Full-frame/APS-C Lens equivalence? Locked

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brettgoulder New Member • Posts: 9
Full-frame/APS-C Lens equivalence?


I know full-frame vs APS-C topics are done-to-death on this forum, but I was hoping someone could clarify my thinking. I am currently comparing a Fujifilm X-H2S and a Sony A7IV and had questions about how to compare lenses.

One thing that gets brought up quite a bit on this forum is that full-frame lenses are more costly and bigger than APS-C. However, my understanding is that the DOF difference between an APS-C lens and a full-frame lens is one stop. Also, the noise performance for full-frame is a 1-1.5 stops better than APS-C. Is it not more appropriate to compare an APS-C f/2.8 lens to a full-frame f/4 lens?

So in this case, these two would be roughly equivalent:
- Fujinon 16-55mm f/2.8 ($1099), 655g, 83.3 x 106 mm
- Sony 20-70mm f/4 ($1099), 488g, 78.7 x 99 mm

Rather than comparing the Fuji lens to $2200 Sony's 24-70 GM II. In this case, the Sony lens actually is smaller, same price, and beats the Fuji on the wide-end.

Since the noise performance is better by 1-1.5 stops on the full frame sensor, then I can just bump the ISO by a stop to get the same image quality.
Is my thinking flawed somehow? If someone could clarify this for me, I would appreciate it.

Sony FE 24-70mm F2.8 GM II
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