# Tutorial - ISO Setting



## Jmax (Dec 4, 2005)

Do you know what ISO is? Perhaps not. And, in fact, you don't need to know what it is - just how to use it. In very simple terms, the ISO setting is a measure of how sensitive your camera sensor is to light.* A low ISO (e.g. 100) will not be very sensitive to light whereas a high setting (e.g. 1600) will be very sensitive.*

How does this affect you?

It's simple, and don't let others tell you otherwise. If you have plenty of light around - say on a sunny day or if it is bright but overcast, use ISO setting 100 or 200. In fact, keep it at that setting for most of your shots. Then just take your pictures as normal.

If however, you are in low light levels, you may wish to use flash (keep the same ISO setting) OR use a higher ISO without flash.

Here is an example of practical use:

You want to take a picture of your friend. Normally, on a normal bright day, you would use programme mode or a semi-automatic mode which will select an aperture of 5.6 and shutter speed of 1/250. No problem.

But if the light is fading and you don't want to use flash, then the shutter speed for the same aperture might reduce to 1/30 or 1/15. At slow speeds like this you will find your shots are not as sharp due to camera shake. Here, you can switch to a higher ISO setting - for every doubling of the ISO you can halve the shutter speed. Therefore you will be able to use a faster shutter speed in low light conditions with a higher ISO.

That's it really.

There are two drawbacks. First, you will get a image with alot of "noise" at a higher ISO setting (more grainy - but this can often create a nice effect) and secondly you must remember to switch back to your usual ISO after the shots have been taken (so that your usual images have the optimum ISO setting).


----------



## Cosmic Hamster (Aug 7, 2006)

Excellent.. i played around taking pics in the dark last nite with my digi camera... it allowed to me to adjust the F number...  f00k knows what that is but here are the results.

F4.3



















F2.something



















Not a lot different apart form the time the camera took to take the pic.. the ones with the hight F rating took longer and seem to be brighter..:thumb:

Any suggestions on how to get a better pic - the cam is a HP 4MP Photosmart  Cheers!


----------



## Brazo (Oct 27, 2005)

f number is the aperture width a low f number such as f2.8 will mean the apeture of the lens is wide open and will allow in more light. A higher number such as f11 will give less light.

Using ahigher number does however give better depth of field but your best ignoring that for now


----------



## Cosmic Hamster (Aug 7, 2006)

haha nice one brazo.. dont think mine allows you to change the ISO its only got set "modes" action, portrait, landscape etc... its only a cheapo


----------



## parish (Jun 29, 2006)

Cosmic Hamster said:


> it allowed to me to adjust the F number...  f00k knows what that is


Strictly speaking it should be written f*/*4.3 etc. because it is the diameter the iris closes down to expressed as a fraction of the focal length of the lens, e.g. with a 50mm lens - which gives the same perspective as human vision on a 35mm film camera - f/4 = 12.5mm (50/4).

The reason for the odd values - especially at larger apertures (smaller numbers) is to create a near linear relationship between aperture and shutter speed - each f-stop is equivalent to halving/doubling the shutter speed - so 1/30 sec at f/4 is the same as 1/15 sec. at f/5.6.

Caveat, I'm doing that from memory of when I used to be "into" photography many years ago so it may not be exactly right, but the principle is correct.
JMax?


----------



## AdamG (Sep 24, 2006)

I always remember F-stop as curtains.
The larger the number, the larger the curtain so the smaller the hole the camera looks out through.

It also effects your depth of field, but thats another lesson.


----------



## leeshez (Dec 26, 2005)

Thanks for that


----------



## TJMurphy (May 29, 2006)

Am I right in thinking a lot of digital cameras don't really "do" depth-of-field properly in the same way as film-cameras used to? Something to do with the technology of the sensors? 
Certainly on my experimenting with my Fuji I get very little difference due to messing about with the F stops.
I like the curtains metaphor - always seemed to have a mental block about the numbers being inversed - that image may just sort me out in future!

Tony


----------



## Brazo (Oct 27, 2005)

Not sure Tony best thing to do is try a test

take a portrait head shot close up of someone using the lowest f number. The image of head should be sharp and background blurred. Then repeat with high f number and background should be sharper.

This can however be affected by zoom and focal lengh but again thats another topic


----------



## TJMurphy (May 29, 2006)

Knew I had read it somewhere ...

Depth of Field and Digital cameras

Probably applies more to the cheaper end of the camera spectrum than digital SLRs but anyway, this is why you have trouble getting a DOF on a digital camera!

Tony


----------



## parish (Jun 29, 2006)

TJMurphy said:


> Knew I had read it somewhere ...
> 
> Depth of Field and Digital cameras


Excellent website - bookmarked for future reference - thanks :thumb:


----------

