[twehr]

About once a year, it seems, I manage to destroy a lens. It happened again a few days ago. (See attached image.)

I ordered a new one from LightObject.com, but went for a higher quality lens this time. The difference is pretty amazing. It actually boosted by effective cutting power by quite a bit. And the few extra dollars it cost was well worth it.

If you want to read more about it - check out the blog post.

[Exsecratio]

Hiya Tim,

You may well find that the increase in cutting ability is down to correct focus, currently lens are available in many focal lengths but all of them are based on imperial figures, ergo 1 inch / 1 1/2 inch / 2 inch / etc etc...

If you were told your original had a 55mm focal length then it's quite likely your supplier has mistaken or miss typed what they had said.

That said the FL of a 50.8mm (2 inch) lens is rarely if ever 2 inches, it can be as much as 2mm either way. Chinese lens are all pretty much the same actual material and standard unless you opt for Gallium Arsenides or something like RMI or II-VI infra red there is going to be a degree of *hit and miss* with quality standards.

Much the same with tubes, you can buy two from the same manufacturer and get grossly different results. Gotta love far eastern quality control

best wishes

Dave

[twehr]

Regardless of what the supplier stated, I always use ramp tests to determine the correct focus. My point was that the two lenses had very different focus points. But the info you posted is valid and valuable for anyone not aware.

Thanks for posting it!