Hi, in my survey I am displaying photos and each photo has 2 versions (original and edited). In total I have 40 photos in each condition. The first thing I did is to randomly present the photos so the participant only sees one version of each photo (i.e. a participant can see Photo1_Original but not Photo1_Edited). I did this by putting each question as it's own block and then using a randomiser for the paired photo. However, I would also like to make sure that a participant views equal amount of photos, for example, they see 20 edited and 20 original (but never the same photo twice).