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-   -   K100, K20 Low Light (https://forums.steves-digicams.com/pentax-samsung-dslr-k-mount-mirrorless/140030-k100-k20-low-light.html)

mtngal Apr 18, 2008 12:08 AM

I went for a walk this morning in the pre-dawn, taking a variety of pictures at ISO 1600, 3200 and 6400. My conclusion is that 6400 isn't very useful unless you seriously downsize the picture and don't mind losing a huge amount of detail.

I used AWB,and P modes, and specified the ISO, until the sun came up and then I changed back to auto ISO. The one thing I didn't quite notice was that the K100 was on center-weighted metering and the K20 was in matrix. I wasn't particularly concerned about lens quality so I didn't change lenses at all - the DA12-24 was on the K20 and the kit lens on the K100. I tried to take all pictures between 18-24, so they would be comparable. All were hand-held.

The first thing I noticed was that my K20 consistently slightly under-exposed the night scenes, while the K100 was slightly overexposed (next time I'll try the K20 on center weighted to see if I get better results). I think I'll try setting a +.3 Ev on the K20 next time if I use matrix - I think it tends to err on the side of caution.

The second thing I noticed was that the two cameras handle strange light differently. In some cases the K20 was more accurate and at others, the K100. In one case, I actually liked thepicture that was off better than the one that was relatively accurate. In some cases, there was very little difference.

These pictures were all taken in PEF, converted in Lightroom default settings, resized in CS2 (they are full frame, no cropping at all), no noise reduction and no pp. You can tell I'm not very good about keeping my vertical lines straight (normally I'd rotate the picture to line up the lines, but decided to leave these unprocessed). This might not be the most exciting scene in the world, but I liked the colors.

K20, ISO 1600:

http://mtngal.zenfolio.com/img/v1/p455331410.jpg

Here's the K100 at ISO 1600:

http://mtngal.zenfolio.com/img/v1/p146124160.jpg

K20 at 3200:

http://mtngal.zenfolio.com/img/v1/p199478069.jpg

K100 at ISO 3200:

http://mtngal.zenfolio.com/img/v1/p132744803.jpg

Finally, the K20 at ISO 6400:

http://mtngal.zenfolio.com/img/v1/p302216303.jpg

As you can see, even at this very reduced size the noise is really distracting (and the picture is more underexposed than the other two). It has a fair amount of detail, but it would lose that texture and detail quickly with a noise reduction software.

When I looked at the pictures at 100%, the K20 has more noise at ISO 3200 than the K100. However, once you resize the K20's picture down to the same size as the K100, there isn't all that much difference. Like any camera, the noise is worse in the darker parts, and since the exposures weren't the same, I wonder if the K20 would have done better without the slight underexposure. Not that I'm complaining, it's still better than my old K10.

thkn777 Apr 18, 2008 12:17 PM

Hm,
I don't think you can judge the noise by those downsized images as denoising works differently at different image/noise sizes for both grain and color noise. If possible give a link to a high quality image in original size...

I tried some basic denoising on the ISO6400 shot and of course some details on the ground seem to vanish - but that's only because they are already so small from downsizing. Other than that it's not that bad for ISO6400 - you know?

Here is my attempt (quick and dirty 2-pass denoise):

http://www.rifiles.de/pics/steve/iso...noised1-80.jpg

The bike for example is still ok, but the pavement (the splices(?) - how do you call the gaps in english) lost a bit - but as I said above - an image with higher resolution should respond with more details here.

Regards,
Th.




thkn777 Apr 18, 2008 12:25 PM

*** double post (for some strange reason) ***

Monza76 Apr 19, 2008 7:25 AM

1 Attachment(s)
OKay, couldn't resist taking a shot at that last K20D image. As you can see Noiseware got rid of the noise but also the detail, I adjusted the levels in PSE first. Total time, about two minutes (this really is quick-and-dirty) but I like the look of the result, even though I wouldn't want to make a large print from it. The noise reduction has increased the contrast around the bicycle so that it really stands out now, a strange, and unexpected, side effect.

Ira

mtngal Apr 19, 2008 5:47 PM

Interesting about the noiseware - I'm not sure I can upload a full sized picture, but maybe if I can put it up at the same size as the K100, I'll post a link so everyone can try their particular noise-ware software - then we could see which software handles the picture the best. It will have to wait until I'm back home, though (I'm on the road again).

mtngal Apr 26, 2008 11:51 PM

If anyone is interested - I uploaded the full size version of the K20's 6400 picture. I was shooting raw+ so I uploaded the raw version that's been converted to tiffusing Lightroom's default settings and saved as a jpg, somewhat compressed in Photoshop (I didn't think about changing my Lightroom export settings to jpg). I also took the jpg version and rather than uploading the original, I did a save-as and re-saved it at a higher compression rate. Neither have been resized, but the jpg version is a smaller file because it was compressed both in-camera and again through Photoshop.

Zenfolio will let you download the original picture by puttingyour cursor over the right hand side of the photo and a pop-up with icons will appear. One of them is for downloading the file - feel free to download it and play with whatever noise reduction software you want (or any other software for that matter).

The link to the smaller file (the one that was compressed twice is at: http://mtngal.zenfolio.com/p780316653/?photo=371651800

The link to the much larger file, the one that was the raw file originally, is at: http://mtngal.zenfolio.com/p780316653/?photo=515389431

I do want to warn you that the files are huge - a K20 picture is 4672 x 3104 pixels, and that's a lot of information. As I mentioned in the first of this thread - the ISO 6400 picture is very noisy and probably only useful if you are really desperate. Have fun with it.


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