Broken old Canon 300mm 2.8

jeffa · November 1, 2007

Hi,

I have a problem, and looking for help and advice.

I have an old, canon EF 300mm f2.8 NON IS lens with the front glass in the light path broken.

I have been trying to get it repaired, but unsurprisingly, parts are no longer available from Canon.

Lens was droped, so the front black retaining ring is also a bit bent out of shape.

So my questions are:

Is there anywhere in the world I can pick up this first glass element?
Is there anyone out there with a 300mm non IS that is broken in a different way that I can make an offer to?
Is the first glass in the light path really an element? The lens still focuses, with a bit of a stuggle.
Should I just give up trying and upgrade to the IS?

In despair

TylerW · November 1, 2007

This may be a bit of a draconian "fix," but isn't it traditional for most Canon L's (at least telephotos) to have the front element be a non-optical flat sheet of glass that just serves to protect the rest of the glass elements that actually do the job of shaping the image? Essentially a built in UV protector? If so, if you can carefully clear the broken glass, it seems to me that the lens should still be able to produce an image. Perhaps slightly more prone to flaring if that front element is coated to help prevent that, but otherwise, you may be still in business.

More informed folks than I will hopefully chime in soon.

claudermilk · November 1, 2007

Well, a couple of ideas. You could try posting a WTB for a broken-in-a-different-way lens at the Flea Market here & the B&S forum at fredmiranda. You could also put it up for sale in the same places for someone else in your boat. Same goes for ebay: they have a want to buy area now & you'd be amazed at some stuff that gets sold there.

pathfinder · November 1, 2007

TylerW wrote:

This may be a bit of a draconian "fix," but isn't it traditional for most Canon L's (at least telephotos) to have the front element be a non-optical flat sheet of glass that just serves to protect the rest of the glass elements that actually do the job of shaping the image? Essentially a built in UV protector? If so, if you can carefully clear the broken glass, it seems to me that the lens should still be able to produce an image. Perhaps slightly more prone to flaring if that front element is coated to help prevent that, but otherwise, you may be still in business.

More informed folks than I will hopefully chime in soon.

The front elements of the Canon super telephotos are supposed to be replaceable. Not sure where I read that, but that is my understanding.

I have not heard that they were non-refracting surfaces though - my 300 does not really look flat so I rather doubt it is just a big UV filter. I think it is the first refracting surface, but I could be wrong about that

ziggy53 · November 1, 2007

KEH is probably your best source for information and parts.

If the front bezel is banged up. there may also be thread damage. It is possible for there to be other internal damage as well. I would not recommend this as a DIY project if you are not familiar with lens repair.

jeffa · November 1, 2007

Hi,

Thanks all for your help so far.

Have mailled KEH

I am in the UK, and just looking to source the parts from anywhere at all. I have an authorised repairer, but just no parts support from Canon.

From the lens block diagram, both the front and back glass look totally flat, I am sure they will be coated at least.

Jeffa

z_28 · November 1, 2007

If both sides are flat - that's piece of glass or just filter !!!
Diagram is probably schematic only, don't use it as a repair guide, please

BTW - if Canon is out of old parts,
it probably means they are out of exactly THAT first lens !
Try to write to different repair shops in USA, maybe somebody still got one lens left ?
Good Luck

pathfinder · November 1, 2007

I just looked at the front of my 300f2.8 IS L, and I honestly cannot tell by looking at it, whether it is flat or curved, so you probably are correct.

When I look at a reflection of window frames off the front of the lens, straight lines are, however, curved, not straight, which would suggest some curvature of the front surface of the element. It still may not be a refracting surface, if both sides of the element are parallel, even if the front surface is curved. If the back surface of the front element matches the front surface, the refracting power would still be zero.

Good luck with your repair.

When trying to repair old machinery that is no longer supported by the manufacturer, one is frequently forced to buy two or three old machines to cobble together enough working parts for one fully functional, restored machine.

jeffa · November 1, 2007

pathfinder wrote:

I just looked at the front of my 300f2.8 IS L, and I honestly cannot tell by looking at it, whether it is flat or curved, so you probably are correct.

If I ask you enough questions about it maybe I can get you to drop it! on the mount though please!

claudermilk · November 2, 2007

pathfinder wrote:

When trying to repair old machinery that is no longer supported by the manufacturer, one is frequently forced to buy two or three old machines to cobble together enough working parts for one fully functional, restored machine.

Thus, the genesis of the "parts car" that every car-nut's wife despises.

Usually multiplies from "car" to "cars" & convinces the neighborhood you are insane.

jeffa · November 9, 2007

Plea
Hi,

Thanks for the tip on KEH, they have been very helpful, and told me what the price is for the spare ($108). However they don't want to sell me the spare, but gave me the Canon US spares number. I said thanks a lot and called the number.

Bottom line is Canon US will not/cannot ship outside the US.

Canon UK, say there is no stock of the part.

Canon UK were also incredibly unhelpful.

The service from the US guys was MUCH better, even though they could not help, they were polite, cheerful and informative.

AARRGGHHH!

Can you believe this?

I am a Canon CPS member. A friend here is a Nikon Professional member. He seems to get much better support from Nikon. If I didn't have so much investment in glass I would seriously be thinking about jumping ship!

Anyway, anyone out there happy to reship this from the States for me? If so please send me a PM.

Broken old Canon 300mm 2.8

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