How to take front element off 55-250 STM?

Well, I hike with this lens routinely and use it A LOT, so I'm not surprised, but it finally happened:

The sharp white speck above and to the left of the glob of flares, is a big dust particle in my trusty lens.

I've been inside several lenses before including my 55-250 IS MkI when I had it, all without incident, so I'm sure I'll be fine doing this one, but I like to watch a video first and I don't see any videos on taking this one apart. Same as the old ones, or do I need to know anything?

saxyomega90125 wrote:

... do I need to know anything?

Things to know:

• That spec is tiny and inconsequential. It has absolutely 0.000000000 effect on your pictures or the lens's resale value. Forget it.
• Unless you have access to an ISO clean room, you'll introduce more dust and other contaminants than you can remove by opening it.
• Once opened it'll be even less dust resistant.
• You may (or may not) be able to put the front group back in the exact same alignment/spacing, so you may (or may not) affect the lens's performance.

IMHO, YMMV.

Lemming51 wrote:

• That spec is tiny and inconsequential. It has absolutely 0.000000000 effect on your pictures or the lens's resale value. Forget it.

This is not the first piece of dust in there, just the first to create a problem. It is visible in some 250mm shots, depending on background, at f/7.1. Almost all by f/13.

That said, you had no way of knowing that.

• Unless you have access to an ISO clean room, you'll introduce more dust and other contaminants than you can remove by opening it.

That has not been the case with any photo lens or telescope I've opened in the past. I don't open them up without a good reason, and while I'm sure my space doesn't meet ISO spec, there's a saying my father has: "I don't do crappy work."

• Once opened it'll be even less dust resistant.

Why?

• You may (or may not) be able to put the front group back in the exact same alignment/spacing, so you may (or may not) affect the lens's performance.

'Collimation' is the word. While this would be an issue if I were to tear it down to individual elements, the groups are collimated almost entirely using their own housings - even in the most expensive L lenses AFAIK.