ISO settings

[MattB]

Can I ask you all a question?

As I've said before, I'm a complete newcomer to this fascinating world of photography.

What's the difference between 'noisy' and low grain shots?

Is this something to do with ISO settings ??

Regards,

[Steve Geronazzo]

Hi Matty,

According to Wikipedia, here is the definition of 'noise' :

Image noise is random (not present in the object imaged) variation of brightness or color information in images, and is usually an aspect of electronic noise. It can be produced by the sensor and circuitry of a scanner or digital camera. Image noise can also originate in film grain and in the unavoidable shot noise of an ideal photon detector.

In general a lower ISO setting gives sharper images than higher ISO settings. A lower setting is used when there is enough ambient light and a higher setting is used when it is darker. It is a known fact that a higher ISO value is more sensitive to light and generates more 'noise'.

Hope this helps.

Why are you asking?

Steve

[Steve Geronazzo]

I didn't think you were talking about films.

When transferring to digital, do you use the highest resolution possible?

There are many members who scan pictures and upload them to the site. I'm sure someone will give you advice on how to get the best results when transferring pictures from film to digital.

Steve

[Kelvin Davies]

Matty,
The simple answer is that when you select a higher ISO setting on your digital camera, you are basically changing the gain on an amplifier. A bit like turning up the volume on your ghetto blaster.
This will effectively amplify both the image information and any random noise generated by the circuitry itself. Any noise in the circuit will appear as tiny blemishes on the image.
A good analogy is listening to a radio. If you are listening to a very weak station, it will be noisy. If you turn up the volume to hear better, you will also increase the amount of noise which means everything just gets louder but not clearer.
It is also another good reason to keep away from cameras that boast umpteen times 'digital zoom'. The same problems apply.
So, keep the ISO setting as low as you can get away with, bearing in mind the available light, the aperture setting etc.
Kelvin

[Ship's Cat]

Further to Ken's post, until fairly recently, sensors with a high pixel density would be noisier than those with lower pixel density, I believe it is something to do with cramming more pixels onto a smaller sensor. This didn't affect full frame (35mm size) sensors so much, due to their physically larger size but did affect APS-C/APS-H size sensors (the size found in most DSLRs). However, with rapid development in the technology over the past few years this is less of an issue and some cameras with APS-C sensors, such as the Canon 7D, are excellent at handling noise at high ISOs. I have used ISO 6400 on mine and needed minimal noise reduction, and I have even tried ISO 12800 with reasonable results.

With an 18MP sensor you can crop a picture more than you can with a 10MP sensor and not lose too much in doing so. That means that you can get away with using shorter lenses.

Here is a photo I took of a model of SS United States (aboard Vision of the Seas last April), at ISO 6400; I couldn't use the flash as it would simply have reflected off of the glass case. There is a bit of noise but otherwise it's a pretty clean picture for such a high ISO.