Help me understand ISO - it's confusing the hell out of me?

[Big Mike]

The best way to use it, is almost a last resort.

Yes and no. I think that the 'last resort' advice is taken too seriously by many who don't fully understand the issues involved.

For example, if someone is afraid to use ISO 800 because they are worried about noise...that they end up taking photos at 1/50 (on say, a 50mm lens)....they will likely get some amount of blur (lack of sharpness). If however, they use ISO 1600 and a resulting shutter speed of 1/200, they are likely to get much sharper photos, but of course, with more noise. But the thing to remember is that you can't truly get rid of blur, but it's much easier to deal with noise. And even so, noise can usually be stomached by the viewer much easier than a lack of sharpness.

The the moral of the story is....don't be afraid to turn up the ISO if it means getting a sharper photo (due to faster shutter speed).

 

[classixuk]

GREAT info in this thread.

i've always known that a higher number was for lower light. and lower number for more light.

but, still wasn't really sure when to use what.

your 1pm, 4pm analogy is awesome !!!! thanks :thumbup: (particularly for me, because i am new, and we are shooting film)

I'm relieved you said that as I thought I was the only one not getting it at all, but you have more than 300 posts so now I don't feel so alone.

I'm glad I didn't learn photography from your onboard friends

I wonder what time of day they would have told me to use my 25 ASA film (2:30 am?) or my 50 ASA film (5am?)...

ISO = ASA by the way.

And all it is is the sensitivity of the film in the days of film and of the sensor today. The difference between film and sensor being that you can change it on the fly when it comes to sensors.

Now if you are trying to get good shots that is really all you need to know. If you're trying to build a digital camera, then we have to talk about more. Although you won't talk about it with me. I don't understand how it works either, lol.


And there is no grain in digital. Grain is with film only. Digital photography has noise.

Luckily I never had to venture as low as 25 ASA or 50 ASA. What on earth do you shoot with that type of film? A white feather in a white room held by an albino model? LOL

To me, noise will always be grain Much the same way as a 10 x 8 will always be known as that, no matter what Brussels tells me I should measure in

The best way to use it, is almost a last resort.

Say you want to Shoot a landscape ISO 100 and you want a Deep DOF, so you want to shoot at f/16 However, your shutter speed is 1/25 and you are hand holding the camera (no tripod around) well you want to maintain that f/16 but you need get your shutter speed to /100. Raise your ISO to 400. Done

Opening the aperture may not be the solution because it would change your DOF

Great. I think I am on the right track then. So as a general rule, decrease the F-Stop gradually to let in more light, but If I start losing too much DoF, and my images are still looking underexposed, that's the time to increase the ISO, but never before that. So it goes like this in stages of steps to try: F-Stop, ISO, Artificial Lightso ???

 

[Rephargotohp]

The best way to use it, is almost a last resort.

Yes and no. I think that the 'last resort' advice is taken too seriously by many who don't fully understand the issues involved.

For example, if someone is afraid to use ISO 800 because they are worried about noise...that they end up taking photos at 1/50 (on say, a 50mm lens)....they will likely get some amount of blur (lack of sharpness). If however, they use ISO 1600 and a resulting shutter speed of 1/200, they are likely to get much sharper photos, but of course, with more noise. But the thing to remember is that you can't truly get rid of blur, but it's much easier to deal with noise. And even so, noise can usually be stomached by the viewer much easier than a lack of sharpness.

The the moral of the story is....don't be afraid to turn up the ISO if it means getting a sharper photo (due to faster shutter speed).

That is why you don't pull ONE LINE out of context. If you look at both your and my example, they are both showing the need for shutter speed as that is a priority, in which case I said to raise the ISO

 

[matthewo]

I dont know if anyone said it but the difference between lower end dslrs and fx or high end crop sensors is hugely dependent on iso. My d5100 is good to about 300-400 then gets noticable grainy. But some higher end dslrs maybe able too do 1600-2000 and still look ok. Which is a huge plus indoors. 2.8f 1/60 sec 1000-1600 iso you can take nice pictures in relatively low indoor lighting with no flash

This is one of the main reasons i want to go full frame

 

[Rephargotohp]

Great. I think I am on the right track then. So as a general rule, decrease the F-Stop gradually to let in more light, but If I start losing too much DoF, and my images are still looking underexposed, that's the time to increase the ISO, but never before that. So it goes like this in stages of steps to try: F-Stop, ISO, Artificial Lightso ???

Mmmm almost

You really have to look at your priorities. If what I am shooting demands either an aperture for DOF or a shutter speed to stop action. I'm going to leave those alone first. And then look at how it affects my Other side. Say I need to have a fast shutter speed, I'll leave that alone. But now it is gving me a small DOF because the aperture has to open up and that would be bad too. So then I turn to ISO

You have to keep asking your self questions about your prorities

I want a Deep DOF, So I need this
How does that affect my shutter speed? Is it fast enough to hand hold? Do I have a tripod? is My subject Moving?

You have to think about all three sides of the triangle

 

[Big Mike]

The best way to use it, is almost a last resort.

Yes and no. I think that the 'last resort' advice is taken too seriously by many who don't fully understand the issues involved.

For example, if someone is afraid to use ISO 800 because they are worried about noise...that they end up taking photos at 1/50 (on say, a 50mm lens)....they will likely get some amount of blur (lack of sharpness). If however, they use ISO 1600 and a resulting shutter speed of 1/200, they are likely to get much sharper photos, but of course, with more noise. But the thing to remember is that you can't truly get rid of blur, but it's much easier to deal with noise. And even so, noise can usually be stomached by the viewer much easier than a lack of sharpness.

The the moral of the story is....don't be afraid to turn up the ISO if it means getting a sharper photo (due to faster shutter speed).

That is why you don't pull ONE LINE out of context. If you look at both your and my exampe, they are both showing the need for shutter speed as that is a parioirty, in which case I said to raise the ISO

I wasn't trying to disagree with you...just point out that too many people take the 'last resort' advice, too much to-heart....and forget (or don't know) that raising the ISO is sometimes a better choice.

 

[Rephargotohp]

We agree I know I state things too empirically sometimes..Cuz I am a grumpy old man

 

[Big Mike]

I dont know if anyone said it but the difference between lower end dslrs and fx or high end crop sensors is hugely dependent on iso. My d5100 is good to about 300-400 then gets noticable grainy. But some higher end dslrs maybe able too do 1600-2000 and still look ok. Which is a huge plus indoors. 2.8f 1/60 sec 1000-1600 iso you can take nice pictures in relatively low indoor lighting with no flash

This is one of the main reasons i want to go full frame

If you're getting much 'noise' at 300-400 on a D5100, you are probably doing something wrong (or you're way too picky).

This opens up another aspect of digital noise...and that is exposure. If you get your exposure right, in the first place, you end up with a lot less noise than if you underexpose and try to fix it in post. Another way of saying this, is that you can minimize visible noise by maximizing the S/N ratio by Exposing to the Right.

 

[classixuk]

Great. I think I am on the right track then. So as a general rule, decrease the F-Stop gradually to let in more light, but If I start losing too much DoF, and my images are still looking underexposed, that's the time to increase the ISO, but never before that. So it goes like this in stages of steps to try: F-Stop, ISO, Artificial Lightso ???

Mmmm almost

You really have to look at your priorities. If what I am shooting demands either an aperture for DOF or a shutter speed to stop action. I'm going to leave those alone first. And then look at how it affects my Other side. Say I need to have a fast shutter speed, I'll leave that alone. But now it is gving me a small DOF because the aperture has to open up and that would be bad too. So then I turn to ISO

You have to keep asking your self questions about your prorities

I want a Deep DOF, So I need this
How does that affect my shutter speed? Is it fast enough to hand hold? Do I have a tripod? is My subject Moving?

You have to think about all three sides of the triangle

OK. That makes sense. A lot.

It's an eye opener coming from a point and click where you don't have to think about aperture to suddenly having it at your disposal to take control over your images.

So I guess the first question I always need to ask is "Does my subject move, and if so, how quickly/fast do they move" and think about my shutter speed before anything else at all.

The shutter is like the mortgage ... always needs to be paid first. Whatever is left over, Mr F Stop gets his cut and then Mr Iso comes last in line. If I don't have enough left over for Mr Iso (or he demands too much), I can always borrow some from Mr Artificial Light as a last resort to see me through?

 

[c.cloudwalker]

What on earth do you shoot with that type of film? A white feather in a white room held by an albino model? LOL

Actually, I would say 75% of my stock photography and 90% of my studio work was done with such films.



To me, noise will always be grain Much the same way as a 10 x 8 will always be known as that, no matter what Brussels tells me I should measure in

Well, I couldn't care less what Brussels sprouts...

But noise and grain will never be the same. Grain has a shape. I even seem to remember people saying that specific types of film had specific looking grain. Noise is just that. Noise.

 

[classixuk]

What on earth do you shoot with that type of film? A white feather in a white room held by an albino model? LOL

Actually, I would say 75% of my stock photography and 90% of my studio work was done with such films.



To me, noise will always be grain Much the same way as a 10 x 8 will always be known as that, no matter what Brussels tells me I should measure in

Well, I couldn't care less what Brussels sprouts...

But noise and grain will never be the same. Grain has a shape. I even seem to remember people saying that specific types of film had specific looking grain. Noise is just that. Noise.

LOL @ the part in bold. I will remember that one!

If noise and grain fall under the category "unwanted artefacts" I think we will agree on the category LOL

Very curious why anyone would need an ISO as low as 25. Is it for a special camera? To me, the uninitiated, it sounds as though (in computer terms) I'd end up with 8 bit colour in all but the brightest of lighting set-ups. Curious.

 

[Rephargotohp]

ISO 25, 50 and 64(Kodachrome) were very common, Their latitude was great and their grain was very fine and it certainly was no problem shooting a landscape on a tripod at 1/25

 

[c.cloudwalker]

LOL @ the part in bold. I will remember that one!

You're welcome to use it,. No copyright involved.

The lower the ISO the least amount of grain you got. The least grain you had the more HD the pictures looked. That is it.

Today you get decent shots with super high ISOs but not in the film days. When 1600 film came out everyone was laughing their heads off. Yeah, really?

And they were right, The grain was bad. However, that was what we had then and we dealth with it.

Just like you need todeal with the noise today.

 

[classixuk]

OK. Just Googled that.

I am guessing that Kodachrome is like the Vidal Sassoon of camera film? No longer at the forefront of innovation because they led the innovation that bore out today's superstars?

Interesting. I am 7 days into my new hobby and already learning about it's vast heritage.

Last time my mind sparked this much was in college!

 

[nickzou]

Actually, the image sensor only has 1 level of sensitivity.

The ISO setting determines how much the signal (amount of light) the sensor recorded gets amplified.
At ISO 100 the signal is amplified less than the signal gets amplified at higher ISO settings.

Most of the image noise we see in a photo that was made at higher ISO settings is actually amplifier noise that is overwhelming the small signal (not much light) the image sensor was able to record.

As shutter speed gets longer, power is applied to the image sensor longer and because of it's electrical resistance it heats up, generating thermal noise that gets added to any amplifer noise caused from boosting the ISO setting.

Lol this is the kind of thing that confused the crap out of me when I was starting out. I would ask "what is ISO in terms of exposure triangle" and then a mountain of technical jargon and I could only answer "uuh thanks..."