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Old Apr 17, 2012, 9:04 AM   #1
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Default Canon SX150 IS - Artefacts even at lower ISO - Help!

Hi All,

I recently purchased a Canon Powershot SX150 IS. Though it is a great camera in terms of features, I am not getting along happily with the image quality.

The two pics below are taken at ISO 200 and you can notice the artefacts.

I have attached the photos along with the EXIF data. (Images resized)

Can some one please help what is going wrong here.


Image 1:

Name:  IMG_0197.jpg
Views: 2516
Size:  86.5 KB

EXIF:

File type: JPEG
File size: 2,370.1*KB
Creation date: 4/14/2012 12:05
Last modification: 4/14/2012 12:05
Make: Canon (http://www.canon.com)
Camera: Canon PowerShot SX150 IS
Lens: 5-60mm
Software: Firmware Version 1.00
Dimension: 4320 x 3240*px*(14 MP, 4:3)
Focal length: 5*mm
Aperture: F7.1
Exposure time: 1/1000"
ISO speed rating: 200/24°
Program: Manual (Manual)
Metering Mode: Center-weighted average
White Balance: Daylight
Focus Mode: Single-point AF
Image Stabilizer: 258
Flash: Flash did not fire, compulsory flash mode

Image 2:

Name:  IMG_0198.jpg
Views: 1820
Size:  91.2 KB

EXIF:

File type: JPEG
File size: 2,421.8*KB
Creation date: 4/14/2012 12:05
Last modification: 4/14/2012 12:05
Make: Canon (http://www.canon.com)
Camera: Canon PowerShot SX150 IS
Lens: 5-60mm
Software: Firmware Version 1.00
Dimension: 4320 x 3240*px*(14 MP, 4:3)
Focal length: 5*mm
Aperture: F7.1
Exposure time: 1/640"
ISO speed rating: 200/24°
Program: Manual (Manual)
Metering Mode: Center-weighted average
White Balance: Daylight
Focus Mode: Single-point AF
Image Stabilizer: 258
Flash: Flash did not fire, compulsory flash mode
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Old Apr 17, 2012, 9:54 AM   #2
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You'll notice less "noise" in pic 2- simply because the shadows are not as dark- due to a longer exposure time.
It's actually a tricky exposure for a camera,due to the high contrast nature of this shot- do you under-expose the foreground to maintain the sky's detail(resulting in noise in shadow areas) or expose the foreground correctly and accept the resulting loss of detail(blown highlights) in the sky?
Most of Canon's current line up has an "iContrast" feature- which can help balance out a tricky exposure- but it has its limitations. It works well on the SX40hs- and if the SX150 has it,I'd switch it on.
Also with the shots above- given that nothing was "racing" around in the shot,you could have used iso 100(reducing noise/artefacts),maybe open up the aperture a touch and you'd still have enough shutter speed to play with.
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Old Apr 17, 2012, 10:24 AM   #3
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I don't see it often mentioned on the forum, I hope there isn't some sort of ban on it... :

If you're feeling adventurous, you can try the alpha (ie, not even BETA software) version of the "Canon Hack Development Kit".. a small firmware plugin (it doesn't really replace firmware) that extends Canon camera software.

I use it for bracketing shots, and for its pseudo RAW file format.. It's an half-assed attempt at RAW, it's only 10 bits per channel and not 12 or 14 like DSL's raw files, but it's still much more information - and unprocessed at that - than in the jpeg's 8 bit per channel.

That means you can, say, under-expose a shot and bring it back up in post-process (or you can do the reverse) depending on what you want to emphasizes, without bringing out the jpeg artifacts.

Top left is out-of-camera jpeg, top right is LightRoom autotuned jpg
Bottom is out-of-camera raw and then LightRoom autotuned raw.




However, raw files will be about 10x heavier than jpegs and they won't be cleaned of noise, sharpened, or lens corrected (which will produce harsh vignetting when you're at the widest angle of that SX150 IS (I know, that's the camera I use).
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Old Apr 18, 2012, 7:07 AM   #4
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Quote:
Originally Posted by SIMON40 View Post
You'll notice less "noise" in pic 2- simply because the shadows are not as dark- due to a longer exposure time.
It's actually a tricky exposure for a camera,due to the high contrast nature of this shot- do you under-expose the foreground to maintain the sky's detail(resulting in noise in shadow areas) or expose the foreground correctly and accept the resulting loss of detail(blown highlights) in the sky?
Most of Canon's current line up has an "iContrast" feature- which can help balance out a tricky exposure- but it has its limitations. It works well on the SX40hs- and if the SX150 has it,I'd switch it on.
Also with the shots above- given that nothing was "racing" around in the shot,you could have used iso 100(reducing noise/artefacts),maybe open up the aperture a touch and you'd still have enough shutter speed to play with.
You hit the nail on the head. It is my mistake too where I tried to get best of both worlds. The sky is good and the camera has tried to highlight the shadows in the glass panes resulting in noise.

The i-contrast was on and I believe it has done the opposite of trying to highlight the shadow but ending up noisy.

Thanks for your tip, I will try with a wider aperture next time.

ISO 200 is fair enough right ? Being a Modern camera, it shouldn't be noisy at this level.


Quote:
Originally Posted by PaulPosition View Post
I don't see it often mentioned on the forum, I hope there isn't some sort of ban on it... :

If you're feeling adventurous, you can try the alpha (ie, not even BETA software) version of the "Canon Hack Development Kit".. a small firmware plugin (it doesn't really replace firmware) that extends Canon camera software.

I use it for bracketing shots, and for its pseudo RAW file format.. It's an half-assed attempt at RAW, it's only 10 bits per channel and not 12 or 14 like DSL's raw files, but it's still much more information - and unprocessed at that - than in the jpeg's 8 bit per channel.

That means you can, say, under-expose a shot and bring it back up in post-process (or you can do the reverse) depending on what you want to emphasizes, without bringing out the jpeg artifacts.

Top left is out-of-camera jpeg, top right is LightRoom autotuned jpg
Bottom is out-of-camera raw and then LightRoom autotuned raw.




However, raw files will be about 10x heavier than jpegs and they won't be cleaned of noise, sharpened, or lens corrected (which will produce harsh vignetting when you're at the widest angle of that SX150 IS (I know, that's the camera I use).
I am aware of the CHDK, but I'm averse to it for 2 reasons

- Canon might start nitpicking with the Warranty, if I want any service with them.
- I am just a casual shooter who likes to shoot his own way and I don't know if the time and effort with CHDK and Post processing is really worth it.

I just want to get a good pic out of the camera.

Is CHDK the only way to go ?

PS: Your pics after CHDK are great. Love the sharpness.
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Old Apr 18, 2012, 9:46 AM   #5
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You can certainly do well without CHDK and its Raw files... Raw only affords you a bit of leeway when you slightly missed your exposure, so you can pick up, say, 2/3 stops on each side for details hidden in the shadows or highlights. And good white balance correction.

In both case it's about correcting your original exposure.

I'm confident that, as I familiarize myself with the camera (it's only two weeks old) and the different controls (Av, Tv, Manual...white balance, AF and metering types...) it allows, I'll be moving OFF of the raw files except for correcting my mistakes or to perfect an already glorious shot (assuming I ever learn how to frame them correctly!).

If you look at those flags above, I under-exposed by one step. Surprisingly, the out-of-camera jpeg was pretty good (better than out-of-camera Raw) and with small tweaks I would have been perfectly happy with that shot too. (Going full manual, you wouldn't use the EV compensation, though : you'd set a faster shutter or a higher F-number)

As for ISO rating... Here's what I suggest (my opinion may change, I AM a beginner myself) : set it as low as your day and shoot will allow. -- First, though, learn what shutter speed you're able to comfortably hand-hold.

Then it's just a matter of looking at the available light and choosing the minimum ISO for your situation. Sports and actions you may want to bring it to 200, 400, 800... But for shots like the ones you linked I think 100 or 80 would have been right. 1/1000 seconds expo is pretty quick, lowering ISO would have brought you to a reasonable 1/600 or 1/400 exposition.

(Edit) About modern camera noise.. Reading reviews and other articles it has come to my attention that while the Megapixel count has kept climbing, the sensor size is still the same, so the "return on investment" isn't linear, and it is diminishing. -- Still, a 14MP picture from this camera, once resized to same resolution, gives me much clearer pictures than my old 8MP camera did so take it for what it's worth.
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Last edited by PaulPosition; Apr 18, 2012 at 10:34 AM.
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Old Apr 18, 2012, 9:53 AM   #6
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paray2x- yes,iso 200 on the face of it would(or should) seem a reasonable setting to use- though even at that level you'll notice noise in shadow areas- though not so much in other well exposed areas- the downside of small sensor cameras I'm afraid..!
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Old Apr 20, 2012, 7:33 AM   #7
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Quote:
Originally Posted by PaulPosition View Post
As for ISO rating... Here's what I suggest (my opinion may change, I AM a beginner myself) : set it as low as your day and shoot will allow. -- First, though, learn what shutter speed you're able to comfortably hand-hold.

Then it's just a matter of looking at the available light and choosing the minimum ISO for your situation. Sports and actions you may want to bring it to 200, 400, 800... But for shots like the ones you linked I think 100 or 80 would have been right. 1/1000 seconds expo is pretty quick, lowering ISO would have brought you to a reasonable 1/600 or 1/400 exposition.

.
This is really a very worthy advice. Thanks, I will try the lowest possible ISO next time.

Quote:
Originally Posted by SIMON40 View Post
paray2x- yes,iso 200 on the face of it would(or should) seem a reasonable setting to use- though even at that level you'll notice noise in shadow areas- though not so much in other well exposed areas- the downside of small sensor cameras I'm afraid..!
@SIMON40, You're right. I believe that is where the trade off is.
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