1785IS EFS to EF Mount Shown Here

Now I'm ticked, Canon should offer to make a modified EF-S (EF) mount for D30/60/10D owners, per request. My local camera repair shop sells some gear and this was a highly requested lens, I'll have to give him a heads up to your post. He may have some clients in need of this type of modified lens, he repairs many a 10D and the 17-85mm is a hot seller for him to 20D users.

So does this mean Short-back-focus was a marketing lie or does the SBF only apply to the 10-22mm lens (if even). Does the EF-S macro 60mm use a real SBF too?

Keep in mind, EF-S is not just short back focus, its also a smaller image circle.

Releasing the lenses with a standard EF mount could have caused mass confusion (and some pissed off customers).

Kudos to the guys with the cojones to try this stuff, I don't know that I'd be willing to risk that much gear as a test.

That's correct, post-conversion the 1785IS is basically like Sigma's "DC" lenses now: works with all 1.6x bodies.

I'm well aware of the image circle, I'm just ticked that lenses that could be used on other Canon 1.6x bodies can't because of a psuedo rear element. To be fair it's not even really an element so much as a bump stop plate.

I don't have any issues knowing what camera's my Sigma DC will and will not work on.

Even if you didn't sell the lenses over the counter with the EF mount, Canon should offer to do conversions for D30/60/10D owners. They could put an orange plastic plate on the rear to let others know this lens is a modified APS-C sensor only lens or something.

Now it appears the mirror will not contact any optical elements of these lenses as we were once lead to believe. Perhaps the 10-22mm may be an exception.

I can understand why you wouldn't sell an EF 17-85mm at BestBuy, but you should be able to special order one for the older APS-C Canon's if needed, if in deed it will work on those models.

I'm at least very glad to know that older APS-C Canon owners can use a 17-85mm IS if they so desire. Why should a 10D owner be forced to own a Rebel-D to use such a wonderful lens.

BTW, another perk now with the EF conversion is that the lens can now use extension tubes. It just gets more interesting by the minute.

Congratulations on being an educated consumer. Too bad everyone isn't so well educated. Just today I saw a post on DPR where it was obvious the OP didn't know the 18-125 DC was APS only.

It sounds like a good idea, but I doubt you could convince Canon.

OTOH - If demand is as high as you seem to think, I could see a cottage industry cropping (no pun intended) up.

How much of a premium would the average user be willing to pay (above the normal 17-85 cost) for the parts and labor to perform the conversion? Keeping in mind the lens will come without a warranty since its been modified.

Good show!

My guess is, eBay prices for the 24-85 USM are about to rise a little - get yours before they do.

Have Fun,

No offense but if you don't take the time to read the print online for this lens, shame on you. Any reputable online site will list this lens as APS-C only. Any camera shop worth it's salt should know this up front in person as well. And last but least it's written on Sigma's web site. It's also written on the directions that come with this lens shame on those who don't read those as well.

Well most grey imports don't have one anyhow so starting with that lens would reduce the cost as well. Plus if you only have D30/60/10D this is many times better then your last alternative to the 17-85mm IS.

As for the other post about this working with extension tubes, are you sure this lens wouldn't vignette a tad on account of the smaller image circle?

CoolToolGuy wrote:
Good show!

My guess is, eBay prices for the 24-85 USM are about to rise a little - get yours before they do.

Have Fun,

Why? you can order the baffle from any reputable local Canon autherized repair shop. Many local camera shops may be able to do this for you. I have a local shop that could order you just the parts you need. Infact he is certified to do most minor repairs inhouse, he could likely do this for any customer if needed, though not warranted he could do this.

No, because as you move the lens further away from the sensor, the image circle expands - it's a cone. With enough extension tubes, you can take (macro) photos on a 1Ds with an 18-55.

Yeah, I realised that after my post. Though the IQ might suffer a tad on the FF don't you think blown up that far? And that far out you'll need the IS

Depends on how far out it has to go, and how badly the image breaks down as you get out of the "zone" it's designed for.

The next question is - will it clear the Elan's mirror?

It should my Sigma cleared the Elan mirror, as far as I know the Mirror in the D30/60/10D was basically the same as that of an Elan series, hence smaller APS-C sized mirrors didn't show up until the Drebel.

If it clears the 10D it should clear the Elan, but it's pointless. I'm telling you I have shots of the the Sigma 18-125mm DC via film in my 35mm Elan 7N (was killing a roll) and they are horrid 15-20% of the frame is wasted on total nothingness, why is anyone thinking of using these APS-C lenses on FF.

Saying these lenses may vignette on FF is like saying the internet may contain a few nudity specific/questionable web sites...(insert sarcasm smiley here)

The mirror of the 10D/D60/D30 is smaller due to the smaller format. I'd check physical clearance - it may fit, and it may not. Not that it matters as serious vignetting is a given.

Besides, the Sigma merely has a smaller diameter image circle - the 17-85, even with the alteration, still has a deeper reach into the mirror box cavity.

I wouldn't bother putting it on full-frame either, but if it physically fits, somebody will try it - which is why Canon won't do it.