February 25, 2018, 07:14:37 PM

Author Topic: Bokeh with a 24-70  (Read 2488 times)

kat.hayes

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Bokeh with a 24-70
« on: January 28, 2018, 10:06:40 PM »
What is the best way to get good bokeh with a 24-70? Get close and have the background far away from the subject?
OR something else?

Thanks.

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Bokeh with a 24-70
« on: January 28, 2018, 10:06:40 PM »

MrFotoFool

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Re: Bokeh with a 24-70
« Reply #1 on: January 28, 2018, 10:41:54 PM »
1) Shoot at 70mm (instead of 24mm).
2) Get close to subject (as you say).
3) Get an f2.8 lens instead of f4 (if you can afford price and weight).

meywd

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Re: Bokeh with a 24-70
« Reply #2 on: January 28, 2018, 11:05:00 PM »
1) Shoot at 70mm (instead of 24mm).
2) Get close to subject (as you say).
3) Get an f2.8 lens instead of f4 (if you can afford price and weight).

and move around until you get the least busy background possible
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aceflibble

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Re: Bokeh with a 24-70
« Reply #3 on: January 29, 2018, 03:15:39 PM »
Depends what you mean by "good bokeh". Some people mistakenly think "bokeh" means the amount of background blur you have, which is mostly a result of longer focal lengths, wider apertures, and having your background as far away as possible. Other people (more correctly) think of "bokeh" only as the quality of the rendering of the background (which is what the term actually means) regardless of the amount of blurring, and that's more about having less contrast in the background.

In terms of rendering quality, you can use flare and halation to exaggerate background smoothness, though that also usually means less contrast across the whole image, not just the background. (Which is a look many people like anyway, so that may not be a bad thing either, depending on your taste.) Shooting contre jour makes use of this, especially as that means your background is often very simple and blown out anyway.

Something I personally use way too much are Tiffen black pro mist filters, which purposefully force halation. 1/8 strength will lift contrast and cause just enough halation to really maximise contre jour shooting; 1/4 strength lifts contrast further and causes light to bleed quite noticeably, so that's better when you have light just out of frame rather than directly towards the lens, and this is the strength I use most often. 1/2 strength and further lift overall contrast and reduce sharpness too much for my taste, as do all of the original (non-'black') mist filters. I use regular black pro mist on older lenses and warm black pro mist on newer lenses, as older lenses tend to have warmer rendering anyway while newer lenses can really benefit from the subtle colour muting of a warming filter.
Mist filters won't make a 70mm f/2.8 shot have the same amount of blur as something like a 135mm f/2, but it'll improve the quality of the blur. Of course you can also do similar softening in post, too, and by doing it digitally you can preserve all the contrast and sharpness on your subject.

Another trick you can do in post is to shift any colour to be closer to its surroundings. For example, if your background is mostly a grey city scene but there's one bright red sign that stands out, you could desaturate that sign; since it's out of focus anyway, people won't really notice that something has been edited. Reducing both luminance contrast and hue contrast can result in your background blur appearing better in both the amount of blur and the quality of the blur.
 

But as a general rule I'd say you don't really use a 24-70 for its separation, a 3D look, or background-blurring capabilities. That's the trade you make for the flexibility of the zoom. If you find yourself often wanting to blur the background more or to a higher quality, I suggest you look into keeping a longer, faster prime lens to use alongside the zoom. Something like a 24-70 f/2.8 and a 135mm f/2 is a classic combination to give you flexible all-round shooting and then really high quality subject separation when you get the opportunity.

Remember that 'bokeh' and image rendering is completely subjective and what one person likes, another may not. So just have a think about what you shoot, how you like to shoot, and what's appropriate for you with that subject and that style.

shizam1

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Re: Bokeh with a 24-70
« Reply #4 on: January 29, 2018, 03:50:26 PM »
if you just want nice background blur, besides the other suggestions about focal length, aperture and distance to subject, make sure your subject is not standing close to something.  So if you're shooting someone standing right up against a wall, it's pretty hard to get a nice blurred wall without a very shallow DOF.  If they're standing 5-10 feet in front of that same wall, no problem.

peterzuehlke

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Re: Bokeh with a 24-70
« Reply #5 on: January 29, 2018, 04:45:46 PM »
one thing to be careful with is the focal length idea.  a lot of people think long focal length gives you limited dof and subject isolation.  maybe because portraits are commonly shot with a longer than normal focal lens and at wide aperture.  that starts with the rendering of facial features. For the same subject size and distance to the bg a short focal length will limit your dof more.  If you do a head shot with the face filling the frame with a 24mm on full frame at f/2.8 you'll have precious little dof, (less than stepping back and using a 100mm or 135) just nobody does that.  (well i know one excellent portrait photographer, from Calarts who shoots her portraits on 4x5 with a 90mm (kinda like 24 on full frame) just for that reason, that plus camera moves really controls what tiny part of her subject that is in focus). That's why we old product people often shot with a 300mm lens on 4x5, with more distance to the subject, to get the whole product in focus.

privatebydesign

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Re: Bokeh with a 24-70
« Reply #6 on: January 29, 2018, 05:54:23 PM »
one thing to be careful with is the focal length idea.  a lot of people think long focal length gives you limited dof and subject isolation.  maybe because portraits are commonly shot with a longer than normal focal lens and at wide aperture.  that starts with the rendering of facial features. For the same subject size and distance to the bg a short focal length will limit your dof more.  If you do a head shot with the face filling the frame with a 24mm on full frame at f/2.8 you'll have precious little dof, (less than stepping back and using a 100mm or 135) just nobody does that.  (well i know one excellent portrait photographer, from Calarts who shoots her portraits on 4x5 with a 90mm (kinda like 24 on full frame) just for that reason, that plus camera moves really controls what tiny part of her subject that is in focus). That's why we old product people often shot with a 300mm lens on 4x5, with more distance to the subject, to get the whole product in focus.

I'm not sure I follow you. For a given subject size (i.e. move backwards and forwards as per the focal length) the aperture number and associated depth of field remains constant.

A portrait shot at 24mm and f2.8 has the same dof as a portrait shot at 200mm f2.8 IF the subject is the same size within the frame.
Too often we lose sight of the fact that photography is about capturing light, if we have the ability to take control of that light then we grow exponentially as photographers. More often than not the image is not about lens speed, sensor size, DR, MP's or AF, it is about the light.

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Re: Bokeh with a 24-70
« Reply #6 on: January 29, 2018, 05:54:23 PM »

aceflibble

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Re: Bokeh with a 24-70
« Reply #7 on: January 29, 2018, 07:54:21 PM »
If you do a head shot with the face filling the frame with a 24mm on full frame at f/2.8 you'll have precious little dof, (less than stepping back and using a 100mm or 135) just nobody does that.
The first part is right in that a wider lens can still get a thin depth of field if you simply get close enough, but it's not less than a longer focal length at the same framing. The blur amount also will not be the same, there's no guarantee of blur quality, and of course the perspective still won't be the same.

And yeah, nobody does a headshot with a 24mm 'cause it's damn ugly, requires severely invading the subject's personal space, and they won't like either the experience or the results.

Quote
That's why we old product people often shot with a 300mm lens on 4x5, with more distance to the subject, to get the whole product in focus.
(Smaller for this not being part of the original topic.)
I am one of those "old product people"—taught on 4x5, 5x7, 8x10, and 11x14 by another "old product person"—and I've never had to or even heard of using a 300mm lens on a 4x5 for any reason, let alone depth of field.
You're talking about what is essentially an 85mm equivalent, which is a plain weird focal length for product photography and doesn't necessitate or lend itself to a particularly long working distance. 160mm is your go-to standard, since from 5' you've got about 4" of sharp focus at f/11 and just a shade under 7" at f/20; you don't want to go beyond that or you run into diffraction. Tilt as need-be, or stack if you really need more than 7" of sharp focus. Added bonus is 160mm lenses (or thereabouts) are pretty much guaranteed to be free of distortion at that distance and transmission isn't a concern.
On 300m you'll need about 10' of working space between the camera and product just to get the same depth of field as the 160mm; to get appreciably more depth of field you'll need to go back another two feet and stay on the edge of diffraction at f/20. You'll also need at least a third more light on the subject, if the 300mm lens has the same transmission as the 160mm. (It's more likely it is slower.) You won't find many 4x5 lenses over 210mm that don't have moustache-esque pincushion distortion, either.
If you've got room to have a 12' working distance and maximising depth of field is your goal then you may as well use a wider lens anyway and come in to 10'. Even dropping just to 210mm and moving in to 10' away will give you nearly half a foot more depth of field, a more neutral perspective, in most cases a lens with less distortion, you'll have less hassle getting enough light all the way back to the stock, and you could ease off the aperture and get a sharper image. The framing won't be quite the same but it's not enough to make anywhere near as much of a difference as the additional 5"+ you're adding to the depth of field will.

Going up to 210mm isn't too bizarre, and certainly going the other way down to 115mm is common, but 300mm? I think you're misremembering or you were misinformed from the beginning. The depth of field isn't any larger there unless you're willing to use an overall softer image, the working distance is needlessly huge, lighting is needlessly more demanding, and the perspective isn't appropriate for any kind of true-to-life representation, to boot. If you're shooting product with a 300mm you're just making life harder for yourself for absolutely no benefit.


I'm not sure I follow you. For a given subject size (i.e. move backwards and forwards as per the focal length) the aperture number and associated depth of field remains constant.

A portrait shot at 24mm and f2.8 has the same dof as a portrait shot at 200mm f2.8 IF the subject is the same size within the frame.
This is correct. The perspective exaggeration is of course different and whether the bokeh is any good or not is entirely dependant on the specific lens in question and the nature of the background, but the same aperture at the same framing results in the same depth of field.

So to bring this back on to the optic at hand, if the depth of field is all you care about, then 70mm f/2.8 will certainly give you a shallow depth of field if you get close enough, but the amount of blur still won't be equal to a longer lens at the same aperture with the same framing, and the bokeh (that's the quality, remember) can still be wildly different.

To run some numbers quickly (this maths is a little rough, bear with me 'cause I'm doing this at half-past midnight):
To get an ultra-thin depth of field of just 1", a 70mm f/2.8 lens on a 35mm camera must be about 4'7" from the subject.
To get the same framing and the same 1" depth of field, a 135mm lens should be at f/2.8 and 8'9" away.
At that framing, and assuming the subject is about 1/3rd of the way into the scene, the 135mm's blur diffusion will be a little over 1mm on the sensor, while the 70mm's will be about just under 0.75mm, meaning the 135mm will still blur the background more strongly.

Again, the quality of the 70mm's blur could still be better than the 135mm! And quality is what bokeh is. But you'll get about 33% more blur from the 135mm, along with of course a much more relaxed working distance and less-distorted perspective on your subject, for that same thin depth of field.

Interestingly, while scrubbing through my maths there, I mocked up 105mm f/4 giving you only 1/7th less blur than 70mm f/2.8 at head-and-shoulders range and about 1/6th less blur at waist-up range on a regular person about 5'9" or so and the common placement of a subject 1/3rd into the scene. So OP is still best off with the 24-70mm f/2.8 if they want to maximise blur from a general zoom, but it's good news for those people who worry about the long end of a 24-105 vs the wider aperture of the 24-70, for portraits or similar single-subject shots. The 105 f/4 gives you more depth of field, a more even perspective, and only a fraction less blur. Still less than the 70mm f/2.8, but not dramatically so unless the background is really close to your subject, in which case of course the wider aperture makes more of a difference.
(Er, that's if my maths is right. It's now 00:55am as I finish writing this and I'm both tired and very cold; someone should probably double-check my results.)

aceflibble

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Re: Bokeh with a 24-70
« Reply #8 on: January 29, 2018, 08:09:48 PM »
You know what, OP, let's clean this up and simplify this for you.

Things which will give you technically more blur:
Get closer to your subject.
Get your subject further away from the background.
Using a longer focal length at the same aperture.

Things which will make it look like you have more blur, though technically the amount of blur is the same:
Shooting against lower-contrast backgrounds.
Lowering contrast in general, such as allowing light flare.

Things which will give you better bokeh (higher quality, but not the amount):
Weak diffusion filters, at the cost of also losing both sharpness and contrast.
Using a lens with an apodisation filter built in, at the cost of also losing light. (The Laowa 105mm is the only one available to Canon, and is all-manual-only.)
Using a lens with naturally smoother rendering, usually meaning a simpler design such as a mid-range prime which has less micro-contrast.

Things which will give you more and higher-quality blurring:
Photoshop. Seriously. That's it. Be careful, because most backgrounds which get run through Photoshop blur filters come out looking very, very obviously fake.

 
So using 70mm at its widest aperture and get as close as possible with a plain, simple background as far away as possible is the best you can do with your lens without adding anything else. If that's not possible or not enough for you then you need to look into either adding another lens for this purpose, or you can fake it with software.

kat.hayes

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Re: Bokeh with a 24-70
« Reply #9 on: January 30, 2018, 03:32:55 PM »
Thanks so much for all of the responses!

If I use a longer lens, like a 70-200mm f/2.8

1. Is it better to shoot closer to 200mm? OR does it not matter?

Thanks.

ajfotofilmagem

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Re: Bokeh with a 24-70
« Reply #10 on: January 30, 2018, 03:48:25 PM »
Thanks so much for all of the responses!

If I use a longer lens, like a 70-200mm f/2.8

1. Is it better to shoot closer to 200mm? OR does it not matter?

Thanks.
For more blur of the background,
maintaining the same aperture,
maintaining the same magnification of the object,
maintaining the same frame,
yes, 200mm is better than short.

Talys

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Re: Bokeh with a 24-70
« Reply #11 on: January 30, 2018, 03:54:35 PM »
Thanks so much for all of the responses!

If I use a longer lens, like a 70-200mm f/2.8

1. Is it better to shoot closer to 200mm? OR does it not matter?

Thanks.

The most important thing is to minimize your distance to the subject while maximizing the distance between the subject and the background.   In addition to you moving, you can also ask your subject to move, so that you can get a better angle.

That's because near subjects have a shallow depth of field and the further away the subject, the deeper the depth of field (and therefore, no bokeh).  If your subject is 30 ft away, you're not going to get bokeh whether you are at 16mm or 400mm.  Just look at the range finder on the top of your lens, and you'll see what I mean -- the gaps for the first few markings are quite wide, and then they get really tiny for big jumps in distance.

Yes, set your zoom as high as you can, but you have to be realistic - don't crop your subject in a way that's unappealing (because who cares about bokeh if it's poorly cropped), and you're not going to photograph a human at minimum focus distance at 200mm.

aceflibble

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Re: Bokeh with a 24-70
« Reply #12 on: January 30, 2018, 04:52:33 PM »
Is it better to shoot closer to 200mm? OR does it not matter?
Yes. Assuming you'll be shooting at the same aperture and you have enough space to frame the shot the same, 200mm will give you a more heavily-blurred background than any shorter focal length. Just bear in mind that at 200mm you'll need a lot of room.

Also, as far as 'bokeh' goes, it's the same no matter what focal length you use. The more you zoom in the more blur you get (which is not what 'bokeh' means) but the lens produces the same quality of blur (which is what 'bokeh' means) at all lengths.
So more blur = longer focal length.
Higher-quality blur = usually a simpler lens.

the deeper the depth of field (and therefore, no bokeh).  If your subject is 30 ft away, you're not going to get bokeh whether you are at 16mm or 400mm.
I know what you're trying to say, but you're misusing the term. All lenses at all apertures and all framing have 'bokeh'. Again, 'bokeh' means quality, not amount. A 16mm lens at f/8 still has appreciable bokeh; bokeh applies to anything which is out of focus, even slightly.
And, for the record, 400mm focused at 30' away will still blur the background (and foreground!) quite heavily. Look up some wildlife photography sometime. Whether that blur is any good or not is another matter. As with any other lens, the only way to get 400mm to not blur something is to use an extremely small aperture and focus at infinity. (And even then, anything close will end up very blurred, so...)

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Re: Bokeh with a 24-70
« Reply #12 on: January 30, 2018, 04:52:33 PM »

Talys

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Re: Bokeh with a 24-70
« Reply #13 on: January 30, 2018, 06:48:15 PM »
the deeper the depth of field (and therefore, no bokeh).  If your subject is 30 ft away, you're not going to get bokeh whether you are at 16mm or 400mm.
I know what you're trying to say, but you're misusing the term. All lenses at all apertures and all framing have 'bokeh'. Again, 'bokeh' means quality, not amount. A 16mm lens at f/8 still has appreciable bokeh; bokeh applies to anything which is out of focus, even slightly.
And, for the record, 400mm focused at 30' away will still blur the background (and foreground!) quite heavily. Look up some wildlife photography sometime. Whether that blur is any good or not is another matter. As with any other lens, the only way to get 400mm to not blur something is to use an extremely small aperture and focus at infinity. (And even then, anything close will end up very blurred, so...)

It's actually a typo on my part; I meant to type 30 m, but had been posting something in imperial =X  My bad.  Yeah, for sure, at 30 ft, you're still going to have background blur, assuming your background disappears into the horizon.  And even at 30m (on a long enough telephoto), some of the background will still be defocused (though at either, it will be terrible bokeh).

Yes, you're absolutely right that bokeh is the quality of the out of focus area (rather than more blur).  Thank you for pointing that out.  There are many lens design wizardry factors that impact how pleasing this is, like the number of blades in the diaphragm.  However, in most cases, given the same gear, narrowing the depth of field and maximizing the distance between the subject and the background will yield more pleasing results (better/more bokeh).

But anyways, a REALLY simple way to get the best results is to remove the subject all together.  Set the camera to MF, zoom wide, and set focus to minimum, then snap some pictures as you increase focus to infinity.  Then zoom tele, and do the same thing.  Decide for that lens what is the prettiest (perhaps also, based on what it is in the background), then position your subject approximately at the distance of the range finder, so that they are in focus, autofocus, and presto :)
« Last Edit: January 30, 2018, 06:55:23 PM by Talys »

Besisika

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Re: Bokeh with a 24-70
« Reply #14 on: January 31, 2018, 11:44:05 AM »
You know what, OP, let's clean this up and simplify this for you.

Things which will give you technically more blur:
Get closer to your subject.
Get your subject further away from the background.
Using a longer focal length at the same aperture.

Things which will make it look like you have more blur, though technically the amount of blur is the same:
Shooting against lower-contrast backgrounds.
Lowering contrast in general, such as allowing light flare.

Things which will give you better bokeh (higher quality, but not the amount):
Weak diffusion filters, at the cost of also losing both sharpness and contrast.
Using a lens with an apodisation filter built in, at the cost of also losing light. (The Laowa 105mm is the only one available to Canon, and is all-manual-only.)
Using a lens with naturally smoother rendering, usually meaning a simpler design such as a mid-range prime which has less micro-contrast.

Things which will give you more and higher-quality blurring:
Photoshop. Seriously. That's it. Be careful, because most backgrounds which get run through Photoshop blur filters come out looking very, very obviously fake.

 
So using 70mm at its widest aperture and get as close as possible with a plain, simple background as far away as possible is the best you can do with your lens without adding anything else. If that's not possible or not enough for you then you need to look into either adding another lens for this purpose, or you can fake it with software.
That is not simple at all. That is a demonstration of theoretical knowledge.
Mine is a lot simpler; too much theory will kill your photography.

Portrait photographers are people photographers, as such the model should always come first.
There is a distance, (depending on your voice, your personality, the subject's vision, previous relationship between the two of you), that will make the interaction between the two of you very efficient. That is the focal length that you should use. This is why some people prefer shooting at 35mm, some at 85 and some at 200mm.
It is the subject comfort, as well as your own comfort, both combined that should determine the focal length and not some bokeh theory.
To answer to OP's question, yes; what creates a nice bokeh (we don't care what is it called as long as we produce the best photo we can) for an optimal working distance (as discussed above) you would use a far background. Memorize the minimum background distance that gives your beloved bokeh for a given F-stop and always choose the future backgrounds based on that, if bokeh is what makes you happy.
For a given working distance; F-stop determines the depth of field, distance btw subject and background determines the isolation and focal length determines the crop.
Hope that helps.

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Re: Bokeh with a 24-70
« Reply #14 on: January 31, 2018, 11:44:05 AM »