ISO equivalent for DVX100?

[JeanD]

Hi all,
does any one know what the ISO equivalent is for the DVX100a?

thanks

Jean

[Barry_Green]

There were several big threads about this, do a search over the last, oh, 9 months or so and it should pop up.

The short answer is: it all depends. Overall, in general, it's around 640 ASA in progressive mode, but the lower the light level, the lower the overall sensitivity: at light levels that dictate f/2.8 it responds at around 400ASA, and at light levels that dictate f/16 it responds at around 1000ASA.

[andre]

Barry, could you elaborate on this? I thought CCD transfert vs film printing density remains "steeper" under low light levels (and deep shadows), so the highest equivalent ASA figure would show at low light conditions.

[Barry_Green]

Not as I observed it. *The exposure curve is definitely non-linear, and less responsive at lower light levels, and more responsive at higher light levels.

I set up a number of test situations, but the most telling was a simple gray card. *Testing was designed to see 55 IRE on the waveform monitor. *I'd then light the card such that the camera delivered 55 IRE under various f-stop conditions. *When set to F/2.8, I'd bring the light level down far enough that the waveform showed 55 IRE, then take a reading on the card with my spotmeter, and change the ASA value until the spotmeter also showed f/2.8. *Under f/2.8 conditions, that meant 400ASA.

Then I blasted light at it, using a dimmer control so I could dial in enough light that the camera's auto-iris system would register f/16 exactly while still delivering 55 IRE to the waveform monitor. *At that fixed light condition, the spotmeter needed to be set to ASA 1000 to deliver an f/16.

Over most of the exposure curve the camera responded as 640 ASA, but when you start pressing the limits it responds differently.

Very brief testing with the XL2 and FX1 show similar response, under low light conditions the ASA equivalency is lowest. *The XL2 was ASA 200 in progressive, and the FX1 was ASA 160. *I didn't test them for their highest values.

[JeanD]

Thanks for the info Barry! Did you ever graph your information (or put it in a table) so it could be used as a reference during filming? It would be great to have something like that...

Jean D

[Barry_Green]

No, never did. Basically it's a lot easier and more accurate to just use a monitor. The ASA/ISO value is only mildly useful in video work -- it may help you get an idea during location scouting, or for setting lighting ratios quickly, but with video the "real" lighting setups should be done by eyeballing a quality production monitor and maybe some scopes, not by a light meter.

[andre]

Thanks Barry. I had a study in mind where I used to be involved in, but this related to much lower light levels. (Google on "sensors vs film")