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nightko
09-13-2006, 08:42 AM
My digital camera is Canon S3 IS.
I wonder if I can take pictures so that the background is blur while the subject stay in focus.

I tried many times changing the F number/trying out the default portrait mode etc. , don't really work out. (It works ok if I shoot something by the window, that is very near object compared to super far away landscape)
Anyone using the same camera as mine or anyone can give me some tips/direction?

Thanks in advance.

shiroin
09-13-2006, 09:01 AM
optical rules in physics is such that when a sensor/film plane is small, the focal length of the lenses will have to be dramatically reduced, resulting a wider depth of field.

is it very hard, if not, impossible to achieve the result on a small digital camera, unless the camera features a prime lens with a really wide aperture (bigger than 1.8)

Test Type
09-13-2006, 09:54 AM
My digital camera is Canon S3 IS.
I wonder if I can take pictures so that the background is blur while the subject stay in focus.

I tried many times changing the F number/trying out the default portrait mode etc. , don't really work out. (It works ok if I shoot something by the window, that is very near object compared to super far away landscape)
Anyone using the same camera as mine or anyone can give me some tips/direction?

Thanks in advance.

That's one of the limitations of cameras with tiny sensors almost infinite depth of field.

The best you can do without changing cameras is to use a large aperture (small F stop number), use a long focal length (but still stay within the normal portrait distance from your subject) and make sure that the background object is as far away from the subject as possible.

staereo
09-13-2006, 10:38 AM
shiroin hit the nail on the head here. Your S3's image sensor is very small. Small refers to the AREA of the image sensor, not the megapixels. The smaller an image sensor is, usually in reference to 35mm equivalent size, the harder it is to shallow out your Depth of Field.

I'm not sure how in depth you would like to learn about Depth of Field, but I'll toss a little info out there, and you can take from it what you want.

First, about focus. Focus is a semi-relative term. Focus essentially relies on a noticable change in how sharp a given point is that you focus on. Let's say you focus on something 4 meters away. For the sake of argument, we'll say its the head of a pin. Now that very defined pinhead reflects light at your camera, and when you're perfectly focused on it, it is the pure point of the pin that you see. Yet, when your focal point away from the head of the pin, it gets blurry, and if you look REALLY closely, you'll see it goes from being a point, to a blurry spot, and the spot gets bigger the further your focal point is from the pinhead itself.

The size of that spot is referred to as the circle of confusion. Because this 'spot' or disc is measurable, we can use circle of confusion to effectively measure how blurry, or out of focus it is. This measurable value is called the circle of confusion, and it is a definable by a concrete number.

Several things affect this value. In the days of film, it had a lot to do with the size of the print you intended to print out. As the smaller the print, the less you would notice of the blurryness. As you made the image larger when printing, the viewer's ability to notice would increase, and thus the circle of confusion from that point would rise.

While that is still true today, now it is more measured by your image sensor's size. Each image sensor can be directly assigned a circle of confusion. The smaller the image sensor (as it was with the smaller the print), the harder it is to notice blur, and also, the smaller the circle of confusion is. (Much the way 35mm had a smaller CoC than medium format.)

Now, circle of confusion deals with how noticable blur is, and thus has a lot to do with your depth of field. When blur is MORE noticable (larger circle of confusion), your effective area in focus (your depth of field) becomes shorter. And as you stray further away from that depth of field, your blur is more and more noticable. Thats how your background gets blurred so well in images you see.

The camera you have, the Canon S3 (IS) has an image sensor that is 7.182mm diagonal (5.76mm x 4.29mm) A 35mm equivalent sensor has a 43.3mm diagonal (36mm x 24mm). As you can see, your image sensor is a LOT smaller than a 35mm size sensor. This means your Circle of confusion is a LOT smaller too.

That means it is that much harder to get a blur effect, as I explained above.

Ultimately, you're not going to be able to get the same kind of blur as others with larger image sensors would be able to get. I'll try to explain a little more about DoF to help understand what other factors may help. Some of the factors are more perceived than actual, but for the sake of an easy explination, I will just list them. If desired, I can expand.

1) Aperture..... The smaller your aperture (bigger the f/ number is), the MORE DoF you will have. The larger your aperture (smaller the f/ number is), the LESS DoF you will have and the more background blur you will get.

2) Focal length of lens.... The wider your angle (shorter focal length, smaller mm number) the MORE depth of field you will have. The longer your focal length (bigger mm number) the LESS DoF you will have, and your bg will be more blurry.

3) Circle of confusion. The larger the circle of confusion, the more blur you will get, and the LESS doF you will get. The smaller the CoC, the more DoF you will get.

4) Distance to subject... The further away you are, the more DoF you will get. The closer you are, the less DoF you will get and the more background blur you will get.

There are other factors, and focal length and distance to subject have a big relation to one another, especially regarding percieved and actual blur. But either way, this is a basic guide to help you. Use that list of DoF factors to maximize your use of bokeh, and you'll at least make the most of the smaller image sensor that you're currently using. Just don't forget that your camera is not going to make a 35mm esque blur, as its sensor keeps the Circle of Confusion very small.

Hope this wasn't too harsh of a read, feel free to ask if I left anything unclear.

Bruce

jtnishi
09-13-2006, 01:09 PM
Pretty much what everyone said above is true. The best chance you have of getting shots with lots of background blur when sensor sizes are small (as they are with most compacts) is to separate the subject and background by as much distance as possible by ratio, and use modes which emphasize large apertures (usually portrait modes).

Compositionally, for cosplay portraits, this means you're going to be tightening shots to half body or closer. To some extent, this means sacrificing shots of the costume itself, so this might not be a reasonable alternative if what you're trying to focus on is a complete outfit. It is doable, however. Half body shots are nice portraits anyways, and I used to get enough background blur with my old F707 on those type of shots, which also suffered from a relatively small sensor (albeit somewhat larger than the sensor in your camera, and with a relatively large wide open setting aperture-wise),

Otherwise, use the other option: make sure you have enough open space in back of the person to have no background close by to begin with. It's easy to blur a background when the background's absolutely empty. :D

Keeping in mind that aperture does have an effect on this, the lighting of the area you shoot in might have an effect if you can't compensate for brighter lighting enough with shutter speed. ie: bright midday sunlight probably is more likely to hurt rather than help your cause.

staereo
09-13-2006, 01:13 PM
In addition, the F707 had a really good knack for nailing bokeh when considering its sensor size. One of the nicer 'digicams' that was released along the evolution of digital cameras, imho.

Bruce

Anime London
09-13-2006, 04:55 PM
I had the effect that Nightko talks about on my Canon SD300 but only by accident as in the case of the picture below.

http://www.animelondon.ca/cosplay/an06/day01/thumbs/an06-117.gif
Full size (http://www.animelondon.ca/cosplay/an06/day01/an06-117.jpg)

The subject remained stationary as the people walked behind her. The blur was more to the camera picking a slower shutter speed. Annoying at times it has ruined many of shot of mine. While small cameras have smaller CCDs they also have smaller lens which make focusing and choosing proper setting more difficult.

ZiggyB
09-13-2006, 06:27 PM
Anime London: That's actually motion blur like you said. I think Nightko is going for something else. :)

But yah, I can't add anything considering the answer has already been giving in quite good detail.

Trelyon
09-13-2006, 08:00 PM
::ducking from all the rotten tomatoes::

you can cheat and use photoshop to blur your background ;)

without photoshop... i 'think' you can use an EF-S 17-55 f/2.8 IS zoom lens... to create a shallow depth-of-field... for the blur you needed... the wise folks above will prolly correct me ::winks::

[Edited: oops... wrong cam... can't use the zoom...]

staereo
09-13-2006, 08:15 PM
Maybe theres some way about attaching a lens to the s3, but i thought the s3 was a digicam, not a dSLR. (In fact, im pretty sure of this.)

That aside, the lens that it comes with is a f/2.7-f/3.5, with what i presume to be an f/8 switch. So, wide it will have a larger aperture than a f/2.8 would offer anyways... The camera has an onboard system in the lens for IS too.

The issue really is in the sensor size as i mentioned.

ANNNNND.....

grrrr I hate fake blur. HATE IT.

That said, if there was a time that I would HATE it least, it would be when the tools you have available to you do not allow you to perform creating a bokeh in camera.

Soo.... if there is ever a time that justifies PS'd blur, it would be here. Not that I like the idea, but its least evil in a situation like this.

Definately stay 'ducked' down. I have a few tomatoes somewhere... :D

Bruce

The-Real-Link
09-13-2006, 10:33 PM
Thanks to everyone else above who pointed out some great info. Although even what Staero stated left me re-reading the post a bit as it's a lot to digest, I may be able to give some tips as I've been using an S1 for awhile which is similar to the S3.

It would seem (and Staero's points do make it hold true) that to get good DoF, you're either going to have to rely on a strong distance between your subject and the objects behind you, or be forced to do a shot very close to the subject.

I think these are decent examples to show, but again sensor-size or f-stop aside, there are only a few ways I've gotten it to work - even if I don't fully understand the technical reason behind it all as Staero does (though I'm learning ^^).

http://images.cosplay.com/showphoto.php?photo=571653 (Example where lens is wide-angle and I'm very close to the cosplayer).
http://images.cosplay.com/showphoto.php?photo=571641 (Example where I'm zooming in a lot already but the background is a good distance away too).
http://images.cosplay.com/showphoto.php?photo=568119 (A mix of both of the above).
http://images.cosplay.com/showphoto.php?photo=684644 (It's more subtle here, as the distance to the building isn't quite enough for a full effect I think).
http://www.youmacon.com/2005/photos.php/Cosplayers%20-%20Saturday/Youmacon%20-%200509/ (Another shot where the flag is very far away).

Hopefully this helps you out a bit and if there's anything I said that's wrong, I'm sure I will be corrected.

staereo
09-14-2006, 08:49 AM
What is done here is almost exclusively increasing distance between your subject and the background. That is a perfectly fine way to increasing background blur. What this does in a technical sense is increase the distance between your background and the focus point, and as I mentioned above, the further you are from your focus point, the larger the blur.

What's important to note, and something that Jason also touched on, is zooming in, tight shots.

The reason this gives an effect of a blurred background is because the longer your focal length, the closer the background appears to the subject. Yet, because the background remains, in reality, just as far away, youre having the same distance from the subject to the background. The difference is, the section of the background you see is blown up (zoomed in on it) the blur is more apparent, because the circle of confusion is larger to the viewer.

Here is a good example, using Link's images.

Here is a shot at a wider focal length:
http://images.cosplay.com/showphoto.php?photo=568118

What I presume to be the same shot, but a longer focal length (zoomed in)
http://images.cosplay.com/showphoto.php?photo=568119

The distance remains a constant, but the background APPEARS closer in the second one, because the longer focal length pulls it in. As the background gets larger to the viewer, the blur becomes more noticable, as those 'spots' blur bigger.

Bruce

jtnishi
09-14-2006, 11:17 AM
What is done here is almost exclusively increasing distance between your subject and the background. That is a perfectly fine way to increasing background blur. What this does in a technical sense is increase the distance between your background and the focus point, and as I mentioned above, the further you are from your focus point, the larger the blur.

What's important to note, and something that Jason also touched on, is zooming in, tight shots.

The reason this gives an effect of a blurred background is because the longer your focal length, the closer the background appears to the subject. Yet, because the background remains, in reality, just as far away, youre having the same distance from the subject to the background. The difference is, the section of the background you see is blown up (zoomed in on it) the blur is more apparent, because the circle of confusion is larger to the viewer.

Here is a good example, using Link's images.

Here is a shot at a wider focal length:
http://images.cosplay.com/showphoto.php?photo=568118

What I presume to be the same shot, but a longer focal length (zoomed in)
http://images.cosplay.com/showphoto.php?photo=568119

The distance remains a constant, but the background APPEARS closer in the second one, because the longer focal length pulls it in. As the background gets larger to the viewer, the blur becomes more noticable, as those 'spots' blur bigger.

Bruce
Sorry, I'm about to get really technical for a sec, beyond what is probably worth thinking about unless you spend way too much time dabbling in photography, so I know this probably won't help nightko so much.

There is one other thing to catch: as I remember it, the rule with DoF is that all other things constant (aperture, film plane size, distance between subject and background), the same composition of subject yields the same Depth of Field, regardless of length of lens. That is, if you shot with a 50mm lens with a subject at 10', with a 100mm lens, the subject will be at about 20' to maintain the same composition, but the depth of field of focus will be the same, presuming you're using a camera of the same film plane size or the same camera outright, and that your aperture setting is the same. This is, of course, subject to whether your camera can focus on a subject that close at a particular setting.

Why should this matter? Because with most zoom lens, especially on consumer cameras, you normally trade off at the long end by having smaller apertures (bigger numbers), which increase depth of field. If you've ever looked at the lens marks on your lens, and saw something like 1:2.8-6.3, this means that the camera can shoot at f/2.8 wide open at the wide end of the lens, but only at about f/6.3 wide open at the long end (a difference of 2 1/3 stops in this case). This runs AGAINST blurring the background, though normally this is traded off against a different composition, since folks tend to shoot tighter shots when they're zoomed in. But, at the wide end, perspective normally skews poorly for a portrait, since it distorts features in a barrel fashion (think about commercial projects like "The Dog", or fisheye lenses which are like the peephole in a door).

As such, at least in theory, the main objective is to normally balance between the two when shooting portraits. In practice, the depth of field differences won't account to much (literally maybe inches), so zooming out as long as reasonably possible without being so long that you blur your shots through handshake tends to be better because of perspective. And separating the background is significantly more important. But the above is something to note, even if it's mostly academic.

The simplest point for everyone is that in general, putting your subject relatively close to the camera compared to the nearest background, as would happen normally in a close-up situation rather than a full body situation is what will help blur the background best for almost any given camera.

staereo
09-14-2006, 08:30 PM
........as I remember it, the rule with DoF is that all other things constant (aperture, film plane size, distance between subject and background), the same composition of subject yields the same Depth of Field, regardless of length of lens. That is, if you shot with a 50mm lens with a subject at 10', with a 100mm lens, the subject will be at about 20' to maintain the same composition, but the depth of field of focus will be the same, presuming you're using a camera of the same film plane size or the same camera outright, and that your aperture setting is the same...

you remember correctly... :bigtu:

nightko
09-17-2006, 08:28 AM
A big thank you everyone! I think my question is being very well answered.

Wow, there's a lot of detailed explanation! :)
I learnt a lot in this thread.
I think I understand the concept now.

I will be going to Japan tomorrow to take lots of photos, hope I can make the full use of my camera there. ^_^ THanks guys!

BTW, the numbers on the lens of my S3 are 6.0-7.2mm 1:2.7-3.5 USM

staereo
09-17-2006, 08:47 AM
Good luck, and remember that background blur is a creative option, but it isn't a requirement to great pictures. Many images that HAVE blurred backgrounds would have looked better without the blur. So just be creative and have fun!

Bruce

Chineseclover
09-17-2006, 03:56 PM
or you could just photoshop the background (blur brush) *for peeps like me that dont know how to use cameras*

staereo
09-17-2006, 07:54 PM
lol refer a few posts above, chinese.. hehe this was mentioned. ;)

TomodachiFriend
09-18-2006, 02:21 AM
Well, it really depends on who does the photoshopping. The problem is that too many go overboard with that gaussian blur when gaussian blur is a poor substitute for real bokeh to start with.

staereo
09-18-2006, 04:47 AM
.......gaussian blur is a poor substitute for real bokeh to start with.
:rockon: :bigtu:

Trelyon
09-18-2006, 08:32 PM
Well, it really depends on who does the photoshopping. The problem is that too many go overboard with that gaussian blur when gaussian blur is a poor substitute for real bokeh to start with.

aye... gaussian is mostly for making drop shaddow... and VERY poor for bokeh... a good convolutional filtering in the alpha channel with the Photoshop >> Blur >> Lens Blur filter... should do a decent job if your camera can't get the right depth of field

staereo
09-18-2006, 08:38 PM
Again, I *really* hate the idea of PP background blur.... BUUUT, if youre going to do it, at least crop the image such that you dont have a plane that points out your single-dimension blur.

An example is how the floor ends up the same blur all the way around the subject, both in the foreground, background, and everywhere in between. Avoid situations by cropping these out first, so that your blur all happens in a relatively equal distance from the lens.

Or... dont do PP blurring.. rofl!

Bruce