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I'm having issues compressing my film scans to a suitable size for use on my website.

for example, I have a .jpg file with a size of 17.4 MB.

I opened the photo in Photoshop and tried two methods:

Save for Web (Legacy)...

even at a quality level of 20%, the image is still 2.6 MB. way too big for web usage.

and Export As...

tried to export as JPEG and same deal, image is > 2 MB with quality at 20%.

as a final effort I tried Save for Web and ran the image through an online compressor tool (compressor.io). strangely the image came out at 2.6 MB again.

I need to get these images down to ~300 KB but I'm clueless as to how.

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    \$\begingroup\$ What are the pixel dimensions of your image? How many pixels wide by how many pixels high? I'm guessing a lightly compressed jpeg of 17.4 MB is somewhere around 40-50 megapixels or more, depending upon scene contents. \$\endgroup\$
    – Michael C
    Commented Sep 10, 2019 at 21:36

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I do not know at which resolution you scanned your image, but i'm willing to bet that it is way larger than needed or useful for web viewing.

The first thing you should do is resize the image down to some useful dimensions. Think about how large it will be viewed and resize accordingly (keep in mind that currently a high end monitor resolution is 2560x1440).

Furthermore, your image might contain a lot of noise, which doesn't compress well. Running a denoising filter might reduce file size and even improve quality (careful there, don't make it look unnatural).

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    \$\begingroup\$ Great note about noise not compressing well! This is almost always overlook. \$\endgroup\$
    – Rafael
    Commented Sep 11, 2019 at 7:42
  • \$\begingroup\$ this is exactly it. the issue is I only just recently took up the habit of storing negatives, so I have a ton of old scans I still want to use that are huge (exceeding 100 MB, for printing as large as possible) \$\endgroup\$
    – ChumiestBucket
    Commented Sep 11, 2019 at 17:19
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    \$\begingroup\$ this is a great answer though. I've been confused with people telling me to crop the image, which to me is not an option. I think they meant to resize it like you mentioned \$\endgroup\$
    – ChumiestBucket
    Commented Sep 11, 2019 at 17:21
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Compression algorithms find ways to clump groups of pixels into like colors in order to save space. For example, if a row of pixels was: Red, Red, Kinda Red, Somewhat Red, Red, then a compression may be: Red x 5. (This is really dumbed down example). Note how you lost some data but the size of the information could get smaller.

All that being said...there are limits. Your image can only compress so small. If you want smaller file sizes, then you need to Crop/Resize. Yep, kill some pixels.

Your 5Dmk4 image size is 6720 x 4480 pixels. This is way, way more than what's needed for web viewing. Even sizing down to 2,000 in the long direction is more pixels than just about every monitor would be able to display.

You'd be better off sizing the image down and compressing less than keeping a super large image and compressing more.

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    \$\begingroup\$ Current wording seems confusing, and answer appears to overlook resizing/adjusting resolution. Cropping suggests using only part of an image as a means to have fewer pixels to deal with, while most users would probably prefer to resize/adjust resolution to show "the same image", but doing so with less detail. \$\endgroup\$
    – TheLuckless
    Commented Sep 10, 2019 at 21:25
  • \$\begingroup\$ @Hueco Cropping and resizing are two different things. I think you mean "resize" rather than "crop." \$\endgroup\$
    – Michael C
    Commented Sep 10, 2019 at 21:37
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    \$\begingroup\$ @TheLuckless Nah, just a hold up in terminology. The goto tool for resizing in PS is the crop tool (just enter parameters and select the whole image). So I've fallen into the habit of calling cropping "cropping" and also calling resizing "cropping". I've changed this to clarify things. \$\endgroup\$
    – OnBreak.
    Commented Sep 10, 2019 at 22:33
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There are two ways to make an image file occupy fewer bits:

  • Resize it (downwards)
  • Use greater compression on the file

You are only trying "option 2". Start with "option 1". If you know the (maximum) pixel dimensions at which you want the photo to display, the first thing you should do (after post-processing) is to resize the image to those pixel dimensions. It is the most sensible way to make an image file use fewer bits. Your scans are undoubtedly at a much higher resolution than is needed for web viewing.

Of course... do not overwrite your original file. Keep the full-resolution file as well - just don't use it for the web.

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