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Manual exposure question

Discussion in 'Pro/Adv Discussion' started by Benny The Ball, Sep 25, 2016.

  1. Benny The Ball

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    I notice that many people use manual exposure when videoing so that the scene doesn't keep changing.

    I want to use manual exposure myself, but which ISO setting do I use? Is there any rule of thumb where you use a particular ISO for sunny and another for overcast? Or is it all just trial and error?
     
  2. matti

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    Lowest ISO 100 has least noise.

    But in low light reaching ISO 100 needs a longer shutter speed that might introduce motion blur to the image. Motion blur might be good for video (to prevent a "Saving private Ryan" film strobe effect) and the rule of thumb is to use a shutter speed that is the inverse double of the frame rate. For instance, if the frame rate is 25fps, use a shutter of 1/50s. In bright daylight you need neutral density ND filters to achieve that.

    But on the other hand you don't usually want motion blur in still images.

    The old general rule of thumb to prevent motion blur while hand-holding a camera is to match the lens 35mm equivalent focal length to an inverse shutter speed. The P3P lens with a 35mm equivalent focal length of 20mm would therefore require a shutter speed of at least 1/20th of a second to prevent blur when hand-held (if the lens or camera has image stabilization, you might decrease the shutter speed by up to four stops for hand-held shots).
     
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  3. beegee

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    The 180degree rule holds good for any kind of video shooting, and that includes aerial filming, as explained above. You want to keep your iso as low as possible to avoid noise, and your shutter speed at 1/50 if you're shooting in pal (although I will often go up to 1/00). Staying at a low iso and using these kind of shutter speeds can be difficult in bright sunshine, which is when you need to use an nd filter to reduce the amount of light hitting your sensor. I carry Taco-RC nd filters in strengths from ND4 to ND32, the higher the number meaning the stronger the filter. Use the zebras in the dji go app before launch to check on your exposure


    Sent from my iPad using PhantomPilots
     
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  4. Benny The Ball

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    Thank you for those helpful replies.

    There's one thing I want to know especially. I'm new to video, and I'm used to still photography using film. With film your exposure has to be almost spot on, otherwise the picture will either be too dark or else washed out.

    But how much leeway is there in the Phantom's Camera? Do you have to set a particular ISO according to the weather, and are there recommended ISO settings for each weather condition?
     
  5. With The Birds

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    We can't provide recommended TV or ISO settings for various weather conditions, theire are too many variables to provide anything meaningful as to what the brightness of a particular scene framing will be. The light metering in your phantom is pretty good and you should learn to trust it, using your overexposure warming and histogram functions to complement it.

    Underexposure will give you increased noise and horrible blacks and shadow detail. Overexposure will throw away the brightest elements of the scene with no chance of recovery.
     
  6. shockwave199

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    If you're gonna use manual exposure, get a set of ND filters. Then set your shutter speed to approximately double your frame rate choice. Then work through iso while hovered at altitude. Depending on the brightness of the day and sky, you'll probably land somewhere around 100 or 200 iso. I do find the exposure can be a bit forgiving. I generally error to overexposure sometimes, which depending on your editing software it can be dealt with very well. There's some wiggle room to fix but just like still photography, too much of an exposure mess is fatal. My latest video was slightly over exposed but fixed nicely enough in post. How critical you need to be about exposure for delivery as opposed to fun will rule the day.

     
  7. Benny The Ball

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    Because it's hard to judge exposure by how the scene looks on the screen, especially in bright sunlight, I would prefer to use the histogram.

    But I like to use the Litchi app and don't know if it does histogram - can anyone help me with this please?
     
  8. matti

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    The histogram and over exposure warning (zebra stripes) best allows to make a correct exposure.

    With still images shooting raw .dng best allows to correct the image exposure in post with apps like Lightroom etc.

    Auto exposure bracketing might allow to make a high dynamic range HDR image in post with app like Photoshop but then the AC should take at least three images at 1-2 EV/f-stops apart which might be difficult do from the same spot.

    For video the LOG color profile also helps -- it looks dull but if you have the patience the results are rewarding because it allows more wiggle room in post with apps like Final Cut, Premiere, DaVinci Resolve etc.

    Also use manual white balance of about 5000K (or 6000K at sunset, or the Cloudy preset etc). Automatic white balance is difficult to control in post.
     
  9. matti

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    I adjust the exposure with DJI GO app's histogram and overexposure zebra stripes. I go to the preferred altitude and direction and adjust the exposure so that the whitest important objects just lose their zebras (i.e. are not overexposed). The whitest clouds or other unimportant objects may have zebra stripes so that the ground is not underexposed.

    Histogram provides similar help but I find adjusting the exposure via the zebra stripes easier. Litchi has histogram but it lacks the zebra stripes so I always first use DJI GO app, then switch to Litchi.

    P3P's raw .dng does not seem to have as much depth as a proper DSLR camera (like Canon 6D) so the exposure errors are not so forgiving.

    If I use a ND filter I test and choose roughly the correct one on the ground. If I use a polarizing filter, I aim the AC 90° from the sun at the preferred direction and turn it to the maximum effect before taking off.
     
  10. shockwave199

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    Oh yes, I agree about the histogram. You can't depend on just the screen of your device. Absolutely the histogram is needed. Litchi also has the histogram too, at least the ios version does. I'm sure the Android does too.