please explain white balance and iso again..

[bluelex]

i just get very confused with these 2 options. i don't think i've ever touched the iso on my camera. its at 100 and never has been moved. when is a good time to play with, i mean like is it more for day shots, night shots, moving shots, action shots. also white balance?. i've never played with this either. what is this mainly used for? any help would be great. i did pick up that polarizer you guys suggested and it did wondors, thanx a lot...

[brendanlim]

ISO is a numbering system for rating the speed of films, devised by the International Standards Organization. Higher ISO means faster speed. The speed means faster shutter time. This is accomplished by increasing the sensitivity to light with a higher ISO. For example, for a FAST simple shot in low light, you want to put the ISO real high. In daytime the ISO will be set to a lower number because if its too sensitive to light in the daytime when there's an abundance of light, the picture will turn out washed out and really WHITE.

As for white balance, here's a link to DP Review's great explanation of it.
http://www.dpreview.com/learn/?/Glos...Balance_01.htm

[bitkahuna]

Originally Posted by brendanlim

ISO is a numbering system for rating the speed of films, devised by the International Standards Organization. Higher ISO means faster speed. The speed means faster shutter time.

That last sentence is a bit confusing Brendan because higher ISO doesn't mean faster shutter time.

bluelex - as Brendan goes on to say though, ISO number really means how SENSITIVE either film or your digital sensor are to be to light received. But there's a trade off. With higher sensitivity usually comes higher 'noise' level (discolored pixels or film 'grain').

This is accomplished by increasing the sensitivity to light with a higher ISO. For example, for a FAST simple shot in low light, you want to put the ISO real high. In daytime the ISO will be set to a lower number because if its too sensitive to light in the daytime when there's an abundance of light, the picture will turn out washed out and really WHITE.

This is only true really if you're setting both manual aperture and shutter speed because if you set ISO higher the camera will automatically compensate with shorter (faster) shutter speeds, or smaller aperture (higher F-stop) settings.

I think I already posted about this in this forum, but overall picture exposure is dependent upon a combination of the following:

- available light (of course)
- how larger the 'opening' of the aperture is (bigger 'hole', more light in)
- how long a period of time the shutter is held open (shutter speed - longer time, more light)
- how sensitive the film or sensor is to light (ISO setting)

Hope that helps.

[bluelex]

ok so if i am taking shots on sunny day , it better if i have the iso lower? when i take pics in the night time i really play in full manual mode, adjusting the appt and shutter my self. but never touch the iso....so you guysthink that if u have t iso a little higher on night shots it will help out more?

and in day shots i usually just use automatic mode but i really want to focus more on day shots now that i have a pretty decent filter to block glare and reflection...so you guys think that if its really sunny outside i should lower the iso to like 50 mayb?

on the G5 i only have 50-100-200-400 as iso options..

[bitkahuna]

Originally Posted by bluelex

ok so if i am taking shots on sunny day , it better if i have the iso lower?

Yes, since there's plenty of light and lower ISO gives a cleaner picture.

when i take pics in the night time i really play in full manual mode, adjusting the appt and shutter my self. but never touch the iso....so you guysthink that if u have t iso a little higher on night shots it will help out more?

A higher ISO at night means you don't such a long shutter speed which might be useful, but there's a trade-off with higher noise.

and in day shots i usually just use automatic mode but i really want to focus more on day shots now that i have a pretty decent filter to block glare and reflection...so you guys think that if its really sunny outside i should lower the iso to like 50 mayb?

An ISO of 200 or less for daytime pictures would be great. I doubt you'd be able to tell the difference between an ISO of 50 or 100. An ISO of 200 you might see a slight difference in noise, but maybe not. On my 20D I can't tell any difference.

on the G5 i only have 50-100-200-400 as iso options..

OK. Well that's a pretty limited range (my 20D goes from 100-3200) and they probably don't offer more than 400 ISO because it will get too noisy. I have a thread somewhere on here showing pictures taken with my point and shoot tiny Canon S400 and the same pictures with my 20D showing that the more expensive camera has much less noise.

Anyway, bottom line, lower ISO in daytime is good, higher ISO at night unless the noise is too objectionable or you can do a REEEALLLLY long exposure with the lower ISO (many seconds). You can also dramatically reduce noise in a pic you've already taken by using the computer and 'noise' or 'despeckle' filter.