Monday, April 15, 2013

Microadjustment for Dummies

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?!
Shooting 201: Focushunting - head shot


Shoni said...

Wow! This is totally over my head at the moment...but I'll be looking into this. I'm intrigued! Thanks for sharing.

Cute blog by the way.

Cary said...

Very cool, thanks for sharing!

Alicia Schmidt said...

There is something on the 5D Mark II that allow you to do that. I have had to do this process with every lens it seems. I had NO focus issues with my Nikon, but I love the creaminess I get with Canon. Very adorable blog:) How do you like the 1.4 btw? I was thinking that was going to be my next lens.

Erica said...

Alicia, I haven't been too thrilled with the lens, but I really think that it's mostly because of it back focusing. I just did the micro adjustment of Saturday, and I've been very happy with the pics I've gotten since then. I love this focal length on a FF camera, and the bokeh is just lovely. It really is a huge improvement over the nifty fifty. I think we're going to have a very happy life together!

Rebecca Spencer said...

This is perfect timing as I know I have some problems with my 50mm lens, thank you so much for the article and the link to the PDF.

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