The Photography Tip of the Week #075

Posted by Philip in Photo Philosophy, Photo Technique, Podcast

That’s a Sweet Brick Wall

075 Photography Tip of the Week (audio)

There are many things in life that have a sweet spot and photography is no exception.  For this tip I’m interested in the sweet spot of your lens, specifically which aperture is the sharpest all around. It’s a very simple test and only requires a few minutes with each lens you want to test.  I call this the brick wall test.  You don’t have to use a brick wall, as long as you use something that has lots of detail.  Some people will put a newspaper on the wall, but I prefer to do this outside and newspaper blows around very easily.  So here’s my setup:

1. Use a tripod about 10 feet or 3 meters away from the wall, because you want all of your images to be almost exactly the same.
2. Set ISO to 100 or 200 and shoot during a sunny day.
3. Aperture priority mode.  Shutter speed doesn’t affect your sweet spot.  You will start with either your largest or smallest aperture and photograph the exact same image on each aperture setting.
4. Autofocus.  It shouldn’t matter how the focus is set since you aren’t moving the camera, but if you must set it, just center focus will be fine.
5. Using a cable release would be nice, but not overly necessary.

Once you’ve made all your images, load them up in a program where you can look at the centers of each image at 100%.  This becomes a value judgment on your part.  Cycle through the images until you determine which one is the sharpest.  Since you have locked down most all the variables and the only variation is the aperture you should be able to determine which f-stop is the sweet spot.

Here’s the images of various apertures side by side from my test.  As you can see they could all be the same image.  There is very little difference in coloring and overall look.  You can be fairly certain that the only measurable difference now is just the aperture.

Now let’s look at a section of the images at 100%.  You can see that f8.0 is noticeably sharper than either f4.5 or f22.  I’ve scrutinized over all my aperture settings for this lens and know that f8.0 is the sharpest or the sweet spot.

With this knowledge you now know that if you want to get sharper images, you will want to get that aperture as close to your sweet spot as possible and adjust your other settings to match.

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