17-55DX owners -- a little help, please

PhilY · Apr 26, 2005

Using my D70, I have been a little disappointed with sharpness when shooting landscapes wide (17-20MM) unless I was stopped down to normal the subject range of F11-F16. I decided to do a little testing from tripod to see if I could figure out what was going on and I made an interesting discovery.

It's a pretty simple check. Set your lens to 17MM and using the center focus bracket in single AF and aperture pri, focus on a far target (say, over 100ft) without taking a shot. After the focus, take a look at the lens focus scale and let me know the reading.

Mine (and now several on DPR) tends to focus at 8-10ft any time the target is over 40 feet or so and the shot is OOF. I can manually focus at infinity and the target is sharp as a tack. At first I thought I had a lens problem but now am beginning to think it's a D70 focus issue when too much "stuff" is in the bracket and the sensor is seeing it as "close". As I said, this si with the D70 but you "big D" guys may want to check as well.

Thanks for the help!

Phil

dkapp · Apr 26, 2005

EDIT

Just read you test again, and my first shots were with it at 55mm.

I re-shot with the lens at 17mm & the lens focused between 10' & infinity on both cameras and the subject was over 100' away. Bringing them into my computer, they are in focus. I shot these at f/2.8.

I also switched the camera to MF, and was able to move the lens closer to infinity & the focus lock indicator still stayed on. I may have to do some more testing & compare the two side by side. I may be able to get around to it this afternoon.

Dave

MontyDog · Apr 26, 2005

#1064 - You have an error in your SQL syntax;

PhilY · Apr 26, 2005

dkapp said:
EDIT

I re-shot with the lens at 17mm & the lens focused between 10' & infinity on both cameras and the subject was over 100' away. Bringing them into my computer, they are in focus. I shot these at f/2.8.

Dave

Thanks for the reply, Dave. I forget what cam you have -- D2H? I have quite a thread going on DPR and, as it turns out, the vast majority are having the exact same problem I am. Go figure! I would appreciate knowing the results if you do any more tests.

Phil

dkapp · Apr 26, 2005

PhilY said:
Thanks for the reply, Dave. I forget what cam you have -- D2H? I have quite a thread going on DPR and, as it turns out, the vast majority are having the exact same problem I am. Go figure! I would appreciate knowing the results if you do any more tests.

Phil

I shoot with the d70 & d2h. I should say that my D70 just came back from Nikon last week after replacing the shutter, adjusting AF and a laundry list of other fixes. I'm not sure how my D70 would have done before the adjustments. It does seem to perform correctly now.

I just dropped my sister off at the airport after a nice weekend visit, and need to catch up on some work. I hope to get outside & snap a few shots in a couple of hours.

Dave

obelix · Apr 26, 2005

Phil

I read your threads with great interest. Please keep us posted. I will be very interested in knowing what you find.

Good luck.

anand

PhilY · Apr 26, 2005

greyflash said:
I just checked my 17-55mm out on my D2H and it zips smartly to the center of the infinity symbol.

Thanks for the check, Gordon. It's beginning to look like the "focus adjustment" Nikon did on my cam's last trip was a focus maladjustment.

'Tis strange, though, many people are experiencing the same.

Phil

PhilY · Apr 26, 2005

obelix said:
Phil

I read your threads with great interest. Please keep us posted. I will be very interested in knowing what you find.

Good luck.

anand

Thanks, Anand -- will do. I have been in an email and phone conversation with the Nikon Tech guys most of the day. They requested sample images and I sent them this afternoon. I pointed them to the thread I started at DRP and, in effect, they said, "holy shat" after they saw how many cams are doing the same. Well, they didn't exactly say THAT but you know what I mean.

Phil

obelix · Apr 28, 2005

PhilY said:
obelix said:

Phil

I read your threads with great interest. Please keep us posted. I will be very interested in knowing what you find.

Good luck.

anand

Click to expand...

Thanks, Anand -- will do. I have been in an email and phone conversation with the Nikon Tech guys most of the day. They requested sample images and I sent them this afternoon. I pointed them to the thread I started at DRP and, in effect, they said, "holy shat" after they saw how many cams are doing the same. Well, they didn't exactly say THAT but you know what I mean.

Phil

. Never under-estimate the power of DPR, I guess.

dkapp · Apr 30, 2005

ianm said:
Using a D2X, distant objects are in focus between the 10ft mark and infinity. Worrying, although I need to test the actual images produced.

My D70 & D2H behave the same way & the images were fine. When I set the lens to infinity, they were horribly out of focus. It was obvious even in the VF.

I guess the distance markings of the lens are off at 17mm, but fine once you move through the range. I'm not worried about it. It works perfectly. I've got 4.5 years left on warranty, so I'll wait until its really broken before I send my baby away.

Dave

Philippe Roger · Apr 30, 2005

Phil,

I think mine is doing this too. Here are 100% crops, on the new (to me) D2H, first in AF mode (center reticle, single area, f/2.8 at 17mm), followed by manual focus with the focus mark half over the first circle of infinity.

These are straight from the NEF conversion with normal sharpening in-camera, not altered afterwards. The AF shot was aimed at the gate lock (1/3 right of the picture), from at least 30ft away: remember this is 100% crop.

Subscribe to see EXIF info for this image (if available)

(ignore the difference in exposure: I must have locked it, on a different spot.)

By the way, this only happens with the 3 sensors in the middle row, and not the vertical ones.

You probably remember what I was worried about with the D70 at infinity before: I think it was a combination of this problem on the 17-55 (all where at wide angle) and a few hazy shots taken with the 24-120.

Has Nikon gotten back to you about this? Are you sending your lens in for service?

ednaz · May 1, 2005

Many, many zooms "focus past infinity" - by design

I've read about this in two or three places before. Autofocus zooms often have more focusing range around the infinity mark than manual focus zooms. Elements in the lens change with temperatures, the old high school physics of expansion and contraction due to temperatures. It may not seem like much, but when you're dealing with 10 or more elements, and several tubes of different materials... it IS significant.

The result is that things at infinity often go into focus before the infinity marker hits your "distance is here" notch, and often the lens will continue on past infinity. It's not a fault, but it is weird if you've been around long enough to remember lenses that go "clunk" into place at infinity. Non-zooms usually don't have as much of this built in, if any. And the bigger the zoom range, the more you'll find. My 24-120VR and 80-400VR have a lot more of this play than my 80-200AFS.

I've experienced times when I noticed that the camera was placing infinity at a different place than usual - once in Sri Lanka on the coastal game preserve around 3pm when I was drinking a litre bottle of water every hour and still losing ground. Not sure what the temp was, but HOT will suffice. And the other time I noticed was on a scary trip down from Mt St Helens in a blizzard when all my lenses were grinding to a halt because the cold was solidifying the lubricants. COLD.

The other issue with autofocus lenses that you should remember is that autofocus works on detection of contrast differences, so at the point that the lens is zipping around and detects a sudden pop in contrast, it stops. Now, given DOF for any lens, there's obviously a RANGE of areas where the lens could stop. It doesn't stop in the center of the focus range, it stops when it detects it. That means that sometimes ALL of your DOF is behind the focus point the lens selected; sometimes all in front. Sometimes it comes to rest just past because of momentum and then your DOF is distributed. That means that sometimes you'll think the lens is not focusing properly, but it is - it's just not autofocusing the way YOU want it to. (Hey, it's a dumb machine.) It's more pronounced with longer lenses and less DOF; having shot with a number of 80-400VRs that people told me "didn't focus correctly" and finding that in my hands they DID focus just fine, I can attest to this phenomenon. (I learned that mine focused correctly from someone else who gave me the demo...and have been passing it along.)

How that two or three inches of depth of field gets distributed can make the 80-400VR AND/OR the photographer look pretty awful if you don't pay attention. That's why the AF lenses allow you to touch focus the last bit without them second guessing you. It's a good habit to learn.

And sometimes you get a bad camera, or a bad lens. But as a doctor friend of mine told me once about diagnoses, if you hear hoofbeats, odds are you should start by assuming it's a horse coming, not a zebra, unless you're on the veldt... In my experience, bad lenses and bad cameras are a really small problem. (Maybe I've just been lucky.)

Flew · May 1, 2005

Excellent analysis Ed.

Thanks,

Frank

PhilY · May 4, 2005

Re: Many, many zooms "focus past infinity" - by de

ednaz said:
The result is that things at infinity often go into focus before the infinity marker hits your "distance is here" notch, and often the lens will continue on past infinity. It's not a fault, but it is weird if you've been around long enough to remember lenses that go "clunk" into place at infinity. Non-zooms usually don't have as much of this built in, if any. And the bigger the zoom range, the more you'll find. My 24-120VR and 80-400VR have a lot more of this play than my 80-200AFS.

Ed,

Thank you for your detailed reply. I appreciate your help. Even though all my previous SLR experience has been split ring/split prism type manual focus, I am well aware of the behavior of zooms and the infinity mark. The focus point will be different even on the same lens from wide to full zoom and can vary according to temp. This cam/lens combo auto-focused perfectly before Nikon adjusted it and, since the problem reared its ugly head, I have tested literally 100s of different targets at various distances using all sensors after my original post. My engineer side demanded I perform critical tests. I will ask you trust me when I say there *is* a problem this time. :wink:

Phil

Beezle · May 4, 2005

There is definitely a problem with this lens and my D70. Same exact behavior as Phil's.

I cannot reproduce this problem using my D2X. Seems to me it is something about the D70's autofocus.

I never knew this to work correctly on my D70, then again I haven't really used the wide end of this lens very much.

ednaz · May 4, 2005

There's always a chance of bad lenses

And I understand your threatening your neighbor's wife given that Nikon adjusted your camera and it produced the problem. I must have missed that in the original post.

I have not had great experiences with Melville - not that they screwed up work, but they're not very good at reporting processes. Ride them close to make sure that you know where your lens is in the process. And in my case, after fixing my lens mount, they gave me a complimentary sensor cleaning - which meant that my camera was returned with enormous amounts of what looked like polar fleece all over the sensor. Took me five swabs to get it all off. Good thing it was "complimentary."