Lens/Camera Calibration

[monkeyleader]

Morning all,

While I've not done any specific focus testing (planning that in the weeks ahead) I was wondering if anyone has experience with Lens/Camera calibration ... Considering this for my 1DX/70-200 and 1DX/400 (two separate bodies) ..

Did you notice any difference after ? Did you get it done as you noted a specific problem? Did you get it done because you thought you needed to get it done and then upon not noticing any difference, regret the outlay of pennies?

Feedback appreciated - also where, in the southern / eastern area (I live in Cambridge) did you get yours down?

cheers,

Nigel

 

[Mark twiglet]

Have you got af fine adjust in camera ? If so do it yourself

 

[Canon Bob]

It's easily achieved yourself, Nigel. You can use trial and error with a suitable focus test chart or some analysis software like the excellent Reikan Focal.

Bob

 

[Mad-Photographer]

Morning all,

While I've not done any specific focus testing (planning that in the weeks ahead) I was wondering if anyone has experience with Lens/Camera calibration ... Considering this for my 1DX/70-200 and 1DX/400 (two separate bodies) ..

Did you notice any difference after ? Did you get it done as you noted a specific problem? Did you get it done because you thought you needed to get it done and then upon not noticing any difference, regret the outlay of pennies?

Feedback appreciated - also where, in the southern / eastern area (I live in Cambridge) did you get yours down?

cheers,

Nigel

Sorry for my ignorance but what is this?

 

[Canon Bob]

Sorry for my ignorance but what is this?

Many modern camera bodies allow you to calibrate the lens/lenses to match the AF of the body. Values are then stored in the body which are used each time you focus on a subject and it (in theory) gives better focus accuracy.

Bob

 

[chris malcolm]

I started my photographic life before AF was invented so I've always been well practised at manual focusing. When AF came along it didn't take me long to discover that my 50mm f1.4 lens suffered from aperture related focus drift and that, like most AF systems of the time, trying to use AF with wide angle lenses was unreliable and inaccurate. In other words, I learned at what apertures and focal lengths I couldn't trust AF and had to use MF to get sharp results.

I also learned that although for some lenses my camera's AF was front focusing a bit, and with others back focusing a bit, that generally speaking on average it was back focusing more and could do with a bit of tweaking. By great good luck it happened to be a camera where it wasn't too hard to gain access to the AF sensor plane adjusting screws and tweak it yourself to a higher standard than the camera service people tended to do.

At that time the top quality and top price DSLRs were offering user customisable lens specific micro focus adjustment tables. I decided that in future I wasn't going to buy any camera without such a feature. Unless of course technology had advanced to the point of offering fast enough image sensor based AF, which is inherently perfectly accurate, no calibration ever required.

I now have a camera with micro focus adjust. It's also got a much improved AF system which needs MFA less. But not only does it still need MFA, but MFA isn't the panacea I'd hoped for. Aperture related focus drift, although less of a problem, is still a problem with old fashioned wide aperture lenses. And change of AF behaviour throughout the zoom range is still a problem with zooms, especially with wide range zooms.

In sum the problem is that the fast phase based AF of DSLRs, which uses specialised AF sensors, can never be perfectly accurate. That's why the most expensive cameras with the most advanced and accurate phase-based AF systems not only offer the most sophisticated MFA systems, but the most sophisticated aids for really precise manual focusing. In fact manual focusing is so much easier than it used to be with the old SLRs with their split prism focusing screens that I often use it use it just as a check that one or another aspect of AF hasn't drifted off.

Then there's the problem of knowing exactly which bit of contrast in the chosen AF box the camera decided to focus on...

Auto exposure and auto white balance aren't perfect either, as I'm sure you know

 

[Mad-Photographer]

Many modern camera bodies allow you to calibrate the lens/lenses to match the AF of the body. Values are then stored in the body which are used each time you focus on a subject and it (in theory) gives better focus accuracy.

Bob

Thanks Bob

 

[monkeyleader]

Cheers for the answers ... so if I take calibration on my 70-200 it would suggest that minimum focus distance @ 200mm would be around 30foot .. does that sound about right? I assume, given the distance, you would need to print the test card onto something larger than A4? I also assume (?) that it matters on what typical focus distance would be - so thinking sitting behind goal at football ... therefore test in those kind of conditions (distance between camera and chart) or does that not really matter ?

cheers,

Nigel