Comments on: "This lens is soft" and other myths

By: Jed

Jed — Fri, 05 Apr 2013 18:43:09 +0000

Well said Jeff! Since getting my Canon 600D nearly 2 years ago, I have learned about the perils of auto focusing and tollerances. Not once did I feel the need to go online and rant about it. I’ve calmly accepted the issues and have had my 2 Sigma lenses and 600D callibrated to 0 (or near as) tollerance. I now have some great auto focusing lenses and the time it took to get the callibrations done was worth it for my long term investment.

By: Jeff

Jeff — Thu, 14 Mar 2013 18:49:35 +0000

I wish Amazon would link to this article from every single SLR lens and make users read it before posting reviews.

By: Roger Cicala

Roger Cicala — Thu, 20 Dec 2012 22:16:25 +0000

Eric, you’re confusing phase-detection and contrast detection AF, I believe.

The lens gives a ton of information to the camera: where it is located in the zoom, what focal distance it is located at before the process begins. Then how much voltage and how many voltage switches it gives the AF motor, how many steps of movement the camera should expect from that, which direction it is moving, how close it is to it’s infinity or to the close focusing limit, when it has started it’s first movement and when it is 80% complete (or whatever completeness the camera rechecks at), when it has reached assumed focus point, how accurate the phase contrast should expect to be (kept in a database in the camera, but the lens notifies the camera which lookup table to use).

With phase detection the camera-lens doesn’t go back and forth and pick best phase like contrast would. It goes in one direction, usually (not always) confirms things are moving as expected, and usually (not always) confirms it has arrived at the proper position. But it doesn’t then jiggling back and forth to find best contrast, except perhaps with the newest Sony cameras. So if the lens gives bad information, the camera believes the lens is where the lens says it is – even if it isn’t.

Simple example: I have a Canon camera and 3 lenses that work great. I buy a 4th Canon lens that frontfocuses. When I contact Canon service, they don’t ask me to send the camera in. Just the lens. They fix the lens and it works like the other 3 now (well 95% of the time). They never see my camera.

By: Eric Jaakkola

Eric Jaakkola — Thu, 20 Dec 2012 19:09:58 +0000

How can a lens front focus or back focus? The lens has no idea what’s going on. The camera just tells it to focus this-way or that-way. There is no focus sensor in the lens.

By: LeadWrist

LeadWrist — Fri, 16 Nov 2012 16:37:17 +0000

I have been noticing a lot of “soft” focusing with my D600 and a few of my lenses, 24-70mm f/2.8 and 70-200mm f/2.8. I ran some tests using FoCal lens focus testing software and found my 24-70mm needed AF Fine Tuning set to -10 and my 70-200mm f/2.8 needed to be set to -18. I contacted Nikon to ask if this seemed reasonable or if maybe I simply had something really out of whack and should send in for recalibration as -18 seems really high. Anyway their response was simply, don’t use Aperture Mode, set to Auto and turn on VR. AF Fine Tuning will interfere with Auto Focus. Sigh….

By: Ian Ross

Ian Ross — Mon, 01 Oct 2012 04:07:39 +0000

Great article thank you very much for clearing this up for me.

By: Roger Cicala

Roger Cicala — Fri, 17 Aug 2012 11:56:56 +0000

Alan,

I don’t believe the D90 has AF microadjustment so the only really accurate choice is to send them to Nikon factory service. Unfortunately right now turnaround times there are several weeks and it’s difficult to do without your equipment that long.

Roger

By: Alan

Alan — Fri, 17 Aug 2012 04:07:19 +0000

Thank you for this article, Roger. You have given me great peace of mind. I am a beginning photographer and have had this “soft focus” issue with two of my lenses: the 50 mm f/1.4 D and the 70-200 mm f/2.8 VII. I thought it was just my poor technique…UNTIL…I purchased my 24-70 f/2.8. WOW!!! It is sharp as a tack, no back or front focusing. I am currently using a D90 and am not a full-time professional photographer (therefore, pro services is out). How should I proceed on getting my lenses and camera calibrated together? I don’t have an authorized Nikon service center anywhere near me (West Virginia), but I travel often. Can you recommend a place / person who is adept at performing this calibration? And can this calibration be accomplished on the D90?
Thank you.

By: Raluca

Raluca — Wed, 27 Jun 2012 07:15:56 +0000

I wish I read this article earlier.
I’ve had some big problems with a Nikkor 35mm f1.8 and I’ve sent it to the Nikon service again and again, only to have them tell me that the lens is fine, and that the fact that I sent it into service is unjustified.
The only problem is, they don’t want to calibrate it with the body. They test the lens and the body differently, not together, and they said clearly on the phone that they can’t calibrate the lens with the body. Even more, I had no problem with focusing until recently, so I can’t ask for a refund or a replacement from the store. This thing really sucks because the 35mm is my favorite lens and now, I won’t be able to take full advantage of it…

But the good thing is, I finally understood what really happened, thanks to this article.

By: Nick

Nick — Sun, 08 Jan 2012 15:58:42 +0000

Well, about 3 years ago when I bought my camera and lenses (kit ones), I noticed that all of them front-focused more or less. I didn’t quite know much about bad focusing back then. Still I suspected it might have been a camera issue. So I addressed various specialized sites and forums, hopefully, to get an answer. Unfortunatelly, the few who tired to answer a noob like me, told me that there’s no such thing as camera bad focus, only lens bad focus. So I accepted the idea that all my online acquired lenses were bad and I had to deal with that. Time passed and I learnt that cameras can focus bad also, I wish I’d remember those a$$hole$…