A couple of months ago I bought a used Canon 50mm f/1.4 off of Craigslist. I was so excited to get it. I really wanted to love it, but I just didn't. Why, you ask? Because all of my pictures were just a tiny bit out of focus. I admit it, I'm an obsessive pixel peeper. I thrive on clearly defined eyelashes, and when I looked at pictures from this lens I was routinely seeing fuzzy eyes.
There was a silver lining though. Right between those fuzzy eyes was a perfectly crisp, clear, and focused nose! This was great news because it meant that the lens was not broken, or soft. It was just back focusing. I knew that one of the benefits of my lovely new camera body is that it can microadjust lenses, and correct this exact problem. Hooray! Except I had absolutely no idea how to do it, and was even a little scared to try. I shouldn't have been. It was actually a very easy process, and more importantly it's an easy process to undo or redo, so there's no reason to be afraid of messing up a lens.
The first thing I did was break out my camera manual. It actually gave very clear and easy instructions for how to set the adjustment (page 104 if you're curious). It was really just a matter of pressing a few buttons. My camera can store one adjustment across the board, or a specific adjustment for each lens (and for zooms, a separate adjustment for each end of the range!). Excellent!
The next step was figuring out what adjustments needed to be made. Enter google. There are actually a variety of tools and software options that you can purchase to automate this process. But I'm cheap. And lazy. And impatient. So I wanted something that I could do NOW! That's when I found the ghettoCAL DIY Lens Calibration Tool It's a great page that offers a printable PDF to make your own calibration target!
I didn't have some of the supplies that David used to make his target, so I improvised a bit. I used a scrapbooking paper cutter to knock out my pieces, and I mounted them to a manila file folder instead of foam core. I had to add a few extra support pieces to attach the ruler, but other than that it worked like a charm. I even broke out my level and protractor to make sure that all of my angles were right!
After that it was just a matter of setting my camera up on a tripod, and taking some pictures with different micro adjustment values applied. Everything that I read said that nailing exposure was important for proper micro adjustment. The aperture needs to be wide open, so that setting was easy. I knew I wanted a fast shutter speed to eliminate the possibility of motion blur impacting my results, and a low ISO so that noise wouldn't make it more difficult to clearly see my depth of field. In order to meet all of those needs, I decided to shoot outside so that I would have plenty of light. I also used a remote trigger to avoid any chance of camera shake.
For each lens I took a series of pictures at -20, -15,-10,-5, 0, 5, 10, 15 and 20. Then I loaded the images onto my computer and zoomed in to see how the plane of focus shifted. It was actually easier than I was expecting to see the change. Once I found the best setting, I went back and took another shot to see if I needed to refine, and then I took a picture of some actual subjects to make sure that I was happy with the results. In the end I adjusted my 50mm to +5, my 100mm to +3, and I learned that my 85mm was spot on.
The whole process took about 90 minutes, including the time to make the target. Once I got into a groove it went very quickly. I'm so happy that I did it. I can see a noticeable difference in the 50, and I'm hopeful that this will make me love it like I know I should! I'm planning on repeating the process for the rest of my lenses later this week.
What's up eyelashes?!