85mm 1.8 non-D backfocusing?

[pom_monico]

<p>It seems my 85mm is backfocusing. I've confirmed it on my D90 and on a borrowed D700. When I try to focus on the eyes, it focuses instead somewhere between the eyes and ears.</p>

<p>Is there a way for me to adjust the focus on this lens myself? It's an old lens and it won't be worth it taking it in for adjustment/repair. I don't mind taking it apart if I have to. Might give me a chance to learn about lens internals.</p>

 

[robert_hooper1]

<p>I'm not certain, but I believe that without an optical bench you will not be able to make any precise adjustments especially since the lens is an f1.8. Also, focus inaccuracy could be due to worn parts, and if even if you reassemble the lens correctly, it may still not focus properly or be correctable with any consistency. </p>

[nsfbr]

<p>My D300 allows you to adjust the focus for specific lenses. Does the D90?</p>

[robert_hooper1]

<p>"My D300 allows you to adjust the focus for specific lenses. Does the D90?"</p>

<p>Unfortunately for fast lens users, the D90 does not. Luckily, my Nikon 50mm f1.8 and Nikon 80-200mm f2.8 lenses mate perfectly with my Nikon D90. Focus is spot on, even close up.</p>

[tomweis]

<p>Mine had a loose element inside of it... I thought lousy focus was the camera body's fault until I had the lens repaired and everything inside tightened up. It might be worth a try to see if yours has any loose glass inside.</p>

[pom_monico]

<p>My D90 does not have an auto-focus fine tune, and I know it's not the camera because my other lenses are fine. Now that I look again it seems to focus maybe an inch in front of where it's supposed to.</p>

<p>It won't be worth the money to have someone try to fix it. Any suggestions on what to do?</p>

[joel_covey]

<p>Auto focus is easy, sometimes fast and often overrated. One of the reasons I own a collection of manual focus lenses.<br>

I assume you are doing portraits and shooting wide open and from a distance of 10 ft. At f1.8 and 10ft your critical Dof is about 2 in. At f4 it increases to about 9 in--right for most portrait shots. And your image quality will go up. A new lens-I would return it. But with an old used lens, I would work around its limitations</p>

[fred_wheeler]

<p>Pom, In your original post you thought the lens was backfocusing. Later, you looked again and thought it was frontfocusing. I would download a good testchart, put the camera on a tripod set wide open at f/1.8 and see what it does then if you haven't already.<br>

Fred</p>

[pom_monico]

<p>I confuses me too, because it's as if sometimes it's frontfocus and sometimes it's backfocus. I can't be certain. Enclosed is a chart image I just took at 85mm, f/1.8. In this shot, it's focusing just slightly back of center. Could this be an indication of a loose element?</p>

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[pom_monico]

<p>Another observation. Unlike my 18-200 and my 50 f/1.8, this one rattles inside when I shake it despite my holding all the external moving parts still. So now I'm leaning towards a loose part inside. Do your 85mm 1.8d lenses rattle also?</p>

 

[dave_wilson1]

<p>Yes, it's the older rear focus setup that rattles some, mine is the same and I bought it new years ago and has been a near perfect performer. If you think it's out of adjustment and don't want to have it fixed, not sure what to suggest except use it as is or manual focus.</p>

[pom_monico]

<p>I ended up taking the lens into a local shop and had the techs look at it, with the intention of placing a value on it. The fellows tested it on their DX and FX cameras and told me there were no problems at all. It works great. So now, I'm wondering if it's just me or some combination of this lens and my specific camera.<br>

Oh well.</p>