I did an image quality test of toilet paper lens and L lens. I know the result before I did, but the result is still interesting. Toilet paper lens only cost you about 26,000 JPY while 400mm f/5.6L cost you 153,000 JPS and Extender 2x III cost you 42,000 JPY, both of them cost you 195,000 JPY. The toilet paper is losing on image quality but it is still acceptable if you consider the price.