Soft (auto) focus on Nikkor 18-200 VR2

Lare

Greetings everyone and happy holidays.
I will beg the moderator's pardon if this topic already exists, but I'm just starting to navigate around the new forum pages and may have overlooked it.

My 18-200mm lens seems to not auto focus properly at the 18mm end.  I noticed it just the other day and did a few tests (line of batteries and a ruler) to see if it was something that could be cleared up with the micro adjustment.  I came to the conclusion that it isn't.  At all the focal lengths beyond about 30 mm the auto focus is dead on.  But at 18mm the entire picture is just enough out of whack to be annoying.  It's not even terribly out, just enough that any magnification starts to show it whereas at all other focal lengths I have to zoom in quite a bit before I start to see it.

I know it isn't the capability of the lens, because I can switch to live view and manually focus it quite sharp.  (Not an acceptable ongoing workaround as almost all my shots are outdoors and live view just doesn't work for me in bright sunlight.)

My question to this august body is whether I am expecting too much or whether I should send in the camera and lens to Nikon while it's still under warranty.

My camera body is a relatively new D7000 and the lens is the 18-200mm f3.5-5.6 G II ED (DX).

Your thoughts appreciated.

spraynpray

Definitely worth sending it back for a tweak Lare.  No doubt about it.

Welcome to NR.

Lare

Thanks, spraynpray. I was really hoping you'd remind me about the custom menu setting for soft focus.

I was hoping to avoid sending in my kit, but I suppose I'll have to. Do you think there's any benefit in waiting a week or so to get out of a Christmas rush that might only be a figment of my imagination?

I also appreciate the welcome although I've been a member for a while, I just seem to have lost my post count with the switchover.

Paperman

I would add a sample photo if I were you. 

It is very hard for focus to be "out" so much that you will notice an error at 18 mm. The DOF  at 18 mm should not allow that.

Just to give an example, even at max aperture of  f3.5 and at a distance of 50 cms( 20"), you will have an in focus depth of 11 cms (+4"). At f8 at same distance, the DOF is almost 25cms (10"). I can't imagine any lens/camera combination being out of calibration that much.

The fact that you have perfect focus when using LV rules out any other lens faults.

Looks like "too high expectancy" from an 18-200 or maybe a user error. Had this been happening at 50 mm or so,  I wouldn't have doubted a focus issue ( as D7000 used to be notorious for it ) but at 18 mm , I'm not so sure.

spraynpray

Lare -  I just spotted this in your post:

"I know it isn't the capability of the lens, because I can switch to live view and manually focus it quite sharp.  (Not an acceptable ongoing workaround as almost all my shots are outdoors and live view just doesn't work for me in bright sunlight.)"

So, if you override focus in live view to get it perfect and take a picture (on a tripod so definitely no movement) then take another picture exactly the same in AF without touching the focus ring, you are saying that there is a difference?  You are also saying that if you increase focal length and do the same procedure, both shots are the same.  On the face if it that is a definitive test so the next step is to send it back.

Just check that you have the camera set to only release the shutter if focus is acquired first and report back on the above summary please.

Lare

Not exactly. Here's what I observed.

Using a tripod I took a picture with AF on, using a single focus point. I then repeated the shot turning AF off (using the switch on the lens) and manually focusing, using live view, magnified. Doing it this way I can see a definite difference in sharpness at the focus point,
.
Oh--the camera is reporting that it has focus. It even shows my single focus point on review.

@Paperman, I didn't provide enough detail in the OP in that I moved on to taking a general picture of my living room because the battery test was inconclusive.

All the pictures I shot, that exhibit the problem, were at 18mm. And all are shot wide open. It's not that the pics aren't ok, but that I can attain a sharper focus manually (at 18 but not higher) than the AF does.

spraynpray

Right, so the same exact shot taken from a tripod one AF the other MF confirmed in Live View (both shots got a focus confirmed indication? - That's wierd).

Sounds to me like for sure the camera needs to go to Nikon and I would send them the two pics as evidence.

Did you confirm the shutter was in the correct mode to only release when focus is confirmed?

Niknik

I think the first thing to do is to check your focus with a focus chart, and adjust it with AF fine tuning, which is found in the set-up menu. It goes from +20 to -20, so there is quite a bit of scope to adjust. I found the best way to do this is to have the camera linked up to a lap-top so you can review each shot immediately on a larger screen, as the one on the back of the camera is not big enough to for this purpose. You can then store the adjustments, and the camera applies them automatically when you change lens. 

This link will provide you with a focus chart and instructions:

http://www.scribd.com/doc/266756/Camera-Focus-Test-Chart

Even with maximum adjustment, I still found my D7000 back-focussed with a couple of lenses, so the camera went back to Nikon for adjustment. I suspect it is your camera rather than the lens that is the problem here, but you might find AF fine tuning sorts it out. My 18-200 mm was ok after adjustment, but my prime lenses were the problem: however all were fine after Nikon tweaked it. 

Unfortunate that D7000s are still leaving the factory with this problem, but that seems to be the case.

Dredden85

@ Lare: Did you send it in for service? If so, was your focus issue fixed?
All of the focus issues around the forum with the D7000 has me pretty nervous. I am still waiting for the arrival of a new D7k and the 18-200mm VRII lens. :-SS

dissent

Could just be my ignorance, but I wonder if you had VR "on" when you were shooting on the tripod. I've read that you can actually induce vibration in the image if VR is left on when on a tripod.

Most of my soft focus is self induced. I'd be interested to see what you hear from Nikon, Lare.

Lare

@Dredden85: I did send it in for service. I got it back after about two weeks (see the "What happens when you send something to Nikon for service" thread for the timetable). It seems much better to me. The paperwork doesn't go into a lot of detail but it does say "adjusted autofocus mechanism." No parts listed as replaced and the micro focus menu setting is still at zero.

@dissent: I can vouch for that. When I was testing it before I sent it in, I noticed that leaving VR on while on a tripod definitely made things worse.

Overall the focus was never very bad. As a matter of fact, without zooming in I thought the quality was right on the borderline of acceptable. It's just that it seemed to me that I shouldn't be able to (or have to) get a better focus manually than the AF computer can.

I'd say not to be nervous. This camera is an incredible piece of equipment and I think you're going to be overjoyed by how well it works. And, if you turn out to need an adjustment it seems like it was a pretty painless thing. I'm willing to bet that my experience was just a matter of tolerances all lining up in the same direction.