5dMkII Iso 50 - is it "real" ?

[runee]

I am wondering about the Canon 5d2 L setting for ISO. It is supposed to be ISO 50 - which is all fine and dandy.

What I am wondering about though, is whether it is "real"? Why I am wondering, is that it is hidden in the "expanded ISO modes" - e.g. it is not available by default, you have to make a concious descision to be able to enable it. This makes good sense for the last two (highest) ISO settings of 12.800 and 25.600 - since the image quality is degraded to an unuseable extend, and you'd only want to use these for specific uses, such as very low light documentary or stuff like that where getting A picture is better than getting NO picture.
But, since the ISO50 is also hidden under the "concious descision" modes, I fear this is because the ISO is not a "real" one, rather it is some approached gimmic, like a software ND filter or some marketing crap.

Anyone have insights on this? For studio work where I can control the light will ISO 50 give me cleaner files than 100 on the 5d2 or is it some pseudo low iso setting ?

I will test this myself when I have the time to do so properly - but I am hoping someone has some insight on this too.

Thanks.

[Ronny Nilsen]

It's a pseudo low iso setting. The camera will take the image at 100 iso and calculate the 50 iso image from the exposure.

Ronny

[runee]

It's a pseudo low iso setting. The camera will take the image at 100 iso and calculate the 50 iso image from the exposure.

Ronny

That's excactly what I thought/feared.

Any practical experience with this? I.e. is it worth it in terms of IQ? Or am I better off staying @100 ISO ?

[adam z]

I have heard of 2 reasons for using it.

1. Shooting long exposures (eg: waterfalls, moving water) for motion blur, sometimes ISO 100 won't get you a long enough exposure and the extra stop might be what you are after without losing DOF by opening the aperture up a stop.

OR
 
2. If shooting with studio lights and 2 cameras (either a MF Digital at ISO 50, or a film camera @ISO 50, alongside your 5D MkII) you can have both cameras set with the same settings so you don't have to think

[runee]

I have heard of 2 reasons for using it.

1. Shooting long exposures (eg: waterfalls, moving water) for motion blur, sometimes ISO 100 won't get you a long enough exposure and the extra stop might be what you are after without losing DOF by opening the aperture up a stop.

OR
 
2. If shooting with studio lights and 2 cameras (either a MF Digital at ISO 50, or a film camera @ISO 50, alongside your 5D MkII) you can have both cameras set with the same settings so you don't have to think

Thanks Adam,

There's some obvious practical benefits I guess - as you say, use it as a pseduo ND filter or for the easy of use with multiple cams, or getting that extra stop to keep a shallow DoF in brigter light etc... But I'm really just interested in whether it degrades, make no difference to or maybe even improve image quality.
I'll do some testing I guess

[canmiya]

Thanks Adam,

There's some obvious practical benefits I guess - as you say, use it as a pseduo ND filter or for the easy of use with multiple cams, or getting that extra stop to keep a shallow DoF in brigter light etc... But I'm really just interested in whether it degrades, make no difference to or maybe even improve image quality.
I'll do some testing I guess

iso 50 has been around for a number of years on several canon bodies.  you may want to goole "canon iso 50" or some variant as there have been numerous threads on various internet forums, articles and blog entries  covering it. as far as better image quality, my own experience has been that there is less highlight headroom using iso 50 than using iso 100.
here is a link to what canon had to say about iso 50 and the original 5d:

http://www.usa.canon.com/dlc/controller?ac...p;articleID=268

 if you scroll down the following link you will find chuck westfalls comment on iso 50 from his column last month:

http://www.digitaljournalist.org/issue0905/tech-tips.html

regards

[runee]

iso 50 has been around for a number of years on several canon bodies.  you may want to goole "canon iso 50" or some variant as there have been numerous threads on various internet forums, articles and blog entries  covering it. as far as better image quality, my own experience has been that there is less highlight headroom using iso 50 than using iso 100.
here is a link to what canon had to say about iso 50 and the original 5d:

http://www.usa.canon.com/dlc/controller?ac...p;articleID=268

 if you scroll down the following link you will find chuck westfalls comment on iso 50 from his column last month:

http://www.digitaljournalist.org/issue0905/tech-tips.html

regards

Awesome, thank you - those links had just the explanations I was looking for

[Luis Argerich]

Unless you shoot JPG there is no real practical benefit.

The waterfalls example doesn't make sense if you shoot RAW.
You may meter half a second at ISO 100 then you can just take the shot at 1 second ISO 100 and pull down the exposure, it will be the same as shooting in ISO50.

In practice the camera will just take the shot at ISO100 overexposed 1 stop and flag it, then the software when seeing the flag will pull down the exposure 1 stop.

Luigi

[Hansen Photo]

I use iso 50 on my 5d and 5d M2 often when I'm using some of my fast lenses at f1.2 and syncing my profoto or dyna-lites and there is a high level of ambient light.  My max shutter speed to sync at is 1/200th and at f1.2 it doesn't take a lot of ambient light to become overexposed.  Even at iso 50 I often have to screw on a ND filter to cut the ambient light down enough to get the effect I want.  I've been pretty happy with the results, even though it's not ideal.  I'd love it if I could get even lower iso setting and avoid using ND filters all together (iso 25, 12, even 6 would come in handy for me at times).  

Ken

[Panopeeper]

It has been posted two times by now, but still not everyone gets it, so I guess it needs to be stressed:

there is no ISO 50 with the 5D2. It is ISO 100 with 1 EV overexposure.

There is absolutely ZERO reason to use it with raw; just the opposite, it is a firm recipe to cause clipping.

Important: DPP and ACR do compensate for the overexposure, i.e. the overexposure is not directly apparent when converting the raw image. However, the compensation does not reverse any raw clipping.