Probably not.  Resolution is best measured by the height and width in pixels..  There are some lossless compression extensions, but the size it is reduced to depends on the image and how much space there is between un-similar pixels.

If you want a smaller copy keep the original and downsize the other.  The real question is what do you intend to do with the image.  Makes a difference if you want to make a poster sized image, a 4x6 print, or just view it on your monitor.

What type of image is it?

DPI is a printing term for dots per inch.  For a screen it is ppi or pixels per inch.

The image size also has to do with how big the document is.

Click on image/image size and change resolution and document size and see what you get.  Check it both ways with resample on an off.

Perhaps it would be a good idea to ask how many pixels the image has in it in each dimension?

And just to be clear, because the terminology can be vague, do you mean by saying the file size is "60M" that it is 60 megabytes on your hard drive?

I wouldn't give up just yet.  I believe we might be able to find a compromise in pixel count and compression amount that meets your goals.

-Noel

I would look in the same place where you determined that you are working with a 300 ppi image.

Image menu->image size

If you are looking to "find how many pixels it has in each dimension", you'd look under "190M".

Your task to reduce to 500kb is impossible. No image that large belongs on a webpage.

If you reduce the width to roughly 1000 pixels and find that the text is unreadable, then you did not design the web page graphic properly. Start over on a document already sized for the web page. When designing web graphics, you should most always be looking at a 100% zoom view. Note the zoom percentage displayed in the image tab or image window title bar. Keep it at 100%.

If you're going to ask for help, you should answer the questions posed.

You were asked for the pixel dimensions.  If you don't know how to find that info, go figure it out, or ask for specific instructions.  Once specific instructions have been given, use them and get the info.

That's the only way you're going to get through this is by providing those who are trying to help you the information they need to do so.  Details matter, and very few of us are mind readers.

It would even be helpful if you'd capture your screen showing your Photoshop editing session and post it here.

-Noel