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Quality Difference in CFV ISO Ratings

Hi all. I just read an interesting article by George Lepp this evening (Outdoor Photographer, Oct 07 issue). In it he states that Canon has always used ISO 100 as the highest quality setting for all its digital bodies. However, on a few newer bodies, Canon has added an ISO 50 - and this was what I found interesting, and wondered if it correlated with the CFV ISO settings: He states that Canon's ISO 50 setting does NOT increase image quality, but is for use only as a "neutral density filter" which allows one to use slower shutter speeds in bright light.
Noting that the CFV has ISO settings of 50~400, I'm now curious if this same design principle was applied to the CFV - in other words, is the CFV's ISO 100 setting the actual optimum quality setting, with ISO 50 useful only as a neutral density filter, or is the CFV's ISO 50 the actual optimum quality setting?
Michael H. Cothran

The optimal setting for the CFV back is ISO 50. It says "Note that the default sensitivity of the CCD sensor is ISO 50...." on page 32 in the CFV User manual v. 3.0 and page 44 in the 503CWD & CFV User manual v. 6/2007.
"But "default" does not necessarily mean "native".

Agreed. The practical difference between 50 and 100 is difficult to detect. With CCD sensors lower is usually optimal in terms of noise as long as the exposures are spot on.

However, unless you are shooting in broad sunlight or using strobes in the studio, ISO 50 is not as practical as 100 or even 200 for shooting a MF camera.

On a tripod, it would be interesting to see the difference between a shorter exposure at ISO 100 or 200 compared to a longer exposure time for 50.

On a related note: Hasselblad's web site has listed the new H3D-II backs has having the same top ISO as the previous H3Ds. Preliminary reports had stated these top ISOs were increasing to ISO 800 for the H3D/39-II and 1600 for the H3D/31-II. My dealer thinks this increase will not happen until the new software is launched ... and it will increase the top ISO of all HD cameras. My hope is that it will also effect the CFV, and our top ISO will increase to 800 !!!

I've found that ISO 800, using the latest version of Flexcolor, is quite usable for many applications like event and street photography.
I didn't copy the entire paragraph from the manual, but if you read it, it says that increasing the ISO leads to higher noise. I read it as ISO 50 is the native sensitivity. It's certainly not ISO 100 (or higher). It could be that the native ISO is 43,45,55, 67 or even 75, but if that's the case, why isn't that a selectable option? (You would think that they would include the non-&lified (or optimally &ified) signal as an option.)