fjo Loc: Georgetown Texas

What determines the number of pixels in a specific photo? The camera I used for the attached photo has a 20.4 megapixel sensor and the image size was set to Raw yet the photo editor shows that the photo is only 4.1 megapixels. Can anyone explain why the photo is not larger?

(Download)

CHG_CANON Loc: the Windy City

Pixels are not the same thing as bytes. They are not interchangeable measurements as they measure different things in digital photography.

Your 20.4 megapixel sensor creates files also as 20.4MP images. This is called the pixel resolution, very simply the length x width / 1,000,000 to yield megapixel. Your particular Olympus OM-D E-M1 Mark II model has "IBIS pixel shift technology" with the ability to output a file at 50MP.

Although you can calculate the maximum byte size of a file based on the pixel resolution, the actual file size depends on several factors. The 'complexity' of the image greatly impacts the resulting file size. An image that is mostly one color has less color 'data' to store as bytes in the file. The amount of JPEG compression applied to the file also impact the byte-size of the file when stored.

Your RAW files have the same pixel resolution as your large JPEGs. The file size difference is the amount of data being stored and the application of JPEG compression. The RAW files have a larger 'bit depth' where they store more color data for each pixel, sometimes twice as much data as an 8-bit JPEG.

Linda From Maine Loc: Yakima, Washington

The files you posted are 4660 pixels by 3494 pixels. That is about 16 megapixels. Do you have your aspect ratio set to the native for your camera, so that you use all the pixels?

Fotoartist Loc: Detroit, Michigan

Next time save it as a Tif instead of a JPEG and check the file size then.

fjo Loc: Georgetown Texas

Thank you for taking the time to answer my question. I thought the size of a specific photo had something to do with the complexity of the scene being photographed, I just wasn’t sure. For example, I shot several cedar waxwings perched in a bare tree with a blue sky and sun shining on them and that photo was almost 20 megapixels. The photo had more light than the cardinal in the example.
Thanks again.

fjo Loc: Georgetown Texas

Thank you for your reply.

CHG_CANON Loc: the Windy City

You still seem to be mixing pixels and bytes when you express your understanding like above. The number of pixels are static, either to the maximum resolution your camera can support, or to some setting change you make to the camera. The specs at the Olympus site says your still images have a maximum of 5184 x 3888 pixels. This is a 4:3 aspect. You might change to another aspect, say 16:9, where the original 4:3 image is cropped by the camera to a smaller pixel resolution.

The byte size of the resulting files will vary for each individual image (file) even when the pixels remain the same.

Consider using <Quote Reply> to respond to specific posts.

LEWHITE7747 Loc: 33773

Is there a different pixel configuration to take into consideration. The size and shape of the pixel on the sensor may be different in each camera?

fjo Loc: Georgetown Texas

Thank you for the reply. I did have the largest pixel configuration set.

bleirer

Think of your camera sensor. You say it is 20.4 megapixels, so it has 20.4 million individual physical photosites. Assuming you set the camera for the largest image size, each photosite will be one pixel in your photo. According to specs your image should be 5184 x 3888 pixels (that multiplies to about 20.2 megapixels). You must have cropped or used a different camera setting since your picture has only 4,660 × 3,494 pixels (16.3 megapixels). The amount of computer storage it takes to store those pixels varies depending on how you save it, for example a jpeg saves space by using file compression, so a complicated scene can use more storage than a simple scene. It looks like it took 2.4 megabytes to store your 16.3 megapixel jpeg. As mentioned the file size for storage (megabytes) is different than the pixel dimensions(megapixels).

fjo Loc: Georgetown Texas

Thanks for your reply.

bleirer

Hope it helps. I was updating while you were replying, so maybe reread my post.