Lens tests

[duncan22]

Most Camera Magazines and websites explain how they carry out lens tests, which is usually along the lines of obtaining a range of lenses covering different makes and subjecting them to the same test and finally awarding marks for price, build, sharpness etc.
However what no one appears to have done is select a number of lenses which are exactly the same and obtained from different sources and put these through the same tests. The results should be identical but will this be the case ?
If there is any sort of variation then potential purchasers should be made aware of this as Lenses are not (in most cases) cheap

[nikonian]

Not even same size lens from the same maker. It used to be fun in the old days,one tester saying "This is like the bottm of a milk bottle. A month later another tester would say about the same lens"A great lens".

[Forseti]

Originally Posted by duncan22;8229[I

]However what no one appears to have done is select a number of lenses which are exactly the same and obtained from different sources and put these through the same tests. The results should be identical but will this be the case ?[/i]
If there is any sort of variation then potential purchasers should be made aware of this as Lenses are not (in most cases) cheap

Good idea in theory I suppose but not too practical in my opinion. In any mass produced product there will always be manufacturing tolerances as indeed there would be for a singularly produced item e.g. the Hubble telescope. Indeed, if you send a lens away for re-calibration it should be returned with a test report which would also indicate the tolerances it was calibrated to. As to the 'potential purchasers should be made aware' etc - well I'm not exactly sure how that would, or could, be made workable. It would be like going into a car show room and expecting to see stickers on the windscreen of the models on offer stating on what day of the week they were manufactured. Would you buy a car that was manufactured on a Monday?

Cheap (or expensive) are subjective terms really and very much dependent upon the depth of the individuals pockets. Overall, taking into account market forces, supply and demand etc, I think they are generally good value. In fact if you look at the price of say a Canon 50mm f/1.8 lens - exceptionally good value.