A great article for the lens geek over at LensRentals.com, Roger and OLAF discussion copy variance between 50mm SLR lenses.
Last week we posted an introductory article on how we measure copy-to-copy variation in different lenses. I'll be continuing to publish these results over the next few weeks for prime lenses. We will eventually have a database put up, but I think it's important to look at the different lenses in smaller groups, illustrating some principles that contribute to variation. It's far too easy (and comfortable) to just believe quality control is the answer to variation. There's a lot more to it than just quality control and I think this series of posts will help illustrate that.
We got a lot of good suggestions about our methods after the first post, considered all of it, and tried out some of it (particularly formula and graphing adjustments). We didn't make any changes to our mathematical formula, but are going to change terminology just a bit. JulianH and several others pointed out that using the term ‘variation number' was counter-intuitive; our numerical score gets higher when the lens has less copy-to-copy variation. It makes more sense to call it a ‘consistency score', because a higher number means the lens is more consistent (it has less copy-to-copy variation). So from now on, the numerical score will be referred to as the Consistency Score. Read the full article…