Why are 48mp images taken with a 4k camcorder very bad?

Question

I bought a 4k ultra HD digital camcorder and took a picture with it. I don't know much about cameras or photography but I expected the picture to be sharp as high-resolution pictures are.

But when I zoom in at 100% it gets pixelated. It was very unpleasant, so i quickly checked the properties of the picture, see it below.

I thought a 4K picture would be much better at 100% zoom than a standard mobile phone picture for that matter. If I zoom in on that picture it looks like it was taken using a 10-year-old mobile phone.

What is wrong with what I am expecting or doing? Is there any settings for taking a high-resolution image.

I am looking at the pic at 8000×6000 resolution on a 17-inch notebook if that matters.

Photo captured with Samsung A20s phone and lighting

Photo captured with camera and lighting

Answer 1

There is a 4k Andoer camcorder that outputs 48mp stills. If this (or similar) is the camcorder you are using, the reason the still images look so bad is a combination of the following:

• Small sensor with native resolution of 13/16mp (specs are inconsistent). The image is being upscaled to 48mp.

• Cheap lens. 7.36mm f/3.2 with digital zoom.

• Heavy noise reduction and other processing. Your sample image has the characteristic "watercolor" effect.

Answer 2

Video cameras can get away with a lot more noise because of the low resolution of video and noise averaging out over time. This camera has a sensor with crop factor of 7.9, meaning that it has 1/64 of the area of a full-frame sensor. It would actually be surprising if it even had the advertised 4K on the longer side, but you have a photograph of 8K×6K, so even assuming a genuine 4K sensor (which would be surprising at that sensor size), only 1 out of 4 pixels has a chance of not being the result of interpolation. But the stair casing of oblique lines does not look like interpolation by a factor of 2 but at least by 4, making only 1 out of 16 (or more like 25) pixels be based on actual image data rather than interpolation.

Which means that this camera is garbage, not a 4K camera. It may produce output of 4000 pixels per line in video mode, but the actual resolution the camera is working with is much smaller.

The image sensor is probably akin to what was used 10 years ago in feature phones. The EXIF data does not even contain a manufacturer or brand name.

Just write it off. This thing is a hoax.

Answer 3

Several theories:

• The camera is really cheap and does not even have a 4k resolution. 4k is a lot! 4k is 8.3 megapixels. Even a typical crop DSLR camera lens may not resolve this much detail, even though the sensor of a typical DSLR nowadays has more than 8.3 megapixels.

• You are running into the optical limits of the lens. In particular, to truly get 4k level of detail, you need to spend at least about 500 US$ on the camera+lens combination (unless buying used parts, in which case you can save a lot). Typical phone cameras may have 4k resolution, apparently, but when you zoom in you will start to see flaws in the optical quality.

• The camera+lens combination could in theory resolve 4k detail, but you are taking photos in poor light, and thus, heavy noise reduction algorithms reduce the level of detail. This is very likely with small sensor cameras like phone cameras. If the camera is not as large as a typical DSLR, chances are it has a small sensor.

To find out which of the three options is the case, you need to ask yourself: did you buy the camera for cheap from China believing claims it's a 4k camera? Also, what is the stated size of the sensor (to estimate its low light capabilities)?

If the sensor size is not stated, you may be able to see the focal length of the lens specified in millimeters. From that, you can estimate the sensor size if it's not the effective focal length but rather the true focal length.

Edit: the info says focal length is 2mm. So, it's a tiny-sensored camera. Its low-light capabilities WILL be very poor.