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02-09-2010, 02:03 PM   #1
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K-x Mixed Results in High ISO Tests?

Greetings all,
Shameless plea for help in explaining test results:

Losing a lot of sleep (literally) doing research on photo quality between the Nikon D5000 and K-x (and browsing this forum). I'm going to be buying my first DSLR soon, and the most important thing to me is noise reduction, both for ISO 200 (daylight mountain scenery, street scenes) and ISO 1600 and above (interiors, wildlife). Here's why: I've given up trying to shoot *way* too many shots with my Panasonic FZ-50 because of camera shake/not being able to freeze the action in low-light conditions. I'm thinking about holiday pictures, pictures in your local Starbucks, museum pictures, interior pictures in general.

Just when I thought that the fantastic dpreview tests made going with the k-x a no brainer ( Pentax K-x Review: 15. Photographic tests (Noise): Digital Photography Review ), I discover (because of this forum) the Comparometer at Imaging resource ( Imaging Resource "Comparometer" ™ Digital Camera Image Comparison Page ) which seemed to produce mixed results.

Looking at the first images the K-x is the clear winner (outdoor, indoor, house poster). I absolutely love how the K-x retains more detail than the D5000 even in low ISOs (this seems to match the dpreview results).

HOWEVER, in the later pictures, starting with the Macro shot things start to go downhill pretty quickly for the K-x. I can appreciate the difference in the Macro functions, but what is really troubling me is that the Still Life photos seem heavily weighted in the D5000's favor. With the D5000 more detail is visible, with less noise even at higher ISOs than the K-x. The tests also seem to indicate a tendency for the K-x to lose detail in bright colors.

These results seem totally out of line with the dpreview results, as well as with Imaging Resource's results above in the Interior shots.
Can anyone explain these results to me (keeping in mind that I'm a total noob to the DSLR world and have a limited vocabulary--try to keep the words small)? Is there maybe another good site where I can compare full-size images between the two cameras?

I was all set to buy the K-x, darnit, but these tests are making me reconsider.

Last edited by aspiring amateur; 02-09-2010 at 02:36 PM.
02-09-2010, 02:08 PM   #2
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Welcome to the forums!
Don't just consider the body, try to look at the available lenses too as you would be buying into a system.
Which lenses are sold at an expensive price, which is more cost effective.
You have to weigh all that with the small differences on the body capabilities or quirks.
If you would rather have in-body stabilization and use any lens off the market without the IS built-into the lens, then consider the Pentax brand.
If you have the cash to shell out for Nikon glass and would end up buying stabilization each time you buy a lens, then go for the Nikon brand.
Consider the system and not just the body.
02-09-2010, 02:35 PM   #3
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Thanks Gerry,

I'm willing to make sacrifices in cost & availability of new lenses as long as I get the detail, noise reduction/high ISO performance I'm looking for. The difference between the two setups I'm looking at is about $350, with the k-x being the less expensive of the two (I've priced out maintenance/insurance, Raynox lens, remote, etc.).

An extra $350 will hurt, but only for a little bit, and I'm willing to make the sacrifice if it means I'll be happier with my pictures.

Your lens comment made me think of something, though. The dpreview site tests with prime lenses so their results are more repeatable. I believe the Imaging Resource Comparometer uses kit lenses.

Could lens difference account for the loss in detail when comaring results from the two sites? And if so, why would the results for the K-x be so strong in the first indoor/outdoor test and yet falter in the still life test (both of these tests would be using the kit lenses since they're both on the Imaging Resource site)?

For me, the kit lens test would probably accurately reflect my real-world results since after my research I've decided to go with the kit 18-55mm (Pentax or Nikon) and branded tele (55-300 Pentax or 70-300 Nikon stabilized, autofocus).

Last edited by aspiring amateur; 02-09-2010 at 05:25 PM.
02-09-2010, 02:35 PM   #4
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Here you go

Any camera, any lens, pixel peeper size..


02-09-2010, 02:43 PM   #5
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Awesome! That one's going on my favorites right away...

Plugging in values now...
02-10-2010, 04:51 AM   #6
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The differences are actually quite small. All cameras lose dynamic range as you go up in iso. Colors will tend to be more muted -- some more so than others. As far as I am concerned, you would not be able to tell the difference between these two cameras in real life shooting. Just remember that for ultimate image quality, the lower the iso, the better your photo will be, even if you go out and get a 7D.
02-14-2010, 09:40 PM   #7
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Well, here's the update, my boyfriend and I just took the plunge and ordered the K-x for Valentine's Day. Happy day to us.

For those out there maybe considering either the Nikon D5000 or the Pentax K-x here was my rationale: we take a lot of low-light hand held photos so the ability to create sharp pictures at any ISO without much noise was very important to us.

As far as the image comparisons on Imaging Resource Comparometer goes, the K-x only blew the socks off the D5000 in the first image tests with the mannequin. Once I saw the direct comparison for the Nikon D5000 at 1600 ISO against the Pentax K-x at 6400 ISO (nearly identical) we took the plunge.

I still wonder about the still life photos at the bottom of the page, and why the K-x seemed more or less equal to the D5000 in the still life tests near the bottom, when it was clearly superior in most of the earlier tests. I've written it off to changing camera settings between the two tests (JPG vs. RAW or different noise reduction levels) because I haven't found any plausible explanation on the site itself.

For me, at least, I was confident that I would achive the image results I was looking for, and the possibility of being wowed every time I took a handheld low-light shot was too much to resist.

Thanks for everyone who responded to my thread.

Last edited by aspiring amateur; 02-15-2010 at 01:39 AM.
02-15-2010, 09:55 AM   #8
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The K-x and the D5000 use essentially the same sensor manufactured by Sony (the K-x uses a slightly weaker Antialiasing filter to capture more detail). IR comparometer samples can be useful for rough comparisons but I've found them highly inconsistent when you try to do anything serious with them.

RAW results from the two cameras should be approximately the same with perhaps a slight advantage to the K-x at higher ISOs, based on RAW file analysis done by falk lumo (I feel like I end up plugging his work every other post, probably since no one else has done such useful RAW analysis yet...).


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