How To Fine-Tune your Lenses using the Green Dot Method
Roger Rowlett (RRowlett)
Keywords: af, focus, lenses, fine, tune, green, dot, rrowlett
Some Nikon DLSR bodies will allow you to store fine-tune autofocus corrections for individual lenses in the camera body. For example, my Nikon D7100 will remember up to 9 different lenses and their fine-tuning correction.
To be perfectly honest, it is highly unlikely that you will need to fine-tune any of your Nikkor lenses. It has been my experience that my Nikon lenses and cameras have performed well right out of the box. However, you may find you can slightly optimize your lenses’ autofocus under specific shooting conditions or when using the lens with a teleconverter. Or you may just be intellectually curious and want to fine-tune anyway.
Autofocus fine-tuning does no harm, and can be reversed at any time. It is relatively easy to search for and find videos that describe the fine-tuning process, but these are not always entirely accurate or clear. The following instructions are appropriate for a D7100, and should be very similar for other Nikon cameras with this feature.
1. Print out a focus target on letter-size paper. There are lots of these on Google. I used one of the Bob Atkins charts. Any high-contrast focus chart will do.
2. Tape the chart to a well-lit wall. The chart must be flat and vertical!
3. Set up your camera on a tripod at a distance that is about 50X the focal length of the lens. If the letter-size chart fills about 1/3 the width of the image, you are at an appropriate distance. Make sure the camera is perfectly level. I used a hot-shoe level to do this.
View of camera with bubble level
Click for an enlargement
View from behind
Click for an enlargement
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7 comments
Scott McManis (dsm61) on August 15, 2016
I have a question. Darrel Young writes that Nikon cameras all focus using the widest aperture in the lens. Accepting that that is correct, how does stopping down the lens (Step 6) have any impact on the procedure you have outlined? Thanks.
Charles Edwards (Reason4334) on June 16, 2016
I just tried it this evening and it worked well. The interesting part is that my prime lenses, with the exception of my 50 mm f/1.8 G, were off, but no more than 7 points. The 50 mm was right on the money. Most were within 1 to 3 points. My slow clumsy kit lenses, that I don't like to use, were right on the money. Thanks for taking the time to right the article!
Raymond Domzalski (RayTD) on June 6, 2016
Am going to have to try out this method of fine-tuning, seems very well-explained! Thanks for the concise article.
Mark Lineham (beanprocessed) on May 18, 2016
Great article, well done.
Jeffrey Gilbert (HDJeff) on May 17, 2016
This is the first article on AF fine tuning that really provides a practical methodology that is easy to follow. Great job Roger!
Bo Stahlbrandt (bgs) on May 11, 2016
Very good article, thanks for this information!
Larry S (larsch01) on May 9, 2016
Roger, that's the best explanation and walk-through of the dot-tune method that I have seen. I even understand it :) Thanks, Larry