So like most of us, I mix breeds of cameras, my Nikon DLSRS with my Canon XF 300s. I've been working on fine tuning my studio work, and my ISO understanding for my Nikon cameras is like butter over pancakes.

However, I said to my self 'self', why don't we figure out the ISO/Gain comparison for the XF 300 so we can do a closer side by side comparison to see what is best for each project. Well.

There is no ISO/Gain in the manual for the XF 300 so I contacted Canon, Twice.

They don't have a record of an ISO/Gain comparison, in other words, what Gain setting equals an ISO.

To me, that's embarrassing for Canon. How can you not know the ISO of your camera.

I'm about to buy a light meter, and it would be nice to know the ISO. 'Things that make you go HUH?'

Vent over.

It doesn't surprise me at all because the XF300/305 is a video camera and the use of ISO numbers have only recently come into vogue by newcomers to video production. Cameras that came out more than 2-3 years ago don't have ISO because nobody cared about those numbers before DSLRS got popular for video. So as DSLR users migrate to real video cameras they now want ISO, histograms, etc. so the manufacturers wrote a few lines of code and gave them those features. But in professional video production ISO has never been used and you won't find it on older cameras like the 300/305. Measuring a video camera's sensitivity by Gain rather than ISO is a much more useful way of using the camera so 90% of operators won't even miss it.

Also, Canon probably cannot give you a definitive answer even if they wanted to because the sensitivity of the camera at any given time is partially dependent on the particular combination of paint menus that have been selected by the operator. If you want to know the ISO of your camera, then configure the camera exactly how you intend to use it, and then rate it yourself. It should only take a few minutes and it's the only way you'll get a trustworthy number.

http://www.vortexmedia.com/DVD_XF305.html

Well, I am trying to kill two birds with one stone. Have the meter for both photos and video,so my due diligence annoyed me I guess. Before I drop 600 on a meter, I'd like to know if I can squeeze all the use out of it I can.

Sure, there's no reason you can't use a meter with the XF300/305 if you want to. I own the Sekonic 758c for testing purposes and love it, even though I'd never actually use it on a real shoot. I can get the same exposure info from zebras a heck of a lot easier.

Don't skimp on a meter if you go that route because you'll own it for decades and it is worth having a good one that is an industry standard.

This sort of question comes up every so often. Mostly from still photographers who are not aligned with the practices common to video.

Still camera's (film mainly) needed ISO because there was no other way to set/judge exposure until AFTER the film was souped. The ISO rating was based on specific assumptions about desired developed image density and density curves for a given film, developer, time, and temperature combinations for a specific reflected light level (e.g., 20% gray card).

The digital still camera came closer to a video camera thanks to electronic capture of the image, but retained much of the film paradigm in use. Also, digital still camera "monitors" tended to be small LCDs and not especially good for judging the image if the user elects to use the screen instead of the optical viewfinder for framing and focus.

Video cameras/camcorders provide immediate point-by-point feedback as as to exposure, including both shadow and highlights, on the monitor (if you have a decent monitor) and you can in real time judge the exposure to get it right for the portions of the image of specific interest. In this case a valuable use of a light meter might be in lighting a set before the camcorder arrives. However, fiddling with a light meter can get in the way of shooting live action that is not staged. After all, the point of video is motion/action.

Manufactures will typically set the 0 dB gain point at the sweet spot in the sensor transfer curve balancing highlights, shadows, and noise performance. From that point you can think of gain as being a bit like to push processing.

Note also that most of the better camcorder let you fiddle with gamma, black, and knee as well as color balance, which will have effects similar to applying filters and adjusting processing with film, and make any ISO setting potentially problematic.

That said, the last time I looked at equivalent ISOs for earlier generation Canon XL/GL-series camcorders they ran around 200-300 or so. The benefits and flaws of relying on auto exposure are common to both.

So as suggested above, develop your own ISO rating for what how you shoot.
- Set up a test shot.
- Adjust exposure to provide the optimum image.
- Note shutter, aperture, gain (say 0 dB) and any other image presets.
- Using your light meter, read the scene and find the ISO that corresponds to the exposure parameters.

+1 good post

Great post Don. Simple and straightforward - I do simple.

Thank you

G