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Improved bokeh

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Offline mkmenuts

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  • 61
  • SD700 (1.01b)
Improved bokeh
« on: 19 / May / 2008, 13:53:58 »
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Good bokeh is more dificult on P&S cameras than DSLRs. I have an idea on how CHDK could help...

The general guidlines to get bokeh:
1. Use the lens wide open
2. Zoom in
3. Use macro
4. Get near the subject

My idea is to use the focus distance creatively to seperate the subject from the background:

C - Camera
S - Subject
B - Background
. - Empty space (let's say 1 meter in length)
[ - Focus begin
] - Focus end


This is the camera, subject & background:

C.....S...B

After half-shoot, the focus is let's (let's say it locks correctly):

C...[..S...B]

This means the subject is in focus, but the background is not blurred. Now CHDK intervenes and moves the focus point closer to the camera (same DOF mind you):

C.[....S.]..B

Now the background is blurred but subject is still in focus. You can emulate this manually for now using Manual Focus.

Now shooting will give a nice bokeh background.

What are your thoughts? What configuration options are needed?

Looking for your comments,


mkmenuts
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Offline A630Lover

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Re: Improved bokeh
« Reply #1 on: 26 / May / 2008, 09:42:33 »
Mmhh, yes, it seems interesting. But you mean that after that you have to "play" with different layers like in photoshop?
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Offline mkmenuts

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  • SD700 (1.01b)
Re: Improved bokeh
« Reply #2 on: 28 / May / 2008, 12:36:00 »
Quote
you mean that after that you have to "play" with different layers like in photoshop?

No, the Jpeg will come out ready, the focus will change before the shutter operates.
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Offline jbourgui

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  • 15
  • SD500 & G9
Re: Improved bokeh
« Reply #3 on: 08 / July / 2008, 02:03:54 »
I'd like to second this request!  I currently don't have any real control over focus on my SD500, and this would rock!  To have DSLR type Bokeh on my camera which can't even manually focus without CHDK is great...  Cheers,

-joe
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Offline wap4

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  • A720IS
Re: Improved bokeh
« Reply #4 on: 09 / July / 2008, 04:48:48 »
I can't see much hope here, as

1. When you zoom in,you may have to sacrifice F-number a little.(But the S-series has high optics F/2.8-F/3.5)

2. My A720 will not focus in macro mode after certain zoom amount, indicated by yellow zoom bar.(Don't know
   the behaviour of of S-series though)

3. In the idea, DOF will be so shallow that there will be not much space between [ & ].

4. The A/S series does not have circular type aperture, which is needed to get good bokeh.

May be I'm too pessimistic!
« Last Edit: 09 / July / 2008, 04:52:57 by wap4 »
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Offline jetzt

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  • [A710IS,(SD200)]
Re: Improved bokeh
« Reply #5 on: 09 / July / 2008, 12:57:25 »
I don't know too much about this topic, but you can get some nice results anyway, but that's nothing objective.
(Not the best example:)
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Offline LjL

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  • 266
  • A720IS
Re: Improved bokeh
« Reply #6 on: 09 / July / 2008, 18:22:01 »
How about this script?


@title Bokeh
@param t Tolerance (mm)
@default t 5
rem We want minimum depth of field
set_av 9
press "shoot_half"
print "Focusing - hold still"
rem could also check propcase 205 (DIGIC II) or 206 (III) instead of sleeping?
sleep 1500
rem Get subject distance and near limit
get_focus s
get_near_limit f
rem Set manual focus - should be click "mf" on some cameras
click "down"
rem Uncomment the following if your camera crashes
rem release "shoot_half"
rem Set new subject distance as old near limit, with some tolerance
let f=f+t
rem Make sure we had enough tolerance
set_focus f
get_far_limit l
if l<s then print "SUBJECT NOT IN FOCUS" else click "shoot_full"
sleep 1000
end
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Offline Harithhaziq

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Canon SX20 or in its class : Improved BOKEH in non-macro distance.
« Reply #7 on: 03 / June / 2010, 10:28:34 »
The problem with p&s cam is that it don't have different auto-focus point like DSLR. This autofocus points will give bokeh effect in various distance instead of macro, so is there anything possibilities of CHDK to make this system particularly for powershot sx20 IS? to have great blur image for foreground or background.please help!
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