Action cam guides for newbies?

I found this 3-minute video on YouTube and thought it explained quite a few things rather well. It mentions both materials of construction and electronic components. Although it's three years old and deals with a still image camera, I thought the hand-drawn depiction of "Billy" was quite good at describing the components step-by-step. I wonder if someone could help explain the differences when compared to a modern action camera.

 
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In another thread https://dashcamtalk.com/forum/threa...e-capabilities-and-image-quality.16627/page-2 DCT members jokiin and kamkar1 were explaining to me about the frame size of sensors. I found this article in Wikipedia that seems to explain image sensor format quite well. Note I did not check the math!!! Many camera manufacturers and models are listed but I don't know how current they are.

https://en.wikipedia.org/wiki/Image_sensor_format


1280px-Sensor_sizes_overlaid_inside.svg.png
 
I've wondered about the terms "active pixels" or "active area size" with respect to sensors. I think the following gives a nice, brief explanation. I believe they're actually instructions for CAD software but just look at the first few bullets of Example 38.

http://cctvcad.com/videocad_help/index.html?prim_sensor_size.htm
 
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Manufacturers make claims about the image size produced by their cameras but these are often achieved by interpolation. Other than the general idea that interpolation makes an image bigger, I never knew what that meant. This article explains interpolation pretty well though with action cameras I'm not sure which types of interpolation are utilized.

http://www.cambridgeincolour.com/tutorials/image-interpolation.htm

The website has many useful tutorials.

http://www.cambridgeincolour.com/tutorials.htm
 
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I found this Wikipedia article about digital video to be quite helpful. The history section is interesting but the heart of the article begins at the overview of basic properties. Terms such as color depth, pixels and bits per frame, frames per second, bitrate, and the relationship of these to one another are explained using very simple mathematics. It also helped me understand why I was so perplexed in another thread here on DCT about the slow speed of a video editing program. There's a huge amount of information to process and it simply takes time!

https://en.wikipedia.org/wiki/Digital_video
 
Currently working on classification and I am a bit stuck.
So far here are some a.camera types that I came up with :
  • Wifi/No WiFI
  • Waterproof/Non Waterproof
  • With LCD/NO LCD
Guys, do you have other categories in mind?
 
Currently working on classification and I am a bit stuck.
So far here are some a.camera types that I came up with :
  • Wifi/No WiFI
  • Waterproof/Non Waterproof
  • With LCD/NO LCD
Guys, do you have other categories in mind?
No Stabilisation / Gyro stabilisation / Other stabilisation

After using the Git2 for a while, a gyro seems essential ... although after using the SJ5000X Elite for a while it seems like something to be turned off in a hurry!
 
Guys, do you have other categories in mind?
Perhaps the following:
- Resolution (without interpolation): 4K, 1080p, 720p
- Combined resolution and frame rate: 4K/15fps, 1080p/60fps, 1080p/30fps, etc.
- Native image size (maximum without interpolation)
- With or without remote (distinct from Wi-Fi)
- Waterproof or splashproof without separate housing vs. separate housing required
 
I just had several interesting discussions on other threads with DCT members jokiin, kamkar1, Nigel and DT MI. I wish I could transfer the discussions wholesale here but I'll just post some of the highlights.

I found this drawing of the "Anatomy of the Active Pixel Sensor Photodiode" from a Florida State University article. I thought it was interesting because it showed that the surface area of a pixel does not consist entirely of the sensor. Other equipment is mounted on it as well.

http://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html

cmoschipsfigure3.jpg

However, Nigel responded: 'Our sensors are BSI CMOS sensors - back side illuminated so although there is other equipment mounted on the "front", the light enters from the "back" where there is nothing in the way and the full surface area can be used to collect light.'

Because action cams don't have shutters, how does one control "shutter speed" and what does that really mean? Again from Nigel: '"Shutter Speed" should more accurately be exposure time since there is not a physical shutter on an action cam, it is the amount of time that photons are collected for.' How does one adjust exposure time? On my SJ4000 it's done with the Exposure setting in the Setup menu. It ranges from -2.0 to +2.0 in 1/3 increments.

I understood that increasing ISO increased the camera's sensitivity to light, but how exactly does it accomplish this? Per Nigel: "Normally the ISO adjustment changes the analog amplification of the pixels before the analog to digital converter so that the analog value is in the correct range for the analog to digital converter to work well. It is like an analog volume control for a microphone. What it actually does in any particular camera may be different, it may even be a fake adjustment, but by definition it is the sensitivity of the sensor and if it is adjustable then you should be adjusting the sensitivity of the sensor, probably before the conversion to digital."

He goes on to say, "The ISO standard applies to both film and digital sensors, it just indicates the sensitivity of the sensor in standard units. A 100 ISO film has the same sensitivity as a digital sensor set to 100 ISO. The sensor works exactly the same for photos and video, although for video it normally only bothers with a 16:9 area and for higher resolution sensors may not process all pixels as doing so would be too slow for 60fps video"

Abraham Lincoln once said "Better to remain silent and be thought a fool than to speak out and remove all doubt." So I decided to leave no doubt and asked how I can tell what the ISO and exposure time actually are for any given photo taken with my camera. Incredibly, I didn't know that this information is readily available for every picture, at least for those I've stored on my computer. Using Windows Explorer, select the Pictures folder and navigate to a particular photo, right-click on the photo, select Properties from the drop-down menu and look at Details. Voila! Everything you wanted to know and more: f-stop, exposure time, ISO speed, exposure bias, focal length, maximum aperture, flash mode and more.

Thanks to all who helped me along in these discussions. Cheers :)
 
Just quickly read through the guide and it looks pretty good so far! In my opinion it would be very important to add a page discussing how many cameras are advertised as far higher spec than they actually are (4k? Nah. 20MP? Nope). Perhaps even discussing some of the more common sensor/processor combinations. For example:

AR0330/Novatek (.mov) - Good video quality, average photo quality. Only 3 MP.
Sony IMX078/Novatek (.mov) - Very good video quality, good photo quality. Only 12 MP.

And maybe even the ones to stay away from:

Omnivision/Sunplus (.avi) - Low movie quality, even worse photo quality.

I know a lot of buyers are confused about what the specs are out there, in an Amazon review group on Reddit I see people asking all the time about these cams. I always tell them if the brand doesn't explicitly state what's inside the camera it's because they have something to hide and I would avoid buying it in that case.

As well, perhaps it's prudent to discuss reviews - specifically Gearbest and Amazon. People who test cameras and don't know what they're doing are given free/discounted samples often on Amazon and tend to 4 or 5-star everything, these reviews can't be trusted and it's best to look for source video footage (I saw that mentioned already)
 
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I found this fascinating video about some elements of the manufacturing process for very high end digital camcorders on the Slow Mo Guys 2 YouTube channel. Obviously action cameras are in an entirely different price category than these expensive high resolution, high frame rate cameras but I was wondering if any of the manufacturers could comment on any comparisons between their manufacturing, software loading and camera testing vs those depicted in the video. Cheers! :)
 
I found this fascinating video about some elements of the manufacturing process for very high end digital camcorders on the Slow Mo Guys 2 YouTube channel. Obviously action cameras are in an entirely different price category than these expensive high resolution, high frame rate cameras but I was wondering if any of the manufacturers could comment on any comparisons between their manufacturing, software loading and camera testing vs those depicted in the video. Cheers! :)
 
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