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Sigma 300mm 2.8 APO MF OM Mount Lens Haze
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PostPosted: Mon Oct 06, 2008 7:28 pm    Post subject: Sigma 300mm 2.8 APO MF OM Mount Lens Haze Reply with quote

I have received this beut of a lens for next to nothing, with the knowlege there are a few problems with it.

1. There is a small amount of fungus on some of the elements. Not enough to cause a problem as it is mostly around the edges of the glass.

2. There is a hazy element somewhere in the focusing group of elements.

Here is the lens (pic from this forum's gallery):


Here is a picture of the haze (and a small piece of the fungus):


I was able to get the lens disassembled all the way down to the focusing group, but I can't get any farther than that.

Here are my steps in taking it apart (for anyone interested):

1: Remove rear mount:




2: Remove rear aperture assembly:






3: Remove Focusing Grip:


4: Remove Focusing "Guide" (black thing with silver sticker in prev pic):


Past this point I am stuck. I can see the hazy element in the focusing group that is inside the metal enclosure, but I cannot get the metal enclosure off. In the last picture you can see a notch on the left side of the picture, and I think that has something to do with removing the metal enclosure, but I dont have any tool that will help me there.

I do not want to go in from the front, as I will need to get some lens spanners. But if someone says that will do the trick, I am willing!

Please help, or comment, or anything! Smile

Thanks!

Ben Vassmer


PostPosted: Mon Oct 06, 2008 7:32 pm    Post subject: Reply with quote

My images aren't showing.

I think I read somewhere on this forum that this is an anti-spam measure for new users.

Please help! Smile

Edit: NM, they are there now! Smile


PostPosted: Mon Oct 06, 2008 8:47 pm    Post subject: Reply with quote

Sorry, the only relevant thing that Google turned up you already saw ...


PostPosted: Mon Oct 06, 2008 8:53 pm    Post subject: Reply with quote

It does look like a nice lens and a shame for it to be unusable ... Even if you succeed in getting the lens element out, I suspect you will end up asking Sigma to quote on servicing it; the faulty lens element looks as if replacement rather than cleaning is needed. That may or may not turn out to be economical.

Oh and welcome to mflenses Smile


PostPosted: Tue Oct 07, 2008 1:53 am    Post subject: Reply with quote

Thank you for the welcome! I have been a lurker for a while, and have been impressed by the knowledge of the people here!

Will Sigma service lenses this old? If so, that may be a good option. Are there any other places that people can recommend that would look at something like this?

Yeah, that thread on fredmiranda is mine! Smile

Thanks!

Ben Vassmer


PostPosted: Tue Oct 07, 2008 2:17 am    Post subject: Reply with quote

Hello Ben and welcome to the group!
You may find that a tech local to you is equipt to do this job.
If Chris is correct about replacing the element and he may well be.
Sigma does have some old dead stock and parts to draw from as most manufacturers do.
This lens is probably not one they had a large production run of so that may work against you.
I would suggest finding a tech that is both willing and able as well as connected so he may order parts as required.
You may get lucky and a $75-$100 cleaning is all that you need to get this big beast back on the tripod.
I look forward to your shots.

Cheers
Andy


PostPosted: Tue Oct 07, 2008 10:22 am    Post subject: Reply with quote

The problem is common with many/most old Sigma lenses.
It is the lens cement used to join two elements.
The problem can't be fixed and I doubt you will find/get a spare from Sigma.
I have seen the problem with all (Zen) Sigma APO f5.6 400mm lenses and mny others. I have two useless 400mm examples.
The lens has little or no value, unless you join the ranks of the unscrupulous on eBay and sell it to a poor chump.


PostPosted: Tue Oct 07, 2008 1:45 pm    Post subject: Reply with quote

Rob Leslie wrote:
The problem is common with many/most old Sigma lenses.
It is the lens cement used to join two elements.
The problem can't be fixed and I doubt you will find/get a spare from Sigma.
I have seen the problem with all (Zen) Sigma APO f5.6 400mm lenses and mny others. I have two useless 400mm examples.
The lens has little or no value, unless you join the ranks of the unscrupulous on eBay and sell it to a poor chump.


Well, shoot! Smile Thank you for the information.


PostPosted: Wed Oct 08, 2008 12:27 pm    Post subject: Reply with quote

Rob Leslie wrote:
The problem is common with many/most old Sigma lenses.
It is the lens cement used to join two elements.
The problem can't be fixed and I doubt you will find/get a spare from Sigma.
I have seen the problem with all (Zen) Sigma APO f5.6 400mm lenses and mny others. I have two useless 400mm examples.
The lens has little or no value, unless you join the ranks of the unscrupulous on eBay and sell it to a poor chump.

I have the same problem with a Sigma 500 f4.5 APO. Sigma USA said buy a new one, I said just repair it please, they said NO ...And for the record I`m a USA sigma reseller.


PostPosted: Fri Oct 17, 2008 3:58 pm    Post subject: Reply with quote

There is a simple lesson here.

NEVER buy a Sigma lens S/H or new without trying the actual lens (Not an example) you are having.

Recent experiences. Myself 4 copies of the 10-20mm before I found a good one, the others had decentred focus. I just prey to the lens Gods that this one doesn't break!

A friends 'Horror Story' A New f4 100-300mm (Not cheap)
The lens was allmost out of focus at anything over 200mm. Instead of getting his money back he did as 'Told' and returned via the dealers to Sigma UK.
Five Months later the lens was returned. The explanation was it had been returned to Japan! (Why didn't they give him a new one?)
The lens is no different.
Sigma have offered him 400 trade in against a new lens?

The bad name Sigma has isn't a myth, it has been hard earned