help with a lens

shewholaughs

Ladies and jellyspoons...
Recently, I have purchased a used lens and I am dissatisfied with it. I'm coming to your for either verification that this indeed a bum lens OR an education about focal lengths and lens capabilities.
The lens in question is an older push/pull zoom Nikkor 35-70mm (2.8). I believe this is the one.
Here's the issue. When I focus infinity at 35mm zoom, the focus is only sharp about 6-10 feet in front of me. When I zoom in to 70mm, this issue seems to go away and I can get sharp focus a longer way away. This is a significant problem ... especially at weddings. I want to show the entire aisle in the photo but I want the focus on the bride and groom who are 40-80 feet in front of me.
The other thing I'm seeing is that the subject distance in the metadata of the raw images seem to either be infinity or 3.6m. Honestly, this is the first time I've investigated my "subject distance" so maybe this is a possible reason.
Below are a couple of test shots that show the kind of things I'm seeing. The first image is at 35mm and the second at 70mm. The focus point (2/3 up from bottom, easily 50 feet away) has not changed from shot to shot.
Main question: Am i going crazy? or does the 35mm focus only at short distances??

Peano

I would fling that lens in the can and buy a new, reliable one.

Imagine this post: I am a cop. I bought this used pistol. I can hit what I aim at if it's 10 feet away, but at 20 feet I miss badly.

Would you advise him to go through a series of analytical bench tests with the used pistol? Or buy a new and reliable one?

angevin1

Beth is it every time? Also, could you link to original sized photos, that'd help too for closer inspection. I own this lens and I haven't had this problem.

shewholaughs

I've only shot two weddings with this lens so I'm not sure if it happens all the time, but I'm starting to get skittish. It just seems to leave the focus at the bottom of the page for 35mm zoom, rather than shift the focus farther away like we can see in the 70mm shot.

here are direct links.
70mm http://www.bethsingley.com/photos/i-G7s4g4s/0/X3/i-G7s4g4s-X3.jpg
35mm http://www.bethsingley.com/photos/i-r4cJWKd/0/X3/i-r4cJWKd-X3.jpg

Further example:
70mm http://www.bethsingley.com/Other/FBStash/i-j32jPj5/0/X3/DSC07341-X3.jpg
35mm http://www.bethsingley.com/Other/FBStash/i-H2tj6zz/0/X3/DSC07351-X3.jpg

Also, Peano, I am tempted. I took it back after the first wedding and we debated with the shop owners. I promised I'd bring images to show what I'm seeing the next time. $400 is a lot to just throw in the can though.

angevin1

shewholaughs wrote: »

I've only shot two weddings with this lens so I'm not sure if it happens all the time, but I'm starting to get skittish. It just seems to leave the focus at the bottom of the page for 35mm zoom, rather than shift the focus farther away like we can see in the 70mm shot.

here are direct links.
70mm http://www.bethsingley.com/photos/i-G7s4g4s/0/X3/i-G7s4g4s-X3.jpg
35mm http://www.bethsingley.com/photos/i-r4cJWKd/0/X3/i-r4cJWKd-X3.jpg

Further example:
70mm http://www.bethsingley.com/Other/FBStash/i-j32jPj5/0/X3/DSC07341-X3.jpg
35mm http://www.bethsingley.com/Other/FBStash/i-H2tj6zz/0/X3/DSC07351-X3.jpg

Also, Peano, I am tempted. I took it back after the first wedding and we debated with the shop owners. I promised I'd bring images to show what I'm seeing the next time. $400 is a lot to just throw in the can though.

If your AF reticule was somewhere other than in the lower areas, I'd say there is a problem.

ziggy53

Please try setting your camera to a single AF point and in the center. Make sure that your AF mode is set to "AF-S".

Large aperture lenses will have limited DOF at maximum aperture (f2.8 in this case.) If you allow your camera to select AF from all points, the camera will often choose the closest AF. I suspect that this is the likely problem, since the closest elements in both images are fairly sharp.