Onquest Loc: Just Wandering

I have a tamron 28-75 lens which I've used extensively and love it, but now I'm noticing the focus point seems to be slightly off. Typically I would focus on the eye of a person and I'm seeing a soft eye and crisp sharp hair beyond. How do I set up a 'for sure, for sure' lens test before I hit the panic button? Is it fixable and what hoops would a need to jump through to get this done? I'm sure I could send it to Tamron but I'm wondering if there are any reasonably price independents that know what they're doing? Oh, if it makes any difference, I use a Nikon 300s body.

ecobin Loc: Paoli, PA

Check your D300s manual for AF-fine tune. This adjustment allows for fine tuning the focus of each of your lenses. If this doesn't work then I suggest that you send it to Tamron for adjustment.

tusketwedge Loc: Nova Scotia Canada

try this site it's pretty easy and quite fast to do.I think someone had this same issue a couple of days ago. Good luck.
https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/51633

Onquest Loc: Just Wandering

Thank you. Will do.

tusketwedge Loc: Nova Scotia Canada

Your welcome ,I"ve been doing my lens for a couple of years like that and it seem to work fine for me.

jerryc41 Loc: Catskill Mts of NY

Here's an article on checking focus. I'm on my old computer, or I could give you more references.

http://photographylife.com/how-to-quickly-test-your-dslr-for-autofocus-issues

camerapapi Loc: Miami, Fl.

Make sure you get the same results using another lens and if you do it is the camera's back focus.
By the way, I have never seen back focus with any Nikon camera but that is my experience and I cannot talk on behalf of anyone else.
Instead of fiddling around with the camera I prefer a competent technician to take care of the problem.

abc1234 Loc: Elk Grove Village, Illinois

This discussion comes at the best time for me. A Sigma 70-200 just came this week and in some down and dirty tests, I found that at f/2.8 and 200 mm, the lens was useless. At other apertures and focal lengths, it seemed satisfactory but overall, no better than my cheap 18-200 Canon kit lens. Why spend all this money for something no better than what I have already?

Out of frustration, I called Sigma and Paul was very helpful to me regarding this known problem. He suspects that the calibration of the auto-focus link between camera and lens is off. This is just the issue described in the two excellent links above. He told me to do the live view test as described in Jerry's link. This is clearly my problem. Sigma will adjust the auto-focus at no charge for white-market lenses under warranty. To do so, they need the lens and camera.

Paul also said that the proper distance for testing lenses is 400 times the focal length. And that is within the recommended range in the article. In addition to the method in the article, I would add that you use the self-timer, a highly stable floor, and not to extend the center column of the tripod. And take notes of each shot. Do not rely upon memory.

selmslie Loc: Fernandina Beach, FL, USA

That's not a small focus error, maybe a couple of inches. The problem may not be the lens or the camera. I suspect that it is actually focusing elsewhere in the frame or that the camera to subject distance changes after focus is locked.

To test this, aim at something flat perpendicular to the lens axis (like a photo on the wall) with the camera on a tripod at about the distance you use for portraits. Set the camera on aperture priority, let auto-focus work and take a picture. Now turn auto-focus off and take a few frames after manually changing the focus slightly in and out or changing the camera to subject distance slightly.

If the first image is in better focus then the problem is one of the causes I mentioned above. You may want to avoid auto-focus for portraits.

Otherwise, you may have a legitimate focus error and the solution is more complicated.

Onquest Loc: Just Wandering

Selmsie, you make a good point and I'm wondering if perhaps this is the case. I will take some time over the weekend to experiment with the camera and all my lenses. If I can narrow it down to just the Tamron then I'll have something concrete to go on. It is the lens I use the most, but perhaps the others are showing the same problem and just haven't noticed.

Thanks for everyone's input.

Onquest Loc: Just Wandering

Ok, I've done the test with my camera and various lenses. Anyone care to comment on the results?

'Control' live view focus


Tamron 28-75


Nikon 70-300

jerryc41 Loc: Catskill Mts of NY

Here is some more focusing info.

Focusing Charts
http://mansurovs.com/how-to-quickly-test-your-dslr-for-autofocus-issues
http://mansurovs.com/wp-content/uploads/2012/07/Siemens-Star-Focus-Chart.pdf
http://mansurovs.com/wp-content/uploads/2012/07/Focus-Test-Chart.pdf
http://regex.info/blog/photo-tech/focus-chart

http://mansurovs.com/how-to-quickly-test-your-dslr-for-autofocus-issues
The author says you should use Live View, but that’s not essential. Just focus as sharply as you can.

selmslie Loc: Fernandina Beach, FL, USA

It does not look like there is a problem with your auto-focus or your lenses.

I would refer you back to my original response. The problem may simply be the process of taking the pictures.

Onquest Loc: Just Wandering

Yes, that's the next on the agenda ;)

Onquest Loc: Just Wandering

Thanks for this, Jerry. I followed your previous link to the letter and it seems as though the lenses are ok. I ran them all through the test then threw one of the lenses on my other camera and tested it, too, although that camera doesn't have live view. Still good.