Hey all, need some info, I have a Canon 75-300mm lens and it has in the past gotten dust on the back side of the front element. That's not really a problem, three screws hold the front bezel on, pop em out, pop out three pins, and the front element slips out, clear off the dust and I'm back in buiness... until now! Now the dust is actually inside the front element, apparently it's two pieces of glass mounted in a plastic band and somehow it got dust inside of it. Any ideas on whether this can be fixed or how much it would cost? Also, I keep my gear and bag clean and don't really shoot in dirty environments, any ideas on how the dust is getting in there? My Tamron lens never gets anything internal.
Compare shots of similar subjects taken before and after the dust problem and compare them. Look for reduced contrast and flare in the shadows. Perhaps the dust isn't affecting performence as much as tinkering with the lens will.
I'd grin and bear it as it's a never ending battle against dust. The inner elements move during zoom and focus operations and therefore displace air. Hence, dust is drawn into the barrel every time you use it. If misalignment of elements occur during disassembly, optical quality will suffer far more than a few dozen particles of dust. Incidentally, Canon uses a laser to align the elements.
Sometimes certain elements are glued together and the glue is breaking up. This can look atrocious, however ... chances are it will not show up on your pictures. Dust on the rear element what you should be concerned with.
Lenses with large scratches on the front will take great pictures....
We put a wire-mash there and it hardly effects the picture!
There is one thing about zoom lenses. Once you take an element out from it's socket, you have to be very careful when you put it back. On one side of the glass assembly there is a plastic washer/spacer. It is possible to misalign the element. Out from the center and then improperly sitting in the location... even angular misalignment... Every few thousands matter when it comes to optical precision. Whatever error you put in there will be greatly magnified by the time it gets to the film!
If you have problem with the image then get Canon to check it out and maybe put in a new piece of glass.
Why not? They made it, they should be able to fix it.
Given the way you descibe "...three screws hold the front bezel on, pop em out, pop out three pins, and the front element slips out, clear off the dust and I'm back in buiness..." for your past fixes, I wouldn't be surprised if this is also the way your current dust situation arose.
At any rate, if you'd like to be able to use the lens in the future, I'd suggest having it cleaned by your favorite repair shop.
Bob- I don't believe it's mold but thanks for the tip.
Water Methodman- I see you list your location as east of nyc, I'm out in suffolk county, any suggestions on a decent shop that has a quality repair center? From what I have seen here I wouldn't drop my 20 year old vivitar ps off with any of the locals for a cleaning, they're "work areas" are stocked with dust, lint, and not much else.
The only portion that I have disassembled,in a clean environment, is a totally modular piece that has no adjustability, I have handled far more precise equipment than this on a daily basis. I do not get into the internals of the lens. I've been using it, and cleaning this portion, for around 7 years. Anyway, my questions remain unanswered, has anyone had this kind of problem cleaned professionaly and if so how much am I looking at. Also, does anyone else have this model lens and have you had this much trouble with it? Like I mentioned before, My Tamron lens that goes everywhere this one does has never experienced this kind of contamination.
I'm in Nassau, on the south shore, and I've been lucky in that I've never had much cause to seek out repair shops. I did have a Pentax flash hotshoe replaced at a place on Jerusalem Avenue in Bellmore called Custom Camera. Nice people, good work, and done much quicker than I anticipated. They're in the book, or you can PM me for details.
I didn't inend to call into question your technical abilities; optics are tricky items, and I still have somewhere a 20X loupe I once tried cleaning the pocket lint from. Only once.