# Is ISO 50 any different than ISO 100?



## hacksaw35 (Jul 27, 2010)

So I recently purchased the 5d Mk II, and when you choose the "expanded ISO" setting you can technically go down to "L" or ISO 50. I read a comment on another board that the "expanded ISO" is a gimmick and not to bother with them. Anyone have some insight on this? Thanks

(should I post this in a different section?)


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## Derrel (Jul 27, 2010)

Extended ISO settings that are lower than the true "base" ISO often have slightly lower dynamic range than the true,base ISO has.


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## Mishel (Jul 27, 2010)

I thought that the lower the ISO, the better the dynamic range. My friends prefer shooting at the lowest ISO settings possible. Tough, I don't know what extended means. There is a reason why some DSLRs only start with ISO 200 and not lower than that?


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## Lipoly (Jul 27, 2010)

Derrel said:


> Extended ISO settings that are lower than the true "base" ISO often have slightly lower dynamic range than the true,base ISO has.



Wow, thats the first I've heard of that.  If so, extended ISO would have pretty limited use...only in cases where you have tons of light, but lower than normal dynamic range in the subject.  Its hard to think of an example...direct pics of only sky?


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## Josh66 (Jul 27, 2010)

Lipoly said:


> Derrel said:
> 
> 
> > Extended ISO settings that are lower than the true "base" ISO often have slightly lower dynamic range than the true,base ISO has.
> ...



No more than any ISO setting other than the native (base) ISO of the camera...
(Which would be 100 for Canon and 200 for Nikon.)


In the film world, there are many 50 and 25 ISO options...


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## Lipoly (Jul 27, 2010)

O|||||||O said:


> Lipoly said:
> 
> 
> > *If so, extended ISO would have pretty limited use...*
> ...



As I understand, ISO is one of the tools in your arsenal to get proper exposure; but for the most part, you want ISO as low as possible (minimum noise).  If, by lowering your ISO into the "extended" range, you actually reduce quality in some circumstances (reducing dynamic range, without increasing sharpness due to faster shutter), then it may not be worth it.  This doesn't hold true for lowering ISO in non "extended" range as far as I can tell.

My point is that the generally accepted rule that you want the lowest ISO you can get while getting a sharp (and properly exposed) shot starts to break down once you enter the extended range...its not always worth it?


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## Josh66 (Jul 27, 2010)

Anything below the base ISO will introduce more noise, etc. - just as anything over it does.

For the least noise, use the base ISO (which until recently was always the lowest).


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## Green Li (Jul 27, 2010)

Lipoly said:


> Derrel said:
> 
> 
> > Extended ISO settings that are lower than the true "base" ISO often have slightly lower dynamic range than the true,base ISO has.
> ...



Lowering ISO makes as much sense as ND filters. Let's say, you want ocean ways look like milk (motion). You need a slow shutter speed. So, you set it low, but there are "tons of light" (sunny day). So, you bump up aperture. There is a good chance that you run into lens aperture limit or won't like the depth of filed or diffraction will affect the sharpness. Thus, you need to lower the sensitivity of the sensor or use a ND filter. 
Just an example. Hope it helps.


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## Lipoly (Jul 27, 2010)

Ok, so there is zero reason to lower into extended (low) ISO unless you will simply over-expose otherwise (or have too fast a shutter)?  Until now I'd lower the ISO to bare min if I had enough light.


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## Josh66 (Jul 27, 2010)

Lipoly said:


> Ok, so there is zero reason to lower into extended (low) ISO unless you will simply over-expose otherwise (or have too fast a shutter)?  Until now I'd lower the ISO to bare min if I had enough light.



If there was no reason to do it, the option wouldn't be there.  There are always reasons to do it.  You just have to know the pros & cons and decide which is more important.


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## Alpha (Jul 27, 2010)

My suspicion is that this option is part of making the camera well-rounded for portrait use. Working with powerful strobes sometimes necessitates low ISO. There are other uses akin to the ND filter as well, such as making daylight appear to be night, where this would be handy.


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## Lipoly (Jul 27, 2010)

O|||||||O said:


> If there was no reason to do it, the option wouldn't be there.



Brilliant...I didn't say I thought it was useless.  Maybe I should've made the word "unless" bold.




Alpha said:


> My suspicion is that this option is part of making the camera well-rounded for portrait use. Working with powerful strobes sometimes necessitates low ISO. There are other uses akin to the ND filter as well, such as making daylight appear to be night, where this would be handy.



That makes sense, although I would think the ND filter itself would mean you wouldn't need such a low ISO.


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## Josh66 (Jul 27, 2010)

Lipoly said:


> O|||||||O said:
> 
> 
> > If there was no reason to do it, the option wouldn't be there.
> ...



Not sure what you're trying to say...

It sounded like you were asking why the option was even there since, apparently, there was no reason to use it - unless you had exposure issues that couldn't be solved with aperture or shutter speed.

Why ever use 1600 or 3200?  It's obviously not as 'good' as 100...


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## Alpha (Jul 27, 2010)

Let's just call it an alternative to an ND filter. But an ND filter isn't always ideal. So sometimes it's a better one. Sometimes it's not.


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## Derrel (Jul 27, 2010)

Kodak's older full frame d-slr the 14n, had its base ISO, as well as an ISO 6 option, to allow the use of very long exposures without use of any ND filtration.

The Canon 5D's ISO 50 setting is pretty useful for me, since I have 1990's era 2400 watt-second power packs...if the doggone thing went down to ISO 25, I'd be even happier.


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## Lipoly (Jul 27, 2010)

O|||||||O said:


> Why ever use 1600 or 3200?  It's obviously not as 'good' as 100...



My point is the fact that 1600 ISO isn't as "good" as 100 is obvious to most people...that 50 ISO is sometimes worse than 100 ISO is certainly not as well known.

I'm still not sure why you'd go below base ISO under controlled (ie w/flash) circumstances since it can lower dynamic range...seems you'd reduce/diffuse the light to keep ISO at or above base.

At any rate, I'm just glad to know the Lo settings on my Nikon are not necessarily where I want to be.


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## Alpha (Jul 27, 2010)

Lipoly said:


> O|||||||O said:
> 
> 
> > Why ever use 1600 or 3200?  It's obviously not as 'good' as 100...
> ...



If the least powerful light in your ratio setup is more powerful than you want at a given aperture, you're screwed unless you can lower the ISO or use an ND filter. I don't like using filters unless I absolutely have to.


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## Lipoly (Jul 28, 2010)

Alpha said:


> If the least powerful light in your ratio setup is more powerful than you want at a given aperture, you're screwed unless you can lower the ISO or use an ND filter. I don't like using filters unless I absolutely have to.



Good to know, thanks :thumbup:


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## emh (Jul 28, 2010)

O|||||||O said:


> If there was no reason to do it, the option wouldn't be there.



I wouldn't put it past marketing departments to include utterly useless features (e.g. digital zoom on P&S cameras). However, to their credit, the camera makers clearly mark the very low and very high ends of the ISO ranges as "Lo" and "Hi" (i.e. outside of the normal/useful ISO range of the camera), which should be a good hint that those should only be used in extreme cases... perhaps only as a last resort.

I've read that the extended "Lo" ISO is implemented by over-exposing the image and then truncating the highlights. That would indeed support Derrel's point about reduced dynamic range in these settings.


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## NateS (Jul 28, 2010)

Just a word to the wise regarding the "dreaded" (for my uses) Lo settings.....  If you use flash and are set at your max sync speed, going to Lo or anything below base ISO will force your camera into auto-fp mode and render your flashes useless unless you have an army of flashes or have the flash nearly touching your subject.  

I found this out the hard way....trying to darken the background a bit more on a bright day for an engagement shoot so I dropped it to the Lowest Lo setting with max sync speed.  Ended up throwing it into auto-fp mode and I couldn't get enough flash output to light the subject...ended up underexposing a lot of shots before I figured out what was going on.

I wish there was a way to disable the Lo/Hi settings alltogether like I did with the auto-fp.  I can see it useful for some situations, but I generally throw on my ND filter for those needs.


Edit:  All the above only applies to Nikon based on my knowledge...not sure what Canon and friends have.


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## hacksaw35 (Jul 28, 2010)

Thanks for all the info/comments everyone. That was quite informative.:thumbup:


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## TiCoyote (Jul 28, 2010)

A related question:  Why does an image shot with a higher ISO require more disk space?


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## Josh66 (Jul 28, 2010)

TiCoyote said:


> A related question:  Why does an image shot with a higher ISO require more disk space?



I've noticed that too...

More information being stored in the RAW data is all I can think of...
Since it's just the base ISO, amplified, I guess it needs more space to tell it how to amplify it.  Just a guess, but it sounds right, lol.


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## Village Idiot (Jul 28, 2010)

Isn't it that the extended range ISO is a software process where native ISO changes are hardware processed?

I was testing out a car rig for rolling shots and to shoot at 1 second shutter speed (less than 30 minutes before dark), I had to shoot at the max aperture of f/22 and ISO 50. I still got a blown out sky. I needed to use filters and lens that would take them...at least the affordable ones.


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## emh (Jul 28, 2010)

TiCoyote said:


> A related question:  Why does an image shot with a higher ISO require more disk space?



RAW file size should not change with ISO.

JPEG file size will often be larger at high ISO. The reason is that JEPG compression works well when you have images with less detail (areas of uniform color and intensity are compressed in the saved file). At high ISO, you get noise even in the areas of the image that would otherwise be uniform. Since the JPEG compression algorithm can't tell the difference between real image detail and noise, high ISO images usually end up with less compression resulting in bigger files.


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## Josh66 (Jul 28, 2010)

emh said:


> TiCoyote said:
> 
> 
> > A related question:  Why does an image shot with a higher ISO require more disk space?
> ...



Oh, but it does.  Check for your self.


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## emh (Jul 28, 2010)

O|||||||O said:


> emh said:
> 
> 
> > TiCoyote said:
> ...



Strictly speaking, it shouldn't. But since RAW isn't a single format and different manufacturers define their own formats, some of them do some amount of lossless compression (some cameras even let you choose between compressed or uncompressed RAW) which have the same effects I described for JPEG.


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## KmH (Jul 28, 2010)

Village Idiot said:


> Isn't it that the extended range ISO is a software process where native ISO changes are hardware processed?


Ding! *Ding!* Ding! *Ding!* Ding! *Ding!* Ding! *Ding!* Ding! *Ding!* Ding! *Ding!* Ding! *Ding!* Ding!

*We have a winner! *

Base ISO changes are implimented in the image sensor amplifier circuts.

Extended ISO is done entirely with software.


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## invisible (Jul 28, 2010)

Derrel said:


> Extended ISO settings that are lower than the true "base" ISO often have slightly lower dynamic range than the true,base ISO has.


While this might be true, that's not what Nikon's official literature says: at ISO settings lower than 200, they warn you that the resulting image will be less contrasty.

I've been shooting at the lowest ISO setting possible for about six months now and haven't been able to notice a difference in contrast vis-a-vis images made at ISO 200. (And even if there was a difference in contrast, it would be easily fixable in post.) I haven't noticed any differences in dinamic range either; however, I find that the image quality is better. Just my personal experience/opinion, of course.


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## Sw1tchFX (Jul 29, 2010)

What happens with the extended Ranges Lo1 (ISO 100 or 50), and Hi1 (ISO 12800) Hi2 (ISO 25600) is that the exposures are shot at normal exposures than pushed the stops. 

For Example, 

On the D700, Lo1 acts as "ISO 100". What it does is expose an ISO 200 shot for twice as long, than the camera darkens the exposure by a stop. That way you get equal brightness, at twice the length of the expsoure and a drop in noise becuase what little amplification is there is getting pushed down. However, you loose highlight latitude because it was overexposed to start with. 

So Hi 1 is just ISO 6400 exposed for half the time, than brightened up. 

Hi 2 is 6400 for a quarter of the time and brightened two stops. 

it's a pretty simple concept. 


Generally, if I can shoot at Lo1, I will. But if my highlights are clipping bad, i'll go to ISO 200 to get an extra stop in the highlights and deal with the noise. 

Another thing you can do to escape noise is to stack exposures. Nikons are the only cameras i know of that can do this in camera, but when it works, it makes ISO 3200 look almost like ISO 200. You turn on "multiple exposure", put auto gain on so the image doesn't get too bright, set to 10 shots, and rack off 10 shots of your subject. The camera then puts the pictures together, adjust brightness and bam! clean images. Granted, you have to be on a tripod, but yeah. 

What it does is since noise is random, over the 10 shots, the noise is averaged out, so you don't see as much of it, and what's great is that you loose zero detail, and zero dynamic range. A shot at ISO 100 or 200 with this yields so little noise, you can basically sharpen with reckless abandon and you won't pull up any noise.


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