Camera/Lens "Calibration"

UncleJake · May 4, 2006

I recently jumped back into photography with both feet (new 30D, 24-105L, some other stuff) and have been lurking a lot here and on dpreview. I'm wondering what the deal is with people sending in their body and/or lenses for "calibration".

I understand this probably means adjusting the lens/body so that the focal point hits the sensor/film dead on, but can a $1000+ piece of gear be off that much?:dunno

Is it necessary for a semi-literate noob such as myself to even worry about? Other than I would KNOW my bad photos are user error, and can't blame front focusing or something else?

I've also seen a number of people mention different "tests" that they've done to determine if the camera/lens is off. Does anyone have any quick and dirty advice on how to set-up and perform some tests of my own? I was thinking of maybe a crisp $20 bill on the wall and shoot from a tripod or ???:scratch

I've gotten some good captures with my new gear, but nothing like some of the razor-sharp stuff I've seen here. :beer I just want to make sure it's me, and not frustrate myself trying for something my gear might or might not be able produce.

Thanks for any info/advice.:thumb

-UJ

ziggy53 · May 4, 2006

UJ,

Don't worry unless you need to. How do you know if you need to?

I generally take a fence row or a brick wall or something similar that is capable of being shot from an angle, 45 degrees or a little more. Work with a tripod or at least use a bright day and ISO 200 - 400 to get the shutter working faster.

Set the camera to only recognize the center focus dot. Identify some subject dead center, something with good contrast in a sharp edge that is easy for the lens to lock onto.

Start with the aperture wide open in AV mode. Take a couple of shots with the autofocus and notice if the lens hunts for focus. If it does, take a couple more shots. Stop down one full f-stop and test again. Keep going at least until f11 or f16.

Repeat this same test at different focal lengths if using a zoom.

Back at the computer, check each image at 100%, starting with the center of the image with the aperture wide open test. If the center is consistantly unsharp, scroll the image left and right until you see maximum sharpness. If the best focus is forward, the lens and camera are front-focussing. If the best focus is backward, you are witnessing back-focussing.

Ideally, the best focus should be in the center of the image. As you progress through the images, check to make sure the lens is consistantly focussing the same place, otherwise you have a different problem.

As you view images with a smaller opening, you should see DOF come more into play. The prime focus should stay in the center.

You really should not use just one lens to make this test, because that one lens could be a problem. You should only have the camera adjusted if you see a pattern of a problem across several lenses, and then send just that lens you deem to be most crucial in with the camera for focus adjustment.

Starting with the 6 MP imagers (or so) the front-focus or back-focus problem became more easily distinguishable. I would bet that the Canon 1Ds MKII, with 16 MPixels, is very tempermental from lens to lens if the owner/operator is very critical.

By all means, don't expect the problem to exist. The manufacturers are very carefull to adjust each camera according to very carefull criteria before each body leaves the company.

Best,

ziggy53

FatNakedGuy · May 4, 2006

Great info Ziggy, thank you sir!

UncleJake · May 5, 2006

I concur with FatNakedGuy (That's not something I thought I say today...:D )

Thanks Ziggy!

-UJ

graeme_7799 · May 7, 2006

The only time I've sent a lens in for calibration was last year, and thats because its the Canon 200mm f/1.8, which was made some 10+ years ago. I only sent it in because over time, lenses can become offset by just a hair, which sadly enough affected my photos. The only time I would recommend sending something in for calibration is if it is an older piece of equipment.

Camera/Lens "Calibration"

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