5D at 50 ASA

Has anydone a test to see if shooting at 50 asa improves on anything from shooting at 100 asa
on the 5D?

Or is it more like an internal nutural density filter?

Thanks...Arnie

www.arnoldadler.com

[John_Sheehy]

[ QUOTE ]
Has anydone a test to see if shooting at 50 asa improves on anything from shooting at 100 asa
on the 5D?

Or is it more like an internal nutural density filter?

[/ QUOTE ]

If ISO 50 is only available through "expansion" than something compromising must be going on with it.

It seems that DSLRs that offer ISO 50 are just over-exposing the images by one stop, and then halving the RAW values.

You should get better results "over-exposing" yourself, if you shoot RAW. The expanded ISOs are usually only beneficial to the JPEG shooter.

[Doug_Kerr]

Hi, John,
[ QUOTE ]
It seems that DSLRs that offer ISO 50 are just over-exposing the images by one stop, and then halving the RAW values.

[/ QUOTE ]
How is it that we know this?

[John_Shafer]

I shot controlled studio controlled tests at all ISO settings, including ISO 50. I didn't look at them very hard. But ISO 50 doesn't really look any different to me than ISO 100. The main value, in my estimation, is that it will allow for slower shutter speeds or larger apertures. To me, that's a big deal. I like slow shutter speeds and larger apertures for outdoor photography.

Here's a link to the all my EOS 5D test photos. They're all posted at full resolution: http://gallery.photographyreview.com/sho...amp;catdrop=527

[Eric_Chan]

[ QUOTE ]
Hi, John,
[ QUOTE ]
It seems that DSLRs that offer ISO 50 are just over-exposing the images by one stop, and then halving the RAW values.

[/ QUOTE ]
How is it that we know this?

[/ QUOTE ]

Hi Doug, it seems to be the case because the dynamic range decreases by roughly a stop in ISO 50 compared to ISO 100. For example, let's say I expose an image at ISO 100, f/8, and that 1 second is the longest exposure time that I can use without clipping the highlights. If I then set the camera to ISO 50, then I need to change the exposure time to 2 seconds to keep the same exposure (nothing should be clipped, still). However, in practice when I do so, things start clipping noticeably. Does this make sense?

Eric

[E_J_Peiker]

Eric explained it well. What you give up is high end dynamic range. In otherwords you will clip whites much more easily as the sensor goes into overmodulation (essentially signal overload). However in a low contrast situation, say the very darkest and very lightest area in the photo are 4 stops or less, you will get a very smooth and noise free photo.

P.S. ASA went the way of the dinasaur about 10 years ago. Its ISO.

[Andy_Farrington]

I still call it ASA too - it's essentially the same thing and the numbers don't change so us oldies need our fond memories intact...(I'm 40 in a few months). It was the DIN that scrambled my wires....Like in the uk we still use Celcius and Fahrenheit.....but I struggle to get to grips with Celcius.
Old dog - new tricks etc etc.

Andy

PS Oh yes, ON topic....I tried a few unscientific tests and couldn't see a difference so I use when large apertures are required.....a lot with big Bron ringflash!!!