Do front (or back) focus issues persist if manual focus is used?

If a lens front (or back) focuses, would the condition persist even if the lens in set to manual focus, and used in that manner?

Also, if a lens is calibrated to correct a front/back focus condition in combination with a specific camera body, does that mean the condition could become worse when used with another body?

Maxdave

the answer to your first question is that front/back focus does not exist when manually focusing.

i'm curious to know the answer to your second question.

No and yes.

Maxdave wrote in post #6363510
If a lens front (or back) focuses, would the condition persist even if the lens in set to manual focus, and used in that manner?

If this is straightforward back or front focus, it should not persist.

Having said that, fast lenses may suffer from residual, uncorrectable or even deliberately introduced spherical aberrations, the latter in order to create great bokeh. This may result in focus shift at relatively short distances (let's say, less than 2 meters) at large apertures, from maximum aperture to, say, up to F/2.8. Focus shift normally causes back focus, and the amount varies with aperture selected. At maximum paperture there is none, it goes up to a certain amount at a certain aperture, and then diminishes again, to disappear within DoF. And it varies with distance too. From a certain distance it will be gone too. This is caused by the fact that less refraction of light rays has to occur for subjects further away, thus introducing less spherical abberrations by default.

From my tests some of the early copies of the 50L suffered from this, but it can now be corrected to have only very little and within DoF, the 85L suffers a little from it but not disturbingly so (within DoF), and the new Sigma 50 F/1.4 does as well. There are a few lenses which are unusable up to F/3.5 as a result, but fortunately they're not part of the Canon stable. The latter category requires trial and error. With focus shift MF is not going to help you either, unless you MF with the aperture closed.

But generally, the condition of back or front focus does not persist in manual mode.

Yes, theoretically it could. Calibration of a body and a lens results in AF solutions that show a statistical distribution, so if you combine a camera which sits at the happy mddle ground, with a lens at an outlier, it may just work fine, while a body at the opposite outlier as the lens, may well result in worse conditions than before.

However, since it is easier to calibrate a body, it seems, chances are that the problem lies with the lens, not so much with the body. Statistically this is also to be expected, because many more lenses are produced than camera bodies.

Kind regards, Wim

Lenses are not calibrated to un-calibrated bodies. Due to tolerances +- in both lenses and bodies a certain combination may exhibit subpar performance, as mentioned above. In those cases, a lens may be, so-called, calibrated to a body but not to the extent that the lens falls outside the acceptable tolerance set by the manufacturer.