Let's talk about subject / background separation

I guess the conventional wisdom is that a faster aperture in a photo always yields the greatest degree of 'pop' in separating a subject from a cluttered background.

For a while now in my own photography I've started to suspect this isn't always the case. I tried to put together a quick test this evening to see what I could figure out. This isn't a perfect test of every scenario, but here goes.

The test subject is me, standing before my cluttered den. I took five test shots at f/1.2, f/2, f/2.8, f/4 and f/5.6 to see how they would look. Take a look and I'll post my thoughts at the end.

First come f/1.2 and f/2:

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Then f/2.8 and f/4:

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Finally, f/5.6

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I guess to me the actual appearance of how I 'pop' from the background is parabolic. In the f/1.2 shot to start, my entire right side (on your left) is quite blurry. While the background is very diffuse, this blurred periphery of the subject seems to melt into it.

By the f/4.0 shot the periphery of the subject has sharpened up nicely, but now the background is starting to get too busy and cluttered. By f/5.6 the background is too busy for sure.

So I guess in my mind the best compromise in this range for this particular shot is about f/2.8. What do you all think? Does it seem like for various shots, the 'best' separation may often be at some middling aperture?

I'd never really thought of that, Jeffrey....that the out of focus part of the head would actually reduce the apparent separation from the background. Interesting.

Of course BG distance is critical in all this as well...a closer BG means you have to use a wider F stop to get your separation or the further parts of the head and the BG will be getting closer in sharpness.

Conversely with a more distant BG you can still get good separation with a smaller F stop...and here's where FL comes into it.

I will think seriously about the implications next time I'm making a portrait. Thanks for sharing.

With portraits, I tend to agree, f/2.8 can ensure you get the subject, especially the face, in proper focus and still get good separation. You can even get good results with f/4 if you have a decent distance from the background.

But sometimes f/1.2 can kick it, as long as you have the subject positioned to maximize the amount of the face that is reasonably within the depth of field. As your first shot shows, shooting head-on will fail at this -- you get the ugly "nose in focus but the rest of the face just turns to a blur" effect or the "nice sharp eye but everything else, including that blurry nose..." effect.

Here's one that I did as a test portrait at f/1.2 a few years ago:

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Jeffrey - for the particular examples you've posted, f/2-f/2.8 (even 2.8 is starting to get too busy for me, personally) seems to be the best compromise, with regard to separation. As you probably know, there is no magic formula... ideal aperture setting will vary with subject distance and background distance. For example, when I am doing traditional portraits, I will shoot around f/2 with my 85L, but will change it up depending on the specific situation.

tonylong wrote in post #11831102
With portraits, I tend to agree, f/2.8 can ensure you get the subject, especially the face, in proper focus and still get good separation. You can even get good results with f/4 if you have a decent distance from the background.

But sometimes f/1.2 can kick it, as long as you have the subject positioned to maximize the amount of the face that is reasonably within the depth of field. As your first shot shows, shooting head-on will fail at this -- you get the ugly "nose in focus but the rest of the face just turns to a blur" effect or the "nice sharp eye but everything else, including that blurry nose..." effect.

Here's one that I did as a test portrait at f/1.2 a few years ago:

A little soft in spots but still shows how a "profile" can take a lot wider aperture.

Generally I do prefer stopped down, like this one at f/2.8:

Good depth of field for the face so you have leeway with the pose/composition, but still a decent "separation"

Tony I think both those shots work well because the large aperture softens the chair backs and give good separation from the subjects. Jeffrey's illustrations had nothing else very close.

In the end it's all a matter of relationships withing the photograph. Your first pic is striking because one sees it in it's entirety, whereas the cropped image makes one want to see more sharpness.

Interesting topic and nice examples.

I think it is a complex topic, which is why I ran this little study.

My prompt was a shot someone posted in another thread some months ago suggesting that really fast apertures were needed for good separation. Their sample shot IMO was anything but because the tightly framed subject was figuratively melting into the very diffuse background. So it set my gears turning on this topic.

I think the relationship between subject framing and DOF is not always well understood among photographers. And just how that plays with varied framing and background spacing can be quite complex obviously...

In the end there will be no formula to follow, but I think it is worth some thinking about how 'wide open' may not always be what makes a subject stand out the most clearly.

Considering only aperture is misleading. Camera to subject and camera to background distance also plays a role in subject "pop". Ansel adames book - "The camera" has a nice section on this.

Jeff,, I'm not really 100% sure what you're trying to convey..

If you have a busy, obtrusive, ugly background, no amount of blurring will make the background attractive.. Therefore, the choice of background is paramount for a successful portrait..

yogestee wrote in post #11831708
Therefore, the choice of background is paramount for a successful portrait..

Sometimes, though, we have to shoot environmental portraits, so...

JeffreyG wrote in post #11831522
... but I think it is worth some thinking about how 'wide open' may not always be what makes a subject stand out the most clearly.

...f/4 with a subtle hairlight from the right-rear would have been my choice for that shot. (Without the picture growing out of your head.)

PhotosGuy wrote in post #11833708
Sometimes, though, we have to shoot environmental portraits, so...

Yes,, and therefore a suitable background is also important for an environmental portrait..

At first Jeffrey, I thought that was a thought bubble coming out of your head--nope, just the overhead light

I see focus separation only as one (an not the very best) means of several object accentuation techniques.

The Jeffrey's example shows one point of this: the face is already wonderfully separated by 1) lighting; 2) and because it is the only face on the scene. The blurred objects at backgroud bring distraction only. The eye makes unneeded efforts to read them. Their form and arrangement does not help to attract attention to the main subject.