As the title says, this is a review of the 10mm Masuyama. Eye relief at the 10mm FL is pretty much on a par with the Takahashi LE & Abbe 12.5mm so if you are happy with that this EP will suit you. NB I am a glasses wearer but take them off to observe. The 10mm appears to be pretty much parfocal with the 12.5mm LE which may add to the claim on a Cloudy Nights thread that these may well be LE clones? Sharpness and contrast are on a par with the 12.5mm LE and as for me I will be purchashing other FL to fill the gaps in my collection of LEs!