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Author Topic: My observations with a Phantom 4 Pro ; DNG vs JPG  (Read 2445 times)

outsider

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My observations with a Phantom 4 Pro ; DNG vs JPG
« on: June 15, 2018, 08:27:37 PM »
I know this is a debated subject (RAW vs JPG for photogrammetry), but I just wanted to share some objective evidence I came across. I'm working on a project to figure out how much detail my Phantom 4 Pro can resolve (will post a full write-up on that soon), I came across an interesting observation.
This only applies to images captured with the Phantom 4 Pro as it's the only sensor I've tested so far.

Took DNG+JPG images with the P4P camera, and ran them through PS. (1/200 shutter, f6.5, ISO 400)

The object that is being reconstructed is a calibration chart I made to do the detail resolution test. The object is not very big in the frame (about 480 pixels across) and the image width is 5464 pixels across (so less then 1/10th of the image)

My observations on the source images: (see attached image)
The JPG image (out of camera) looks cleaner. Less image noise. (likely smoothed and sharpened by the jpg compressor)
In contrast, the DNG image looks full or grain and noise.

My observations on the reconstructed mesh:
The mesh created from the DNG files is cleaner while the mesh created from the JPG files is noticeably rougher looking/noisier.

Just to note that DJI doesn't provide ability to change settings for JPG creation.

If you're using a P4P, I'd love to hear from you and what your experience has been with JPG vs DNG.
« Last Edit: June 15, 2018, 08:29:42 PM by outsider »

outsider

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Re: My observations with a Phantom 4 Pro ; DNG vs JPG
« Reply #1 on: June 15, 2018, 08:33:03 PM »
Increasing the distance to the object by a factor of 2 (so the object is smaller in the frame by a factor of 2), creates even more extreme results with the mesh reconstruction.

The mesh reconstructed from the JPG image is all noise, whereas the mesh reconstructed from DNG files actually resembles the real object.
« Last Edit: June 15, 2018, 08:35:03 PM by outsider »

bgroff

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Re: My observations with a Phantom 4 Pro ; DNG vs JPG
« Reply #2 on: June 21, 2018, 12:49:08 AM »
Try setting the focus to manual and 'infinity' and compare the two image formats. It's not clear if your focal length is exactly the same for both images in your example. We run into big problems when the focal length is not fixed to a known position.

outsider

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Re: My observations with a Phantom 4 Pro ; DNG vs JPG
« Reply #3 on: June 21, 2018, 03:51:36 AM »
There is no difference in focus between the images, and the focal length can't change... ihe focal length of the lens is  8.8 mm/24 mm (35mm equivalent)

The camera on the P4P aloows for RAW+JPG to be saved at the same time, which is what we did.
So I'm comparing the RAW vs the JPG that was taken at the same exact moment.