How does a Nikon D3200 produce lower-resolution images?
Asked 1/26/2017
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My Nikon D3200 has a 24 MP sensor, but it can save smaller JPEG sizes. What actually changes when I choose a lower resolution? Does the camera use only part of the sensor like a crop mode, or combine sensor pixels into larger ones, or does it capture the full image and then reduce it afterward?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
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Let's say that with your 24 megapixel digital camera, you have selected an output size of 6 megapixels.
Usually what this means is that the camera captures the scene at the full 24 MP, performs some internal processing to shrink the number of pixels, and writes out a 6 MP image. The shrunken image has the same field of view (framing) and aspect ratio as the full-size image. This mode of shrinking images is by far the most popular because it's the most intuitive and gives the most desirable output.
Does the camera shoot in a crop-mode, ignoring some pixels to bring resolution down? Or does the camera merge multiples pixels to behave as a larger pixels?
I'm quite certain the former is correct, however I would like to be sure about this.
We are quite certain that the latter idea is correct.
However, some cameras do crop the full image to create a smaller output image with a different field of view. For example:
- In video mode, some DSLR cameras will crop the sensor for various reasons - extra zooming, matching the 4K video resolution to the sensor's native resolution, etc.
- Various cameras (smartphones, Panasonic MFT, etc.) have options for different output aspect ratios - such as 4:3, 3:2, 16:9, etc. This necessarily involves cropping the sensor's image.
- On Nikon DSLRs when a DX lens is mounted on an FX camera body, the camera will crop the image by default to match the smaller image circle.
Originally by user6273. Source · Licensed CC BY-SA 4.0
user6273
9y ago
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Generated from our catalog & community — verify before relying on it.
On the D3200, selecting a smaller image size for JPEG does not normally change how the sensor is used. The camera still captures the full sensor area at full resolution, then processes and downsamples the image before saving the JPEG. That’s why the framing and aspect ratio stay the same.
It is generally not using a crop mode for this, because a crop mode would reduce the field of view and change what part of the scene is recorded. Some cameras do offer separate crop modes, but that is a different feature.
It also is not typically “merging pixels” on the sensor into larger pixels for normal still photos. Instead, the full-resolution image is reduced in-camera.
A good clue is RAW: on cameras like this, RAW files remain at full sensor resolution, while only the JPEG output size changes.
So in practice: lower-resolution JPEG mode usually means full-resolution capture plus in-camera downsampling, mainly to create smaller files.
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