Serene Life

by garik

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

I know that this lens is known to exhibits focus shift if the object is less than 4 feet away within the range f/2-f/4.

However, I've done quite a lot of close-up photography (mostly flowers), definitely within that aperture range and with the subject less than 4-5 feet away (I would say around 3 feet away), and I did not notice any focus shifting.

I was wondering if this effects can only occur under some specific conditions, or if there is some randomness that results in some lenses to not exhibit this effect.

share|improve this question

2 Answers 2

up vote 3 down vote accepted

As with many technical specifications that are used to compare cameras and lenses, much more is often made of the differences they exhibit in precise, controlled testing environments than the effects of those differences in real world situations.

In the case of the EF 50mm f/1.2L, the focus shift issue seems to come into play most often when extension tubes are used to achieve Minimum Focus Distance (MFD) considerably shorter than the 17.76" MFD the lens is capable of when mounted directly to the camera. If your subject is 3' away, that is twice the MFD of the EF 50mm f/1.2L and I would not expect the minimal amount of shift under those conditions to be detectable unless you were shooting very precise tests at high contrast test targets. With flowers as your subject, the slightest breeze could move them further during the time between focusing and exposing the image than the effect the focus shift would have on your photo.

It is also conceivable that if you are using Auto Focus your body/lens combo is slightly out of calibration in the opposite direction and the AFMA error and the focus shift are effectively canceling each other out. If you are focusing manually this would not be a factor.

share|improve this answer

Focus shift with the EF 50mm f/1.2L is not a flaw in manufacturing or quality control that certain lenses exhibit. It's due to the optical design,which leaves some spherical aberration uncorrected, meaning that each point of light does not hit the sensor in a uniform plane, the circle of confusion has a curve to it, that causes the plane of sharpest focus to move upon stopping down.

It's a subtle effect that is probably not as big a deal as people make out, which might be why you haven't noticed it.

share|improve this answer
    
+1. Indeed, the wide-open plane of focus almost always stays within the DoF when the lens is stopped down, so your subject stays subjectively sharp; it's only the range of acceptable sharpness (the DoF itself) that shifts. In practical terms, if you focus on the eyes and set an aperture that theoretically brings the tip of the nose into the the zone of sharpness, you may find the nose is still somewhat blurry, the eyes are still sharp, but more of the hair (or hat) is in sharp than you would have anticipated. –  user2719 Mar 10 '13 at 18:51

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.