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I have used a Sony A57 since they became available. I always have the resolution set for 16M and FINE for JPEGs. I just took an important set of photos that were intended for large blow-ups. But for some reason I cannot fathom, the images are all low resolution from 2-7 MB. What could be doing this? I can find no other setting that could reduce file size so drastically.

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    \$\begingroup\$ Presumably you mean 7MB, not 7KB. 7MB actually seems reasonable for a 16 megapixel JPEG. Ultimately however, you need to look up the pixel dimensions to find if it's shooting the right resolution, because the file size alone doesn't tell you with certainty. \$\endgroup\$
    – thomasrutter
    May 20, 2015 at 1:12
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    \$\begingroup\$ You are complaining about the resolution yet you mention storage space. What is in fact the resolution? You should see this in the Properties dialog or with any program that shows EXIF. If using nconvert just use nconvert -info <filename>. \$\endgroup\$
    – Itai
    May 20, 2015 at 2:01
  • \$\begingroup\$ If you want the best photo possible ( file to print ) then why are you letting the cameras software make the editing decisions for you by shooting in jpg and discarding significant amount of data in order to compress to jpg. Your camera will shoot RAW files, You can then CHOOSE how to edit and save the file in a format that is best for large prints. ( "for large blow-ups" ) \$\endgroup\$
    – Alaska Man
    Jan 4, 2018 at 18:54

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Based on the information you've given so far, I'm not yet convinced there is a problem.

Assuming you mean 2-7 MB (Megabytes), not KB (Kilobytes), that file size could be consistent with a full resolution JPEG. 2-7 KB would not actually fit an image, except maybe a tiny thumbnail or icon.

Look up the dimension of the image in pixels in your file browser - often by, for example, right-clicking and looking at image properties. Multiply the width by height to get number of pixels, and if it's near 16,000,000, you have a full resolution 16 megapixel image.

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JPEG is a compressed format so the filesize does not correspond directly to the image resolution, but rather to it's content.

The JPEG algorithm achieves lower filesizes with images that contain less detail, so if you have areas with very little detail, such as out of focus backgrounds or blown out skies then that can lead to dramatically smaller filesizes, however there's nothing to worry about because you are not losing any resolution.

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