Photo Envy

Why don’t my photos look as good as the ones shot on the Leica Q?

Here’s what happens:

  1. I see a photo that I really like, which was shot with Leica Q (with full frame sensor and Summilux 28mm lens) at f/2.
  2. I’d like to make a photo like that on my Fujifilm X-T4. The “equivalent” lens in my bag is the XF18mmF2 R. I choose that and shoot.
  3. My photo sucks.

Well.... It doesn’t necessarily suck, but it lacks the depth that the one taken with the Leica has. Why?

Light?

My lens at f/2 is just as “fast” as the Q’s Summilux at f/2, isn’t it?

Yes, but that isn’t the problem.

Depth of Field, My Old Friend

Here’s the formula for approximating depth of field:

If aperture and circle of confusion are kept (more or less) constant, then we can see that to shorten the depth of field we must either reduce the subject distance or choose a longer focal length.

This is super important because despite being “equivalent” lenses, 18 is not and can never be equal to 28. The two lenses simply have different physical properties. Moreover, because 18 is (and always will be) less than 28 the depth of field of the 18mm lens will always be greater than that of the 28mm lens.

Consulting a depth of field calculator bears this out. If the photo I admired was taken of a subject 10 feet away, then the depth of field is 4.88 feet. For my 18mm crop sensor combination, that figure nearly doubles to 8.7 feet for the same scene. No wonder I can’t get the same look and feel!

Workarounds?

Swapping the 18mm lens for a 28mm does make a difference, but the need to back up (increase the subject distance) created by the cropped sensor negates any change in depth of field.

Increasing the aperture to f/1.2 or so would work, but that lens doesn’t exist (as far as I know). The $1,000 XF 18mm f/1.4 lens comes close but still falls short, and it’s gigantic, weighing in at 370 grams.

So now I guess I have mathematical justification for buying a camera with a full-frame sensor. 😆