50mm and more, a closer look at 50mm lenses
Monday, May 25, 2009 at 12:17AM What's so great about 50mm lenses? They are kinda puny with a small filter size (not like the 77mm filter size on some other lenses I have shot with), they are mostly made of what feels like cheap plastic, and you can get one for under $150. That can't be a good lens, right? Wrong. It is a fantastic lens and a blessing in disguise for us shooting with a non-full frame DSLR.
↓ 50mms
Disclaimer: I am using two Nikon 50mm lenses for this post. This does not mean that: 1) I am strictly a Nikon fanboy (I use to shoot Canon. In fact my first DSLR was the original Canon Rebel); 2) the findings only apply to Nikon. I would say that pretty much all the findings here are directly applicable to the equivalent Canon lenses.
So why is this 'cheapo' lens a godsend? Well, because on a DSLR with an APS-C sized sensor (which the majority of DSLRs have) the 50mm acts like a 75mm lens. And that's the butter-zone for portraits.
Here is why your 50mm lens effectively becomes a classic portrait lens.
Looking at the picture above, the full square is what a 50mm lens sees (technically it should be a circle, but just work with me here). The white outline is what will be projected from the 50mm lens onto a full size (36x24mm) image sensor. The inner, black line is what will be projected onto a smaller APS-C (23x15mm) sized sensor. Less of what the 50mm lens actually 'sees' gets projected onto the smaller sized sensor, simply because it is smaller. That makes sense, right?
To find the new, effective focal length of your lens you multiply the original focal length printed on the lens (50mm) by 1.5 ending up with a 75mm lens. (In parenthesis noted, you have to multiply a Canon lens by 1.6 due to their APS-C sized sensor being a hair smaller. A 50mm lens then effectively becomes a 80mm. But you already figured that out, I am sure). What is so great about this 75-85mm focal length is that it allows you to be a natural distance (1-1.5 m) from your subject and still get nicely tight-framed head and shoulders (no, not the shampoo) portraits.
Some of these shots above were grabbed with a 17-55mm lens, which in terms of focal length essentially is identical to the typical 18-55mm kit lens that most DSLRs come with. 55mm times 1.5/1.6 still puts you in the portrait butter zone (75-85mm), so next time you take portraits of your kids, husband or dog, try to zoom all the way out on your 18-55mm lens and see the difference yourself.
I see two types of 50mm lenses, a f1.8 and f1.4 aperture. Which one should I get? Good question. The obvious differences are that the f1.4 is half a stop faster (allows a bit more light to travel through the lens), has a better build quality and is 3-4 times the price tag compared to the f1.8 version. But honestly, image quality wise the less expensive f1.8 version is 93% (I couldn't decide whether it was 90% or 95%, so in all fairness I averaged it out and rounded up) of what the more expensive f1.4 lens is.
↓ Showing just how little depth of field f1.8 is. Taken with the Nikon 50mm f1.8.
↑ All taken @ f2 with Nikkor 50mm f1.8 lens.
↑ Mr. Monkey kindly let me take his picture with the 50mm f1.8 @ f1.8 (left), f2 (center) and f2.8 (right). Notice how the picture gets slightly sharper from left to right, and the background gets less 'creamy'/'smooth'. This is the lens' bokeh.
A 50mm f1.4/f1.8 lens is really one of those lenses with almost no downside. If you opt for the f1.8 (which is 93% of the f1.4) you get a relatively inexpensive lens that will boost your portrait work, secondly enable you to take better pictures indoor, and thirdly allows you to get aperture-creative (read my write up on why aperture matters). Minor downsides count a bit of chromatic aberration (purple/green fringing on highlight edges) and maybe not razor-sharp @ widest opening.
Got a question on which lens to get, how to take certain types of pictures or just photography in general? Post a comment below.
For the technically interested: Nikon D300 with Nikkor 50mm f1.8 D, Nikkor 50mm f1.4 AfS G and Nikkor 17-55mm f2.8 AfS DX lenses. Some shots are with available light only, and others (the portrait work and museum shots) are grabbed using the Nikon SB900 flash, either bounced off the ceiling or with softbox mounted. The test shots of the 50mm f1.8 lens started to impress me @ f2, just half a stop above the maximum aperture.
Reader Comments (2)
One other great advantage of the f1.8 is that it has so little distortion. It's a great lens when you have to photograph rectilinear objects: artwork, architecture and the like. Very straight lines all across the image.
I love my f1.8 50mm.
@ Dual: good point. Thanks for the insight.
Klaus