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Recommendations for correcting overexposure due to sun+snow

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Recommendations for correcting overexposure due to sun+snow

Postby Sergeant HCR » Wed Apr 13, 2011 9:27 am

I recently had a snowmobile trip where the country was all snow (no trees, rocks, etc, all snowy hills) and it was sunny. My videos have bad wash-out / overexposure. I've tried Adobe Premiere and Pinnacle Studio to fix it but I'm not an expert with these programs and didn't have much luck. I understand that the details may have been drowned out due to the overexposure but if I had a process or two to try, it would be worth it to me. Any advice? suggestions?

Before trying it in the mentioned programs, I had to convert to mpeg for VCD. Those 2 programs would not import that MP4 file format (Adobe treated it as audio) and other formats I converted to wouldn't work.

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Re: Recommendations for correcting overexposure due to sun+s

Postby suryaprihadi » Wed Apr 13, 2011 10:34 pm

HCR,

It is interesting for me on snow over exposure because I dont have snow in my country.
The brightest I can get is the blue sky. The nearest I can mimick snow over exposure is taking a shot of a very white fiberglass yacht and a big one so that all I see is white fiberglass.

If you have a short clip and would deposit somewhere I would like to see.
Why I am asking is because if snow can reflect sunlight like how when I dive and suddenly camera see the bright surface water with sunlight , I get that white ball over exposure, since the center weighted exposure setting will defend the majority of the image, which is the blue blue ( dark ).
What firmware are you on ?

Thanks
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Re: Recommendations for correcting overexposure due to sun+s

Postby Sergeant HCR » Thu Apr 14, 2011 12:02 pm

Thanks for the reply.

Try getting the video from here...it's about 80 megs.

http://myaccount.dropsend.com/file/7cf34e3d00b71200

I haven't updated my firmware. I got the camera in January, 2010. I read recently that updating the firmware may make it worse.
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Re: Recommendations for correcting overexposure due to sun+s

Postby suryaprihadi » Fri Apr 15, 2011 9:50 am

Look at C1, is that another mountain I marked neon green ?
is the sun behind you when you shoot this video, I mean rather behind you at an angle ?


C2
Can you see the green tint ( over exposure I think ) on the picture ?
Attachments
c1.JPG
c1.JPG (142.37 KiB) Viewed 1412 times
c2.JPG
c2.JPG (91.78 KiB) Viewed 1412 times
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Re: Recommendations for correcting overexposure due to sun+s

Postby SloopDog100 » Fri Apr 15, 2011 11:43 am

Am using GoPro HD in lake louise. In bright sunshine the snow is completely over exposed - no detail at all. Solution. Buy a $25 polarizing filter and put it in front of the lens. Used 'White Tack' to fasten it. This is Canada version of UK 'Blue Tack' and almost the same. Result. Good news. Snow over exposure problem almost fixed excpet in very very bright sunlight. Bad news. Pine trees are slightly under exposed. Conclusion. Filter fixes the problem for 95% of time. Further development. Make a more solid fixing attachment for the filter. Comment on other blogs. If the camera sensor is over exposed, it will saturate and no amount of post-processing will extract the detail because the data is not there.

Just returned to UK and have viewed older footage taken in same places and same bright sunlight BUT before firmware upgrade to allow use of LCD panel. Washed out snow is not there..... unfortunately I cannot go back to the earlier firmware. ?? is the problem with the new firmware or is it a manufacturing tolerance problem? For interest, my other headcam is a Sony HXR-MC1P. Bit more pricy than the GoPro but same probs with tree details. Snow is exposed very well but trees dark. Have emailed GoPro who say they are working on the problem.
Last edited by SloopDog100 on Sun Apr 24, 2011 4:43 am, edited 2 times in total.
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Re: Recommendations for correcting overexposure due to sun+s

Postby Rambo » Fri Apr 15, 2011 12:24 pm

The details are definitely there, the frame is perfectly exposed for the subjects (peoples faces, snowmobil etc) but it is overexposed overall a stop to much. If the GoPro exposed for the white snow then their would be no details in the subjects. That image is what is known as flat, washed out, lacking colour, contrast etc, but it is how video is preferred by Professional Colorists.

Notice there are no shadows, it's overcast, that's why there is little contrast in the snow. A polarizer will allow slightly more contrast but most likely you will loose the subject detail like you did in the trees.
Correction in Sony Vegas using just the colour corrector sliders - gamma/offset/gain and saturation.
Click on the image for the correct resolution
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Re: Recommendations for correcting overexposure due to sun+s

Postby suryaprihadi » Fri Apr 15, 2011 1:29 pm

Rambo wrote:The details are definitely there, the frame is perfectly exposed for the subjects (peoples faces, snowmobil etc) If the GoPro exposed for the white snow then their would be no details in the subjects. That image is what is known as flat, washed out, lacking colour, contrast etc, but it is how video is preferred by Professional Colorists.

Notice there are no shadows, it's overcast, that's why there is little contrast in the snow. A polarizer will allow slightly more contrast but most likely you will loose the subject detail like you did in the trees


Dang, how could I not verify the sun position by the people's shadow....... :lol: Good one Chief.
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Re: Recommendations for correcting overexposure due to sun+s

Postby Rambo » Fri Apr 15, 2011 2:28 pm

There's definitely a colour balance shift in the video when you play it right thru. I would attach a good quality UV filter to the outside of the polarizer, it might help more to retain the details in the darker tree footage.

This is the sort of original image that is optimal for grading/correction.
[vimeo]16913400[/vimeo]
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Re: Recommendations for correcting overexposure due to sun+s

Postby Sergeant HCR » Sun Apr 17, 2011 11:32 am

Thanks all for the help and advice.

C1 does have hills in the background as marked with the neon lines.

That particular point in time there were clouds with sunny breaks. You could see the sunny breaks running all over the hills for the first half of the day and then the sun stayed out after mid-day. Thats why the video looks ok one second and bright the next...I got caught in a sunny break.

Rambo, I was using Vegas to try and correct the overexposure and I sort of made progress but didn't quite get the detail you managed to achieve in color correction. What settings did you use?

I got a bunch more videos to try and fix up but next year I will be having something over the lens to help prevent overexposure. :)
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Re: Recommendations for correcting overexposure due to sun+s

Postby Rambo » Sun Apr 17, 2011 12:18 pm

Sergeant HCR wrote:Rambo, I was using Vegas to try and correct the overexposure and I sort of made progress but didn't quite get the detail you managed to achieve in color correction. What settings did you use?

I got a bunch more videos to try and fix up but next year I will be having something over the lens to help prevent overexposure. :)


They will be different every time, just try the sliders i posted above in Colour Corrector. There's a heap more you can do with other techniques including layering, but this was a quick fix. In the video the white balance goes off bad, but those parts should be edited out anyway. The problem with polarizers (linear and circular) they require rotation depending on the angle of the sun, difficult to assess in run and gun style shooting.
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