40mm 2.8 or 50mm 2.8 ii?

In my situation what do you think?
I know the 50 is a good lens for what it is but I have a T4i and it's 1.6x 50 (I know the 40 is only 10mm difference but still there has been times with my lens that I'm at 50 and back out to like 40). So that's one plus for the 40mm also it's got a new STM motor and it would be nice to have at least 1 STM lens for my T4i (the 18-135 probably won't be a buy). I heard the build quality is better on the 40mm so that's another pro. I will in a few years go full frame so that's another pro for the 40mm (I heard 40 is the sweet spot, 30 is too wide- 50 is too long). I take pictures of my fish in aquariums and landscapes (not super wide ones but those styles). I like the idea since I have a T4i to at least have ONE STM lens in my collection and I like the fast auto focus it can provide for vlogging / home videos.


40MM 2.8 STM lens PROS
-STM motor
-Shorter distance for my crop frame
-Better build (maybe a better long term investment?)
-If I decide to ever buy a better prime like a L I will still have at least 1 STM lens for my T4i and any future cameras.

(I'm not going to list cons because I feel the cons are obvious and not really cons after all that's why there a good price)

50MM 1.8 II PROS
-Bigger (I like the size of the 50 series a lot)
-Proven lens (you know what your getting SOOO many people have reviewed this lens)
-1.8 (But 2.8 can't be that bad I mean the 70-200 doesn't have a 1.8 and look how many people love that lens/aperture)


The current lens I have is a 28-90 that broke and only shoots a F5.6 & higher so honestly haven never shot at 2.8 or 1.8 to begin with I don't even feel like those matter. I'm just looking quality and which is the better one to buy.

Specially in conjunction with T4, I say no doubt to go with 40mm STM.

samsen wrote in post #15812349
Specially in conjunction with T4, I say no doubt to go with 40mm STM.

This is what I'm thinking.. I still get a nice aperture and get to try out the STM. I plan to get a full frame later down the road and I would want a better prime then the 1.8 version (build q) anyways. I know the 40 isn't killer build quality but it has the benefit of being newer design and smaller and no plastic mount.

First off, this is probably the most common debate between lens out there.

The point of the 40mm is to be small (hence called the pancake) and have STM (for video). The point of the 50mm is to be very fast and cheap, but not small, and not for video. If your primary uses aren't video or to have a very small/light/thin DSLR, then the 1.8 is probably the better fit. Really though, they are both very cheap lens as far as DSLR lens go to the point you could buy both new and still be less than 250$. If the 40mm was an F/2 it would be an easy decision for the 40mm, but with it being a 2.8, you should probably give some serious consideration to the 50mm F/1.8 despite the lower build quality and older motor. If there was an easy answer to this question, it wouldn't be asked so often.

Ultimately the question is do you want a wider frame or a wider aperture?

vengence wrote in post #15812555
If there was an easy answer to this question, it wouldn't be asked so often.

The easy answer is to just get both.

Ceece911 wrote in post #15812687
The easy answer is to just get both.

this. They are both great lenses and dirt cheap I bought both and I'm into them for maybe $300 if that.

I had both; sold 50 f/1.8 due to markedly slower/less accurate AF; and i found 40mm a more useful perspective on 1.6 crop. Size was a bonus.

if you're shooting aquarium things, i think the faster aperture would be more beneficial...the STM could be good if you do a lot of video...personally I think getting a wide slow prime doesn't make much sense...you could grab a 17-50mm f2.8 tamron zoom, and use that instead

f2.8 is the fastest aperture for any canon zoom lens...but that doesn't mean that people don't want faster lenses...if the 70-200mm was offered in an f2 for a decent price...people would buy that over the f2.8

I got it because for the price I just leave it in my bag in case I need a f2.8 when I am using my 15-85 as a walk around.

It's small enough that I can just have it there all the time.

50/1.8 Mk I

DreDaze wrote in post #15813797
if you're shooting aquarium things, i think the faster aperture would be more beneficial...the STM could be good if you do a lot of video...personally I think getting a wide slow prime doesn't make much sense...you could grab a 17-50mm f2.8 tamron zoom, and use that instead

I tried the 50 f/1.8 once at an aquarium when I owned that lens, and found the experience very frustrating due to the poor AF performance of the lens. It would work for stationary objects with some patience, but anything moving was impossible to lock onto. I got much better results with the EFS 17-55 f/2.8 that I was also carrying, even though I had to crank up the ISO (I was using a 40D at that time, so higher ISO was a concern).

im impressed by the sharpness of the 40mm. if you don't need the f1.8 go with that instead, plus its a tad wider since you are on a crop.