5D Mk IV – EF100mm Macro – MT-24 EX Macro Twin Light – 1/125, f/2.8, ISO 100

Today was nothing more than a demonstration in depth of field – I mean really razor thin depth of field! I initially put on the 100mm Macro lens and the Macro Twin Light flash and went outside in search of a macro target. Even though it was 58 degrees, it was still wet and windy so I wasn’t successful in finding something tiny outside that would make a good model – i.e., a bug. I practiced on a leaf, and focusing from about 3 inches away was very difficult because any tiny bit of vertical (up and down) movement (think breathing) threw the focus off. I needed a tripod.

That gave me the idea for this shoot. I went inside and grabbed my keys, and set the camera on the tripod with the flash still attached. I set a key so the left side was ever so slightly lower than the right side. Again, I was about 3 inches away and was focusing through my computer using the LiveView function. I set up the aperture so it was wide open at f/2.8 and I focused on the right side of the letter ‘R’ on the key. You can see how razor thin the depth of field is at these very close distances – note the left side of the ‘R’ is starting to get out of focus, and the ‘D’ is very out of focus.

For reference, I took a pic with the aperture set to f/32. This is better in terms of depth of field, but you can still see the focus is starting go soft around the ‘D’. In contrast, if you were taking a landscape photo using f/32, depending on the distance to the target, the depth of field could be in the hundreds or thousands of feet, maybe more.