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Some questions blurred background photos.
Hi, hopefully someone can help me with this question..

I'm now using a F717 and always liked to zoom all the way to the far end to take potraits because I like the blurred effects of the back ground..

Unfortunately I can only achieve minimal result when I'm in a tight space, hence I resort to use the max F2.0 at wide end with macro mode, the results are OK for me but I would like to have a better blurred background..

I'm tempting to upgrade to DSLR in near future, as I've see a lot of my friends photo have a nice blurred background even when shooting at rather wide angle..

My questions is: why DSLRs can achieve better blurred background compared to my F717? Is it the lens? Aperture? Sensor? or my skill?.

Many thanks for educating me. Appreciated!..

Comments (8)

A larger sensor means a larger aperture (for a given f-stop) than your current camera. If you are after bokeh, you need a dSLR..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #1

What you're basically talking about is depth of field and the bokeh of the lens, usually obtained with a f/2.8 or faster lens..

Here's an article on bokeh - I'm sure you can find many more.http://www.luminous-landscape.com/columns/sm-04-04-04.shtml.

Canon lenses you can Google for samples: 85mm 1.2, 35mm 1.2, 50mm 1.0, 50mm 1.4...

Comment #2

YA Tan wrote:.

My questions is: why DSLRs can achieve better blurred backgroundcompared to my F717? Is it the lens? Aperture? Sensor? or my skill?.

Specifically to answer your question, DSLRs generally have a larger sensor than digicams and this is one of the factors responsible for determining depth of field. The soft backgrounds you like are caused by a shallowing of the DOF (the amount of the image from front to back that is of an acceptable level of sharpness) and this is easier to achieve with the larger sensor of a DSLR along with perhaps a greater range of available lenses with even wider apertures..

DOF is a geometrical phenomena, the amount of which is determined by several variables; aperture, focal length, distance from the subject and film plane/sensor size. A larger aperture (i.e. bigger hole in the lens iris, a smaller number), a longer focal length (i.e. zoomed in) and being closer to the subject all result in a shallowing of the DOF - as you found with the more acceptable results at full zoom. Same with the sensor size, the larger it is, the shallow DOF you will achieve for the same other variables. A medium format camera will have much less DOF than a pocket digicam for the same aperture and composition/field of view.** Hence DSLRs tend to be capable of shallower DOF for the same sort of shots..

** A 100mm lens at 2m from your subject will give approximately the same composition and field of view as a 50mm lens from 1m away (so largely the same DOF), so really it is the composition of the image that determines DOF - composition being determined by a combination of focal length and distance from the subject - how much you see in the frame. So whilst adjusting distance from the subject and/or focal length will change your DOF, not if you alter both by the same amount and keep the image framing the same..

I've written a tutorial on DOF, in respect of DSLRs: http://www.zenadsl5251.zen.co.uk/photos/doftut.html.

And see this DOF calculator and type in some variables and see what it does to DOF between different cameras and settings with your current camera: http://www.dofmaster.com/dofjs.html.

So many photos, so little time.http://www.peekaboo.me.uk - general portfolio & tutorialshttp://www.boo-photos.co.uk - live music portfoliohttp://imageevent.com/boophotos/ - most recent images.

Please do not amend and re-post my images unless specifically requested or given permission to do so...

Comment #3

Wow..! Many thanks for the explaination and it helped me a lot. Will chew all these inputs and update myself.Cheers!..

Comment #4

YA Tan wrote:.

Wow..! Many thanks for the explaination and it helped me a lot. Willchew all these inputs and update myself.Cheers!.

Unfortunately much of the information you have been given here is wrong..

'Bokeh' is not the amount of background blur, it is the 'quality' of it. Using all the same settings - focal length, aperture, sensor size, subject distance, background distance - which will give the same *amount* of background blur, the smoothness and appeal of the background blur will vary from one lens to another. This is what is referred to by 'bokeh'..

There are errors on Boo's web page, such as the old chestnut about depth of field extending one-third in front of the focal point and two-thirds behind, which is *wrong*. Also the web page fails to address the variation in depth of field with sensor size, although granted Boo did mention it in his post. But more importantly, background blur (which you asked about) and depth of field (which you didn't) are different things and only indirectly related. This is from Boo's post:.

A 100mm lens at 2m from your subject will give approximately thesame composition and field of view as a 50mm lens from 1m away (solargely the same DOF), so really it is the composition of the imagethat determines DOF.

That is true - to a good approximation, depth of field is constant if the magnification (or 'framing') is constant - and is not dependent on the focal length of the lens. But (a) that result only holds if the sensor size is constant, which is not what you asked about, and (b) background blur is *not* constant in that situation - far from it in fact. The 100 mm lens will give you considerably greater background blur..

But to answer your question - something nobody has actually done yet:.

If you are taking the same composition, i.e. same subject from the same camera position, same field of view (therefore different focal length but same 'equivalent' focal length) and same aperture, the larger sensor will always give you more background blur. So it's not your skill, it's inherent in the equipment you are using...

Comment #5

Steve Balcombe wrote:.

There are errors on Boo's web page, such as the old chestnut aboutdepth of field extending one-third in front of the focal point andtwo-thirds behind, which is *wrong*..

With respect, this is the 'Beginner's Questions' forum and my tutorial is aimed at beginners and does also come with several explanatory caveats about some of the generalisations and rules of thumb it contains, such as:.

There's a complex geometry at work and the finer technicalmathematical points of it are beyond the scope of this article, butI'll explain enough of the fundamentals ~ hopefully in simple andpractical terms ~ to at least give you a basic understanding toapply in the field when taking pictures. I've stretched some of themathematics a little to make the generalisations easier to remember.Accuracy is only worthwhile if you can actually remember it. In thisinstance, I've erred towards practicality over strict accuracy..

And specifically the sentence about *where* DOF occurs within an image states:.

As a very rough guide, about a third of the DOF extends in frontyour point of focus and two thirds extends behind it..

In extreme cases you might get 20% in front and 80% behind and landscapes at wide focal lengths clearly work rather differently, but for most practical purposes, like the portraits the OP was asking about, around 35-43% is in front of your point of focus and the balance behind. A third and two thirds is a good enough generalisation for a beginner to remember - especially as many beginners think that DOF starts at the point of focus and only extends behind it. I also later explain how to check DOF using focus confirmation spots and the like where you have infinite DOF for landscapes etc...

Also the web page fails toaddress the variation in depth of field with sensor size, althoughgranted Boo did mention it in his post..

That would be *her* post. The introduction to the tutorials does state as below, which as I was linking directly and in respect of a camera model other than the intended models, I did explain the relevance of sensor size in my post:.

.. the tutorials are written specifically for users of crop formatsensor DSLRs, in my case the 300D and 20D and any specifics ornumbers given relate only to this range of cameras with the samerelative sensor size. Whilst the principles can be applied to anycamera, specific numbers and figures may not be appropriate to othermodels - you will need to make adjustments for the relative cropratio of your own sensor. They are also written very much from apersonal perspective and you are free to draw your own conclusions..

That is true - to a good approximation,.

I would have thought using words like 'approximately' and 'largely' would have made it pretty clear that it was an approximation..

So many photos, so little time.http://www.peekaboo.me.uk - general portfolio & tutorialshttp://www.boo-photos.co.uk - live music portfoliohttp://imageevent.com/boophotos/ - most recent images.

Please do not amend and re-post my images unless specifically requested or given permission to do so...

Comment #6

Steve Balcombe wrote:.

If you are taking the same composition, i.e. same subject from thesame camera position, same field of view (therefore different focallength but same 'equivalent' focal length) and same aperture, thelarger sensor will always give you more background blur. So it's notyour skill, it's inherent in the equipment you are using..

To avoid ambiguity I ought to have said 'f-stop' for 'aperture'. The same f-stop because we are taking the same shot so we need the same exposure. The word 'aperture' is used in two different senses - and has been the cause of much confusion, debate and disagreement on these forums!..

Comment #7

Boo wrote:.

Steve Balcombe wrote:.

There are errors on Boo's web page, such as the old chestnut aboutdepth of field extending one-third in front of the focal point andtwo-thirds behind, which is *wrong*..

With respect, this is the 'Beginner's Questions' forum and mytutorial is aimed at beginners and does also come with severalexplanatory caveats.

Yes, but with equal respect wrong is wrong. In your own example under the hyperfocal distance topic, you give the depth of field at 11 feet, f/11, 30 mm as 5-6 feet in front and infinite behind. Hardly one-third/two-thirds is it?.

I am growing very tired, recently, of reading this "Beginner's Forum" excuse trotted out by people who give incorrect answers. The 1/3-2/3 myth is not simpler, it is passing on misinformation to another generation of beginners..

[snip].

In extreme cases you might get 20% in front and 80% behind.

No, in extreme cases almost 100% behind, as in your own example quoted above..

Andlandscapes at wide focal lengths clearly work rather differently, butfor most practical purposes, like the portraits the OP was askingabout, around 35-43% is in front of your point of focus and thebalance behind..

Absolute rubbish. A head and shoulders portrait taken with a 50 mm lens on a 1.6x crop DSLR (i.e. a popular and appropriate combination for portraits), at f/2.8 or f/4 for maximum background blur consistent with enough depth of field - 49% in front and 51% behind. Equal depth of field in front and behind, as near as makes no difference..

[snip].

Granted Boo did mention it in his post..

That would be *her* post..

My apologies for that. I will know next time...

Comment #8

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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