D70 back focus problem - HELP!!

[tone55]

I have been a cinematographer/videographer and photographer for 15 years now I have run into the strangest problem with my D70. If I manually or auto focus a zoom lens when on the telephoto end of the lens, (and keep that distance/setting on the lens barrel), then zoom out to a wide angle, the focus plane invariably shifts to several feet behind the target. I have sent the camera to Nikon 5 separate times, they've remarked on 3 of those occasions that they made adjustments. Each time I got the camera back, I shot tests with two different lens which proved the problem and sent them in. Finally, they just said that the camera was opperating within factory standards and that I had to use autofocus everytime I changed the focal length! I like using manual focus, or even auto when I zoom into the target to focus - I have been doing this with all sorts of cameras (motion picture, video, SLRs) for years and have had no issues, unless the camera had a back focus problem (i.e. an Eclair NPR 16mm cam). Any suggestions??

[erichlund]

I have been a cinematographer/videographer and photographer for 15 years now I have run into the strangest problem with my D70. If I manually or auto focus a zoom lens when on the telephoto end of the lens, (and keep that distance/setting on the lens barrel), then zoom out to a wide angle, the focus plane invariably shifts to several feet behind the target.
Well, there's no guarantee that the lens will have the same focus plane when in the two different configurations. The markings for distance may not always be exact. What lens/brand are we talking about? Have you considered that it may not be the camera, but the lens?

My 18-200 holds focus when zooming (focus then zoom out), but I try not to make a habit of that (I did a test to be sure). However, if I auto focus, zoom in, auto focus, zoom out, repeating several times, the focus will reset a slight amount after every zoom. So I suspect I'm not right on critical focus when I just focus then zoom.

I remember my old Canon 100-300 fd lens on my Canon A-1. An old push-pull to zoom and rotate to focus. I seem to recall focus was significantly different at each end of the throw. Not sure about that though.

Basically, I guess I'm saying they may not be wrong.

[tone55]

I tested this problem with two different lens, a Nikkor 28-85mm AF and the lens that comes with the D70, the Nikon 18-70mm DX, Same exact problem with both lens. I've yet to encounter this problem using the Nikkor lens with my Nikon FM2. I've also varied the tests - I've used a chart, I've used objects, I've varied the distance - same thing every time. I once tested the distance on the lens barrel compared to the actual focus - the lens calibrations always displayed the right distance at the telephoto end of the lens and the wrong distance at the wide end of the lens. Pro equipment just shouldn't work that way...

[erichlund]

Pro equipment just shouldn't work that way...
Then no worries. Neither of those lenses are "Pro" equipment. Both are consumer grade lenses.

If you zoom out and then refocus using autofocus, do they focus accurately. If so, it is as I have described. Not much you can do about that.

I found manually focusing on the D70 darn near impossible because of the small viewfinder. Okay, my eyes had something to do with it as well, but I can manually focus just fine with my D200.

[tone55]

Then no worries. Neither of those lenses are "Pro" equipment. Both are consumer grade lenses.

If you zoom out and then refocus using autofocus, do they focus accurately. If so, it is as I have described. Not much you can do about that.

I found manually focusing on the D70 darn near impossible because of the small viewfinder. Okay, my eyes had something to do with it as well, but I can manually focus just fine with my D200.

Thanks for the input - you're right about these being consumer grade lens, though I've always thought of the Nikkor 28-85mm being a grade higher. Also, the Nikkor worked just fine on my FM2 and I had no problems zooming in to focus and knowing that the lens calibrations were correct at each focal length. That's what really gets me - if a lens is at the wide end, the lens calibrations should still be correct. I guess that's not how it works, though...
I am interested in the D200, though - do you think it is a vast improvement over the D70?

[Warin]

I am interested in the D200, though - do you think it is a vast improvement over the D70?

vast? no.

But I think the viewfinder size, LCD size and clarity, and the faster shooting speed make it worth the price of upgrading.