When I started collecting orchids percivaliana semi-alba was my dream. I, at that time, bought two divisions of what I was told were two different clones, 'Farah Diba' and 'Jewel'. No need to say that when they bloomed for me, I couldn't see any difference between them. I took them to my orchid society meeting to see what happened. Opinions there were for every taste, but nobody there was able to point out any consistent difference between the two. Later I learnt that both were the same and more, the correct name for both was ‘Carache’, not ‘Farah Diba, nor ‘Jewel’. The first photo shows ‘Jewel’, the original division I bought. The second photo shows ‘Carache (or ‘Farah Diba’), also the original division I bought, side by side with ‘Jewel’. The third photo shows the two lips in detail. Note that even the small twist in the left (of the flower) margin repeats in both.
Finally, the fourth photo shows a light coloration at the tip of the petals, something many ignore, I mean, that ‘Carache’ is not pure semi-alba, but albescens or some like that.