Another lens question thread

Hi all. New here. Been a lurker on FM for several months, and recently joined here. I'll hop right in and ask my question. Currently I shoot on a 5D Classic. I've just recently switched to full frame, and have enjoyed it thus far. I have two Sigma lenses that fit it that I don't use because, well they're not very sharp. I've got a 50mm 1.8 Canon, and a 70-200F4L. Since going to full frame, I've noticed that the 50mm 1.8 isn't all that great around the edges, and I hate how slow/loud it is. I would like to upgrade to the Sigma 50mm 1.4, but I also want to get an 85mm 1.8. My question is, do I live with the 50mm 1.8 for the time being and get the 85 now? Or go for the Sigma now since I shoot so much with the 50mm? Thanks for the help. I look forward to spending some time on here, and hopefully learning a lot.

Since you use it more, upgrade the 50mm first

Understand your 50 is going to be wider on the fullframe than it was on whatever crop you may have used before (speculating you had a crop camera).

Whether you go for the Sigi 50/1.4 or Canon 85/1.8 will have to be your choice depending on what you shoot and all that jazz.

Regardless, if you can afford it, I would dump the hockey puck (50/1.8) asap.
Either of the replacements above are going to be miles above it.

I very much like the focal length of the 50mm on full frame. I do a lot of low light shots that I think either the 50mm or the 85mm would work well in. I'm leaning toward the 50mm because my 70-200 covers the 85mm, and I haven't really had much need for the increased speed of the 85mm so far.

I may be wrong, but the 85 is going to be sharper than you 70-200 @ 85.
They'll still both be nice.

Sounds like you should go for the 50! It's built nice, you'll like it!

I would go for the 50mm because:
1. You like the 50mm FL and use it a lot, it make sense to upgrade that lens.

2. f/1.4 vs f/1.8 - You mentioned using it for low light. You'll be getting 2/3rds more light, not to mention you can hand hold a longer shutter speed with 50mm rather than 85mm.