The Fast-Fifty dillema

A lot of people own the 50mm f/1.8 lens. It is dirt-cheap, delivers good quality for its price (optically). Build quality… Well it has the nickname “plastic fantastic” for a reason. I hear a lot of people wanting to upgrade to a 50mm f/1.4, but very often for the wrong reason. In this blog post I’ll describe the why and how to this.

“I need a faster 50mm”

I hear this all the time. People have a Canon EF 50mm f/1.8, and are looking to upgrade to a 50mm f/1.4 all for the wrong reasons. Do not be fooled by wide a faster 50mm lens just because it is faster; people mostly shoot portraits using a 50mm lens on a cropped camera (beware: for a full frame camera, use at least 85mm!).

Cheap to expensive: Canon 50mm f/1.8, Canon 50mm f/1.4, Sigma 50mm f/1.4, Canon 50mm f/1.2 L


For portraits consider this situation on a cropped body:

Distance [m]	Aperture	Depth Of Field [cm]
1,5	f/1.2	2
1,5	f/1.4	2
1,5	f/1.8	3
1,5	f/2.2	3
1,5	f/2.5	4
1,5	f/2.8	4
2,0	f/1.2	7
2,0	f/1.4	8
2,0	f/1.8	11
2,0	f/2.2	13
2,0	f/2.5	15
2,0	f/2.8	17

Table 1: Depth of Field (DOF) in centimeters for a 50mm lens on a cropped body


As you can see, shooting a 50mm at portrait distance at f/1.4 will give you a DOF so shallow, it is almost unusable (one eye sharp, other one not and tip of nose also out of focus before you know it). For a decent portrait you’d need a DOF around 10-15cm, which would put you at the 2 meter distance, 50mm at a setting of f/2.5 or f/2.8.

As you can see, a lens faster than f/1.8 is hardly worthwhile in this respect, unless you want to shoot at a really shallow DOF.


Shooting “wide open”

A lot of people tend to shoot their 50mm f/1.8 wide open. For a shallow DOF, of just because there is so little light. This is all good, but remember the DOF you get.

There is another problem with shooting some 50mm lenses wide open: Optical quality is often hardly acceptable when shooting the lens wide open. This goes especially for the Canon 50mm f/1.8 and Canon 50mm f/1.4 lenses. If you really want some optical performance, you need to stop these lenses down to at least f/2.0 or f/2.2.

If you require a 50mm lens that performs well wide open, you could consider the Canon 50mm f/1.2 L (which is around 1300 euros so not really cheap), or the Sigma 50mm f/1.4. The Sigma produces pretty good results, even when shot at f/1.4 .


So why WOULD you upgrade your dear Canon 50mm f/1.8 ?

Of course there are many valid reasons to upgrade your Canon 50mm f1.8 lens:

1. Build quality. The “plastic fantastic” has poor build quality (forgiven though for its price!);
2. AF-motor. The 50mm f/1.8 features an old micromotor AF drive. Noisy, slow, often inaccurate;
3. Focusing manually is a pain, given the very obscure focus ring on the lens. No full-time manual focusing too;
4. Front or back focus. My copy of the 50mm f/1.8 has severe front focus. Luckily my 7D can adjust for this, but if you have a camera that cannot it might be a reason to upgrade the lens;
5. Bokeh. This is one of the prime reasons to upgrade (for me). The 50mm f/1.8 has just 5 aperture blades, and bokeh is not the greatest;

Do not get met wrong; the 50mm f/1.8 is a GREAT lens. I hear people say “everyone should have one in their kit”. Still you can gain a lot by upgrading to another 50mm. Just make sure you upgrade for the right reasons!