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11-29-2010, 11:02 PM   #1
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I am getting a lot of noise at ISO 800 and ISO 1600....

I am very confused, I thought at these ISO's it was virtually non existent.

Iso 800:

Name:  Raw1 (1 of 1).jpg
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Close Up:

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Iso 1600:

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Close Up:

Name:  Raw2close (1 of 1).jpg
Views: 1848
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Purple Fringing also seems to be a problem...

I am using a Pentax-M 50mm 1.4 in perfect condition, flawless.

What could I be doing wrong here?


Last edited by Abstract; 11-29-2010 at 11:09 PM.
11-29-2010, 11:10 PM   #2
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I'm not sure what you're referring too, but as far as I know, any camera that I'm aware of, can and will exhibit noise at 800 and 1600.

In fact... I've found noise from the K-5 at ISO200 even.
Having said that, I think the noise is none destructive in nature, nor would it ever translate in 1:1 prints or higher until much higher than that.

As for the PF, can you tell us what aperture you were shooting at and... most of all, what areas it is manifesting itself in the image?
11-29-2010, 11:11 PM   #3
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Not sure of your experience level with digital sensors, but you aren't going to find a much better noise pattern at ISO800 or ISO1600 on any other APS-C sized sensor. And what you are calling purple fringing on the streetlight is not. It is reflected light off dust around the light itself.
11-29-2010, 11:13 PM   #4
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I was shooting between 2.8 and 1.4 F-stop, shutter was about 80-120. I know that but from what I have seen around here noise was a non issue at these ISO's...

I might have been mistaken though, I am not here to bash the camera, just wondering what I am doing wrong if anything.

11-29-2010, 11:20 PM   #5
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QuoteOriginally posted by Abstract Quote
I was shooting between 2.8 and 1.4 F-stop, shutter was about 80-120. I know that but from what I have seen around here noise was a non issue at these ISO's...

I might have been mistaken though, I am not here to bash the camera, just wondering what I am doing wrong if anything.
No worries, as far as I'm concerned, its your camera and you are perfectly entitled to bash it if you want too

Having said that, I'm going to side with jbinpg and say that I think the noise looks quite nice in this image(no need to clean that up).

However, the PF might be something worth investigating a bit further.
From my own experiences with the 1.4, I'd say say some fringing around hard contrast lighting(such as night lights) is perfectly acceptable for anything at f/3.5 or wider.
However, if you're seeing it at f/4 or higher then it might be worth looking into a little further.

But a little fringing around direct light sources at 2.8 or less is more or less normal based on what I've seen with the 50/1.4 and 1.7's. Especially if it falls in the short end of the OOF region(early bokeh).

JohnBee added later...

As for the second image, there is something odd about the grain on that image.
I don't know what it is, but it looks altered or processed in some way(shutter speed?)

Last edited by JohnBee; 11-29-2010 at 11:27 PM.
11-29-2010, 11:26 PM   #6
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I see, I guess some images here just misled me a bit, like the one in your sig Johnbee, no offence but I was a little confused. The camera does handle beautifully though.
11-29-2010, 11:34 PM   #7
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QuoteOriginally posted by Abstract Quote
I see, I guess some images here just misled me a bit, like the one in your sig Johnbee, no offence but I was a little confused. The camera does handle beautifully though.
Behold the power RAW shooting and Post Processing(PP )!
Though in defense of the K-5, I'd say that it would be tough to exceed its noise performance this side of the best of Full Frame systems.

Also, for what it's worth... the images you posted would clean-up very well with a little post processing if you wanted to go take things up a notch. So there's always room for improvements.
11-29-2010, 11:37 PM   #8
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I have tried noise reduction in Lightroom 3, not a fan, never seems to help. These are RAW's btw. Well I am off to bed, maybe someone can point me in the direction of a better noise software product?

11-29-2010, 11:49 PM   #9
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QuoteOriginally posted by Abstract Quote
I have tried noise reduction in Lightroom 3, not a fan, never seems to help. These are RAW's btw. Well I am off to bed, maybe someone can point me in the direction of a better noise software product?
Okay I wasn't sure if these were RAW or JPG.
Well that may explain the grain in the second image(processing?).

However... in my own experiences, I've found Adobe Camera RAW(same engine as Lightroom 3 btw) to be an very good RAW developer with regards to demosaic'ing and local adjustement. Though as you yourself mentioned, it may not be most proficient luma noise reduction solution. Which incidentally is most likely what the images you posted are exhibiting. Though LR3 does have a good reputation for chroma(color) noise reduction(if not the best) to date. So I wouldn't write the software off just yet.

With that in mind, I've found that combining ACR/LR3 with a plugin called Topaz Denoise produces what I'd call the ultimate NR solution across the board. Which may very well prove more profitable than with LR3 on images such as these. Though I don't think they warrant any chroma noise reduction, you would still benefit from LR to develop and adjust the RAW files prior to NR.

If you're interested, you can download a demo and see how it works out firsthand. Who knows, it might even surprise you.
11-30-2010, 02:02 AM   #10
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I'm surprised that you used such high ISOs in these two shots. Were these hand-held?

Unless there's subject movement involved, at night I use a tripod, the lowest ISO I can & set the aperture of the Pentax-M 50/1.7 to F4-F5.6 or the Pentax-M 28/F2.8 to F5.6-F8 with a K20D.

Dan.
11-30-2010, 02:17 AM   #11
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The problem here is that these are very dark exposures. Because of the nature of digital imaging, dark areas will have a worse signal-to-noise ratio and use fewer bits, therefore making noise more apparent. What you're showing above is actually a beautiful performance (very little chroma noise!) considering what you are asking the sensor to do. This is what your histogram looks like in the landscape picture:



As you see, there's no real information in the upper half, which is doing a lot of damage to IQ. What you want to do in a situation like this is deliberate overexposure (as far as you can go without clipping highlights,) so you get the signal as far as possible above the noise floor and use the maximum bit depth, and then pull back exposure in the raw conversion. This would allow the K-5's true capabilities to shine.
11-30-2010, 03:17 AM   #12
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I agree with Erik. My first impression was that those are underexposed.

In the first one it doesn't harm, by the way.
11-30-2010, 03:39 AM   #13
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It's in fact a great performance to have so little noise on these shots (they are very nice BTW). As Erik said they are very low-key, the histogram is mostly on the left where the noise can show up even at low ISO on any camera.
11-30-2010, 04:19 AM   #14
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If this comes from a raw converter, then the ISO number isn't very significant anymore to start with.

Any amount of added brightness, exposure, or fill light actually shifts the effective ISO to higher values. All sliders combined can push ISO 80 into 80,000

And still, the resulting image seems to be pleasing. Nice "grain".


As for purple fringing.
Please google for "Bokeh CA". It's the lens, not the camera. Smaller pixels magnify lens properties. Bokeh CA isn't an aberration, it isn't Lat. or Long. CA. But it's still cuased by the lens and proportional to aperture and glass dispersion.
11-30-2010, 04:54 AM - 1 Like   #15
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Here's a (very quick and dirty) example:



These were both taken at ISO 1600 with a K200D. One was underexposed 2 stops (so effectively ISO 6400) then pushed, and one was overexposed 2 stops then pulled (equivalent to an ISO 400 exposure.) So yeah, this is basically what you're seeing, although you haven't pushed your images back up to a "correct" exposure -- if you did, you would be seeing a lot more noise. Nevertheless... Mind the histogram.
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