Strange high ISO noise pattern on K20D...Normal?

[trevor_newman1]

<p>Hello All,<br /> So I just received my first Petax! It is a K20D w/ an 18-55WR and I am very excited. I have been putting it through a couple of tests (my least favorite part of getting a new camera/lens). I did a couple dark frame shots (withe lens cap on) to make sure the sensor was okay. At ISO 1600 and pp I noticed that there was quite a bit of...I don't know if you would call it grain or noise...but there was a great deal more "gain" at the top and bottom of the frame than in the middle. I produced images in JPEG and RAW and they both exhibit similar effects. For some reason when I upload them online the grain turns into blocky looking JPEG articats which are still clearly grouped at the top of the frame and bottom of the frame. Having Just come from Nikon I am not used to seeing this pattern. I just want to know if this is normal for the K20D or if it is a deffective sample. Could anyone with a K20D try this out and let me know if they get something similar. Thank you all so much. This image is ISO3200 shot in raw with a little Exposure Compensation added to accentuate what I am talking about. Any comments would be greatly appreciated. Thank you so much!</p>

[trevor_newman1]

<p>Here is the sample image I was referring to. Thank you again =)</p>

[jpo3136b]

<p>I couldn't see the image. So, I guess your equipment is perfect! If you can't upload the image, then give us a count by how many pixels of what color, and maybe we can tell you. </p>

[trevor_newman1]

<p>Hi john,<br>

I have been having problems uploading the picture. I will try it again =)</p><div></div>

[trevor_newman1]

<p>Success!</p>

[jpo3136b]

<p>Cap the viewfinder and run the test again. That graduation from a top or bottom edge is often indicative of light contamination in small amounts wrapping around the mirror. The small amount of light will be bouncing off of the black matte metal sides of the mirror well housing.</p>

[miserere_mei]

<p>Welcome to Pentax, Trevor!</p>

<p>All I can see in your pic is a black frame. My work monitor is a bit dark though. Follow John's recommendations.</p>

<p>As for Pentax noise, it's quite different to Nikon noise. Nikon tend to work hard at eliminating chroma (colour) noise, which is to the detriment of detail. Pentax follow the opposite philosophy: they let chroma noise run free while conserving as much detail as possible. When comparing my ISO 1600 shots to those of my Nikon friends, I have found that converting mine to B&W gives me grainy images with lots of detail, while with Nikon you get smooth images with less detail.</p>

<p>Personally, I like the Pentax approach, which also allows you to apply noise reduction in postprocessing if you want to remove/improve the chroma noise. The problem with removing detail in the camera is that it can't be recovered later, but noise can always be worked on afterwards. But it's all a matter of taste :-)</p>

[trevor_newman1]

<p>Hi Miserere and John,<br>

Miserere I know what you mean by the screen looking blank black. On on of my monitors it looks straight black and the problem is hard to see. On my laptop screen it is pretty clear. But yes, I agree with you about liking Pentax's approach to noise. I was a b&w film shooter and though I knew I could ultimately coax something like film from my nikon I liked Pentax's approach much better =).<br>

John,<br>

I tried the test again with the viewfinder covered...same result =(. Does this mean something is wrong? I hope not. I am in love with the way this camera handles and feels...low ISO image quality is outstanding. Though I will rarely shoot at high ISOs and will probably never shoot too many frames with the lens cap on =P, this is quite an investment and i just want to make sure my camera does not have a deffective problem that will get worse and worse and require me to send it in.<br>

Thank you both for your quick responses!</p>

<p> </p>

[michael_elenko]

<p>Trevor, welcome.</p>

<p>Please post a problematic shot that you would typically take for us to evaluate. I'm not doubting your concerns, but I don't intentionally take shots with the lens cap on.</p>

<p>Thanks,</p>

<p>ME</p>

[trevor_newman1]

<p>Hello all,<br>

I was shown a link to this thread on Pentaxforums and it shows the exact issue I am having.<br>

http://www.pentaxforums.com/forums/pentax-dslr-discussion/67532-how-use-k20s-black-pixels-hidden-dngs.html<br>

I am guessing from this thread that this is a normal occurance in the K20D. I am going out now to shoot a bit and I will post some of the results for review. Thanks!</p>

[shaloot]

<p>wow so people actually do these kinds of test?? that's dedication to your equipment right there; taking a photo with the lens cap ON to "see" what the results are.... as it is my wife thinks I'm off the deep end with just the amount of photos I take, can't imagine her reaction if she seems me taking pics with the lens cap on and then studying the pic on the computer...<br>

I'll just take photos of dimly lit bars to see how the noise is, thanks... :P<br>

Welcome to Pentax Trevor!</p>

[trevor_newman1]

<p>Haha, I hear you Somanna. I can't say I am proud of this affliction. I don't enjoy it much either. I just want to make sure that everything is a-ok as a new camera is a pretty big investment for a first year law student who is techincally owned by money lenders! I totally deserve the banter too...I mean I kind of laught at it myself. Thank your for being so light hearted =). I look forward to contributing to the forum in the years to come!</p>

[jgredline]

<p>Trevor, Honestly, I don't blame you for making sure your equipment is fine. I am as far from a pixel peeper as there is, but after the QC issues I read about, I too test things and once I am done and happy, the pixel peeper in me goes back in the drawer. :) This problem of QC is not a Pentax only problem by the way.</p>

[trevor_newman1]

<p>I completely agree. Once I am happy I am happy. Thanks for understanding Javier. I noticed that you have a couple K20Ds as well... is this camera behavior I am experiencing normal? The link from PentaxForums seems to indicate that I am not alone. By the way Javier, I love your street photography. I live close to the LA area and I recognize a lot of the places you photograph! You really nailed the LA experience with your photos. Great great stuff Javier. <br>

Also one quick question. What is the specific day of the picture of the week. Can't wait to contribute! </p>

[miserere_mei]

<blockquote>

<p>I was shown a link to this thread on Pentaxforums and it shows the exact issue I am having.<br /> <a rel="nofollow" href="http://www.pentaxforums.com/forums/pentax-dslr-discussion/67532-how-use-k20s-black-pixels-hidden-dngs.html" target="_blank">(link)</a></p>

</blockquote>

<p>Ahhh, that's very interesting. And I hadn't heard of that issue. I'd like Peter to chime in as he's been using the K20D at high ISO a lot.</p>

[jeremy_corbin]

<p>I put the sample in The GIMP and increased the brightness and contrast, <em>a lot</em> . I then zoomed in 400%, and scrolled top to bottom. I now see the issue that you are talking about, but I don't believe that this phenomenon would be at all visible under normal shooting conditions. I would have made the photo pretty darn ugly before I'd notice something like that. If it can be seen or not depending on monitor settings, I would say that this is more of a characteristic more than an issue. Frankly, I <em>like</em> being full of character.</p>

<p>Welcome to Pentax!</p>

[r.t. dowling]

<p>Trevor, the picture of the week is on Sundays. Although sometimes the thread has been known to start on Saturday evenings.</p>

[jgredline]

<p>Trevor,<br>

Thanks for the kind words. Truly, I love L.A.<br>

As for problems with the K20D, I have not seen any that I could tell. They may be there, but up to now I have not noticed. I have been spending more and more time with high ISO on the K20D od late and little by little I am getting a grasp on it. The in Camera setting to control really work well. I just wish it could be fine tuned a little bit better...<br>

 <br>

Here are some recent ISO3200 images. The only thing I did to them was run them through noise ninja and was done. There was still plenty of room in the Histogram to move them to the right, but did not see this until I was home. I need to chimp more, but usually with these kind of shots, chimping is not an option...Still, for quick grab shots inside a dark meat market, not bad and the larger images look much better and cleaner...K20D with Tamron 17-35F/2.8-4.0 lens.<br>

<img src="http://i404.photobucket.com/albums/pp128/jgredline/ISO%20special%20shots/SO32009.jpg"><br>

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<img src="http://i404.photobucket.com/albums/pp128/jgredline/ISO%20special%20shots/SO320011.jpg"><br>

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<img src="http://i404.photobucket.com/albums/pp128/jgredline/ISO%20special%20shots/SO320013.jpg"><br>

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<img src="http://i404.photobucket.com/albums/pp128/jgredline/ISO%20special%20shots/SO320014.jpg"><br>

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<img src="http://i404.photobucket.com/albums/pp128/jgredline/ISO%20special%20shots/SO32003.jpg"><br>

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<a href="http://jgredline.smugmug.com/gallery/9293869_gjRjA#621069802_LQHXE">Large images scattered here.</a><br>

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 </p>

[michael_kuhne]

<p>I agree with Mis that I like the idea of leaving noise control up to the user. There are numerous software programs that do a good job. I have occasionally used the K20D at ISO 1600, and even ISO 2,000 where I employed the camera's inboard user control. Test reviews stated this was effective. I used the "weak" setting and found in my case, that it was so with very little loss of detail.</p>

<p>Javier provides fine examples above!</p>

[trevor_newman1]

<p>You had to post food images Javier!!! I am starving...your images look delicsious mmmmm =)</p>

[jgredline]

<p>By the way...The farther to the right you get the histogram, the lessssss noise you will have. Had I exposed those images correctly, I would not have needed noise ninja.<br>

Oh and another thing. As Mis noted Converting Pentax High ISO images to black and white, looks like pleasant grain, not noise with great detail...Just though I would mention that.</p>

[trevor_newman1]

<p>Okay so I went out and shot a couple test images at ISO3200 and I am happy to report that the effect is hardly present. I don't even know if it actually exists in real shots since the image looks uniformally grainy with a greater amount in shadows regardless of their orientation in the frame (normal). Since I won't be shooting too much at ISO 3200 I don't think this will be a huge problem for me. I am posting a sample...even at ISO 3200 I like the look of the Pentax files better than the Nikon files. It is just a personal thing for me but (sans the chroma noise) they remind me of film files...I guess it is just what I am used to. Hey Seurat didn't get famous by applying noise reduction to his pointalist paintings ;). Plus the 18-55 is dang sharp in the middle...even though the corners are pretty soft wide open...I gotta say that is quite a performance for a kit lens! Thank you again to all who contributed. Now that I am not so worried it's happy fun picture taking time! =)</p><div></div>

[jgredline]

<p>Trevor,<br>

What did you focus on in the image?</p>

[trevor_newman1]

<p>I focused on that flower in the back to the left</p>

[trevor_newman1]

<p>Oh and just to clarify, when I said the lens was soft in the corners I wasn't refering to the out of focus portions in that image specifically...I tested it out shooting a wall (yay walls!) haha. And it was a little soft in the corners but it sharpened up around F8 which I am pretty sure is normal for most cheaper zooms.</p>