Focusing Problems on Canon and Nikon DSLRs - Real

[jani]

What exactly is "back focusing"?

"Back focusing" means that the camera consistently focuses behind the intended focus point when using one-point autofocus.

How should I test my system for it?

Apply intelligence to the following suggestion:

Mount your camera on a tripod, and find a table or something that can be slightly below the camera's level (just a few inches will do) to set up your test target on.

Select a nice and contrasty target for focus, such as a calling card with crisp, black print on a white background, place it facing the camera and in plane with the focus plane, and so that the card is close enough to be reasonably easy to focus on.

Select a wide aperture (to reduce DoF effects, but not so wide that your lens is too soft), focus on the target, and switch to manual mode afterwards.

Place objects near the calling card, both in front and back, and make sure that those objects also have nice and contrast-rich detail that will enable you to see whether they're in focus or not. One typical trick is to use a black-on-white ruler, lying on the table. You can also place e.g. another calling card diagonally in the frame, so that the center of the card should be in focus (in plane with the original calling card), while e.g. the left side is closer to the camera and the right side further away.

Take test shots in RAW mode, compare at 100% zoom with no sharpening.

Are there any web sites with authoritative information and not just hearsay?

What do you think is "hearsay" and what do you think is "authorative information"? Is a personal experience report one or the other?

You'll find several such reports here, on both front-focusing and back-focusing.

[jani]

When an image is front/back focused (soft), IMO, I believe it is because of shallow DoF or poor technique.

Shallow DoF in itself doesn't mean that you will front-focus or back-focus, it will only reveal that you do so.

Poor technique is probably relevant, and is what I thought was a large contributor to my own front-focusing problems with my 20D. I tried using more DoF to hide my problems, but the results were (rather unsurprisingly, if you think about it) unsatisfactory.

Repeated problems -- even after very careful test setups -- revealed that this was not the case.

I reported the problem to my local Canon service center, and delivered the camera and my lenses.

They checked, agreed that there was a problem -- even admitted that this was a fairly common problem with the 20D -- and performed the adjustment as a warranty service, free of charge.

This is not to say that the same problems are frequent with the 1-series cameras. I sincerely doubt they are. But it's surprisingly frequent when the Canon service senter admits that "many people experience these problems" with the 20D (translation from Norwegian, of course).


Any reasonably competent photographer who thinks there may be a problem should of course test their camera, and if they think there is a problem, get in touch either with their reseller or with the local Canon (or Nikon, Konica Minolta, etc., as the case may be) service senter.

[hdomke]

I keep hearing about "back focusing" but have never seen it and am skeptical. Is it real?

Currently I shoot with a Canon 1Ds Mk2 and I hear it is a serious problem with that camera.

I remember identical discussions about the Nikon D1X when that was my camera.

I have never seen the problem and being a trained skeptic, I am
wondering: Is it real?

What exactly is "back focusing"?

How should I test my system for it?

Are there any web sites with authoritative information and not just hearsay?

Since it seems to plague the two top manufacturers of DSLRs, is it
perhaps some inherent limitation of auto focusing systems?

Henry Domke
Henry Domke Fine Art

[ThePhotoOp]

My favorite quote of all time:

Paraphrased:
Most lenses are better than most photographers. (MR)
(To me, this quote means it’s usually the photographers fault, not camera/lens)

I've owned four canon digital cameras and shot with lots of Pro Nikon digital gear and have yet to have a focusing issue with any camera.  I had a lens with dirty contacts a few times, but that’s expected occasionally.

When an image is front/back focused (soft), IMO, I believe it is because of shallow DoF or poor technique.

A very few reputable photographers have experienced a real problem, (and proven it by methodical testing) but buy far, the 1-series Canon cameras are some of the best cameras ever produced anywhere.

Most of these alleged focusing issues are hype, trolls or cr@p.

JMHO

Peace,
Jim

[drh681]

search for front/back focus test.

you should find some variation on the target and ruler test.

this takes some careful, but not difficult, set up.

as Jani said, working at the widest aperture, focus on the target and look at the image of the ruler for where the actual focus falls.

if it is at the target, you win! no focus issues.

if it is not, then you need to find out if the problem is the lens or the camera's system. (you will need more than one lens.)
if the second lens shows a similar 'miss' then you can suspect the body.
If there is no miss with the second lens, then you can suspect the lens of bieng miscalibrated.