Shadow Dancer wrote:
Speaking from considerable experience, I would say a small note with full disclosure on it would be appropriate.
If I listed it on ebay I would note all problems.
Until recently, Sigma lenses have had focusing problems on Canon cameras.
I am not sure about the newer Sigmas with the multi-zone focus adjustment technology but I am skeptical since the Canon lenses have not had the same level of problems.

Fungus usually continues to grow. It would be costly to repair, if there are parts available.

To be completely honest, if I had an opportunity to purchase this lens that included your description, I would leave it to become somebody else's problem.

So, maybe $15?

I have not had any problems with Sigma lenses on Canon cameras.

Jerry Nemeth wrote:

I have not had any problems with Sigma lenses on Canon cameras.

The OP's lens cannot be used to auto focus at all, according to his description.
That AND fungus make this particular lens an "iffy" choice at best and nearly useless at worst.
My assessment is based on that single lens.

Many people are happy with their Sigma lenses or Sigma would no longer be in business.

On the other hand...

I purchased a Sigma 50-150 2.8 on ebay, a bit older but not as old as the OP's lens. It was in excellent condition and worked fine on my T2i with no error codes, weird sounds, fungus or problems.

It was the perfect focal length. It was sharp wide open. It focused quickly, but not quite where the focus point indicated.
I test every lens I intend to keep by taping a piece of newspaper on the wall, setting my camera on a tripod and shooting a series of images with the lens set at apertures from wide open down to f11.

This lens could not focus accurately unless I used Live View and manually focused. That is slow and difficult to do hand held or when a model/dancer may be moving. I googled the lens and found that many photographers have problems with Sigma lenses on Canon cameras, especially the older ones. 

So I returned the lens for a full refund.

Recently I purchased a Tamron 24-70 lens at Goodwill for a few bucks, it was made in the early 1990's with a Canon EF mount. It focuses perfectly, I like it. I am not a lens snob but accurate autofocus is a minimum requirement.
I also disliked my plastic "nifty fifty" because the focusing was not good and I could not use my Canon 50mm 2.5 macro on the T2i because it "hunted" for focus and drove me insane.

So, even Canon goofs up sometimes. I do love my new STM nifty fifty, that was a HUGE improvement in all ways over the cheap plastic one they used to sell.

Shadow Dancer wrote:
Speaking from considerable experience, I would say a small note with full disclosure on it would be appropriate.
If I listed it on ebay I would note all problems.
Until recently, Sigma lenses have had focusing problems on Canon cameras.
I am not sure about the newer Sigmas with the multi-zone focus adjustment technology but I am skeptical since the Canon lenses have not had the same level of problems.

Fungus usually continues to grow. It would be costly to repair, if there are parts available.

To be completely honest, if I had an opportunity to purchase this lens that included your description, I would leave it to become somebody else's problem.

So, maybe $15?

I wouldn't pay $5 for any piece of Sigma junk. Learned my lesson multiple times before.

Chuckarelei wrote:

I wouldn't pay $5 for any piece of Sigma junk. Learned my lesson multiple times before.

As I said, I would leave it there. Some people love to tinker with things, they could have fun with it.
Worst case, it will be excellent for burning ants!!!

Camera Buff wrote:
As I said this AF lens works beautifully on my old Canon 450D camera set to MANUAL mode. I have actually tested it and was more than happy with the sharpness wide open. More to my story is that I asked my young MUA who is a Canon shooter looking to buy a similar sized lens to bring over her new Canon 80D and the lens connection error stopped her camera from working. After she had left disappointed I realised that I had been shooting the 450D in MANUAL mode, but when I placed it in a PROGRAM mode it too came up with the lens error problem.

I'm not a lens snob but knowing the types of children pictures my MUA wants to take I recommended that she should look at a much lighter prime or shorter fast zoom. However she has used my Canon 70-200mm f2.8 and loves the pictures she can take with it. IMO both lenses are too long and too heavy on her crop sensor Canon. However if the Sigma  had of worked properly it would have been a super cheàp lens purchase for her to experiment with.

Pricing a lens with light fungus and compatiility issues is difficult, I could possibly sell the lens case, front and rear lens caps and the lens hood and throw in the problematic Sigma lens.  Such a shame to find such a pristine looking lens with fungus, but using this big lens in MANUAL mode to photograph young children would be an equally big ask, regardless of the price.

I understand your frustration. It was a pretty nice lens at one time. It may have had the auto-focusing problem that some Sigma lenses have but no way to know it now.

I am sticking with my estimate of $15. Bear in mind that the owner of the lens liked it so much he gave it free to charity so he would not have to try to use it anymore. Sad, but that's the real world.