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Old August 2nd, 2015, 07:39 PM   #1
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Canon G20 auto exposure too bright

I use a Canon G20 as my backup/safety camera during weddings alongside two Canon C100s and my 70D. I set it up as a wide, static, unmanned camera so that I know that I always have that camera to cut to in the event that the other shots aren't usable for a few seconds. I film mostly outdoor weddings and I will set the G20 to auto exposure because quite often the sun will go behind the clouds and I (and my other camera operators) have to rush to open up our apertures to adjust for the change in lighting. The G20's autoexposure does a great job of quickly and smoothly adjusting its aperture so that I will always have a usable shot in these situations. However, I've noticed that if the subjects are in direct sunlight then it will consistently overexpose skin tones and the wedding dress will be completely blown out. When the sun comes back out it will smoothly readjust the aperture but then much of the shot is overexposed again.

I was looking into the Exposure Compensation options for the camera, but it appears that this will only help out when the exposure is taken off automatic and switched to manual. I would like to be able to tell it to automatically expose about 1 stop darker than it currently is, but I'm not sure if there is a way to do this. If there is can you please let me know how to do this?

One idea I had is to by a ND 0.3 filter and screw it onto the lens. However, I'm wondering if the G20 will just open up the iris even wider and continue to overexpose.

Any ideas on how I can tell the camera to expose the image so that nothing is over 100 IRE?

Thanks!

Mike
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Old August 3rd, 2015, 07:07 AM   #2
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Re: Canon G20 auto exposure too bright

Does the G20 support the Highlight AE capability? That should expose for highlights and should void blown out whites (at the expense of shadows). If it does, run some tests to see if it works for you.
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Old August 3rd, 2015, 09:32 AM   #3
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Re: Canon G20 auto exposure too bright

I have the G30 and I can set the camera to one of the auto exposure functions and designate one of the function buttons to 'exposure'. When pressed it brings up an compensation slider where you can shift the auto exposure up or down by 3 stops.
On some settings, Spotlight, for instance, you can only reduce by 3 stops (you can't increase).
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Old August 3rd, 2015, 01:29 PM   #4
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Re: Canon G20 auto exposure too bright

Don, thanks for the suggestion. The G20 has AE Lock (touch) which allows you to select from "Normal" or "Highlights" but unfortunately when this is used then the camera reverts to manual exposure which is not what I'm looking for. I thought that it might work but when I tried it out, the camera would expose for the sky and then stay at that aperture regardless of how the lighting changes outdoors. I need to make sure that when the sun goes behind the clouds that the camera will open up the iris a little bit.

Mark, when you make those adjustments on the G30 does it stay in auto-exposure mode? If so, that's really what I'm looking for. The G20 lets me adjust the dial on the back of the camera to exposure, but it reverts to manual exposure once I do this. So if I adjust the exposure then I'm back in manual mode.

I did experiment a little bit and found that the issue with overexposing only happens when I'm outdoors while there are mostly well lit trees in the background. If I point the camera in a direction where half of the frame is filled up with bright sky then the camera will expose so that there are no 100% zebras in the sky. However, when I point it back to the spot where there are lots of trees then I notice that the places where I can see the sky in the frame will fill up with zebras which doesn't work well for skin tones and the bride's dress. When shooting indoors it works great, but it's just outdoors where it does this.

I did experiment with the Spotlight setting and it seemed to help a little bit as it reduce the amount of zebras, but I'm not sure how the camera will react when the sun goes behind the clouds. Any thoughts on the ND filter idea?
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Old August 7th, 2015, 10:36 AM   #5
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Re: Canon G20 auto exposure too bright

The ND filter will probably not help your auto exposure - it will likely just shift the baseline exposure (shutter, aperture, & gain) by the filter amount, resulting in higher gain and/or slower shutter and/or more open aperture.
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Old August 7th, 2015, 11:24 PM   #6
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Re: Canon G20 auto exposure too bright

Quote:
Originally Posted by Don Palomaki View Post
The ND filter will probably not help your auto exposure - it will likely just shift the baseline exposure (shutter, aperture, & gain) by the filter amount, resulting in higher gain and/or slower shutter and/or more open aperture.
That's exactly what happened. I found an ND 0.9 that I placed on the lens and shot some trees with bright sunlight on them and it actually overexposed slightly more than without the ND (according the WFM). However, I did try some of the different recording modes and found that Spotlight actually exposed the image much better so that there were just a couple 100% zebras in the sky behind the trees while the trees themselves looked quite good.

It's hard to tell how this will work in other situations, but at least I can try it out when setting the camera up and see if it looks decent. I don't need this shot to be perfect but I would like for it to look a bit better than it has at times.
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Old August 8th, 2015, 10:12 AM   #7
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Re: Canon G20 auto exposure too bright

If used for cut-aways and the like, avoiding blown highlights and then adjusting gamma in post can give usable results. The main problem I see is if there are very bright point sources of light (e.g., bare bulbs) in the view when shooting indoors. That could lead to undesired results if your keep it in highlight mode.

All auto exposure modes/programs are designed around "average" conditions for the stated mode/program; e.g., typical back lighting or typical spotlight as defined by the maker. They will still miss the boat in extreme conditions, but not by as much,
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