You asked
Is the sony fe 100mm f 2 8 stf gm oss worth it?
Here is what the site says about that.
From Sony FE 100mm f/2.8 STF GM OSS: Sony FE 100mm f/2.8 STF GM OSS: A prime lens by Sony for Full frame cameras, 100mm f/2.8. Its apodization filter makes very smooth out-of-focus backgrounds, at the cost of light (T5.6). Specs - Maker: Sony - Focal length: 100mm (prime) - Maximum aperture: f/2.8 - Made for: Full frame sensors - Mounts: Sony E - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Sony E): as marked, 100mm. - On APS-C ...
From Sensor sizes: Is full frame worth it?: For low light, events, and portraits with very shallow depth of field, yes. For travel, street, wildlife on a budget, and most hobby photography, a good APS-C camera with good lenses is enough, and you'll carry it more. Lenses and light matter more than the last stop of sensor performance.
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