'Re-chipping' Sigma lenses for digital

[Joe]

Has anyone had experience of re-chipping the older 'film' lenses for use with Canon digi bodies?
There's an awful lot of older Sigma 400mm f/5.6 glass about going for very cheap money.
We had some experience of an older 28-200mm Sigma which kept displaying an err99 message on a 300D body.
In this case the lens wasn't worth much, and a replacement was sought , but surely the bigger optics maybe merit some modification/time and effort spent on them?
Maybe there's a definative list of lenses that can be modified, somewhere?

[Adey Baker]

If you've got an older example of a current model then you should be able to get it re-chipped without too much hassle.

Once the lens is discontinued then you only have as long as it takes for Sigma to run out of stock of chips before it becomes redundant. Unfortunately the 400mm lens has reached this stage some time ago. I believe it's possible to use one at full aperture but as soon as you try to stop down you get the dreaded Error 99.

Anyone selling one of these secondhand will know whether it's been re-chipped and will surely emphasise this point as it means a higher price can be asked

[miketoll]

If you have a lens that can be rechipped and have the original receipt that shows you bought it new then Sigma will not charge you. Have had this done twice, once when I upgraded from an EOS 100 (film) to an EOS 3 (film) and then again to a 20D. The 18mm wide angle I had could not be rechipped the second time as was no longer current and they had no stock. I suppose other independant makes have the same problems? All very annoying though as it means an expensive Sigma lens may eventualy become redundant as new models are introduced. Canon obviously like this situation as they hope it will make you buy only their lenses which are always backward compatible.

[Leif]

That particular lens went out of production before many if not all digital SLR cameras were released. So it is questionable whether or not Sigma can update the chip.

I would not be surprised if Canon design the lens camera signaling to ensure problems with third party lenses. And who could blame them?

[Joe]

That's a good point Leif.
I've been pondering this possiblity.
I'm intrigued about the use of full aperture to aviod the err99 situation, as Adey suggested.....I wish we'd thought of it before getting rid of the sigma 28-200.
We should have played at blanking some of the contacts off too....maybe the AF would need to be blanked off too??
I believe that the very early digi bodies like the D30 and D60 used earlier chips than the 300D,350D,400D etc.
I can fully understand the reasons and reasoning behind progress.....It just seems very strange, somehow wrong, that for example, I can fit one of my elderly manual Tamron adaptall lenses to wife Jacky's canon digi body, but full auto purpose made EF mount lenses from not half as long ago are no longer compatible.
Certainly from our perspective, many of my higher magnification lenses Jacky feels are too heavy for her. A lightweight 400mm would seem to fit the bill better to extend her shooting range beyond the 100-300 she uses at the mo.(ironically more often than not used at full 5.6 open aperture)

[Adey Baker]

I wouldn't want to be restricted to full aperture on something like a 28-20mm but it's no great problem on the 400mm, which I often use at either F5.6 or just one stop down - the very close-focus of the lens does benefit from a bit more stopping-down for depth of field purposes, though.

I've seen comments before about the D30 and D60 being OK, which is quite interesting as both of these models came after the EOS 30 which seems to be where Canon first got around Sigma's chips.

It's a competitive world out there and price is everything these days, but one wonders just how much extra each lens would cost if only Sigma had paid Canon a licence fee for using their technology - I suppose they thought that they were being very 'clever' getting around Canon's patents without realising that Canon would do the same to them!