How to Pick a Portrait Lens - Experiment

There have been a few discussions about selecting various primes or zooms for portraits and I've noticed that some of the details of focal length, DOF and background blur are not always well understood. I shot a quick demonstration in my backyard that I thought might be helpful to people looking to shoot portraits.

My first two example shots are to show the benefit of the very fast prime lenses for people looking to take loosely composed full length portraits. In this shot, I used the 50L at f/1.2 and then at f/2.8.

As you can see, the huge f/1.2 maximum aperure of this lens is useful in creating a nicely blurred background. And since the subject is completely in focus, he seems to 'pop' out from the blur.

The second shot at f/2.8 shows the best a zoom could do for this same shot, and for this type of picture I think most people would prefer the faster prime. My conclusion: For loose portraits, fast primes are good, and since the shot will be loose, shorter focal lengths (35L to 50L) are easier to work with than longer lengths.

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But where I see fast apertures start to become a bit, well, abused is when people look to shoot tighter portraits. Here I've moved a lot closer with the 50L and again shot at f/1.2. The background is nice and diffuse to be sure, but now the subject is also partially out of focus. To me, I think this real thin DOF loses a lot because the blurry subject no longer 'pops' from the background.

So check out the second shot. I moved the camera back 4X and used a 200mm lens at f/2.8. Despite the much slower f/2.8 aperture, this shot still makes for a very diffuse background thanks to the longer focal length. And now the DOF on the subject is deeper and the 'pop' is back.

Conclusion: Your are better off looking for longer focal lengths when shooting tight portraits. And as much as the super fast aperture of primes like the 35L, 50L and 85L can blur out a background, a longer lens can do the same despite being much slower. I hope these quick example shots are helpful to people in understanding how these lenses may work for them.

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Thanks for the information!

Oh, and great modeling too. ;]

Nice writeup and comparison shots. However I think you could have shown 135 or 200mm with the f2.8 zoom for the full body portrait. The same priciples would apply as for the tight portrait. You'd be farther away, the background would compress more making it appear more blurred, and you'd have more DOF. I would rather use my zoom at 85-100mm f2.8 (on 1.6x) for a full body portrait than my 30mm f1.4 given the room. More blur and more DOF.

This is great information. Because I'm the "camera guy" in the family I get asked to portraits at family get-togethers and I always dread it because I don't know enough about it and how to get the right look for a given type of shot.

tkbslc wrote in post #12968433
Nice writeup and comparison shots. However I think you could have shown 135 or 200mm with the f2.8 zoom for the full body portrait. The same priciples would apply as for the tight portrait. You'd be farther away, the background would compress more making it appear more blurred, and you'd have more DOF. I would rather use my zoom at 85-100mm f2.8 (on 1.6x) for a full body portrait than my 30mm f1.4 given the room. More blur and more DOF.

True, but I'd have run into the common problem of long focal lengths and loose portraits. Specifically, I would have had to set the tripod in my neighbor's yard.

I don't have the space to shoot the loose portraits shown here with a 200mm lens, but I do understand what you are saying.

I have owned the 35L as well as the 85L in the past. I find the 35L is just a touch short for me a lot of the time, and the 85L, while a cracking lens, is too long for the type of framing that I'm willing to use at f/1.2. 50L is about right for me.

Yeah, that's why I said "given the space".

I do often end up at 30mm f1.4-2 for full body for that reason. But if I am out in an open space, I always grab the longer lens and use f2.8-4 instead of a short one with hard to manage DOF at f1.4.

I don't have any perfect side by side tests, but this shows full body at 85mm f2.8:

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I couldn't agree more. I have both and REALLY prefer the 70-200 at 2.8 over the 50L for portraits. That second post you put up there really does a nice job of proving the point. I use the 50 mostly for indoor sports where I'm not allowed to use flash and really need the fast glass because of the poor lighting.

How about a comparison of 50mm 1.4 vs. 1.2 where the difference in cost can be around $1,000.

Also, comparison of 1.4 vs. Zoom 2.8 (24-70?)....

So, for people who are cost conscious in picking a portrait lens.

I also carry a DOF calculator app with me on my smartphone phone because as you point out, how physically close you are to your subject really makes a huge difference as well. The 50 is fine as long as you are further away but I generally prefer to shoot in closer most of the time.

rxjohn wrote in post #12968503
How about a comparison of 50mm 1.4 vs. 1.2 where the difference in cost can be around $1,000.

Also, comparison of 1.4 vs. Zoom 2.8 (24-70?)....

So, for people who are cost conscious in picking a portrait lens.

Why the 50mm is more expensive

1) L series
2) F/1.2
3) Ring USM
4) Build quality and better optics
5) Chick magnet...lol

rxjohn wrote in post #12968503
How about a comparison of 50mm 1.4 vs. 1.2 where the difference in cost can be around $1,000.

Also, comparison of 1.4 vs. Zoom 2.8 (24-70?)....

So, for people who are cost conscious in picking a portrait lens.

The point of this thread was strictly to look at focal length and maximum aperture, not so much the details of specific lenses. From the standpoint of this discussion, the 50/1.4 and 50/1.2 are practically the same.

My points (I think, now that I'm mulling it over from tkbslc's comments):

1) When it comes to blurring backgrounds and generating subject separation, longer focal lengths are more important than fast apertures because they give greater DOF for the same amount of background blur. For a tight portrait, the EF 200/2.8L is a better lens than the EF 85/1.2L

2) The time and place for really large apertures is when the subject framing is loose. Then you need a fast aperture to blur the background, and the DOF is adequate even with a huge aperture. Given the difficulty of working with long focal lengths and loose framing (you are standing waaaay back), this functionally means that very fast lenses are probably more useful around the short telephoto range than longer.

So if I were going to pick two lenses for portraits (say, one prime and one zoom) I'd rather have the speed on the short end (35mm or 50mm prime) and the slower zoom for the long end (70-200 or similar). I would not prefer a slower zoom like the 24-70 with a long fast prime (85L or 135L) as I need the speed less on the long end.

rxjohn wrote in post #12968503
So, for people who are cost conscious in picking a portrait lens.

If you are on a real budget, a basic telephoto makes a pretty respectable portrait lens. No need to rush out and buy a fast prime on day 1.

Here's from the 55-250 (just snaps, but you get the idea):

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Jeffrey, I agree that too small an f-stop in tight portraits doesn't separate the subject enough from the background. Obviously, the light and clothing/background colors make a big difference as well, but I prefer the entire head being in focus for shots like those.

You mention that in tight shots, slow lenses can accomplish this as well. But it should be understood that f/2.8 on a zoom (max aperture) is not the same as f/2.8 on a prime.

awesome info. this really helps out