They obviously have an interferometer. See if they
will agree to include an interferogram with matching
serial numbers for each lens. And promise that minimum
quality is 0.25 wave PTV, and RMS is no
worse than 0.025 wave, on the interferogram.
(Strehl in green then about 96% or better). That would
make the deal in my view. Also find out what their
after-sale warrantee is. For example, if it goes out
of collimation during shipping from China, etc.
Or has bad behavior at cold temperatures. I would try
to get this agreement, rather then pushing the price
much lower. For a good lens, this is a great price
already. But if quality is bad, any price is too much.
will agree to include an interferogram with matching
serial numbers for each lens. And promise that minimum
quality is 0.25 wave PTV, and RMS is no
worse than 0.025 wave, on the interferogram.
(Strehl in green then about 96% or better). That would
make the deal in my view. Also find out what their
after-sale warrantee is. For example, if it goes out
of collimation during shipping from China, etc.
Or has bad behavior at cold temperatures. I would try
to get this agreement, rather then pushing the price
much lower. For a good lens, this is a great price
already. But if quality is bad, any price is too much.
