Nearsighted camera body or farsighted lenses?

[Straightshooter]

Dear All,

Looking for some advice regarding the following problem: I have 3 Canon bodies (one EOS 1D series, and two 7D's) and a bunch of EF lenses, and am very frustrated with the AF being 'all over the place' on all 3 camera's... :
Lens -A would be doing kind of okay on the 1D but at the same time needing quite a lot of AF adjusting on one of the 7D's and just a little on the other one ???
My first question is: why on earth do these big differences excist? I will be the first to admit I am NOT an engineer, so the ones amongst you who are will probably scold me now , but is it really so hard for the smart people of Canon to make sure their brilliant cameras and lenses leave the factory in some kind of harmony

I could / should of course send in the whole bunch and have it calibrated, but I don't have the money for that at the moment :-[ so question number two: Would choosing one or two camera bodies for calibration - without the lenses - make any sense? It sure would save me some money, but I wonder if letting the kind Canon folks handle my cameras without matching the results to my lenses would do the trick? Please advice! Thanks!!

PS: of course I tried to micro adjust as much as possible, but it is not all that easy (well for me that is) :'(

PS2: if this has been posted before I do apologize...

 

[Mt Spokane Photography]

Its not easy to do AFMA, the issue first of all is making sure that the camera focuses exactly where you think its focusing. Having that red square on a certain spot does not mean that the camera did not focus elsewhere.
That's why professional targets are flat, and large enough so that the camera will focus on the flat surface. There may be a slanted ruler to one side, but the camera does not focus on it.

Lenses are also notorious for variable focus, and third party lenses like Sigma, or consumer lenses like the Canon 50mm can be all over the place.

Yet another issue is lighting, color, and content of the image.

Its not easy to do a proper test that eliminates variables that affect autofocus.

Autofocus usually does a reasonably good job, but it is far from perfect. You can do better manually if you go about it carefully.

 

[Logan]

its not easy to get the lens mount and the sensor perfectly parallel and a precise distance from each other. Sigma claims to get +- 3 microns from the injection moulds, and i doubt anyone is getting anything a lot better than that.

the metal parts in a lens are very difficult to machine, they are very small, difficult to hold on to, and delicate. this is one of the reasons you see more plastic parts in lenses these days, its much easier to get it to an accurate size without huge cost. look at some youtube videos of a lathe working and you will see how violent it is, its actually using much more force than it looks like, and its easy to squish tiny parts out of shape, even on the fanciest cnc machines that canon has.

The different ways of forming the lenses all come with their own sources of error, some from cost-cutting measures (ring bokeh from hard transitions between sections, think bifocal glasses) Even the flourite crystals grown for the big white lenses have some impurities.

sometimes these errors stack up and you get a really far out lens, which is perfect on a different body because various errors are compensating for each other.

look up the lensrentals article on sample variation in lenses, its very interesting.

 

[Straightshooter]

Its not easy to do AFMA, the issue first of all is making sure that the camera focuses exactly where you think its focusing. Having that red square on a certain spot does not mean that the camera did not focus elsewhere.
That's why professional targets are flat, and large enough so that the camera will focus on the flat surface. There may be a slanted ruler to one side, but the camera does not focus on it.

Lenses are also notorious for variable focus, and third party lenses like Sigma, or consumer lenses like the Canon 50mm can be all over the place.

Yet another issue is lighting, color, and content of the image.

Its not easy to do a proper test that eliminates variables that affect autofocus.

Autofocus usually does a reasonably good job, but it is far from perfect. You can do better manually if you go about it carefully.

Dear Mt Spokane,

Thanks for your input! AFMA is such a pain in the derriere that I wished the kind makers of photographic equipment could somehow manage to ship their stuff 'perfectly calibrated'! But apparently that's not possible and I would be very interested in hearing, in non-specialist terms, why with all those computers and advanced technology at their dispossal, Canon, Nikon etc. cannot do better... :-\

 

[Straightshooter]

its not easy to get the lens mount and the sensor perfectly parallel and a precise distance from each other. Sigma claims to get +- 3 microns from the injection moulds, and i doubt anyone is getting anything a lot better than that.

the metal parts in a lens are very difficult to machine, they are very small, difficult to hold on to, and delicate. this is one of the reasons you see more plastic parts in lenses these days, its much easier to get it to an accurate size without huge cost. look at some youtube videos of a lathe working and you will see how violent it is, its actually using much more force than it looks like, and its easy to squish tiny parts out of shape, even on the fanciest cnc machines that canon has.

The different ways of forming the lenses all come with their own sources of error, some from cost-cutting measures (ring bokeh from hard transitions between sections, think bifocal glasses) Even the flourite crystals grown for the big white lenses have some impurities.

sometimes these errors stack up and you get a really far out lens, which is perfect on a different body because various errors are compensating for each other.

look up the lensrentals article on sample variation in lenses, its very interesting.

Oops, this came in just after I posted my reply to Mt Spokane... Very interesting! Thanks!

 

[Straightshooter]

Anyway, from these two replies I guess I should conclude it's 'sending in the whole bunch' or nothing....? :'(

 

[Mt Spokane Photography]

Anyway, from these two replies I guess I should conclude it's 'sending in the whole bunch' or nothing....? :'(

If one of the lenses is really bad, send it in first, and see if they are able to help it. Its entirely possible that the lens is OK, and its a tolerance stackup, but a check focusing with camera on a tripod on a brick wall or equivalent 50 X focal length, taking 10 or more shots and resetting the lens to mfd or to infinity before each autofocus should point up any wild focus issues. its normal to have one or two be off, but not more than that. If its ok, your issues might lie somewhere else.

 

[Straightshooter]

By the way, does anybody knows if a 'dock kind of thing' (Sigma) could be the answer for people who (think they) need something slightly more 'powerful' than just AFMA for their off camera-lens combination? A question to the really smart ones here: is it possible for Canon the market such a device that would allow us to modify many, most of our EF lenses? ;D

 

[Straightshooter]

Anyway, from these two replies I guess I should conclude it's 'sending in the whole bunch' or nothing....? :'(

If one of the lenses is really bad, send it in first, and see if they are able to help it. Its entirely possible that the lens is OK, and its a tolerance stackup, but a check focusing with camera on a tripod on a brick wall or equivalent 50 X focal length, taking 10 or more shots and resetting the lens to mfd or to infinity before each autofocus should point up any wild focus issues. its normal to have one or two be off, but not more than that. If its ok, your issues might lie somewhere else.

Will try, but the problem is that for example, one of my lenses is frontfocusing very very badly on my 1D (needs the full 20 to get anywhere near acceptable results) while it does less so on one 7D and almost okay on the second one...

A silly question maybe, but am I right assuming mirroless systems do not (or far less) suffer from these issues (i.e. front - backfocussing)? Or is that being seriously mis-informed

 

[Maximilian]

Lens -A would be doing kind of okay on the 1D but at the same time needing quite a lot of AF adjusting on one of the 7D's and just a little on the other one ???
My first question is: why on earth do these big differences excist?

Hello Straightshooter!

Did you recognize and read this article here on CR?
http://www.canonrumors.com/tech-articles/this-lens-is-soft-and-other-myths/

I think after reading it, a lot of things will becom clearer to you.
When I read it the first time, I really enjoyed it. And I read it several times, because I really like it.

After that you will understand, why AFMA exists and must be done seperately on every DSLR to achieve the best results.
And of course why mechanical adjustment will only work on one specific camera-lens combination and not with other bodies.

Enjoy reading and relaxing. It really helps.