Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure? at DVinfo.net

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Old March 20th, 2015, 08:58 AM   #1
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Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure?

Hello there! Please see my attached YouTube-link to see my footage:

It is of the 20th March, 2015, solar eclipse that I recorded in two hours and then cut it down to just 30 seconds.

I recorded with my Canon Legria HF G25 PAL-version camcorder with the following settings:

- Automatic white-balance
- Manual exposure settings such as 1/25 shutter speed, 6.7 1/4 (or 1/8, I don't remember) ND iris, 0 dB gain
- Maximum recording quality (PF25, 24Mbit/s)

What you can see is that the picture still seems "corny" or "grainy" or like it is almost pixels flimmering around on the picture? I do not mean the obvious picture noise during the actual solar eclipse, I mean throughout the whole clip, you can see picture flimmering and I just don't get it.

It seems like this camera (or at least mine) has some extremely poor picture quality when you look closely. You should just see pixels, not pixels that seem to change colors because of this flickering.

I am still learning to handle my camcorder, but for $1100 you should at least expect a non-flickering picture? I had no other lights interfering in the picture, I even used a matte hood or what it is called in front of the lens to block out other lights.

I filmed from my kitchen window which is dirty, so don't worry about that. Any camcorder expert who knows whether my footage is actually my fault (therefore something I can improve and learn from?) or if this is a case of "you get what you pay for"-case, so it is a technical limitation of this camera's sensor?

From what I have read, the Canon Legria HF G25 has a smaller sensor than its big brother G30 who is suppose to have the same kind of sensor as the XA10-series? Advice and info is appreciated! :-)

Take Care & Have An Awesome Weekend! / Max "Max K" Karlstedt.
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Old March 20th, 2015, 09:56 AM   #2
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

Hi Max

I saw the still Picture of the houses and they looked familiar. I happend to live near you, at Sidsj÷n!

About the noise, it's really hard to tell from the short film, but I don't see anything unusually noisy with it.
I see that you are using automatic white balance. That can definately introduce flicker, especially doing time laps. White balance adjustments are done continusly, especially during a solar eclips, as the light outside changes. Also while the amount of light decreases, the Picture will get more noisy as the image processor is trying to get details from the dark areas in the Picture. In low light conditions, try to open the aperture as much as possible and avoid zooming in as this further reduces light as the f-number increases.

I don't own a HF G25 myself but know that they aren't so good in low light. My experience of my own camcorders is that they allways introduce noise and loses sharpness as soon as the light decreases.
Run in manual mode as much as possible, open up the aperture and avoid using gain, as gain also introduces noise.

Regards,

/Bosse
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Old March 21st, 2015, 12:12 PM   #3
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

The dirty windows you mention are the main image issue I see on my computer monitor.

The time lapse effect achieved by doing intervals, and whatever YouTube does, pretty effectively mask any other issues you may have.

If by flimmer you mean the sort of subtle jumps you see in the sky shading for example, that can be compression artifacts cause by large GOP and changing lighting conditions.
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Old March 23rd, 2015, 10:07 AM   #4
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

Hello there again! Thank you very much for your replies.

Yes, I live nearby those houses, Bosse! :-)

Hm, I understand the noise and weird artifacts in the sky due to manual exposure that I didn't change during the timelapse.

The kind flicker/flimmer I mean is that if you look closely at the right house's red roof (in full-rendered 1080p from start and few seconds in) you will see that the red roof details shift and becomes blurry, then clear/detailed, then blurry again and so on, even in the beginning of the video. It almost looks like semi-white blocks. Since I only used the sun as light source, I doubt it is because of mixed color temperatures.

I exported it as H.264, and a preset labeled "YouTube 1080p 25" in Premiere Pro CC 2014; here's info from the file properties in Media Classic Player:

Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 29.5 MiB
Duration : 30s 0ms
Overall bit rate mode : Variable
Overall bit rate : 8 248 Kbps
Encoded date : UTC 2015-03-20 13:48:43
Tagged date : UTC 2015-03-20 13:48:43
ęTIM : 00:00:00:00
ęTSC : 25
ęTSZ : 1

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 30s 0ms
Bit rate mode : Variable
Bit rate : 8 000 Kbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 fps
Standard : PAL
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.154
Stream size : 28.3 MiB (96%)
Language : English
Encoded date : UTC 2015-03-20 13:48:43
Tagged date : UTC 2015-03-20 13:48:43
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

Might the colorspace be wrong here? Isn't the Internet's standard colorspace sRGB? I also understand that my camera has a pretty bad chroma subsampling, 4:2:0, which might be another factor of how well it rendered it out?
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Old March 23rd, 2015, 01:18 PM   #5
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

I believe that YUV is standard for video (or perhaps more precisely YCbCr for digital video).

4:2:0 is standard sampling for PAL DV, HDV, DVD, Blu-Ray and AVCHD - it is not unique to your camcorder. The main issue with 4:2:0 or 4:1:1 is the artifacts and losses that can arise if doing heavy filtering/processing of the image.

From Wikipedia:
The sRGB color space, or standard RGB (Red Green Blue), is an RGB color space created cooperatively by Hewlett-Packard and Microsoft Corporation for use on the Internet. It has been endorsed by the W3C, Exif, Intel, Pantone, Corel, and many other industry players. It is also well accepted by Open Source software such as the GIMP, and is used in proprietary and open graphics file formats such as SVG.
sRGB is intended as a common color space for the creation of images for viewing on the Internet and World Wide Web (WWW), the resultant color space chosen using a gamma of 2.2, the average response to linear voltage levels of CRT displays at that time.

YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently masked by the human perception than using a "direct" RGB-representation. Other color spaces have similar properties, and the main reason to implement or investigate properties of Y'UV would be for interfacing with analog or digital television or photographic equipment that conforms to certain Y'UV standards.
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Old March 23rd, 2015, 05:53 PM   #6
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

Thank you very much again for the reply!

I see. I have been told before that 4:2:0 is not optimal for what I want to really film (in front of a green screen) because of the chroma subsampling. For that 4:2:2 is preferred, I wish I knew this and more before I got my camera! T_T

Do you know how (or a link to a guide for it) to best export from Premiere Pro in terms of choosing video codecs and settings to bitrate, this thing called GOP which I have seen before but never known what it is or does, and so forth?
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Old March 24th, 2015, 06:54 AM   #7
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Re: Why does my footage (Canon Legria HF G25 PAL) seem "grainy" even in good exposure

GOP - group of pictures. To simplify greatly, the highly compressed video formats, like mpeg, generally operate by recording a full (compressed) image every 15th frame or so, and then sending only the significant changes for the other 14 frames. This is computationally intensive to encode, but saves bandwidth and storage space. it works because under typical viewing conditions people do not notice the resulting artifacts or "missing" image information. You can see the GOP effect if you watch a background crowd in a sports event, it seems to update every half second or so while the main action is smooth. Formats like DV did not use a GOP structure.
Group of pictures - Wikipedia, the free encyclopedia

Because chromakey is based on detecting image color information, it can be more precise if there are more color samples in the image. 4:2:2 has twice the color information of 4:2:0 or 4:1:1, so it can be keyed more precisely.

Some keying software does a better job that other. Many people speak highly of Robuskey, but I've not used it.

As to best format to export from Premiere - that would depend on the intended use of the exported video. It maybe driven by a client's specification and/or viewing system limitations.
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