Is ISO 50 any different than ISO 100?

[hacksaw35]

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?)

 

[Derrel]

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

 

[Mishel]

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?

 

[Lipoly]

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?

 

[Josh66]

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?

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...

 

[Lipoly]

If so, extended ISO would have pretty limited use...

No more than any ISO setting other than the native (base) ISO of the camera...

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?

 

[Josh66]

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).

 

[Green Li]

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?

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.

 

[Lipoly]

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.

 

[Josh66]

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.

 

[Alpha]

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.

 

[Lipoly]

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.

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.

 

[Josh66]

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.

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...

 

[Alpha]

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.

 

[Derrel]

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.