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What lens do I need to get background blurred


petjordan

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Hi! I am new here!

 

I have a recording studio for my youtube channel with 3x4 meters.

It's in my garage, actually. The camera stays in the garage gate and I am 1 meter off. I have a canon 70D and a Sony A7r II. What is the best lens to use in both cameras to have the background blurred?

 

Thank you for your support.

 

---

I forgot to mension that I have a FE 1.8/55 Zeizz for my Sony camera and yes, I am getting the background blurred, but it's not wide enought. I need to show up more of my background/

Edited by petjordan
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That's complicated! - I assume you 'd need a wider lens with wider aperture and also need fully working AF with the Sony? - Are you shooting it in FF or crop mode?

You could maybe adapt a Voigtländer Nokton 35mm f1.2 via Techart but that AF is limited compared to a native lens? - I am not sure if the Nokton plays well on a stock Sony, so maybe you'll also need a thin filter conversion by Kolarivision? - In summary a whole lot of money! Try doing some research before you 'll get that stuff and in doubt rent before you 'll buy. It would probably be much cheaper to move yourself into the garage gate and the camera further away. If that isn't enough blur wide open you could at least get significantly faster lenses like the 7artisans 50mm f1.1 or, if you fancy to go crazy, a Noctilux f0.95.

If your to be blurred background doesn't change; why don't you take a sufficiently blurred picture of it, print it out at the right size and place it behind you?

I fear you are basically lost.

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I'd first check which focal length will do the trick for you (assuming you have something like a standard zoom for either 70D or A7). And once you know the focal length you need, start searching for the lens with the widest aperture for either one of the cameras, of course considering that one is APS-C and one full frame.

Wide fast lenses tend to cost quite a lot, and old(er) wide fast lenses typically are quite special at wide apertures - it may add a character to your images that you're not looking for, so be sure to check samples images of the lenses you consider to get an idea of what you will get.

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  • 11 months later...

You're talking about a concept called "depth of field" The more a lens aperture is closed down (made into a smaller hole, something you can see in a manual lens by just moving the aperture ring to smaller apertures. Counterintuitively, f/16 is smaller than f/4), the bigger (front to back) the zone of "apparent" sharpness is and the less sharp the background (what you are not focused on) is. So you need to use a lens with a low aperture (such as f/2 or smaller, like f/1.4) set all the way to that more open aperture. Then focus carefully on what you want to take pictures of, and the background will be more blurred. Some lenses blur the background in a more pleasing way than others. Additionally different film formats (or sensor sizes) have an effect on zone of sharpness.

 

So look on your lenses for the one with the widest aperture (low f/ numbers) and set it to that low aperture (either manually for manual mode or aperture priority mode) and then try it out. Experiment.

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Counterintuitively, f/16 is smaller than f/4

 

The intuitive way to think of it is to realise that the f-stop is a fraction: you're describing the size of the entrance aperture as a fraction of the lens focal length, which is the "f". That's why there's a forward slash in the way it's written. 1/16 is smaller than 1/2, so f/16 is smaller than f/2.

 

For a given size of the subject in the frame (which means moving the camera relative to the subject as you change focal length), depth of field mostly depends on f-stop. Bear in mind that if you're large in the frame and shooting at a wide aperture, depth of field will be narrow, and not all of you will be in focus. If you're shooting a video with manual focus, you'll probably have to hold quite still if you want everything sharp at f/1.8.

 

For the more distant background, focal length affects how out of focus it is - effectively everything is blurred by depth of field, but a wider (shorter focal length) lens makes the blurred background smaller in the frame than a longer focal length; the latter magnifies the blur. So even an 35mm f/1.4 won't blur the background as much as your 55mm f/1.8 can.

 

There are tricks to get around this in photography by stitching, but not so much for video.

 

The farther you can get the background from the subject and the camera, the more blurred it'll be. But otherwise: cheat, as others suggested. Fake a background, or even make your own green screen (since software can patch a background in quite well these days).

 

Good luck! And yes, do experiment, and as cd says, there's more to pleasing bokeh than aperture.

 

Edit: Wait, 2017. Darnit; I misread the date. Well, I hope it worked out.

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The intuitive way to think of it is to realise that the f-stop is a fraction: you're describing the size of the entrance aperture as a fraction of the lens focal length, which is the "f". That's why there's a forward slash in the way it's written. 1/16 is smaller than 1/2, so f/16 is smaller than f/2.

 

(snip)

 

 

That is the way I always thought, and I believe the way most photographers do it.

 

It seems, though, that in optics (that is, other than for photography) they use the f-number, not written as a fraction, such that it works the other way around.

 

But then for shutter speeds, it works the other way around. They are commonly written as a fraction, in time units, though described in terms of speed with time in the denominator. 1/60 is faster (higher speed) than 1/30. Oops.

 

For both f/stop and shutter speed, the dials are commonly labeled with just the denominator, and not as a fraction.

-- glen

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That is the way I always thought, and I believe the way most photographers do it.

 

I hope so. I've had a word with people teaching it the other way ("bigger number, smaller aperture") because I think they cause unnecessary confusion. We've had our share of people who find the numbering unnatural on this and other forums, so I'm keen to encourage this way of thinking about it.

 

It seems, though, that in optics (that is, other than for photography) they use the f-number, not written as a fraction, such that it works the other way around.

 

I don't care how they write it, a fraction is how it's defined! Astronomers tend to talk about the physical aperture size - I have a 10" Dobsonian telescope, for which the mirror is 10" across. That defines the absolute amount of light gathering, especially for stars which aren't spread out by magnification. Astronomers also choose different eyepieces (effectively teleconverters), and only really think about the eyepiece/focal length pair in determining magnification. But my telescope is still roughly f/5 if I stick a camera at the eyepiece location. (The t-stop is less, of course - partly because it's mirrored, partly because the secondary mirror blocks some light.)

 

But then for shutter speeds, it works the other way around. They are commonly written as a fraction, in time units, though described in terms of speed with time in the denominator. 1/60 is faster (higher speed) than 1/30. Oops.

 

Meh. More speed, less duration. Arguably "speed" is the wrong way to think anyway, even though it's common terminology - the actual speed of the shutter blades is usually fixed, what changes is the time between the first and second curtains moving. From a physical unit point of view, it's the time in seconds that matters, not the m/s at which the shutter blades move (which you can vaguely work out from the camera's fastest flash sync speed and the sensor size).

 

For both f/stop and shutter speed, the dials are commonly labeled with just the denominator, and not as a fraction.

 

True, although it would take more space to do otherwise. Focal lengths on zoom lenses don't tend to have "mm" marked either. Nikon, at least, describe their lenses themselves with a ratio (e.g. 16-35mm 1:4G); Sigma and Canon seem to do the same. Tamron actually appear to say "f/2.8" on their 70-200. Tokina's 11-16mm is labelled "F2.8" however; boo. Sony and (presumably not coincidentally) Zeiss write the fraction upside down (FE 2/28, Distagon 2,8/21), which is just weird - at least they don't write "mm" or "f" anywhere in the name.

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. . . although it would take more space to do otherwise. Focal lengths on zoom lenses don't tend to have "mm" marked either. Nikon, at least, describe their lenses themselves with a ratio (e.g. 16-35mm 1:4G); Sigma and Canon seem to do the same. Tamron actually appear to say "f/2.8" on their 70-200. Tokina's 11-16mm is labelled "F2.8" however; boo. Sony and (presumably not coincidentally) Zeiss write the fraction upside down (FE 2/28, Distagon 2,8/21), which is just weird - at least they don't write "mm" or "f" anywhere in the name.

 

Zeiss isn't writing a fraction. They are using the "/" as separator for the two values, max aperture and focal length, just as they follow the European tradition of using a comma in place of a period as a decimal point.

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Zeiss isn't writing a fraction. They are using the "/" as separator for the two values, max aperture and focal length, just as they follow the European tradition of using a comma in place of a period as a decimal point.

 

Indeed - it's just a slightly confusing choice of separator in this case.

 

I first met the comma convention when a company I worked for advertised their product for £20,000 and we had a confused inquiry from Greece (IIRC) wanting to pay £20 for one.

if we could agree on everything?
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  • 2 weeks later...

As for blurring and background, I believe you can get glass filters that are clear in the middle, and slightly frosty around the edge.

 

The idea of this is to blur the parts that are away from the center.

It won't exactly follow foreground vs. background, but sometimes it works.

 

It seems that now there are digital blur systems, to post-process digital images,

with a similar idea.

 

If the background isn't far enough back, that might be the only way.

-- glen

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As for blurring and background, I believe you can get glass filters that are clear in the middle, and slightly frosty around the edge.

 

On a wide-angle (for which light is typically leaving the front element in different places according to where its falls in the image), I'd expect that to work; I'm not sure I'd expect it to work so well on a telephoto lens - usually the whole front of the lens is contributing to each part of the image and approximating the aperture. In fact I've thought about using a reverse centre filter for softening bokeh. Other than general softening, I'm not really sure what diffusing the light around the edges of the aperture would do.

 

I'm assuming the blurred background was actually wanted for aesthetic reasons. Otherwise I'd just have turned off the lights behind the subject!

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From the member information got by clicking on his/her name:

 

"petjordan was last seen: Oct 6, 2017"

 

- Meaning that 'petjordan', the originator of this thread, hasn't visited photo.net since the day they joined, nearly a year ago now.

 

So why are we still offering answers to this thread and keeping it near the top of the list?

 

FWIW. f/4, or whatever number, is definitely a fraction. Since it's near impossible to type a horizontal divider sign, the forward slash has become common mathematical shorthand for signifying a following divisor. It's not 'European'. It's internationally recognised as the symbol for splitting dividend from divisor to give a quotient. The same as a colon is internationally used to designate aperture as a ratio.

 

Thus if we have an f/2 50mm lens; we divide f (50mm) by 2 to find the physical aperture size. It can also be shown as '50mm 1:2'. In each case the physical aperture diameter is the same - 25mm.

 

If QWERTY keyboards had a readily accessible dot-over-hyphen-over-dot symbol, then I'm sure it'd be used. But they don't!

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From the member information got by clicking on his/her name:

 

"petjordan was last seen: Oct 6, 2017"

 

- Meaning that 'petjordan', the originator of this thread, hasn't visited photo.net since the day they joined, nearly a year ago now.

 

So why are we still offering answers to this thread and keeping it near the top of the list?

 

See carbon_dragon's post above. He (presumably) felt inclined to add something to an old thread. I don't think we're helping the OP, but I concede that it might help someone searching the database. It's not something we used to do much, partly because the old search system was so abysmal, but it might be more useful since the web site redesign.

 

Yes . . . f/4 is a fraction . . . But, that's not what we were talking about.

 

Well, we were at one point. My bad for picking up on carbon_dragon saying f/16 is smaller than f/4 and claiming that this is "counterintuitive", but it's a bugbear of mine, and I think it helps people to understand aperture numbering, especially if the same person comes back and starts talking about equivalence and calculating depth of field.

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From the member information got by clicking on his/her name:

 

"petjordan was last seen: Oct 6, 2017"

 

- Meaning that 'petjordan', the originator of this thread, hasn't visited photo.net since the day they joined, nearly a year ago now.

 

So why are we still offering answers to this thread and keeping it near the top of the list?

 

(snip)

 

Often enough, I feel that answering a question might help others, and not only the OP.

 

Some questions are too specific, though I might reply anyway, but it seems that others

might be interested in this one.

 

Also, tt is less than a year old. Sometimes 5 or 10 year old questions come back up!

-- glen

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