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.
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.
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. 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 cropping 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 cropping the image down and compressing less than keeping a super large image and compressing more.