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SD 1100 IS Digital Macro Mode with forced flash

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SD 1100 IS Digital Macro Mode with forced flash
« on: 15 / July / 2009, 02:42:43 »
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This is a fantastic combination.  I would like to put together a script to do this.  The various controls interact in a complicated manner.  I want to reduce the shutter speed or otherwise tone down the available light, so the flash is dominant.  I have been getting double exposures, except a few lucky shots, and I'm not sure which controls were responsible.  I think the shutter speed override.  Not sure.

I would really appreciate to learn more about how the Digital Macro works.  I would also like to override focus distance for Macro Mode itself, but haven't tried.

Any discussion would be of great interest.


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Offline Anaglyphic

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Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #1 on: 15 / July / 2009, 13:32:48 »
I would really appreciate to learn more about how the Digital Macro works.  I would also like to override focus distance for Macro Mode itself, but haven't tried.

Hi.

Uhm, I'm not sure what you're asking. Macro focus works the same way as in Normal mode, although it's focal range is much less. It also only works with the lens at it's widest setting, if you try to zoom in even one tick, you'll have to increase the camera's distance from the subject. Minimum macro focus mode for an SD1100 is 3cm at wide angle, but at maximum optical zoom this jumps to a whopping 30cm.

Now, Digital Macro mode pulls the lens to wide angle, but when you use the zoom lever it digitally zooms (interpolation), leaving the lens alone. If you have the camera set to it's highest resolution, it's going to have noise when you do this; conversely if you have it at a lower resolution, then digitally zooming causes the camera to increase resolution and toss away the extra bits outside the frame.

One way to know if you're in a noisy digital zoom situation is to look at the zoom value on-screen. If it's in blue,like 7.7x, then you are going to have image deterioration. If it's in white, you are good to go.

hth
Since we cannot know all that there is to be known about anything,
 we ought to know a little about everything.
-- Blaise Pascal

Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #2 on: 18 / July / 2009, 08:55:05 »
I am waiting for another post to show up here.

Meanwhile, further questions occured to me, and I tried to shoot some macros, using digital macro and non-digital macro.

  - How about setting subject distance overrides with macro?  I tried with Macro Mode, zoomed in, and zoomed wide.  Zoomed wi\de is quite good, but I need to verify whether setting subject distance made any different.  Manual flash override, with intensity of "0" toned down the flash from the standard (Standard flash settings are too bright for this camera using macro mode at closest distance). 

   -  It also looked like digital macro was less magnified than regular zoom.  There are a number of tradeoffs, and different settings.  ND, distance, flash intensity, and ISO.  I shot with iso of 10, and a fast shutter speed.

   

Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #3 on: 18 / July / 2009, 08:59:56 »
I took the following shot with this camera.  The experiments were not documented.  I think this was shot in Digital Macro mode with flash manual override. 


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Offline Anaglyphic

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Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #4 on: 20 / July / 2009, 23:35:48 »
I still am not entirely sure what you are asking. I'm sorry that I can't figure it out. Someone else please jump in...

How about setting subject distance overrides with macro?
...
I need to verify whether setting subject distance made any different.

No. Not if it was lower than what the lens can focus at. I mean, OK look at it this way ... It's got very little to do with overrides and more to do with the optics. Most of these tiny pocket-sized PowerShots use a technology called "annular folded optics". It lets them cram a fairly useful zoom (usually around 3.2x max) into a tiny, tiny protrusion. The downside is they have a narrow focus range. This is compounded by the fact most of the SD cams don't have an aperture, in the traditional sense.

If you set focus to macro, and zoom out fully, the nearest object you'll be able to focus on is 30mm away. So if you override focus and set it to it's lowest setting, nothing is going to be in focus closer than 30mm. Not possible. It is a physical limitation. There's no "trick" or anything that CHDK can pull off. (maybe if you had a supplemental lens...)

Now, say you zoom fully telephoto. That's 3x optical zoom, but now, because the way the lens elements are positioned, you won't be getting anything in focus in ten times the distance above, or 300mm. Again, you can set the focus to any override under that, but it won't help anything. It's a physical limitation.

Digital Zoom is like resizing a small picture in a paint program. It gets resampled, it's interpolation. The bad part being that this is approximation based on surrounding pixels, so the more you "zoom" the less sharp your image will be. However if you lower the resolution of your image, this also provides "digital zooming" without the image degradation.  Does that make sense?

I shot with iso of 10
No. Sorry. :(

It's not really ISO 10. For these cameras lowering ISO does nothing. While you can force it to display ISOs lower than 80, if you do an ISO bracketing test, you'll notice both in the histogram and in the noise pattern when zoomed in ~800% in your favourite image editor, that there is zero difference between images shot at any ISO < 80 and images at ISO 80. The sensor in these cameras are already maxxed out. I mean it's staggering that Canon is pulling 8.3 million pixels off a tiny 5.75mm x 4.31mm CCD... I'm quite surprised that ISO 80 is relatively clean.

You can test this yourself, the steps are outlined on the Camera Features Chart - ISO Tests wiki page.

I hope this is answering some of your questions.
Since we cannot know all that there is to be known about anything,
 we ought to know a little about everything.
-- Blaise Pascal

Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #5 on: 31 / July / 2009, 16:06:38 »
Thank you for your helpful reply.  I have a couple of questions.  Most of what you are saying makes complete sense.

You wrote
Quote
Digital Zoom is like resizing a small picture in a paint program. It gets resampled, it's interpolation. The bad part being that this is approximation based on surrounding pixels, so the more you "zoom" the less sharp your image will be. However if you lower the resolution of your image, this also provides "digital zooming" without the image degradation.  Does that make sense?

Just for discussion.  A friend and I have argued about what's going on with Digitial ZOom.  He claims that there is something more than just selecting a portion of the full-res shot.  You suggest this is the case, but I hadn't thought of the possibility that the image is interpolated.  What I have noticed is the refined ability to focus on specific details.

I also understand what you are saying about ISOs and focal distances, and the physical limitations of the hardware.  When unsing digital zoom and forced flash, as well as with other modes, I have noticeable double exposure like effects.  SO I've tried to limit that shutter speed.  I think the shutter speed is pinned at 1/1,500.   Is the shutter a traditional one?  I have seen references to electronic shutters. 

The reason for using lower iso was to try to force side effects, but I think that isn't working.  I am hoping to lower the contribution of ambient light when using digital macro, and I think several settings are involved.

Thank you for your helpful posts.


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Offline Anaglyphic

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Re: SD 1100 IS Digital Macro Mode with forced flash
« Reply #6 on: 01 / August / 2009, 12:53:35 »
« Last Edit: 01 / August / 2009, 12:57:51 by Anaglyphic »
Since we cannot know all that there is to be known about anything,
 we ought to know a little about everything.
-- Blaise Pascal

 

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