C300: Firmware update question: Auto-iris or 32% IRE rule???

[Nicholas Natteau]

With Canon's latest firmware update, I'm delighted to see that the C300 now has both auto focus and auto-iris. Since I mostly shoot with Canon EF lenses, especially the EF24-105 f/4, I find this invaluable.

But the auto-iris feature causes me to doubt whether or not the scene is correctly exposed when shooting C-Log.

Canon says that in C-Log mode, an 18% grey card should be at 32% IRE on the C300 waveform monitor. But if you enable auto-iris, the C300 increases the exposure until the grey card reads 50% IRE on the waveform. I know that an 18% grey card should sit at 50% IRE in a "Normal" picture (baked) mode. But should the auto-iris be increasing exposure that much in C-Log?

I watched Jem Schofield's Canon tutorials on Canon's "digital learning center" web site, but there's no mention of auto-iris mode, perhaps because the firmware update is so recent. Or could it be that auto-iris should never be used in C-Log mode, but only in Normal picture mode?

Thank you in advance for any advice.

 

[Mark Smith]

you can dial up an AE shift that would be appropriate for Canon Log. There is a +2, -2 range for AE exposure in the menu, so try that option for getting your exposure right for C Log

 

[redhouse]

Typically I don't shoot C log, but I just after I updated my C300 I used it on a documentary. I had already decided that auto iris looked more accurate at -1 for normal profiles, so I used that setting for C log, and I thought it worked pretty well. Auto iris gets you in the ball park, but you still have to make adjustments and keep important highlights under control.