PowerShot SX220 HS - Porting Thread - page 31 - General Discussion and Assistance - CHDK Forum
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PowerShot SX220 HS - Porting Thread

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Offline Blablaat

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Re: PowerShot SX220 HS - Porting Thread
« Reply #300 on: 25 / July / 2011, 08:14:59 »
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Quote from: funnel on 25 / July / 2011, 05:32:24
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But if it doesn't "calculate" the new ISO after CHDK overrides the shutter speed (when autoiso is selected) then the picture is useless. Is there a way to enable autoiso in manual mode?
Probably can be done. Try using custom autoiso with with it's custom shutter speed.

Did some test shots and Tv in combination with custom autoiso will do the trick.
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Offline funnel

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Re: PowerShot SX220 HS - Porting Thread
« Reply #301 on: 26 / July / 2011, 18:25:49 »
Quote from: abderian2004 on 25 / July / 2011, 00:26:45
Quote from: funnel on 20 / July / 2011, 13:29:18
I wasn't sure if the camera can go up to f11. Now I have proof.  8)

I checked sx230 till f16, The camera doesnt close its shutter to f16 aperture when shutter is half way pressed, however when pressing full shutter the apertue closes further up to a small "pin size" hole.

tested on taliesin's prealpha version.

I was playing with the Av override and I noticed that it can really go up to f16 but only at full zoom. Actually goes even two 1/3 steps more, I don't even know what f value is that(f18?). I found that with Av bracketing(+) starting from 5.9 at full zoom and comparing the histograms in review mode.

EDIT: it's f20
« Last Edit: 26 / July / 2011, 19:02:43 by funnel »
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Offline Microfunguy

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Re: PowerShot SX220 HS - Porting Thread
« Reply #302 on: 27 / July / 2011, 06:21:11 »
Quote from: funnel on 26 / July / 2011, 18:25:49
EDIT: it's f20

Do you realise that is equivalent to f110  on a 35mm camera ?

I would be VERY interested in seeing a sample photo.

According to theory, resolution should be terrible compared to wide-open aperture.

With small sensor cameras there is rarely any need to use a smaller aperture at all.
In fact, at telephoto setting ANY stopping down decreases resolution.
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Offline funnel

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Re: PowerShot SX220 HS - Porting Thread
« Reply #303 on: 27 / July / 2011, 07:08:41 »
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I would be VERY interested in seeing a sample photo.

I used + av bracketing 1/3 step, start at 5.9 full zoom. What do you think?

http://www.zshare.net/download/930310371d69c8ae/
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Offline Microfunguy

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Re: PowerShot SX220 HS - Porting Thread
« Reply #304 on: 27 / July / 2011, 07:27:56 »
Problem is, the subject is of limited depth-of-field.

Use a flat subject such as a detailed printed image or food package.

Bracket by one EV (fewer images for me to stack in PSP) and reduce shutter speed by one EV to compensate.


David
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Offline funnel

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Re: PowerShot SX220 HS - Porting Thread
« Reply #305 on: 27 / July / 2011, 07:45:04 »
I don't understand. A flat surface with or without background?

EDIT: what about this one?  http://www.zshare.net/download/93032582e935a3fa/
« Last Edit: 27 / July / 2011, 07:59:39 by funnel »
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Offline funnel

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Re: PowerShot SX220 HS - Porting Thread
« Reply #306 on: 27 / July / 2011, 09:35:54 »
I took a pic of inside of the lens when at full zoom and no zoom. Looks like there's no difference.
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Offline Microfunguy

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Re: PowerShot SX220 HS - Porting Thread
« Reply #307 on: 27 / July / 2011, 09:58:14 »
We are trying to detect changes in sharpness due to aperture rather than subject distance.

So, the entire flat object should fill the photo and be exactly parallel to the camera.

You did not override the shutter speed as requested so the images are too dark to compare.

Try to use something with smaller, far more  detail.

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Offline funnel

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Re: PowerShot SX220 HS - Porting Thread
« Reply #308 on: 27 / July / 2011, 10:40:43 »
Ok, here's another attempt :)

This time I started with +2EV.

http://www.zshare.net/download/93037627785ccf75/
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Offline Microfunguy

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Re: PowerShot SX220 HS - Porting Thread
« Reply #309 on: 27 / July / 2011, 19:12:29 »
Well, I appreciate your persistence but you are still not overriding the shutter speed.

Instead of bracketing, manually increase the aperture number by one EV and at the same time double the exposure time.

Repeat for each new aperture.

That previous test changed by +1EV per step, not +2EV.

The subject you used does not have fine detail.

You need something with tiny printed letters or lines close together.

Anyway, the previous test does prove each image became darker than the one before.
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