B&W files exporting smaller than color images

[defaultkw36ey3mo8yh]

Hi! I recently imported some files into Lightroom and made a copy of each so I had two identical collections. One collection I edited in color and the other as B&W. I exported each collection with the same settings - JPEGS at the highest quality (these are for print). I noticed that the color exports are several megs larger than the B&W exports. Does anyone know why this happened and how to prevent it? Thank you in advance!

[dj_paige]

Ignore megabytes of exported photos. These are meaningless, and do not indicate quality. JPG is a compression technology, and it is not unusual for different photos to export at different megabytes, because they compress differently. 

So how to prevent it? You can't, and as stated, its not a problem when it happens.

[defaultkw36ey3mo8yh]

Oh great to know! Thank you! 

[cmgap]

Can you post a screen shot of your export window settings for both color and B&W?

[JohanElzenga · Accepted solution]

B&W images will compress much better than color images, even if the B&W images are still in RGB and not in greyscale. That is because 8 bits allows 256 shades per channel, so color images can have 256x256x256 colors, while B&W images will only have 256 shades of grey. So this is completely as expected.