There is no definitive answer to this question as it depends on personal preferences and the specific needs of the person using the desk lamp. However, based on customer reviews and expert opinions, it seems that a good range to aim for is between 400 and 800 lumens. This will provide enough light for most people without being too bright or causing eye strain. Of course, you may need more or less light depending on your individual circumstances, so it is important to experiment until you find the perfect level of brightness for your needs.