's sensor, lower levels of noise and larger sensor area (more light = louder signal at the same amplification level), and thus, a cleaner picture... or one of the same level at a higher ISO number. Some cameras also employ digital noise reduction techniques at higher ISOs to deliver a clean photo. This is the real factor of importance in your camera buying search, not so much just the ISO number.

Most detailed review sites online include a rating for noise levels at different ISO values for each camera. While you should look for a camera with a relatively high ISO maximum, you'll find one with very sharp imagining at ISO 1600 is better than one with an ISO 3200 setting too noisy to be of any real value.