Newbie here. Be gentle.
Question. I bought that SL3 and love the camera, but one thing I wanted to do was record whisky review videos on products in 4K but find that the 4k on setting "M" is so zoomed in that it doesn't get that wide frame needed to get my torso, cabinet in the background and height...more or less dimensions needed for it to look normal. I have changed the settings from 4k to 1080p and everything is where I like it.
Now here's the question - again, "be gentle". Would buying a wide angle lens allow me to record in 4k such as the Canon EF-S 24mm F2.9 STM Lens? Also, I'm also only able to connect my Mic / Yeti to a 1080p setting and 4k doesn't allow this. I have no idea how a wide lens would alternate the view or allow the mic option. Any advice is appreciated. Thanks in advance!
Consumer (and some professional) DSLR-based video will only use part of the sensor when filming in 4K (i.e. crop the image). As you've found, the only way to compensate for this with the SL3 is to use a wider-angle lens.
The ability to use an external microphone should work for both HD and 4K. So not sure why it's not working when filiming in 4K.
Adding to Ricky's post. 4k video shoots in crop on the SL3 regardless of the lens used. While the FOV can be increased marginally with a wide angle lens, shooting in 1080 is the only way the entire sensor will be used. I suggest you test the pancake lens before buying to ensure it will meet your needs in 4K.
When you bought the SL3 did you not get the kit lens with it? It is 18-55mm so you should be able to see whether a more WA lens will help. I would not recommend the Canon EF-S 24mm F2.9 STM Lens. I have never liked it. A better solution might be one of the Rokinon cine lenses. Perhaps the Rokinon 24mm T1.5 CINE WIDE ANGLE. Another might be the designed for the SL3 type camera, the Rokinon 10mm T3.1 ULTRA WIDE ANGLE.
You would just have to experiment and try.