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01-18-2013, 09:18 PM   #1
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Pentax K-x Photo issues

I've noticed that images taken with the Pentax K-x that I purchased about 2 years ago are, and I'm searching for the correct word here, grainy or have matte like color discrepancies. I've taken two photos. one with the Pentax K-x in JPG format at 6 Megapixal setting, & 2.5 MB file size using Auto Pict setting, and the same image again with my samsung galaxy 3 phone camera. The phone seems to take a better photo, as far as this undesirable matte effect goes. Hopefully, the two pictures are attached. The color is truer with the K-x as far as comparisons to my eyes go, but moving the phone towards darker or lighter areas can correct for that pretty well.

I've also tried RAW, and increasing the file size to maximum, but same effect. I can take a photo of the sky and see this grainy/matte effect. I'm a very casual photographer so please treat me like I don't know much.

Any ideas?



(firmware updated to 1.03)

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01-18-2013, 09:21 PM - 1 Like   #2
Ole's Avatar

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Your K-x image was taken at ISO 6400 so what you see is electronic noise which you will get at high ISO.

In good light as you had available you should use ISO 200 and your images will be clean.

The camera was set to Landscape mode which will use a small aperture (F14 here) and compensate by using a high ISO. You should practice using Av mode and set the ISO yourself (to 200) and a more reasonable F-stop like 8. In poor light you'll have to bump the ISO up to avoid too slow shutter speeds but that's another matter. Using ISO 6400 on the K-x is rather aggressive, though.
01-18-2013, 10:35 PM - 1 Like   #3
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Wow, Auto Pict failed about as badly as it possibly could here. In this kind of light, your camera phone can come surprisingly close to a DSLR, but only if the DSLR uses the right settings, which these are not. The DSLR has a few more variables to contend with than the phone, but still, that's hard to defend.

The best solution is to learn to take some control yourself. As your example shows, the camera can mess up the shot if it has to do all the thinking. If you provide some input, the camera will do a better job. Explaining all the details would take a book, which already exists, Understanding Exposure by Bryan Peterson. The really quick version I told my brother recently: start with values in the middle somewhere, tthen change one thing based on the photo you want. Middle values I suggested are based on using an 18-55 lens. They are f8, 1/125 sec., ISO 200 outside, 800 inside. With a single-dial camera such as the K-x, you can use Av mode and have direct control over aperture. The camera will suggest a shutter speed, which you can adjust by using exposure compensation. I like to have a fixed ISO, but you can use an Auto setting that limits the range the camera can use (page 90 in the manual). You can cover yourself further by turning on highlight correction (page 189) and shadow correction (190), sort of a safety net.

Now your camera can probably take a decent shot by itself, and you can take one setting at a time to see how it influences the photos.
01-19-2013, 01:40 AM   #4
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I figured out with my K-x that I need to set the max ISO to something reasonable when in auto mode. It will invariably use high ISO over slow shutter when it has the choice, and similar results will inevitably happen.

01-19-2013, 05:10 PM   #5
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Original Poster
Issue resolved

Thanks for the information, I now understand the cause and resolution to this noise issue, which is the proper term. And I appreciate the 'middle' setting values and references to the pertinent pages in the manual in Just1MoreDave's response. Thanks again, I will now "take some control".

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