Convert JPG files to grayscale format

[HONG KONGer]

I have some files taken by digital camera which saved in 24 bit jpg format. I want to convert them to grayscale to save as much space as possible without lossing detail.

As I know jpg files are 24 bits and gif are 8 bits only. So should I convert them to grayscale gif format? And how do I do it in photoshop?

 

[w1retap]

Go in photoshop and turn down the color saturation all the way. It is under the image adjustments menu.

 

[HONG KONGer]

which format should I save in to save more space?
And how do I convert all file at once?

 

[w1retap]

jpg is a pretty good quality to size compression format. Just try some different settings and see what looks best to you.

 

[engiNURD]

And how do I convert all file at once?

Create a batch job.