Lens dilema

[terryuk]

I have just got myself a 650d with the 18-135mm stm lens and looking to get an additional lens for low light
Now should I try the canon 40mm f/2.8 STM or the good old 50mm f/1.8
Other option would be to get a used tamron 17-50 f/2.8
Would the tamron be as good as the 40mm pancake at 40mm

 

[woof woof]

Would the tamron be as good as the 40mm pancake at 40mm

Dunno.

I have had a Tamron 17-50mm f2.8 non VC and it was a very sharp lens with just a little distortion at the wide end.

Personally I don't like non macro f2.8 primes unless they have something else going for them apart from the f2.8 spec (like being very compact or very cheap) as you can get zooms that are f2.8, like the Tamron.

In your position, looking for a low light lens, I'd go for a f1.4/1.8 prime at something between 20 and 50mm. There's a few to choose from in that range.

 

[ernesto]

Agree. If specifically for low light then aim for lower than 2.8 as difference between 2.8 and 1.4 is pretty significant.