Reduce 30MB image to less than 50KB without significant loss
I am creating figures for a scientific paper. The journal I am submitting to seems confident "all figures can easily be reduced to less than 50kB each (gzipped) without significant loss of quality". One figure I am starting with in photoshop PDF format is ~30MB. I cannot comprehend how I am possibly going to reduce this down to ~50KB without significant loss, but perhaps there is a way?
My image has text, symbols, colour charts and sharp lines that represent functions. I include a screenshot of the image below, and a dropbox link to the actual file just in case that is helpful: https://www.dropbox.com/s/m3p6j6fmccnfvgw/figure2.pdf?dl=0
Any help greatly appreciated :)
A ~620% file size reduction is asking a great deal.
It's possible, but I'm not sure what restrictions should be watched, file dimensions? color depth? etc.
^^50k gif file.
This is a reduction of the dimensions by 85%, set as a gif with only 32 colors in the color table.
As @Ryan points out, if the text and labels were vector in nature it may allow file reduction without dimension reduction. Another possible alternative is to forego gradients if possible in favor of solid colors.