If you use Lightroom – especially if you have to be careful about the file sizes of your exported files – you need to read this. Here’s the executive summary:

• There are 12 possible output settings, not 101. The 0–100 scale is an illusion.
• There is no correlation between the output settings in Lightroom and those in Photoshop.
• If there’s lots of fine detail or texture in the image, you can use shockingly low settings (even 0!). The JPEG can still look pretty good, and the size will be quite small.
• However, if there are smooth gradients (for example, the sky), a setting of 70 is the sweet spot: higher than that and the file size explodes with little visible improvement in the JPEG.

And do experiment with your own images and tastes, instead of blindly following advice on the internet.

(Via Daring Fireball)