Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Started May 18, 2014 | Discussions thread
DAVID MANZE Veteran Member • Posts: 4,870
Re: Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Joseph Tainter wrote:

I've had two badly decentered copies of the DA* 16-50. My current one is slightly decentered, but it is only visible at 100% so I use it.

My copy of the DA 55-300 is slightly decentered, but again, it is only visible at 100%.

I've had no problems with A, F, or FA lenses. The current problem seems to have originated when Pentax switched lens production to Hanoi. Pentax clearly reduced quality control at the same time that they made this move.

In the manufacturing process, I don't understand why it is so hard to place lens elements correctly. Can someone clarify this?


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It's not a question of placing of elements correctly in the lens body, it's the doublets and triplets which are poorly aligned, ie at pre-assembly they are placed in a machine with a laser light beamed down to show alignment of the elements, the glue has a certain setting time and until the glue sets the top element is floating, often in modern production where time is at an essence the setting time is not respected and the elements misalign before the glue sets and when it does set the damage is done. Most lens manufactures supply "tested" doublets and triplets to their service departments so any decentered lenses can be corrected with new elements. Both Sigma and Tamron service centers have spoken to me on this when I pushed the question about what spares they were awaiting for. That and wobbly plastic lens bodies and you have the ideal recipe for below spec. lenses often at a high percentage ratio.

The bottom line is that it is us the customer who is the quality controller, if we say nothing, nothing will be done, so if you find yourself with a decentered lens send it back, lens manufacturers know they are making lots of below par optics so return them!

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