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This is the picture I took:

enter image description here

I had a Nikon-D610 and a 24-70mm f 2.8 lens on it and I used it on Manual mode and metering was f:2.8, Shutter speed: 1/20 sec and Focal length: 62mm. Also I was as close to him as possible, about 2 meters away and the background at his back was about one meter behind him.

I will be happy to know as many issues and suggestions you have on the photo but my main question is this: Notice the background is not blurred enough, not to be fully blurred but still some more blurring that makes the background less distracting. So do I need a 85mm lens to achieve this? or I should be able to do it with this lens too and need more practice? or is it just that with this distance of me and him and he and the back, it is not just possible?

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    This is kind of a weird question. Since you made the photo with a 24-70mm zoom at 62mm, clearly you don't need an 85mm lens. But presumably you think a lot 85mm lens would do better, apparently particularly for background blur. But I'm puzzled as to why you've chosen 85 as the magic number. Can you elaborate? – mattdm Jan 18 '15 at 4:26
  • I agree with what @mattdm said, the only reason I can think that you'd want the 85mm in that situation is wider aperture? If so why not look at a 50mm f1.2? With that you could shoot at 50mm f1.2 and then crop down to that same composition. – drinxy Jan 18 '15 at 4:54
  • @mattdm because they say 85mm is good for bokeh portraits, so I thought the way to make a blurred background is to use a 85mm – user1899082 Jan 18 '15 at 5:00
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    Totally unrelated - is that Elijah Wood on the decks? – NickM Jan 18 '15 at 14:04
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    @NickMiners yes, Lord of the Rings guy! he has a DJ group called Wooden Wisdom – user1899082 Jan 18 '15 at 15:25
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Okay, so, really, two aspects here. First, would an 85mm lens let you blur the background more? Probably, because the framing for a longer focal length decreases the apparent depth of field, and because there are reasonably-priced and readily available 85mm prime lenses with wide apertures and generally nice technical image quality . But it's not a particularly magic number — any long, fast lens will give you that kind of result. If you want more of that than you can get with your current lens, and you can't get closer for the framing you want, any lens that's a longer focal length and the same or wider max aperture will do.

But, second (and unstated): are you sure that that's what you really want? Getting rid of "distractions" is an easy way to get straightforward, obvious results (and therefore win Internet photo competitions), but isn't necessarily automatically better. In this particular case, I think the records in the background add significantly to the context of the image and would be much more distracting were they out of focus.

In fact, I wish for more sharpness in the turntable in the foreground left — I want more depth of field, not less. The whatever-it-is behind the DJ's head is a bit unfortunate, but I'd solve that by moving slightly, or by removing it digitally, or just not worrying about it. (A little more blur wouldn't remove it anyway — what you need is lighting separation, and in this situation that's probably not under your control.)

If I were to be concerned about anything technical in this image overall, my main concern would be the blown-out details on the DJ, probably due to poor lighting. His hands are particularly unfortunate here, since they are naturally a center of attention — I'd go so far as to say that for me, they are the main part of what the image is about, so it hurts to have them looking so... compromised. Unfortunately, this is a really tough situation — and a different lens won't really help that aspect (85mm or otherwise).

  • I agree. The framing is quite nice as is. – dpollitt Jan 18 '15 at 20:54
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Although going with a longer lens would give the illusion of a shallower depth of field, it doesn't actually change in a situation like the one you propose.

I created ƒ/Calc to help photographers work out the answers to problems of this sort. As far as I'm aware, it is the only photographer's calculator that incorporates several different calculators into a single app, and ties the outputs of one calculator to the inputs of all the others, where that makes sense. This means you can move from tab to tab in the app, exploring the consequences of a change, without copy-pasting values between them. This removes a lot of the work that makes photographers give up on answering a question before they've found the answer.

Here's how it works in this particular case:

  1. Go to the Depth of Field (DoF) tab and tell it about your 62mm focal length, 2m focus distance, and ƒ/2.8 aperture.

    It reports that the total DoF is about 0.143m. This seems plausible, given that healthy adult humans are about 0.2m thick.

  2. Now switch to the field of view tab. Its values are already filled out from the DoF tab. It tells us that the horizontal field of view is about 1.125m. That's what you'd get if you measured the visible width of that DJ console, assuming your 2m subject distance is correct.¹

  3. Still within the FoV tab, change the focal length to 85mm, and then experiment with the subject distance value until you get the same horizontal FoV that you had before. I came up with 2.74m. That means you'd have to back up by about ¾ of a meter to get the same amount of the subject in the frame as before.

  4. Now go back to the DoF tab. Surprise! Total DoF is still 0.143m. (Why? Because physics.)

  5. You shake your head, tell yourself that can't be right, and go back through the process with a 200mm lens. The FoV tab tells you that you need to back up to 6.45 meters from the DJ, and the DoF tab then informs you that total DoF remains 0.143m. Huh. That's weird.

Now, all of that having been said, the illusion that is behind the myth that started this question is still in play. It has to do with background compression, which appears to magnify the background. This increases the background's apparent blur, just as if you'd blown up the background digitally. This means you get the effect of less depth of field, even though DoF hasn't actually changed.

I don't think the difference between 62mm and 85mm is enough to give you the effect you want, though. I think you'll get a lot more value out of going to a wider aperture.

You could go snag an old 85/2 off of eBay, for example, which would knock about 0.4m off the DoF when wide open. Be careful: manual focus will slow you way down on a shot like this, because you have very little DoF to work with and not a lot of light to make the judgement call with. If you switch to a newer autofocus 85/1.8, you cut DoF to about 0.09m wide open, and can let the camera figure out the focus distance. There is also an ƒ/1.4 lens in Nikon's current lineup which will cut DoF down to 0.071m for about twice the cost.

You have my blessing to buy all of these lenses. :)


Footnotes:

  1. You may not need to guess at the subject distance value, by the way. Nikon cameras can record accurate information for this in some cases. If you don't have software that will dig this value out of the raw photo file, you can use exiftool. On a Mac, the command would be exiftool my_photo.nef | grep -i distance.
  • my_photo in my_photo.nef is the name of the actual photo I have? – user1899082 Jan 18 '15 at 16:01
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    @user1899082: Yes. If you're using a Mac, you can drag the photo to the Terminal window, and it will paste in the full path to the file. – Warren Young Jan 18 '15 at 16:02
  • Got any source on f/calc? – Alec Teal Jan 18 '15 at 16:49
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    @AlecTeal: If you're asking where the program came from, I wrote it. If you're asking for the program's source code, I keep the current code to myself, but I did release the source to the original Windows version under the GPL. I wrote it back in 1998. Its LensMath.c module is similar to the code behind the current Online and Local versions. (The manual also gives all the equations.) I rewrote ƒ/Calc in Tcl/Tk + Tix for Linux in 2001, but I haven't been able to get it running again, so it is not currently available. – Warren Young Jan 18 '15 at 17:43
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Photoshop: "select in focus", a fairly new feature. (Optional step: grow selection and feather the edge 2 px.) Invert Selection. Apply blur filter, or other creative background effects not limited to lens bokah.

Personally, the background is great. Mostly bare but a couple mood-setting items. Just paint out the stick coming out of his shoulder. Perhaps intensify the red-black wash effect.

The problem with the photo isn't the background at all, but the foreground. The arm and hand is brighter and higher contrast then the face. So make that the focus of the composition. But you can't see anything intetesting there.

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Aperture Aperture Aperture

To get that exact shot, with the same perspective and framing but with shallower depth of field, your only option is to use a wider aperture.

Since you took it at maximum aperture on that lens, you'd need a different lens whose zoom range covers 62mm with a wider aperture.

Alternatively a wider lens (e.g. 50 or 55mm prime, f1.8 or f1.4) and crop the image in post processing. You could probably find a prime with better bokeh and wider max aperture.

  • I have a prime f1.8, 35mm .. maybe next time should use that. – user1899082 Jan 19 '15 at 14:24
  • In terms of depth of field, assuming you print or view the final result at the same size, and assuming high enough resolution that it's not a factor, cropping the center half of an image taken with a 35mm f/1.8 will give you results identical to one taken at 70mm f/3.6. – mattdm Jan 22 '15 at 14:09

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