Digital ISO's ?
Discussion
Ok , i know they are to change the speed of film and different iso's effect the exposure etc, but I don't really, truly understand them.
Where and how I should be using them properly.
What sort of iso's shopuld I be using in different situtions ?
Can the PH massive please explain ?
(I generally keep mine set at 100.)
Shady
Where and how I should be using them properly.
What sort of iso's shopuld I be using in different situtions ?
Can the PH massive please explain ?
(I generally keep mine set at 100.)
Shady
The only time you need higher ISO is when there isn't enough light available to use the Aperture and Shutter speed combination you require.
In the event that this happens you increase the ISO - but will get more noise as you would get more grain with film.
For instance, at a party a few weeks back I shot the entire day at ISO1600 to avoid having to use flash, which allowed me to stay relatively unobtrusive and get some nice candid images.
In the event that this happens you increase the ISO - but will get more noise as you would get more grain with film.
For instance, at a party a few weeks back I shot the entire day at ISO1600 to avoid having to use flash, which allowed me to stay relatively unobtrusive and get some nice candid images.
ISO = sensitivity to light.
As with all things, there's a tradeoff. Higher sensitivity results in increased noise (film or digital). It's therefore best to stick with the lowest ISO that you can expose with the available light at the appropriate shutter speed and aperture.
If you want to non-stationary objects indoors with ambient light (no flash) it's necessary to have high sensitivity. You can stick with low iso and use a slow shutter speed, but that gives blur (either from motion or camera shake).
I'd suggest setting the camera on aperture pri, and playing with changing the ISO to see the effect on your results. Won't cost you anything. As you increase the ISO, the shutter speed will come down, and the noise will go up. Bit of noise can be better than underexposure or blur.
>> Edited by MEMSDesign on Tuesday 20th September 11:52
As with all things, there's a tradeoff. Higher sensitivity results in increased noise (film or digital). It's therefore best to stick with the lowest ISO that you can expose with the available light at the appropriate shutter speed and aperture.
If you want to non-stationary objects indoors with ambient light (no flash) it's necessary to have high sensitivity. You can stick with low iso and use a slow shutter speed, but that gives blur (either from motion or camera shake).
I'd suggest setting the camera on aperture pri, and playing with changing the ISO to see the effect on your results. Won't cost you anything. As you increase the ISO, the shutter speed will come down, and the noise will go up. Bit of noise can be better than underexposure or blur.
>> Edited by MEMSDesign on Tuesday 20th September 11:52
I've only ever shot 1 one photo om my 20D on anything other than Iso 100, and that was to give a grainy effect on an image than I knew was going to end up as a B&W. I think noise is the enemy. As a way of staying on Iso 100 I use a bean bag, a monopod, a tripod, image stabilizing lenses and a flash, (not all at the same time! 
) just choose the right one for any given situation.
Martin.
) just choose the right one for any given situation. Martin.
ISO (International Standards Organisation) ratings are a hang over from silver halide days.
Historically there were various measures of sensitivity that photographic material might be rated against, ASA or DIN are just two that servived until relatively recently.
The beauty of the ISO rating is that a doubling or halving of the rating is the equivalent of "one f-stop". So as you get familiar with it it's easy to deal with!
Think about capturing an image: there are three variables you can control (leaving aside lighting and additional lighting for the moment!).
Aperture: i.e. how much light in each "snap"
Shutter speed: i.e. how long you "snap" for
Sensitivity: i.e. how many photons you need to hit the target to make something happen.
With film, clever chemistry meant you could arrange for an emulsion to be more sensitive. But the trade off was that you got bigger "lumps" of silver halide when you'd finished the process - grain.
With electronics, you get signal to noise ratio. Accept less signal - you get more noise.
Hence a small number on the ISO scale => more light (by way of longer shutter and bigger aperture) => better signal to noise and so finer detail (as a practical result).
In practice, lower light levels and higher ISO tend towards more noise. Where this becomes noticeable or even unacceptable is subjective. Some people like noise, just like some people like grain. If you're a RAW shooter, or you use Ye Olde Photoshoppe or similar, you can always do things to "manage" the noise. (I particularly like the way I can magic it out of images using RSE.)
So (and recapping): when you pick up your weapon you've got three scales:
Speeds, which increase by halving
1/60 1/125 1/250 1/500 etc
Aperture which does something funny mathematically, but gets less by two stops by doubling:
f4 f5.6 f8 f11 f16 etc
...and ISO which also doubles
100 200 400 800 1600
(and you've usually got the choice of intermediate 1/2 or 1/3 stops)
All to keep you in control of getting the right number of photons to do the right thing to your sensor!!!!
Historically there were various measures of sensitivity that photographic material might be rated against, ASA or DIN are just two that servived until relatively recently.
The beauty of the ISO rating is that a doubling or halving of the rating is the equivalent of "one f-stop". So as you get familiar with it it's easy to deal with!
Think about capturing an image: there are three variables you can control (leaving aside lighting and additional lighting for the moment!).
Aperture: i.e. how much light in each "snap"
Shutter speed: i.e. how long you "snap" for
Sensitivity: i.e. how many photons you need to hit the target to make something happen.
With film, clever chemistry meant you could arrange for an emulsion to be more sensitive. But the trade off was that you got bigger "lumps" of silver halide when you'd finished the process - grain.
With electronics, you get signal to noise ratio. Accept less signal - you get more noise.
Hence a small number on the ISO scale => more light (by way of longer shutter and bigger aperture) => better signal to noise and so finer detail (as a practical result).
In practice, lower light levels and higher ISO tend towards more noise. Where this becomes noticeable or even unacceptable is subjective. Some people like noise, just like some people like grain. If you're a RAW shooter, or you use Ye Olde Photoshoppe or similar, you can always do things to "manage" the noise. (I particularly like the way I can magic it out of images using RSE.)
So (and recapping): when you pick up your weapon you've got three scales:
Speeds, which increase by halving
1/60 1/125 1/250 1/500 etc
Aperture which does something funny mathematically, but gets less by two stops by doubling:
f4 f5.6 f8 f11 f16 etc
...and ISO which also doubles
100 200 400 800 1600
(and you've usually got the choice of intermediate 1/2 or 1/3 stops)
All to keep you in control of getting the right number of photons to do the right thing to your sensor!!!!
shadytree said:I am still using steam powered version 6 of PS, I am sure that things have moved on a bit with what the current version will do, but you have loads of filters and effects (even in 6.0) which mean it's easy to simulate more noise in various ways. You can even do things like be selective across an image.
Can you tell me a bit more on the above in PS please ?
Perhaps someone with later CS or CS2 will let you know what PS can do.
Just a thought, but some people use "Neat Image" here as a method of reducing noise. I have downloaded it (it's free) and applied it to a few shots with some success. (But now everything I take goes through Raw Shooter Essentials.)
shadytree said:Noise Ninja is your friend here. I use the PS plugin, and it works very well.
If you're a RAW shooter, or you use Ye Olde Photoshoppe or similar, you can always do things to "manage" the noise. (I particularly like the way I can magic it out of images using RSE.)
great explanation beano
Can you tell me a bit more on the above in PS please ?
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