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Posts: 11,697
Registered: ‎08-13-2015

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

[ Edited ]

@ChrisMadog wrote:



Oh my, you people that are so dependent on automation.  You guys should have grown up when we had none.  If you can't figure out how to make that work, you picked the wrong hobby.


Oh dear - the "I'm so freakin' smart" people are here !
Stand your ground everyone - they may go away.





Please, accept my apologies for some of the replies.  I have no idea what that one remark you singled out was all about.  Back in the day before auto focus lenses were invented, the entire concept of front/back focusing was entirely non-existent.  All lenses were manual focus, and you had focusing aids in the viewfinder.




In today's world, some camera bodies have the capability to compensate for lenses that have focusing systems that may not be precisely calibrated for your camera body.  The fact that a given lens and a given camera may not be a match made in heaven is usually a reflection of manufacturing tolerances than manufacturing defects.  


Canon's Rebel camera bodies do not offer AFMA, Auto Focus Micro-Adjustment, but the camera bodies with ##D or #D model numbers do offer this feature in two basic forms.  First, AFMA allows the camera to recognize the type of CANON lens that you have mounted on the camera body, but it cannot distinguish between one serial number or the next.


Second, Canon camera bodies make no attempt to recognize third party lenses, which is probably for the best.  Third party lenses may sometimes fool the camera body into thinking that they are a specific Canon lens model, but sometimes the camera body may think the third party lens is one model, and at other times another model.  This confusion can only lead to errors over the long run, and Canon seems to have washed their hands of it by not recognizing third parry lenses, at all.



As for your immediate issue, I strongly suggest taking as many test shots as practical.  You should expect to get inconsistent results from one test shot to the next.  The problem is determining and distinguishing whether or not, or how much, the inconsistentencies are a result of lens performance or testing errors.  The best assumption to make is that inconsistencies in test shots is a result of testing flaws, and not the lens.  This perspective should force you to become more meticulous and accurate with your test shots, thereby reducing the sources and causes of out of focus shots.


What can you do about a lens that front or back focuses?


With a Canon Rebel body, there is very little that you can do, because they lack AFMA.  Seeing how today's auto-focusing DSLRs lack the viewfinder manual focusing aids, your options in that direction are limited, too.  You have some not so pretty choices to make.  


Keep using the lens, and trying to compensate for its' focusing behaviors.  Buy a new camera body with the AFMA feature, which has its' limitations because you're using a third party lens and the body may not always correctly recognize it.  Or, you could sell the lens.


"Doctor told me to get out and walk, so I bought a Canon."
Posts: 13,998
Registered: ‎12-07-2012

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

"I'm not stupid and I don't deal well with people who insist everyone else is 'stupider' than they are."


Chris this is an open public forum.  You are free to take or ignore the advice posted here.  Most of the comments are meant to help but you may not like some of the answers.  Nobody claimed that made anybody " 'stupider' ".  Some folks write posts about which they have no practical experience with.  It is up to you to decide which will benefit your situation.  I don't think anyone insists on anything!


BTW it is, surreptitiously.

EOS 1DX and 1D Mk IV and several lenses!
Occasional Contributor
Posts: 8
Registered: ‎02-16-2017

Re: Having problems with a Sigma DG 28-300mm 3.5-6.3 lens - just not quite right in focus.

Hi Waddizzie,


No need to apologise. It's all good in the end.


What you have said is what I needed to find out. Thank you.

I can't afford a new camera body but maybe in the future if I can find a job again. Anyone need an electronics Tech ?? LOL
People don't fix things, they throw them away these days and buy a new one Smiley Sad ... and who wants to emply a 60+ year old these days ?


I will try to compensate for the lens until the flex cable arrives to fix the 18-55mm Canon lens.
I've got a Canon 70-300mm lens too but I need a new front lens part for it - mould is growing between the two pieces of glass. It's not a great lens but it would do if I had to but as I said, I need a front lens assembly for it.


Thank you again. You were very clear with what you said. Smiley Happy


Kind Regards,


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