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Old March 17th, 2005, 01:04 PM   #1
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Disappointed in Auto-Grain...I mean Auto-Gain

So I shot a live event at the House of Blues the other night. Pretty dark, but I had an on-camera light that was good (Lite Panels). I thought if ever there was a time to use the full auto features, it was this event. So, I turned full auto (A) on and put gain on Auto. The footage turned out VERY grainy. In the conditions, I could see it was a little grainy in the viewfinder, but NOTHING like how noisy it turned out.

Anyone have an idea about how the auto features are prioritized? In other words, when the camera needs more light to the chips, does it start gaining before Irising up? This would seem odd, but so did my footage. It's almost as if the camera wasn't acknowledging my light at all. (I oftened turned camera on and pointed before turning on light. Anyways, I learned my lesson about using Auto anything...never again.

Thanks for any comments, answers or sympathy!

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Old March 17th, 2005, 04:43 PM   #2
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I suspect you're going to be told "don't count on auto-anything to do what you expect." There are times when you really can't help but use some auto settings, but only do so to the extent needed. In your setting, I probably would have gone full manual exposure, manual gain, manually set the white balance. I probably would have avoided manual focus unless all your subjects are fixed at roughly the same distance. Even then it depends on how much you need to zoom.

So like... 1/60th at +6 or +12 gain (however much grain you can stand) and F-stop to taste.

Personally (keeping in mind I'm still a relative newbie), I've been quite surprised by the *lack* of grain the XL2 exhibits, even at +18. ...and the colors... Oooo the colors... Outdoors at night and that sort of thing. This beastie has really impressed me.

I agree though, you really can't see the grain through the EVF. Best to play with the various settings in comparable conditions and check the results on a good monitor before the "big shoot."

Charlie Wilkinson
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Old March 17th, 2005, 05:03 PM   #3
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I would recommend that you not use auto-gain for the reasons you stated. However, I would start with gain at 0 and do what I could with iris open, shutter as slow as possible, and then, and only then would I add gain. I shot some stuff in a night club recently like this using 6db and the images are virtually noise free. Don't forget also that there is a noise reduction menu setting that is tailor made for these shooting situations. I would also advise against using auto focus in low light cause it's not going to be very reliable.

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Old March 17th, 2005, 06:09 PM   #4
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in this situation, I would set my iris wfo (all the way open), my shutter to 1/60th and my gain at 0. then I would check the zebras to make sure nothing is overexposing. Most likely, nothing is going to clip in this setting. Naturally, there will be parts of the image that fall off the map, but this is ok, in a concert setting, there is supposed to be alot of darkness, just make sure the subject is exposing. My philosophy is to over-expose (but not clip!) so that you can adjust your levels in post, but only DOWN, otherwise you'll introduce unwanted grain. This way, you retain as much detail in the shadows as possible. If that is vague, my apologies.

In other words, lets say pure darkness (as far as the tape is concerned) is 0, while pure white is 100.
If you expose using a grey card, you are telling your camera exactly how to expose for 18% grey (which basically tells it how to expose it so that mid tones are actually mid tones, regardless of where black and white fall) instead of averaging all the information together. If you set your camera to that f-stop/shutter speed, and there are no values above 60, you have alot of wasted dynamic range. Because there are no values between 60 and 100, and you have a high cocentration of values between 0 and 60 (as well as information being lost in the shadows), it is best (in my opinion) to over-expose so that your highest value is in the 90's, even if its supposed to be a mid-tone. Then you've brought any info that was below zero up to register, and you've got all the necessary info to acheive a proper exposure, its just in the wrong place. You can make adjustments in post to liking. Note that your image is going to look washed out in this scenario, and will only look better after you've adjusted the levels, however the end result should be much better than just exposing by auto or averaging all values.

My $0.02.
If anyone disagrees, feel free to voice your argument! I shoot like this and if I'm wrong, I'd sure like to know!

stephen birdsong
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Old March 17th, 2005, 07:09 PM   #5
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In trouble I'll cheat and use 1/30 shutter. I guess that's a no-no, but sometimes I go into a "get anything" mindset ahead of a theatrics one.

I also toyed with auto mode a bit, pointing at the floor in a poorly lit room. To get a certain image to match in manual to what a full auto image looked like, I needed 18db of gain. So when the GAIN light is on, it means it! lol
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