Toronto Photography Meetup Group

Hi all,

I just got a D700 and I'm seeking your advice on autofocus.
I'm trying to determine if my new camera and new lens (24-70 f2.8 ) suffers from any autofocus issues. I have noticed that in my images it appears that there is some back or front focusing though I'm not sure if this was simply due to user error.

The reason why this is so important to me is because I'm starting to get into wedding photography and I would like to be able to rely on my gear.

I tried downloading the Jeffrey Friedl autofocus test chart.http://regex.info/blog/photo-tech/focus-chart#prepare and there appears to be front focusing issues.

Assuming that this is correct I attempted to use the AF Fine Tune option. I cranked it up by +20 and -20 but neither seemed to have any appreciable differences after I tried the test again. I'm not sure what I'm doing wrong. Ie the fine tuning or using the test chart.

Does anyone have any experience in adjusting the autofocus themselves and if so what tools do you use?
Has anyone tried the http://www.the-digital-picture.com/Reviews/Datacolor-SpyderLensCal-Review.aspx?

Or do you just send your camera and lens into the manufacturer for testing and fixing?

Thanks!

Zeekid

Try this one: http://focustestchart.com/chart.html

At least it has a target to aim the autofocus at.

Or if you want something serious, then: http://neilvn.com/tangents/2009/05/06/review-lensalign/

Your focusing issue most likely arises from the lens. After a period of usage, lens might need calibration. I got a Nikon 35mm f/1.8G a year ago and it started back-focusing on me so I had to send it back to Nikon Service. You definitely need to get it checked and calibrated if you plan on shooting wedding. I had a 50mm f/1.4D (got it used without warranty) that back-focused on me on a wedding shoot. On the small LCD camera screen, it wasn't that noticeable, but once I got home I realized good half of my shots were back-focused and that had ruined lots of my good shots. After fiddling with AF fine tune to -14 finally got my 50mm f/1.4D to work normally.
It would be a lot harder to detect focusing issue with f/2.8 ap, but if you do see focus issue it's best you send it in for calibration. You got it new so it should still be covered by warranty.

The first one looks like the Jeffrey Friedl test that I'm using.

Thanks for the reply.
I tested my 50mm f1.4D which I've had for a few years and it also appears to have front focusing issues when I'm shooting at 1.4 and at a more shallow angle when shooting on the test paper.

I'm not sure what I'm doing but the AF Fine Tune doesn't seem to do anything. I've set the default value to +20 and -20 and the differences is very minimal and hasn't corrected my focus issue. This is why I'm hesitant to get a more "serious" test chart. There's not much point in getting a serious test chart if I can't fine tune the autofocus myself

Although the lens was new it was actually purchased in China so I don't have a Canadian warranty

But the wedge gives you a clear target plane to focus on - conceptually closer to the Lensalign than aiming at a piece of paper on the floor. I still have one assembled at home somewhere.

I always thought I had autofocus problems too. But doing a little more research led me to discover the difference between phase detect focusing (viewfinder) vs contrast detect focusing (Live Viewer). Though I don't understand all the technical aspects quite yet, something to do with phase detect being an older way of focusing, (The ever increasing megapixels in cameras makes capturing sharper images harder than before....) ... each have their respective strenghts.... For still life, the live viewer can capture sharp images easier.

Anyways... I'm no guru... just a rookie trying to share some stuff i found between the 2 focusing systems so you can avoid the frustration i went through.

Send it in! Nikon service center is very easy to deal with and they will tell you what's wrong and fix it. It's part of your expenses that you can write off anyway.

The AF adjust feature is a very fine adjustment to help match a lens to a camera body when they are both built within tolerance. From what you wrote, it appears that you have tried only 2 settings: +20 and -20. If that is the case, you are overcompensating to the 2 extremes. To start, you should take photos at single increments and compare them to find the sharpest setting. If none of the settings are in focus, then either the camera or the lens is not built within tolerance and would need servicing.